U.S. patent application number 13/793758 was filed with the patent office on 2013-07-25 for internal clamp for surgical procedures.
This patent application is currently assigned to GENZYME CORPORATION. The applicant listed for this patent is GENZYME CORPORATION. Invention is credited to Alexander Schwarz.
Application Number | 20130190814 13/793758 |
Document ID | / |
Family ID | 34594883 |
Filed Date | 2013-07-25 |
United States Patent
Application |
20130190814 |
Kind Code |
A1 |
Schwarz; Alexander |
July 25, 2013 |
Internal Clamp for Surgical Procedures
Abstract
One aspect of the present invention relates to a method of
occluding a vascular site in a mammal, comprising the step of
introducing into the vasculature of a mammal at or proximal to a
surgical site, a composition comprising at least one optionally
purified inverse thermosensitive polymer, wherein said inverse
thermosensitive polymer gels in said vasculature, thereby
temporarily occluding a vascular site of said mammal, wherein said
temporarily occluded vasculature site is kept in a substantially
cylindrical shape.
Inventors: |
Schwarz; Alexander;
(Brookline, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENZYME CORPORATION; |
Cambridge |
MA |
US |
|
|
Assignee: |
GENZYME CORPORATION
Cambridge
MA
|
Family ID: |
34594883 |
Appl. No.: |
13/793758 |
Filed: |
March 11, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12732781 |
Mar 26, 2010 |
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13793758 |
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10983164 |
Nov 5, 2004 |
7700086 |
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12732781 |
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60520888 |
Nov 18, 2003 |
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60517929 |
Nov 6, 2003 |
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Current U.S.
Class: |
606/214 |
Current CPC
Class: |
A61B 2017/12004
20130101; A61B 17/12109 20130101; A61B 17/11 20130101; A61K 31/765
20130101; A61B 2017/1135 20130101; A61B 2017/1139 20130101; A61B
17/1204 20130101; A61K 31/785 20130101; A61L 31/12 20130101; A61K
31/77 20130101; A61B 17/12045 20130101; A61B 2017/1107 20130101;
A61B 17/00491 20130101; A61L 31/06 20130101; A61K 9/0024 20130101;
A61B 17/12186 20130101; A61B 17/0057 20130101; A61B 2017/1132
20130101; A61K 51/1213 20130101; A61K 31/00 20130101; A61B 17/12022
20130101; A61K 31/74 20130101 |
Class at
Publication: |
606/214 |
International
Class: |
A61B 17/00 20060101
A61B017/00 |
Claims
1. A method of occluding a vascular site in a mammal, comprising
the steps of: (a) introducing into the vasculature of a mammal, at
or proximal to a surgical site, a composition comprising at least
one purified inverse thermosensitive polymer, wherein said at least
one purified inverse thermosensitive polymer gels in said
vasculature, thereby temporarily occluding said vascular site of
said mammal; and (b) performing an anastomosis.
2. The method of claim 1, wherein said anastomosis comprises
connecting a first vessel and a second vessel, wherein the
anastomosis is end-to-end anastomosis, side-to-end anastomosis, and
side-to-side anastomosis.
3. A method of occluding a vascular site in a mammal, comprising
the steps of: (a) introducing into the vasculature of a mammal, at
or proximal to a surgical site, a composition comprising at least
one purified inverse thermosensitive polymer, wherein said at least
one purified inverse thermosensitive polymer gels in said
vasculature, thereby temporarily occluding said vascular site of
said mammal; and (b) performing a surgical procedure comprising
anastomosis wherein said anastomosis controls blood oozing.
4. The method of claim 1, wherein said inverse thermosensitive
polymer is a poloxamer or poloxamine.
5. The method of claim 1, wherein said inverse thermosensitive
polymer is poloxamer 407, poloxamer 338, poloxamer 188, poloxamine
1107 or poloxamine 1307.
6. A method of occluding a vascular site in a mammal, comprising
the steps of: (a) introducing into the vasculature of a mammal, at
or proximal to a surgical site, a composition comprising at least
one purified inverse thermosensitive polymer, wherein said at least
one purified inverse thermosensitive polymer gels in said
vasculature, thereby temporarily occluding said vascular site of
said mammal; and (b) performing an anastomosis, wherein the inverse
thermosensitive polymer is poloxamer 407, poloxamer 338, poloxamer
188, poloxamine 1107 or poloxamine 1307.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 12/732,781, filed Mar. 26, 2010, which claims priority under 35
U.S.C. .sctn.120 to U.S. application Ser. No. 10/983,164, filed
Nov. 5, 2004 which claims the benefit of U.S. Provisional
Application No. 60/517,929, filed on Nov. 6, 2003 and U.S.
Provisional Application No. 60/520,888, filed Nov. 18, 2003. The
entire teachings of the above applications are incorporated herein
by reference.
BACKGROUND OF THE INVENTION
[0002] Blood vessels are cut during surgical procedures.
Electrocautery is effectively used to reduce or stop hemorrhaging
by "burning" the bleeding blood vessels, which seals them off.
Various types, shapes, and sizes of tips (probes) are available for
specific treatments. A small electrode is applied to the skin near
the surgical site. This is used to collect the electricity from the
body and safely discharge it back to the machine. A grounding pad
is placed on the person's body (usually the thigh) before the
surgery starts to protect the patient. Electrocautery prevents
bleeding from small sized blood vessels and capillary beds. Larger
blood vessels require temporary ligation during surgery.
[0003] There are two archetypical ways to achieve temporary
ligation. The first way is to ligate from the outside of a blood
vessel using clamps, clips and tourniquets or snares. Such devices
press against opposite sides of a flexible hollow tube so that the
walls flatten out and bear against one another. This produces an
axially-extending fold at the two edges. For stopping the flow of
fluid through the vessel, this squeezing or pinching action is very
effective. However, the lumen of these vessels have linings
(intima), which should not be traumatized by strong distortions.
Strong pressures, and excessive bending (axial folding), can
traumatize them leading to complications after the occluder is
removed.
[0004] Surgical clamps exist in many sizes with many different
types of clamp shapes (e.g., curved jaws, straight jaws, etc.). In
addition, many different types of jaw surfaces exist, as adapted to
the specific function performed by the clamp. When a different
function is to be performed, either one must use a different clamp,
or in some circumstances replaceable pads may be added to the jaws.
Many existing surgical clamps have jaws with hard clamping
surfaces. Some replaceable pads for these clamps are designed to
fit over the jaws to provide a softer clamping surface. Vascular
clamps, once they are clamped to the blood vessel, are usually held
in the closed position manually by the operator, or with a locking
mechanism.
[0005] Clamps and clips have some shortcomings in that
atherosclerotic plaque in blood vessels and calcified blood vessels
do not withstand the pressure exerted by these devices. It is well
known that in crossclamping of the aorta for bypass operations,
plaque may be released when the clamps are opened again and the
plaques may lead to strokes (Boivie P, Hansson M, Engstrom K G.
"Embolic material generated by multiple aortic crossclamping: a
perfusion model with human cadaveric aorta." J Thorac Cardiovasc
Surg 2003 June; 125(6):1451-60; van der Linden J, Hadjinikolaou L,
Bergman P, Lindblom D. "Postoperative stroke in cardiac surgery is
related to the location and extent of atherosclerotic disease in
the ascending aorta." J Am Coll Cardiol 2001 July; 38(1):131-5). In
addition, especially in older patients, calcified blood vessels,
when clamped, may lead to vessel damage.
[0006] A second way to achieve temporary ligation is to occlude the
blood flow internally. In temporary ligation using for example
balloon angioplasty, a deflated balloon catheter is placed at the
arterial or venous site to be occluded; and then, the balloon is
inflated, thereby blocking blood flow at the site. When the
ligation is no longer necessary, the balloon may be deflated and
the catheter removed (Matsuoka S, Uchiyama K, Shima H, Ohishi S,
Nojiri Y, Ogata H. "Temporary percutaneous aortic balloon occlusion
to enhance fluid resuscitation prior to definitive embolization of
posttraumatic liver hemorrhage." Cardiovasc Intervent Radiol 2001
July-August; 24(4):274-6; Joseph N, Levy E, Lipman S.
"Angioplasty-related iliac artery rupture: treatment by temporary
balloon occlusion." Cardiovasc Intervent Radiol 1987; 10(5):276-9).
However, the inflated balloon leads to dilation of the artery and
the injury to the intima can lead to thickening and narrowing of
the artery (Wainwright C L, Miller A M, Wadsworth R M.
"Inflammation as a key event in the development of neointima
following vascular balloon injury." Clin Exp Pharmacol Physiol 2001
November; 28(11):891-5; Labropoulos N, Giannoukas A D, Volteas S K,
al Kutoubi A. "Complications of the balloon assisted percutaneous
transluminal angioplasty." J Cardiovasc Surg (Torino) 1994
December; 35(6):475-89). Another way to internally occlude blood
vessels is a "T" shaped device with a bulbous tip placed at either
end of the "T." These devices are manufactured from silicon rubber.
The bulbous tips of the device are inserted into each of the two
parts of the vessel. The bulbous tips have to be the right size to
effectively occlude the blood vessel. Too large and the bulbs will
damage the intima, too small and the bulbs do not efficiently
occlude and stop blood flow. See e.g. U.S. Pat. Nos. 3,889,685;
4,168,708; 4,946,463. In clinical practice, these devices reduce
bleeding at the arteriotomy, but do not stop bleeding. The surgeon,
therefore, has still to rely on additional devices like misted
blowers and suction devices to clear the surgical field of blood.
Further, the surgeon has to take great care not to stitch through
the device and be careful during removal of the device from the
arteriotomy and not entangle the device in the suture.
[0007] Consequently, there is still a need for reversibly stopping
blood flow during surgery, without damage or trauma occasioned by
clamps or balloons. This holds great promise in terms of, for
example, patient outcome.
SUMMARY OF THE INVENTION
[0008] In certain embodiments, the present invention relates to a
method of occluding a vascular site in a mammal, comprising the
step of introducing into the vasculature of a mammal at or proximal
to a surgical site, a composition comprising at least one
optionally purified inverse thermosensitive polymer, wherein said
optional purified inverse thermosensitive polymer gels in said
vasculature, thereby temporarily occluding a vascular site of said
mammal.
[0009] In certain embodiments, the present invention relates to a
method of occluding a vascular site in a mammal, comprising the
steps of introducing into the vasculature of a mammal at or
proximal to a surgical site, a composition comprising at least one
optionally purified inverse thermosensitive polymer, wherein said
optional purified inverse thermosensitive polymer gels in said
vasculature, thereby temporarily occluding a vascular site of said
mammal; and performing a surgical procedure.
[0010] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition comprises at least
one optionally purified inverse thermosensitive polymer selected
from the group consisting of poloxamers and poloxamines.
[0011] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is selected from the group
consisting of poloxamer 407, poloxamer 338, poloxamer 118,
Tetronic.RTM. 1107 or Tetronic.RTM. 1307.
[0012] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is poloxamer 407.
[0013] In certain embodiments, the present invention relates to the
aforementioned method, wherein said temporarily occluded vascular
site, at or proximal to a surgical site, is a substantially
circular or substantially elliptical right cylinder, a
substantially circular or substantially elliptical oblique
cylinder, a substantially circular or substantially elliptical
right truncated cone, or a substantially circular or substantially
elliptical oblique truncated cone.
[0014] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition comprises at least
one optionally purified inverse thermosensitive polymer selected
from the group consisting of block copolymers, random copolymers,
graft polymers, and branched copolymers.
[0015] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is a polyoxyalkylene block
copolymer.
[0016] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition comprises at least
one optionally purified inverse thermosensitive polymer selected
from the group consisting of poloxamers and poloxamines.
[0017] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is selected from the group
consisting of poloxamer 407, poloxamer 338, poloxamer 118,
Tetronic.RTM. 1107 or Tetronic.RTM. 1307.
[0018] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is poloxamer 407.
[0019] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition comprises at least
one optionally purified inverse thermosensitive polymer selected
from the group consisting of purified poloxamers and purified
poloxamines.
[0020] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse they nosensitive polymer is selected from the
group consisting of purified poloxamer 407, purified poloxamer 338,
purified poloxamer 118, purified Tetronic.RTM. 1107 or purified
Tetronic.RTM. 1307.
[0021] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is purified poloxamer
407.
[0022] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition has a transition
temperature of between about 10.degree. C. and about 40.degree.
C.
[0023] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition has a transition
temperature of between about 15.degree. C. and about 30.degree.
C.
[0024] In certain embodiments, the present invention relates to the
aforementioned method, wherein the volume of said composition at
physiological temperature is about 80% to about 120% of its volume
below its transition temperature.
[0025] In certain embodiments, the present invention relates to the
aforementioned method, wherein the volume of said composition at
physiological temperature is about 80% to about 120% of its volume
below its transition temperature; and said composition has a
transition temperature of between about 10.degree. C. and about
40.degree. C.
[0026] In certain embodiments, the present invention relates to the
aforementioned method, wherein the volume of said composition at
physiological temperature is about 80% to about 120% of its volume
below its transition temperature; and said composition has a
transition temperature of between about 15.degree. C. and about
30.degree. C.
[0027] In certain embodiments, the present invention relates to the
aforementioned method, wherein the volume of said composition at
physiological temperature is about 80% to about 120% of its volume
below its transition temperature; said composition has a transition
temperature of between about 10.degree. C. and about 40.degree. C.;
and said composition comprises at least one optionally purified
inverse thermosensitive polymer selected from the group consisting
of poloxamers and poloxamines.
[0028] In certain embodiments, the present invention relates to the
aforementioned method, wherein the volume of said composition at
physiological temperature is about 80% to about 120% of its volume
below its transition temperature; said composition has a transition
temperature of between about 15.degree. C. and about 30.degree. C.;
and said composition comprises at least one optionally purified
inverse thermosensitive polymer selected from the group consisting
of poloxamers and poloxamines
[0029] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition comprises about 5%
to about 35% of said inverse thermosensitive polymer.
[0030] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition comprises about 10%
to about 30% of said inverse thermosensitive polymer.
[0031] In certain embodiments, the present invention relates to the
aforementioned method, wherein the inverse thermosensitive polymer
has a polydispersity index from about 1.5 to about 1.0.
[0032] In certain embodiments, the present invention relates to the
aforementioned method, wherein the inverse thermosensitive polymer
has a polydispersity index from about 1.2 to about 1.0.
[0033] In certain embodiments, the present invention relates to the
aforementioned method, wherein said surgical site is at or proximal
to a hemorrhage, cancerous tissue, tumor, or organ.
[0034] In certain embodiments, the present invention relates to the
aforementioned method, wherein said surgical procedure comprises
anastomosis.
[0035] In certain embodiments, the present invention relates to the
aforementioned method, wherein said anastomosis comprises
connecting a first vessel and a second vessel.
[0036] In certain embodiments, the present invention relates to the
aforementioned method, wherein said connecting a first vessel and a
second vessel comprises suturing, laser welding or laser
soldering.
[0037] In certain embodiments, the present invention relates to the
aforementioned method, wherein said anastomosis is selected from
the group consisting of end-to-end anastomosis, side-to-end
anastomosis and side-to-side anastomosis.
[0038] In certain embodiments, the present invention relates to the
aforementioned method, wherein said occlusion reduces bleeding
during said surgical procedure.
[0039] In certain embodiments, the present invention relates to the
aforementioned method, wherein said occlusion enables controlled
ischemic preconditioning of said surgical site.
[0040] In certain embodiments, the present invention relates to the
aforementioned method, wherein said occlusion is at or proximal to
an incision site for minimally invasive surgery and decreases
bleeding through the incision.
[0041] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition occludes said
vascular site for less than about one hour.
[0042] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition further comprises a
contrast-enhancing agent.
[0043] In certain embodiments, the present invention relates to the
aforementioned method, wherein said contrast-enhancing agent is
selected from the group consisting of radiopaque materials,
paramagnetic materials, heavy atoms, transition metals,
lanthanides, actinides, dyes, and radionuclide-containing
materials.
[0044] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition further comprises a
biologically active agent.
[0045] In certain embodiments, the present invention relates to the
aforementioned method, wherein the biologically active agent is
selected from the group consisting of antiinflammatories,
antibiotics, antimicrobials, chemotherapeutics, antivirals,
analgesics, antiproliferatives, plasmids, DNA and RNA.
[0046] In certain embodiments, the present invention relates to the
aforementioned method, wherein said mammal is a human.
[0047] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition is introduced to
said vasculature through a percutaneous access device.
[0048] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition is introduced to
said vasculature using a catheter.
[0049] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition is introduced to
said vasculature using a syringe.
[0050] In certain embodiments, the present invention relates to the
aforementioned method, further comprising the step of injecting an
aqueous solution at or proximal to the occlusion site, thereby
dissolving said occlusion.
[0051] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition comprises at least
one optionally purified inverse thermosensitive polymer selected
from the group consisting of poloxamers and poloxamines.
[0052] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is selected from the group
consisting of poloxamer 407, poloxamer 338, poloxamer 118,
Tetronic.RTM. 1107 or Tetronic.RTM. 1307.
[0053] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is poloxamer 407.
[0054] In certain embodiments, the present invention relates to the
aforementioned method, further comprising the step of cooling the
occlusion site, thereby liquefying the gel and dissolving said
occlusion.
[0055] In certain embodiments, the present invention relates to the
aforementioned method, said occlusion site is cooled by using a
cold aqueous solution or ice.
[0056] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition comprises at least
one optionally purified inverse thermosensitive polymer selected
from the group consisting of poloxamers and poloxamines.
[0057] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is selected from the group
consisting of poloxamer 407, poloxamer 338, poloxamer 118,
Tetronic.RTM. 1107 or Tetronic.RTM. 1307.
[0058] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is poloxamer 407.
[0059] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition comprises at least
one optionally purified inverse thermosensitive polymer selected
from the group consisting of poloxamers and poloxamines; and said
surgical procedure comprises anastomosis.
[0060] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is selected from the group
consisting of poloxamer 407, poloxamer 338, poloxamer 118,
Tetronic.RTM. 1107 or Tetronic.RTM. 1307; and said surgical
procedure comprises anastomosis.
[0061] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is poloxamer 407; and said
surgical procedure comprises anastomosis.
[0062] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition comprises at least
one optionally purified inverse thermosensitive polymer selected
from the group consisting of poloxamers and poloxamines.
[0063] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is selected from the group
consisting of poloxamer 407, poloxamer 338, poloxamer 118,
Tetronic.RTM. 1107 or Tetronic.RTM. 1307.
[0064] In certain embodiments, the present invention relates to the
aforementioned method, wherein said at least one optionally
purified inverse thermosensitive polymer is poloxamer 407.
BRIEF DESCRIPTION OF THE DRAWINGS
[0065] FIG. 1 depicts a graph of viscosity versus temperature for
purified poloxamer 407 solutions.
[0066] FIG. 2 depicts a graph of blood volume collected from an
anastomosis site with and without purified poloxamer 407.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
[0067] For convenience, certain terms employed in the
specification, examples, and appended claims are collected
here.
[0068] The articles "a" and "an" are used herein to refer to one or
to more than one (i.e., to at least one) of the grammatical object
of the article. By way of example, "an element" means one element
or more than one element.
[0069] The term "anastomosis" as used herein refers to a surgical
connection between tubular structures, such as blood vessels.
"Beating heart" bypass surgeries, also known as "off-pump" bypass
surgeries, are examples of surgical procedures in which anastomoses
are performed.
[0070] The term "ischemia" as used herein refers to a lack of blood
supply (and thus oxygen) to an organ or tissue.
[0071] The term "ischemic preconditioning" as used herein refers to
a technique in which tissue is rendered resistant to the
deleterious effects of prolonged ischemia by prior exposure to
brief, repeated periods of vascular occlusion.
[0072] The terms "reversibly gelling" and "inverse thermosensitive"
refer to the property of a polymer wherein gelation takes place
upon an increase in temperature, rather than a decrease in
temperature.
[0073] The term "transition temperature" refers to the temperature
or temperature range at which gelation of an inverse
thermosensitive polymer occurs.
[0074] The term "contrast-enhancing" refers to materials capable of
being monitored during injection into a mammalian subject by
methods for monitoring and detecting such materials, for example by
radiography or fluoroscopy. An example of a contrast-enhancing
agent is a radiopaque material. Contrast-enhancing agents including
radiopaque materials may be either water soluble or water
insoluble. Examples of water soluble radiopaque materials include
metrizamide, iopamidol, iothalamate sodium, iodomide sodium, and
meglumine. Examples of water insoluble radiopaque materials include
metals and metal oxides such as gold, titanium, silver, stainless
steel, oxides thereof, aluminum oxide, zirconium oxide, etc.
[0075] As used herein, the term "polymer" means a molecule, formed
by the chemical union of two or more oligomer units. The chemical
units are normally linked together by covalent linkages. The two or
more combining units in a polymer can be all the same, in which
case the polymer is referred to as a homopolymer. They can also be
different and, thus, the polymer will be a combination of the
different units. These polymers are referred to as copolymers.
[0076] The term "biocompatible", as used herein, refers to having
the property of being biologically compatible by not producing a
toxic, injurious, or immunological response in living tissue.
[0077] The term "degradable", as used herein, refers to having the
property of breaking down or degrading under certain conditions,
e.g. by dissolution.
[0078] The term "poloxamer" denotes a symmetrical block copolymer,
consisting of a core of PPG polyoxyethylated to both its terminal
hydroxyl groups, i.e. conforming to the interchangeable generic
formula (PEG).sub.X--(PPG).sub.Y--(PEG).sub.X and
(PEO).sub.X--(PPO).sub.Y--(PEO).sub.X. Each poloxamer name ends
with an arbitrary code number, which is related to the average
numerical values of the respective monomer units denoted by X and
Y.
[0079] The term "poloxamine" denotes a polyalkoxylated symmetrical
block copolymer of ethylene diamine conforming to the general type
[(PEO).sub.X--(PPO).sub.Y].sub.2--NCH.sub.2CH.sub.2N--[(PPO).sub.Y--(PEO)-
.sub.X].sub.2. Each Poloxamine name is followed by an arbitrary
code number, which is related to the average numerical values of
the respective monomer units denoted by X and Y.
[0080] The phrase "polydispersity index" refers to the ratio of the
"weight average molecular weight" to the "number average molecular
weight" for a particular polymer; it reflects the distribution of
individual molecular weights in a polymer sample.
Overview
[0081] Vascular anastomosis is a procedure by which two blood
vessels within a patient are surgically joined together. Vascular
anastomosis is performed during treatment of a variety of
conditions including coronary artery disease, diseases of the great
and peripheral vessels, organ transplantation, reconstructive
surgery and trauma. In coronary artery disease (CAD) an occlusion
or stenosis in a coronary artery interferes with blood flow to the
heart muscle. Treatment of CAD involves the grafting of a vessel in
the form of a prosthesis or harvested artery or vein to reroute
blood flow around the occlusion and restore adequate blood flow to
the heart muscle. This treatment is known as coronary artery bypass
grafting (CABG).
[0082] In the conventional CABG, a large incision is made in the
chest and the sternum is sawed in half to allow access to the
heart. In addition, a heart lung machine is used to circulate the
patient's blood so that the heart can be stopped and the
anastomosis can be performed. During this procedure, the aorta is
clamped which can lead to trauma of the aortic tissue and/or
dislodge plaque emboli, both of which increase the likelihood of
neurological complications. In order to minimize the trauma to the
patient induced by conventional CABG, less invasive techniques have
been developed in which the surgery is performed through small
incisions in the patients chest with the aid of visualizing scopes.
Less invasive CABG can be performed on a beating heart, thereby
avoiding the need for a cardiopulmonary bypass.
[0083] However, in both conventional and less invasive CABG
procedures, the surgeon has to connect one end of the graft vessel
to the coronary artery and the other end of the graft vessel to a
blood supplying vein or artery. This process is a time consuming
and difficult procedure and is often further complicated by
incomplete occlusion leading to blood oozing. This is especially
problematic in minimally invasive surgeries where in the surgeon
uses small ports to access the anatomy and robotics to perform the
operation. These procedures often utilize an endoscopic camera to
visualize the surgical field. When this is the case, maintaining a
bloodless surgical field is especially important; a single drop of
blood on the camera and the operation might have to be converted
into a more invasive surgery.
[0084] Current medical practice uses a variety of devices to
prevent or minimize blood oozing in the surgical practice of
anastomosis. The simplest device to use would be a clamp, however,
the use of clamps in arteriosclerotic vessels is dangerous due to
potential dislodgement of plaque and damage to the artery.
Peripherally, tourniquets are often used, e.g., in hemodialysis
access surgery. A form of tourniquet commonly used in heart surgery
is ligation bands, also called snares, around the artery to be
bypassed. If the ligation band is tightened too tightly, damage to
the artery might occur; if the ligation band is too loose, blood is
still oozing out of the arteriotomy. Therefore, the surgeon has to
find a compromise between visibility in the surgical field and
damage to the artery.
[0085] Alternatively, an internal vessel occluder device, for
example "Flo-Rester" from Synovis, Inc., which is shaped like a
Q-Tip, can be inserted into the arteriotomy and mechanically
occlude the artery internally. The device is extracted just prior
to closing the anastomosis. However, the surgeon has to estimate
the vessel diameter correctly for proper fit of the device.
[0086] Additionally, a coronary shunt can be deployed. It is shaped
similarly to a Q-Tip, but with a hollow tube for blood flow through
the tube. Again, the surgeon has to correctly estimate the diameter
of the blood vessel for proper fit of the device. The shunts and
the internal vessel occluders might be dangerous to deploy in
highly arteriosclerotic vessel with heavy plaque build-up.
Furthermore, these devices damage intima due to mechanical forces
on the lining of the blood vessel (see e.g. Demaria R G, Fortier S,
Malo O, Carrier M, Perrault L P. "Influence of intracoronary shunt
size on coronary endothelial function during off-pump coronary
artery bypass." Heart Surg Forum. 6 (2003)160-8; Hangler H B,
Pfaller K, Ruttmann E, Hoefer D, Schachner T, Laufer G, Antretter
H. "Effects of intracoronary shunts on coronary endothelial coating
in the human beating heart.: Ann Thorac Surg. 77 (2004) 776-80.;
Demaria R G, Malo, O, Carrier, M, Perrault L P, "The Monoshunt: a
new intracoronary shunt design to avoid distal endothelial
dysfunction during off-pump coronary artery bypass (OPCAB",
Interact Cardiovasc Thorac Surg 2 (2003) 281-286). There are a
number of other disadvantages to these internal vessel occluders:
great care has to be taken during the anastomosis not to sew in the
device as well as not to stitch through the device. Further, the
removal of these devices is not trivial as great care has to be
taken to not entangle the device in the suture.
[0087] In one embodiment of the present invention, purified,
reverse thermosensitive polymers are used to occlude blood vessels
during anastomosis. The purified, reverse thermosensitive polymer
solution is easy to deploy by injection into the arteriotomy
utilizing a syringe equipped with either a needle or a cannula. As
the polymer solution quickly warms to body temperature and forms
the gel plug, it prevents blood oozing due to filling of the artery
with the polymer plug and provides the surgeon a clean, bloodless
surgical field. Furthermore, as the gel fills the artery at the
arteriotomy site, the blood vessel is kept in a cylindrical shape;
contrary to all other devices used which result in flaccid blood
vessels due to the emptying of the blood vessel of fluid. As the
polymer is highly water-soluble, the polymer plug dissolves in
blood and is excreted through the kidney. Cooling the bypass area
with sterile ice or cold saline can speed up the dissolution
process and enables control of the dissolution time.
[0088] In a preferred embodiment, the present invention seeks to
replace the combination of inadequate products and technologies
that are used by surgeons to control blood oozing during
anastomosis. In these surgical procedures, bleeding is a major
difficulty of the procedure. Often it is not the amount of bleeding
that is dangerous for the patient, but any "oozing" makes it
difficult for the surgeon to see what he is doing.
[0089] Temporarily halting blood flow in the case of hemorrhaging
may also be achieved by the instant invention. Often in traumas a
surgeon would benefit from halting blood flow for a short period of
time to establish from where the patient is bleeding. In a
preferred embodiment, the present invention seeks to halt
hemorrhaging by use of a thermosensitive polymer plug as described
herein.
[0090] The instant invention may be applied to all surgical
procedures, which involve the connection of two blood vessels,
e.g., coronary bypass, peripheral bypass, hemodialysis access
(creation of a fistula), and free-flap surgery (breast and face
reconstruction surgery). The instant invention may aid in the
establishment of end to end, side to end and side to side
anastomoses.
[0091] Interestingly, a number of devices, existing or under
development, aim at simplifying bypass surgery by automating the
sewing of arteries to each other, or eliminating sewing altogether.
They are sometimes called anastomosis devices. Far from competing
with the instant invention, these devices require perfectly
cylindrical blood vessels to interact with. Unlike clamps or
snares, which can flatten and damage the artery, the method of the
instant invention maintains the cylindrical shape of the artery
once it is filled with gel, a feature that is very attractive to
the suppliers of anastomosis devices.
[0092] Laser welding has been shown to work as an alternative to
suturing, however, the process is made more difficult by the need
to have a cylindrical vessel. Since an artery occluded with gel
maintains its cylindrical shape, an additional advantage to the
instant occlusion method is that alternatives to traditional
suturing, such as laser soldering or welding, may be performed.
While various inventors have proposed devises, e.g., an albumin
hollow tube to be inserted into the anastomosis site to keep the
artery cylindrical, the instant invention will dramatically ease
the technical difficulty of these suturing alternatives.
Methods of the Invention
[0093] In a preferred embodiment, the present invention
significantly simplifies anastomosis by assuring a bloodless
surgical field, obviates the surgeon from having to guess the size
of the artery at the arteriotomy site, and maintains a
substantially cylindrical shape of said artery, by injecting
temporary plugs in the vessels being joined thereby occluding said
vessels. The plugs consist of an aqueous solution of inverse
thermosensitive polymers. These polymer solutions are soft gels at
about 20.degree. C. and as they are injected into the body the gels
further stiffens to form hard gels at about body temperature. The
polymer solution starts externally of the body and thus at a
temperature below body temperature.
Introduction/Removal of the Plug
[0094] In one embodiment, the polymer solution can be introduced
through a catheter. Said catheter can be a dual or multi-lumen
catheter. In one embodiment, the catheter is 3-10 French in size,
and more preferably 3-6 French.
[0095] In another embodiment, a syringe used to inject the inverse
thermosensitive polymer into the body can be, for example, a 0.1-10
cc syringe or a syringe with volume of 1-3 cc or with a volume of
0.1-1 cc. Pressure applied to the syringe can be applied by hand or
by an automated syringe pusher (see Example 2 below).
[0096] The gelation of reverse thermosensitive polymers is
dependent on the temperature and the concentration of the polymer.
Therefore, after the anastomosis procedure, the gel can be removed
by instilling a fluid around the gel, which leads to dissolution of
the gel. The fluid may be chilled to help in the dissolution with a
preferred temperature of about 10.degree. C. below the gelation
temperature. The fluid can be instilled through a catheter or
syringe percutaneously. Alternatively, the site of the anastomosis
can be chilled by placing sterile ice on the procedure site,
thereby cooling the gel to below its gelation temperature. The
liquid polymer dilutes in blood and is washed away from the
anastomosis.
Inverse Thermosensitive Polymers
[0097] In general, the inverse thermosensitive polymers used in the
methods of the invention, which become a gel at or about body
temperature, can be injected into the patient's body in a liquid or
soft gel fill. The injected material once reaching body temperature
undergoes a transition from a liquid or soft gel to a hard gel. The
inverse thermosensitive polymers used in connection with the
methods of the invention may comprise a block copolymer with
inverse thermal gelation properties. In general, biocompatible,
biodegradable block copolymers that exist as a gel at body
temperature and a liquid at below body temperature may also be used
according to the present invention. Also, the inverse
thermosensitive polymer can include a therapeutic agent such as
anti-angiogenic agents, hormones, anesthetics, antimicrobial agents
(antibacterial, antifungal, antiviral), anti-inflammatory agents,
diagnostic agents, or wound healing agents. Similarly, low
concentrations of dye (such as methylene blue) or fillers can be
added to the inverse thermosensitive polymer.
[0098] The molecular weight of the inverse thermosensitive polymer
is preferably between 1,000 and 50,000, more preferably between
5,000 and 35,000. Preferably the polymer is in an aqueous solution.
For example, typical aqueous solutions contain about 5% to about
30% polymer, preferably about 10% to about 25%. The molecular
weight of a suitable inverse thermosensitive polymer (such as a
poloxamer or poloxamine) may be, for example, between 5,000 and
25,000, and more particularly between 7,000 and 20,000.
[0099] The pH of the inverse thermosensitive polymer formulation
administered to the mammal is, generally, about 6.0 to about 7.8,
which are suitable pH levels for injection into the mammalian body.
The pH level may be adjusted by any suitable acid or base, such as
hydrochloric acid or sodium hydroxide.
Poloxamers (Pluronics)
[0100] Notably, Pluronic.RTM. polymers have unique surfactant
abilities and extremely low toxicity and immunogenic responses.
These products have low acute oral and dermal toxicity and low
potential for causing irritation or sensitization, and the general
chronic and sub-chronic toxicity is low. In fact, Pluronic.RTM.
polymers are among a small number of surfactants that have been
approved by the FDA for direct use in medical applications and as
food additives (BASF (1990) Pluronic.RTM. & Tetronic.RTM.
Surfactants, BASF Co., Mount Olive, N.J.). Recently, several
Pluronic.RTM. polymers have been found to enhance the therapeutic
effect of drugs, and the gene transfer efficiency mediated by
adenovirus. (March K L, Madison J E, Trapnell B C.
"Pharmacokinetics of adenoviral vector-mediated gene delivery to
vascular smooth muscle cells: modulation by poloxamer 407 and
implication for cardiovascular gene therapy" Hum Gene Therapy 1995,
6, 41-53).
[0101] Poloxamers (or Pluronics), as nonionic surfactants, are
widely used in diverse industrial applications. (Nonionic
Surfactants: polyoxyalkylene block copolymers, Vol. 60. Nace V M,
Dekker M (editors), New York, 1996. 280 pp.) Their surfactant
properties have been useful in detergency, dispersion,
stabilization, foaming, and emulsification. (Cabana A, Abdellatif A
K, Juhasz J. "Study of the gelation process of polyethylene oxide.
polypropylene oxide-polyethylene oxide copolymer (poloxamer 407)
aqueous solutions." Journal of Colloid and Interface Science. 1997;
190: 307-312.) Certain poloxamines, e.g., poloxamine 1307 and 1107,
also display inverse thermosensitivity.
[0102] Some of these polymers have been considered for various
cardiovascular applications, as well as in sickle cell anemia.
(Maynard C, Swenson R, Paris J A, Martin J S, Hallstrom A P,
Cerqueira M D, Weaver W D. Randomized, controlled trial of RheothRx
(poloxamer 188) in patients with suspected acute myocardial
infarction. RheothRx in Myocardial Infarction Study Group. Am Heart
J. 1998 May; 135 (5 Pt 1): 797-804; O'Keefe J H, Grines C L, DeWood
Mass., Schaer G L, Browne K, Magorien R D, Kalbfleisch J M,
Fletcher W O Jr, Bateman T M, Gibbons
[0103] Poloxamer-188 as an adjunct to primary percutaneous
transluminal coronary angioplasty for acute myocardial infarction.
Am J. Cardiol. 1996 Oct. 1; 78(7):747-750; and Orringer E P,
Casella J F, Ataga K I, Koshy M, Adams-Graves P, Luchtman-Jones L,
Wun T, Watanabe M, Shafer F, Kutlar A, Abboud M, Steinberg M, Adler
B, Swerdlow P, Terregino C, Saccente S, Files B, Ballas S, Brown R,
Wojtowicz-Praga S, Grindel J M. Purified poloxamer 188 for
treatment of acute vasoocclusive crisis of sickle cell disease: A
randomized controlled trial. JAMA. 2001 Nov. 7; 286
(17):2099-2106.)
[0104] Importantly, several members of this class of polymer,
poloxamer 188, poloxamer 407, poloxamer 338, poloxamines 1107 and
1307 show inverse thermosensitivity within the physiological
temperature range. (Qiu Y, Park K. Environment-sensitive hydrogels
for drug delivery. Adv Drug Deliv Rev. 2001 Dec. 31; 53(3):321-339;
and Ron E S, Bromberg L E Temperature-responsive gels and
thermogelling polymer matrices for protein and peptide delivery Adv
Drug Deliv Rev. 1998 May 4; 31(3):197-221.) In other words, these
polymers are members of a class that are soluble in aqueous
solutions at low temperature, but gel at higher temperatures.
Poloxamer 407 is a biocompatible polyoxypropylene-polyoxyethylene
block copolymer having an average molecular weight of about 12,500
and a polyoxypropylene fraction of about 30%; poloxamer 188 has an
average molecular weight of about 8400 and a polyoxypropylene
fraction of about 20%; poloxamer 338 has an average molecular
weight of about 14,600 and a polyoxypropylene fraction of about
20%; poloxamine 1,107 has an average molecular weight of about
14,000, poloxamine 1307 has an average molecular weight of about
18,000. Polymers of this type are also referred to as reversibly
gelling because their viscosity increases and decreases with an
increase and decrease in temperature, respectively. Such reversibly
gelling systems are useful wherever it is desirable to handle a
material in a fluid state, but performance is preferably in a
gelled or more viscous state. As noted above, certain
poly(ethyleneoxide)/poly(propyleneoxide) block copolymers have
these properties; they are available commercially as Pluronic.RTM.
poloxamers and Tetronic.RTM. poloxamines (BASF, Ludwigshafen,
Germany) and generically known as poloxamers and poloxamines,
respectively. See U.S. Pat. Nos. 4,188,373, 4,478,822 and
4,474,751.
[0105] The average molecular weights of the poloxamers range from
about 1,000 to greater than 16,000 daltons. Because the poloxamers
are products of a sequential series of reactions, the molecular
weights of the individual poloxamer molecules form. a statistical
distribution about the average molecular weight. In addition,
commercially available poloxamers contain substantial amounts of
poly(oxyethylene) homopolymer and
poly(oxyethylene)/poly(oxypropylene diblock polymers. The relative
amounts of these byproducts increase as the molecular weights of
the component blocks of the poloxamer increase. Depending upon the
manufacturer, these byproducts may constitute from about 15 to
about 50% of the total mass of the polymer.
Purification of Inverse Thermosensitive Polymers
[0106] The inverse thermosensitive polymers may be purified using a
process for the fractionation of water-soluble polymers, comprising
the steps of dissolving a known amount of the polymer in water,
adding a soluble extraction salt to the polymer solution,
maintaining the solution at a constant optimal temperature for a
period of time adequate for two distinct phases to appear, and
separating physically the phases. Additionally, the phase
containing the polymer fraction of the preferred molecular weight
may be diluted to the original volume with water, extraction salt
may be added to achieve the original concentration, and the
separation process repeated as needed until a polymer having a
narrower molecular weight distribution than the starting material
and optimal physical characteristics can be recovered.
[0107] In certain embodiments, a purified poloxamer or poloxamine
has a polydispersity index from about 1.5 to about 1.0. In certain
embodiments, a purified poloxamer or poloxamine has a
polydispersity index from about 1.2 to about 1.0.
[0108] The aforementioned process consists of forming an aqueous
two-phase system composed of the polymer and an appropriate salt in
water. In such a system, a soluble salt can be added to a single
phase polymer-water system to induce phase separation to yield a
high salt, low polymer bottom phase, and a low salt, high polymer
upper phase. Lower molecular weight polymers partition
preferentially into the high salt, low polymer phase. Polymers that
can be fractionated using this process include polyethers, glycols
such as poly(ethylene glycol) and poly(ethylene oxide)s,
polyoxyalkylene block copolymers such as poloxamers, poloxamines,
and polyoxypropylene/polyoxybutylene copolymers, and other polyols,
such as polyvinyl alcohol. The average molecular weight of these
polymers may range from about 800 to greater than 100,000 daltons.
See U.S. Pat. No. 6,761,824. The aforementioned purification
process inherently exploits the differences in size and polarity,
and therefore solubility, among the poloxamer molecules, the
poly(oxyethylene) homopolymer and the
poly(oxyethylene)/poly(oxypropylene) diblock byproducts. The polar
fraction of the poloxamer, which generally includes the lower
molecular weight fraction and the byproducts, is removed allowing
the higher molecular weight fraction of poloxamer to be recovered.
The larger molecular weight poloxamer recovered by this method has
physical characteristics substantially different from the starting
material or commercially available poloxamer including a higher
average molecular weight, lower polydispersity and a higher
viscosity in aqueous solution.
[0109] Other purification methods may be used to achieve the
desired outcome. For example, WO 92/16484 discloses the use of gel
permeation chromatography to isolate a fraction of poloxamer 188
that exhibits beneficial biological effects, without causing
potentially deleterious side effects. The copolymer thus obtained
had a polydispersity index of 1.07 or less, and was substantially
saturated. The potentially harmful side effects were shown to be
associated with the low molecular weight, unsaturated portion of
the polymer, while the medically beneficial effects resided in the
uniform higher molecular weight material. Other similarly improved
copolymers were obtained by purifying either the polyoxypropylene
center block during synthesis of the copolymer, or the copolymer
product itself (e.g., U.S. Pat. No. 5,523,492 and U.S. Pat. No.
5,696,298).
[0110] Further, a supercritical fluid extraction technique has been
used to fractionate a polyoxyalkylene block copolymer as disclosed
in U.S. Pat. No. 5,567,859. A purified fraction was obtained, which
was composed of a fairly uniform polyoxyalkylene block copolymer
having a polydispersity of less than 1.17. According to this
method, the lower molecular weight fraction was removed in a stream
of carbon dioxide maintained at a pressure of 2200 pounds per
square inch (psi) and a temperature of 40.degree. C.
[0111] Additionally, U.S. Pat. No. 5,800,711 discloses a process
for the fractionation of polyoxyalkylene block copolymers by the
batchwise removal of low molecular weight species using a salt
extraction and liquid phase separation technique. Poloxamer 407 and
poloxamer 188 were fractionated by this method. In each case, a
copolymer fraction was obtained which had a higher average
molecular weight and a lower polydispersity index as compared to
the starting material. However, the changes in polydispersity index
were modest and analysis by gel permeation chromatography indicated
that some low-molecular-weight material remained. The viscosity of
aqueous solutions of the fractionated polymers was significantly
greater than the viscosity of the commercially available polymers
at temperatures between 10.degree. C. and 37.degree. C., an
important property for some medical and drug delivery applications.
Nevertheless, some of the low molecular weight contaminants of
these polymers are thought to cause deleterious side effects when
used inside the body, making it especially important that they be
removed in the fractionation process. As a consequence,
polyoxyalkylene block copolymers fractionated by this process are
not appropriate for all medical uses.
[0112] As mentioned above, the use of these polymers in larger
concentrations in humans requires removal of lower molecular weight
contaminants present in commercial preparations. As was
demonstrated in U.S. Pat. No. 5,567,859 (Examples 8 & 9), the
lower molecular weight contaminants are mostly responsible for the
toxic effects seen. In a clinical trial using unpurified poloxamer
188, an unacceptable level of transient renal dysfunction was found
(Maynard C, Swenson R, Paris J A, Martin J S, Hallstrom A P,
Cerqueira M D, Weaver W D. Randomized, controlled trial of RheothRx
(poloxamer 188) in patients with suspected acute myocardial
infarction. RheothRx in Myocardial Infarction Study Group. Am Heart
J. 1998 May; 135(5 Pt 1):797-804), while another clinical trial
using purified poloxamer 188 specifically mentioned that no renal
dysfunction was found (Orringer E P, Casella J F, Ataga K I, Koshy
M, Adams-Graves P, Luchtman-Jones L, Wun T, Watanabe M, Shafer F,
Kutlar A, Abboud M, Steinberg M, Adler B, Swerdlow P, Terregino C,
Saccente S, Files B, Ballas S, Brown R, Wojtowicz-Praga S, Grindel
JM. Purified poloxamer 188 for treatment of acute vasoocclusive
crisis of sickle cell disease: A randomized controlled trial. JAMA.
2001 Nov. 7; 286(17):2099-2106.) Therefore, it seems imperative to
utilize only fractionated poloxamers and poloxamines in vascular
applications like the ones envisioned here. Furthermore,
fractionation of these thermosensitive polymers leads to improved
gels with stronger mechanical resistance and due to the improved
thermosensitivity requires less polymer to achieve gelation (See
for example U.S. Pat. No. 6,761,824 on a purification scheme and
the resultant viscosities).
Anastomosis in Conjunction with Drug Delivery
[0113] Effective therapeutic use of many types of biologically
active molecules has not been achieved simply because methods are
not available to cause delivery of therapeutically effective
amounts of such substances into the particular cells of a patient
for which treatment would provide therapeutic benefit. Efficient
delivery of therapeutically sufficient amounts of such molecules
into cells has often proved difficult, if not impossible, since,
for example, the cell membrane presents a selectively-permeable
barrier. Additionally, even when biologically active molecules
successfully enter targeted cells, they may be degraded directly in
the cell cytoplasm or even transported to structures in the cell,
such as lysosomal compartments, specialized for degradative
processes. Thus, both the nature of substances that are allowed to
enter cells, and the amounts thereof that ultimately arrive at
targeted locations within cells, at which they can provide
therapeutic benefit, are strictly limited.
[0114] Although such selectivity is generally necessary in order
that proper cell function can be maintained, it comes with the
disadvantage that many therapeutically valuable substances (or
therapeutically effective amounts) are excluded. Additionally, the
complex structure, behavior, and environment presented by an intact
tissue that is targeted for intracellular delivery of biologically
active molecules often interfere substantially with such delivery,
in comparison with the case presented by populations of cells
cultured in vitro. Therefore, new ways of delivering drugs at the
right time, in a controlled manner, with minimal side effects, and
greater efficacy per dose are sought by the drug-delivery and
pharmaceutical industries.
[0115] The reversibly gelling polymers used in the anastomosis
methods of the invention have physico-chemical characteristics that
make them suitable delivery vehicles for conventional
small-molecule drugs, as well as new macromolecular (e.g.,
peptides) drugs or other therapeutic products. Therefore, the
composition comprising the thermosensitive polymer may further
comprise a pharmaceutic agent selected to provide a pre-selected
pharmaceutic effect. A pharmaceutic effect is one which seeks to
treat the source or symptom of a disease or physical disorder.
Pharmaceutics include those products subject to regulation under
the FDA pharmaceutic guidelines, as well as consumer products.
Importantly, the compositions used anastomosis methods of the
invention are capable of solubilizing and releasing bioactive
materials. Solubilization is expected to occur as a result of
dissolution in the bulk aqueous phase or by incorporation of the
solute in micelles created by the hydrophobic domains of the
poloxamer. Release of the drug would occur through diffusion or
network erosion mechanisms.
[0116] Those skilled in the art will appreciate that the
compositions used in the anastomosis methods of the invention may
simultaneously be utilized to deliver a wide variety of
pharmaceutic and personal care applications. To prepare a
pharmaceutic composition, an effective amount of pharmaceutically
active agent(s), which imparts the desirable pharmaceutic effect is
incorporated into the reversibly gelling composition used in the
anastomosis methods of the invention. Preferably, the selected
agent is water soluble, which will readily lend itself to a
homogeneous dispersion throughout the reversibly gelling
composition. It is also preferred that the agent(s) is non-reactive
with the composition. For materials, which are not water soluble,
it is also within the scope of the anastomosis methods of the
invention to disperse or suspend lipophilic material throughout the
composition. Myriad bioactive materials may be delivered using the
methods of the present invention; the delivered bioactive material
includes anesthetics, antimicrobial agents (antibacterial,
antifungal, antiviral), anti-inflammatory agents, diagnostic
agents, and wound healing agents.
[0117] Because the reversibly gelling composition used in the
methods of the present invention are suited for application under a
variety of physiological conditions, a wide variety of
phatmaceutically active agents may be incorporated into and
administered from the composition. The pharmaceutic agent loaded
into the polymer networks of the thermosensitive polymer may be any
substance having biological activity, including proteins,
polypeptides, polynucleotides, nucleoproteins, polysaccharides,
glycoproteins, lipoproteins, and synthetic and biologically
engineered analogs thereof.
[0118] A vast number of therapeutic agents may be incorporated in
the polymers used in the methods of the present invention. In
general, therapeutic agents which may be administered via the
methods of the invention include, without limitation:
antiinfectives such as antibiotics and antiviral agents; analgesics
and analgesic combinations; anorexics; antihelmintics;
antiarthritics; antiasthmatic agents; anticonvulsants;
antidepressants; antidiuretic agents; antidiarrheals;
antihistamines; antiinflammatory agents; antimigraine preparations;
antinauseants; antineoplastics; antiparkinsonism drugs;
antipruritics; antipsychotics; antipyretics, antispasmodics;
anticholinergics; sympathomimetics; xanthine derivatives;
cardiovascular preparations including calcium channel blockers and
beta-blockers such as pindolol and antiarrhythmics;
antihypertensives; diuretics; vasodilators including general
coronary, peripheral and cerebral; central nervous system
stimulants; cough and cold preparations, including decongestants;
hormones such as estradiol and other steroids, including
corticosteroids; hypnotics, immunosuppressives; muscle relaxants;
parasympatholytics; psychostimulants; sedatives; and tranquilizers;
and naturally derived or genetically engineered proteins,
polysaccharides, glycoproteins, or lipoproteins. Suitable
pharmaceuticals for parenteral administration are well known as is
exemplified by the Handbook on Injectable Drugs, 6.sup.th Edition,
by Lawrence A. Trissel, American Society of Hospital Pharmacists,
Bethesda, M D, 1990 (hereby incorporated by reference).
[0119] The pharmaceutically active compound may be any substance
having biological activity, including proteins, polypeptides,
polynucleotides, nucleoproteins, polysaccharides, glycoproteins,
lipoproteins, and synthetic and biologically engineered analogs
thereof. The term "protein" is art-recognized and for purposes of
this invention also encompasses peptides. The proteins or peptides
may be any biologically active protein or peptide, naturally
occurring or synthetic.
[0120] Examples of proteins include antibodies, enzymes, growth
hormone and growth hormone-releasing hormone,
gonadotropin-releasing hormone, and its agonist and antagonist
analogues, somatostatin and its analogues, gonadotropins such as
luteinizing hormone and follicle-stimulating hormone, peptide T,
thyrocalcitonin, parathyroid hormone, glucagon, vasopressin,
oxytocin, angiotensin I and II, bradykinin, kallidin,
adrenocorticotropic hormone, thyroid stimulating hormone, insulin,
glucagon and the numerous analogues and congeners of the foregoing
molecules. The pharmaceutical agents may be selected from insulin,
antigens selected from the group consisting of MMR (mumps, measles
and rubella) vaccine, typhoid vaccine, hepatitis A vaccine,
hepatitis B vaccine, herpes simplex virus, bacterial toxoids,
cholera toxin B-subunit, influenza vaccine virus, bordetela
pertussis virus, vaccinia virus, adenovirus, canary pox, polio
vaccine virus, plasmodium falciparum, bacillus calmette geurin
(BCG), klebsiella pneumoniae, HIV envelop glycoproteins and
cytokins and other agents selected from the group consisting of
bovine somatropine (sometimes referred to as BST), estrogens,
androgens, insulin growth factors (sometimes referred to as IGF),
interleukin I, interleukin II and cytokins. Three such cytokins are
interferon-13, interferon-.gamma. and tuftsin.
[0121] Examples of bacterial toxoids that may be incorporated in
the compositions used in the occlusion methods of the invention are
tetanus, diphtheria, pseudomonas A, mycobaeterium tuberculosis.
Examples of that may be incorporated in the compositions used in
the occlusion methods of the invention are HIV envelope
glycoproteins, e.g., gp120 or gp 160, for AIDS vaccines. Examples
of anti-ulcer H2 receptor antagonists that may be included are
ranitidine, cimetidine and famotidine, and other anti-ulcer drugs
are omparazide, cesupride and misoprostol. An example of a
hypoglycaemic agent is glizipide.
[0122] Classes of pharmaceutically active compounds which can be
loaded into that may be incorporated in the compositions used in
the occlusion methods of the invention include, but are not limited
to, anti-AIDS substances, anti-cancer substances, antibiotics,
immunosuppressants (e.g., cyclosporine) anti-viral substances,
enzyme inhibitors, neurotoxins, opioids, hypnotics, antihistamines,
lubricants tranquilizers, anti-convulsants, muscle relaxants and
anti-Parkinson substances, anti-spasmodics and muscle contractants,
miotics and anti-cholinergics, anti-glaucoma compounds,
anti-parasite and/or anti-protozoal compounds, anti-hypertensives,
analgesics, anti-pyretics and anti-inflammatory agents such as
NSAIDs, local anesthetics, ophthalmics, prostaglandins,
anti-depressants, anti-psychotic substances, anti-emetics, imaging
agents, specific targeting agents, neurotransmitters, proteins,
cell response modifiers, and vaccines.
[0123] Exemplary pharmaceutical agents considered to be
particularly suitable for incorporation in the compositions used in
the occlusion methods of the invention include but are not limited
to imidazoles, such as miconazole, econazole, terconazole,
saperconazole, itraconazole, metronidazole, fluconazole,
ketoconazole, and clotrimazole, luteinizing-hormone-releasing
hormone (LHRH) and its analogues, nonoxynol-9, a GnRH agonist or
antagonist, natural or synthetic progestrin, such as selected
progesterone, 17-hydroxyprogeterone derivatives such as
medroxyprogesterone acetate, and 19-nortestosterone analogues such
as norethindrone, natural or synthetic estrogens, conjugated
estrogens, estradiol, estropipate, and ethinyl estradiol,
bisphosphonates including etidronate, alendronate, tiludronate,
resedronate, clodronate, and pamidronate, calcitonin, parathyroid
hormones, carbonic anhydrase inhibitor such as felbamate and
dorzolamide, a mast cell stabilizer such as xesterbergsterol-A,
Iodoxamine, and cromolyn, a prostaglandin inhibitor such as
diclofenac and ketorolac, a steroid such as prednisolone,
dexamethasone, fluoromethylone, rimexolone, and lotepednol, an
antihistamine such as antazoline, pheniramine, and histiminase,
pilocarpine nitrate, a beta-blocker such as levobunolol and timolol
maleate. As will be understood by those skilled in the art, two or
more pharmaceutical agents may be combined for specific effects.
The necessary amounts of active ingredient can be determined by
simple experimentation.
[0124] By way of example only, any of a number of antibiotics and
antimicrobials may be included in the thermosensitive polymers used
in the methods of the invention. Antimicrobial drugs preferred for
inclusion in compositions used in the occlusion methods of the
invention include salts of lactam drugs, quinolone drugs,
ciprofloxacin, norfloxacin, tetracycline, erythromycin, amikacin,
triclosan, doxycycline, capreomycin, chlorhexidine,
chlortetracycline, oxytetracycline, clindamycin, ethambutol,
hexamidine isethionate, metronidazole, pentamidine, gentamicin,
kanamycin, lineomycin, methacycline, methenamine, minocycline,
neomycin, netilmicin, paromomycin, streptomycin, tobramycin,
miconazole and amanfadine and the like.
[0125] By way of example only, in the case of anti-inflammation,
non-steroidal anti-inflammatory agents (NSAIDS) may be incorporated
in the compositions used in the occlusion methods of the invention,
such as propionic acid derivatives, acetic acid, fenamic acid
derivatives, biphenylcarboxylic acid derivatives, oxicams,
including but not limited to aspirin, acetaminophen, ibuprofen,
naproxen, benoxaprofen, flurbiprofen, fenbufen, ketoprofen,
indoprofen, pirprofen, carporfen, and bucloxic acid and the
like.
Occlusion in Conjunction with Gene Therapy
[0126] Another application of the compositions and methods
described in the instant invention would be to aid in the delivery
of a wide variety growth factors or gene therapeutic agents.
Although defective genes associated with numerous inherited
diseases (or that represent disease risk factors, including cancer
risk factors) have been isolated and characterized, methods to
correct the disease states themselves, by providing patients with
normal copies of such genes (the technique of gene therapy), are
substantially lacking. By way of example only, diseases that it is
hoped may be treated by gene therapy include inherited disorders
such as cystic fibrosis, hemophilias, Gaucher's disease, Fabry's
disease, and muscular dystrophy (myopathy). Again by way of
example, acquired disorders that can be treated include cancer
(e.g., multiple myeloma, leukemias, melanomas, ovarian carcinoma
and small cell lung cancer), cardiovascular conditions (e.g.,
progressive heart failure, restenosis), and neurological conditions
(e.g., traumatic brain injury).
[0127] Gene therapy requires successful transfection of target
cells in a patient. Transfection may generally be defined as the
process of introducing an expressible natural or synthetic
polynucleotide (e.g., a gene, a cDNA, or a mRNA) into a cell.
Successful expression of the encoding polynucleotide leads to
production in the cells of a normal protein and leads to correction
of the disease state associated with the abnormal gene. Therapies
based on providing such proteins directly to target cells (protein
replacement therapy) are often ineffective as methods are not
available to cause delivery of therapeutically effective amounts of
such substances into the particular cells of a patient for which
treatment would provide therapeutic benefit.
[0128] Early in the 1990s, Wolff et al showed that transfection is
achievable using "naked DNA" injected into muscle (Wolff, J A, et
al, Direct Gene Transfer into Mouse Muscle in Vivo", Science 247
(1990) 1465-1468; Wolff et al, Long-Term persistence of plasmid DNA
and foreign gene expression in mouse muscle", Hum Mol Genet. 1
(1992) 363-369). This transfection method usually leads to a
transient expression of the encoded proteins. Furthermore, due to
the highly localized nature of the injection, only local areas of
gene expression might be achieved. This is highly disadvantageous
in disease like Duchenne's disease, for example, in which the whole
or large parts of the diaphragm needs to be transfected to achieve
a cure. Further, the transduction levels achieved with naked DNA
are not sufficiently high for therapeutic use.
[0129] It was earlier discovered that addition of transfection
agents increased the transfection rate and therefore, the
expression level. There are numerous transfection agents that have
been described in the literature (Feigner P L, Gadek T R, Holm M,
Roman R, Chan H W, Wenz M, Northrop J P, Ringold G M, Danielsen M.,
Lipofection: a highly efficient, lipid-mediated DNA-transfection
procedure. Proc Natl Acad Sci USA. 1987 November; 84(21):7413-7.
for reviews: Rocha A, Ruiz S, Coll J M., Improvement of DNA
transfection with cationic liposomes. J Physiol Biochem. 2002
March; 58(1):45-56; Pedroso de Lima M C, Simoes S, Pires P, Faneca
H, Duzgunes N., Cationic lipid-DNA complexes in gene delivery: from
biophysics to biological applications. Adv Drug Deliv Rev. 2001
Apr. 25; 47(2-3):277-94). Further dramatic improvements in
transfection efficiencies were discovered when using non-ionic
polymers in combination with transfection agents (Rolland A P,
Mumper R J., Plasmid delivery to muscle: Recent advances in polymer
delivery systems. Adv Drug Deliv Rev. 1998 Mar. 2; 30(1-3):151-172;
Nishikawa, M, Huang, L., Nonviral vectors in the new millennium:
delivery barriers in gene transfer, Hum Gene Ther 20 (2001) 861-70;
Ross P C, Hui S W., Polyethylene glycol enhances lipoplex-cell
association and lipofection. Biochim Biophys Acta. 1999 Oct. 15;
1421(2):273-83). Among non-charged polymers discovered to improve
the transfection were poloxamers and poloxamines (Prokop A, Kozlov
E, Moore W, Davidson 0.1M., Maximizing the in vivo efficiency of
gene transfer by means of nonviral polymeric gene delivery
vehicles. J Pharm Sci. 2002 January; 91(1):67-76.; Kabanov A V,
Lemieux P, Vinogradov S, Alakhov V. Pluronic block copolymers:
novel functional molecules for gene therapy. Adv Drug Deliv Rev.
2002 Feb. 21; 54(2):223-33; Park J S, Oh Y K, Yoon H, Kim J M, Kim
C K. In situ gelling and mucoadhesive polymer vehicles for
controlled intranasal delivery of plasmid DNA. J Biomed Mater Res.
2002 January; 59(1):144-51).
[0130] It has also been noted that physical effects can increase
the rate of transfection. Liu et al demonstrated a simple method of
intravascular gene transfection by injection of large volumes of
DNA containing solutions into the tail of mice (Liu F, Song Y, Liu
D. Hydrodynamics-based transfection in animals by systemic
administration of plasmid DNA. Gene Ther. 1999 July; 6(7):1258-66.;
Jiang J, Yamato E, Miyazaki J. Intravenous delivery of naked
plasmid DNA for in vivo cytokine expression. Biochem Biophys Res
Commun. 2001 Dec. 21; 289(5):1088-92.). They termed this method
hydrodynamic transfection. Presumably the increase in transfection
versus control is due to an increase in pressure in the blood
vessels, increasing the permeability of the cell walls.
[0131] A similar effect was discovered by Song et al when the
retention time was increased in the vasculature (Song Y K, Liu F,
Liu D. Enhanced gene expression in mouse lung by prolonging the
retention time of intravenously injected plasmid DNA. Gene Ther.
1998 November; 5(11):1531-7). The increase in retention was
achieved by injecting the liposomes prior to the injection of the
naked DNA. As the liposomes increase in size due aggregation caused
by different components in blood, they reach the size of
capillaries and temporarily occlude the blood vessels. An increase
in DNA retention time in the lung results in a higher level of gene
expression in the targeted lung area. Controls using naked DNA
without prior injection of liposomes did not enhance gene transfer
(Barron L G, Uyechi L S, Szoka F C Jr., Cationic lipids are
essential for gene delivery mediated by intravenous administration
of lipoplexes. Gene Ther. 1999 June; 6(6):1179-83). These results
suggest that prolonging the exposure time of DNA to the target
cells in vivo may be an important strategy in achieving a high
level of gene expression.
[0132] While Song et al utilized liposomes to increase the DNA
retention in the target area, Liu and Huang used surgery to reach
the target area and utilized clamps to temporarily stop blood flow
and increase the residence time of the DNA in the target
vasculature (Liu F, Huang L, Improving plasmid DNA-mediated liver
gene transfer by prolonging its retention in the hepatic
vasculature. J Gene Med. 2001 November-December; 3(6):569-76). They
stopped blood flow for a very short time and demonstrated that
effective gene transfer occurred. Barron et al also showed that the
gene transfer occurs rather rapidly within less than 60 minutes
after injection of the lipoplexes (Barron L G, Gagne L, Szoka F C
Jr. Lipoplex-mediated gene delivery to the lung occurs within 60
minutes of intravenous administration. Hum Gene Ther. 1999 Jul. 1;
10(10):1683-94).
[0133] However the gene therapy approach described by Liu and Huang
(surgical clamping, prior to injection of liposomes) is not
practical in a clinical setting, as it would be preferable to
introduce the polynucleotide via a catheter or a syringe. It is
well understood that liposome-mediated or naked DNA gene
transfection can be successfully performed to all vessel layers or
muscles in vivo by using a local delivery catheter (Hagstrom J E.
Plasmid-based gene delivery to target tissues in vivo: the
intravascular approach. Curr Opin Mol. Ther. 2003 August;
5(4):338-44). However, unwanted transfection at a distance may
occur with catheter-based local delivery and therefore a device is
needed to occlude the target area to achieve an increase in
retention time. While this could be achieved by using a balloon
catheter and the injection through the balloon, balloon angioplasty
is known to lead to arterial damage and even rupture of the artery
(Wainwright C L, Miller A M, Wadsworth R M, Inflammation as a key
event in the development of neointima following vascular balloon
injury. Clin Exp Pharmacol Physiol. 2001 November; 28(11):891-5;
Labropoulos N, Giannoukas A D, Volteas S K, al Kutoubi A.,
Complications of the balloon assisted percutaneous transluminal
angioplasty. Review article. J Cardiovasc Surg (Torino). 1994
December; 35(6):475-89).
[0134] In a preferred embodiment the methods and compositions of
the instant invention can be used to temporarly occlude a blood
vessel, either independently our in conjuction with a surgical
procedure such as anastomosis, prior to or concurently with the
introduction of nucleic acids behind the occlusion, therby
increasing the residence time of nucleic acids in an intravascular
target area. The nucleic acids are then injected through the gel by
either a syringe or a catheter and the nucleic acid are retained
behind the gel in the target area. If the occlusion is on the
venous side, the nucleic acid is injected in the arterial side and
as there is no drainage until the gel erodes, the nucleic acids are
retained on the arterial side. Alternatively, both proximal and
distal sites from the target area may be occluded with a reverse
thermosensitive polymer composition of the instant invention. As
described above, the polynucleotide can be "naked" or complexed
into lipoplexes constituting nucleic acids, cationic lipids, and
optionally helper lipids.
[0135] In certain embodiments, the present invention relates to the
aforementioned method, in which a reverse thermosensitive polymer
is injected into a blood vessel proximally to the target area, in
vivo, in such a way that the mixture gels and temporarily and
reversibly occludes the vascular site and the nucleic acid is
injected through the gel into the stagnant blood of the target
area.
[0136] In certain embodiments, the present invention relates to the
aforementioned method, in which a reverse thermosensitive polymer
is injected into a blood vessel proximally and distally to the
target area, in vivo, in such a way that the mixture gels and
temporarily and reversibly occludes the vascular site and the
nucleic acid is injected through the gel on the proximal side into
the stagnant blood of the target area.
[0137] In certain embodiments, the present invention relates to the
aforementioned method, in which a reverse thermosensitive polymer
is injected distally from the target area, in such a way as to
occlude blood drainage from the target area and nucleic acids or a
nucleic acid complex are injected into a blood vessel proximally to
the target area.
[0138] In certain embodiments, the present invention relates to the
aforementioned methods, in which a reverse thermosensitive polymer
is injected into a blood vessel proximally to the target area, in
vivo, in such a way that it gels and temporarily and reversibly
occludes the vascular site, and a nucleic acid is injected into the
same blood vessel at the same time.
[0139] In certain embodiments, the present invention relates to the
aforementioned method, in which a reverse thermosensitive polymer
is injected distally from the target area, in such a way as to
occlude blood drainage from the target area and nucleic acids or a
nucleic acid complex are injected in a hypertonic solution into a
blood vessel proximally to the target area.
[0140] In certain embodiments, the present invention relates to the
aforementioned method, in which a reverse thermosensitive polymer
is injected distally from the target area, in such a way as to
occlude blood outflow from the target area and nucleic acids or a
nucleic acid complex are injected hydrodynamically into a blood
vessel proximally to the target area.
[0141] In certain embodiments, the present invention relates to the
aforementioned method, in which the nucleic acid is injected at the
same time as the occlusion of the blood vessel.
[0142] In certain embodiments, the present invention relates to the
aforementioned method, in which the nucleic acid is injected within
less than about one minute after occlusion of the blood vessel.
[0143] In certain embodiments, the present invention relates to the
aforementioned method, in which the nucleic acid is injected within
less than about ten minutes after occlusion of the blood
vessel.
[0144] In certain embodiments, the present invention relates to the
aforementioned method, wherein the nucleic acid is a plasmid, cDNA,
mRNA and PNA.
[0145] In certain embodiments, the present invention relates to the
aforementioned method, wherein the nucleic acid is not complexed
("naked").
[0146] In certain embodiments, the present invention relates to the
aforementioned method, wherein the nucleic acid is complexed with
cationic lipids into lipoplexes.
[0147] In certain embodiments, the present invention relates to the
aforementioned method, wherein the nucleic acid is complexed with
cationic lipids and helper lipids into lipoplexes.
[0148] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition is introduced into
the vasculature of said mammal using a catheter.
[0149] In certain embodiments, the present invention relates to the
aforementioned method, wherein said composition is introduced into
the vasculature of said mammal using a syringe.
Exemplification
[0150] The invention now being generally described, it will be more
readily understood by reference to the following examples, which
are included merely for purposes of illustration of certain aspects
and embodiments of the present invention, and are not intended to
limit the invention.
Example 1
In-Vitro Testing and Principal of Operation
[0151] The viscosity changes were measured in a Brookfield Cone and
Cup viscometer with temperature control. A graph of the viscosity
changes (FIG. 1) clearly shows polymer concentrations from
approximately 12.5 w % until at least 20 w % will show steep
increases in solution viscosities with temperature. The onset of
gelation is dependent on the temperature and higher polymer
concentrations lead to earlier onsets of gelation. Furthermore,
polymer concentrations below approximately 12.5 w % do not
demonstrate an increase in solution viscosity with temperature and
remain liquid even at body temperature.
[0152] These two findings demonstrate the potential operation
principle of the purified poloxamer 407. The polymer solution is
injected as a soft gel at the temperature of a typical OR (about
18.degree. C.) into the arteriotomy and the rise in temperature
leads to a stiff gel. The gel will start to dissolve in blood and
when the concentration of the polymer decreases below approximately
12.5%, it turns back into a liquid, without any possibility to turn
back into a gel at physiological temperatures. Alternatively,
cooling of the gel with ice or cold saline would liquefy the gel as
the temperature falls below the gelation point. As a liquid, it
quickly dilutes in blood and again there is no possibility for it
to turn back into a gel at physiological temperatures.
Example 2
Injectability of Purified Poloxamer 407 Through Various Needle
Gauges
[0153] A three milliliter polycarbonate syringe (Merrit Medallion)
was loaded in the cold with three milliliter of 20 w % purified
poloxamer 407. Various sized needles were attached via a luer lock
and the injectability of the polymer solution was tested at
6.degree. C. (liquid state) and at room temperature (23.degree. C.;
soft gel state) as shown in the table below.
TABLE-US-00001 TABLE 1 Injectability of 20 w % purified poloxamer
407 through a 3 mL syringe Needle 6.degree. C. 23.degree. C. 16G
easy easy 18G easy easy 21G easy easy 25G easy pushable 27G easy
required hard push
[0154] The same experiment was repeated using a one milliliter
polycarbonate syringe (Merrit Medallion) and in all cases, the
polymer could be easily injected through the various needle
gauges.
TABLE-US-00002 TABLE 2 Injectability of 20 w % purified poloxamer
407 through a 1 mL syringe Needle 6.degree. C. 23.degree. C. 16G
easy easy 18G easy easy 21G easy easy 25G easy easy 27G easy
easy
Example 3
In-Vivo Feasibility Animal Trial: Occlusion Experiments
[0155] The experiments described below were conducted in pigs. A
segment of the distal half of the LAD was selected for the
experiment. The diameter of the LAD varied from about 1 to 2
millimeter. An ultrasound flow probe was placed distally from the
injection site around the LAD. A one milliliter syringe equipped
with a 27 G needle was used to inject approximately 200 .mu.L of 20
w % purified poloxamer 407 into the LAD. Flow stopped immediately
as evidenced by the flow probe. The occlusion remained between 6
minutes and 18 minutes, averaging approximately 9 minutes. Blood
flow was reestablished immediately after the occlusion dissolved, a
typical hyperemic response was seen with an approximate doubling of
the blood flow. Blood flow returned to normal values within 20
minutes.
Example 4
In-Vivo Feasibility Animal Trial: Arteriotomy Experiments
[0156] The experiments described below were conducted in three
mongrel dogs. A segment of the distal half of the LAD was selected
for the anastomostic site. Silicone Elastic tapes were passed deep
to the LAD approximately 2 cm apart, flanking the chosen site. A
Genzyme Immobilizer OP-CAB stabilizer was positioned to stabilize
the LAD and the tapes snared to transiently interrupt coronary
flow. The Immobilizer was left in position for 3 minutes to provide
pre-ischemic conditioning, so that the animal would subsequently
tolerate longer periods of regional ischemia. After 3 minutes, the
tapes were loosened to allow reperfusion. After an additional 5
minutes of reperfusion, the tapes were snared once again, and the
cycle repeated two additional times.
[0157] After 3 cycles of pre-ischemic conditioning, the
Silicone-Elastic tapes were snared and the LAD arteriotomy created.
In this acute animal model, hemostasis was excellent, given the
elastic nature of disease-free coronaries, and the lack of
collaterals in the absence of coronary stenosis or occlusion.
Therefore, the proximal tape was loosened slightly until modest
bleeding occurred, approximating the amount of bleeding seen in
difficult anastomosis. About one milliliter of a 20 w % solution of
purified poloxamer 407 was instilled into the coronary through the
arteriotomy via a cannula to improve hemostasis. Bleeding stopped
immediately and the surgical field was bloodless. The arteriotomy
was not sutured and the site started rebleeding after approximately
17 minutes. The experiment was repeated at the same site and
rebleeding occurred after approximately 19 minutes.
[0158] All three dogs underwent the same procedure and could be
evaluated. The occluded site on the LAD was excised and evaluated
by histology. Neither ischemic damage nor early necrosis was
detected and normal myocardium was found.
Example 5
In-Vivo Feasibility Animal Trial: Control of Dissolution Time
[0159] The same experiment as described above was performed on the
LAD of a mongrel dog and approximately 0.6 milliliter of a 20 w %
purified poloxamer 407 solution was injected into the arteriotomy
via a cannula. Bleeding stopped immediately. The gel kept the
artery in a cylindrical shape and the lids of the arteriotomy were
clearly visible. Suturing was performed through the gel and was
completed within 7 minutes. The LAD was still occluded and small
amounts of sterile ice were placed on the LAD at the occlusion site
to convert the polymer plug back into solution. The LAD opened up
again nearly instantaneously. This experiment demonstrated A) the
possibility to control the occlusion time by using ice placed onto
the arteriotomy. This is a very important feature as surgeons would
want to be able to reopen the occlusion should something go wrong
during the surgery and blood flow is needed. And B) that gel keeps
the artery in a cylindrical shape during the occlusion, making
suturing very easy.
Example 6
In-Vivo Feasibility Animal Trial: Comparison of Blood Loss with
Snares, and Snares & 20 w % Purified Poloxamer 407 Gel
[0160] The following experiments were conducted in 4 .mu.Lgs. The
goal of the experiment was to measure blood loss as a distinction
between ligation bands and polymer plug. Further, the patency of
the graft was evaluated by fluoroscopy after utilizing the polymer
plug for the anastomosis.
[0161] The same approach for OPCAB was used as described above to
create the acute animal model with some modifications as described
below.
[0162] The Immobilizer was modified by attaching a drape to make a
shallow well that captured all coronary blood and allowed the
amount of bleeding from the arteriotomy to be quantified.
[0163] After 3 cycles of pre-ischemic conditioning, as described
above, the Silicone-Elastic tapes were snared and the LAD
arteriotomy created. At this point, the adequacy of hemostasis was
assessed. The proximal tape was loosened slightly until modest
bleeding occurred, comparable to what is generally encountered
clinically.
[0164] While maintaining blood pressure, the bleeding was allowed
to continue for 15 minutes to approximate the time required for a
distal anastomosis. During these 15 minutes, blood that accumulated
in the modified stabilizer well was drawn intermittently through a
syringe and measured in a volumetric cylinder. After the 15 minutes
had passed, a shunt was deployed in the LAD for 20 minutes to allow
for reperfusion of the myocardium. After reperfusion, the tapes
were again tightened to very similar tension as before, bleeding
out of the arteriotomy was assured and blood pressure was
maintained.
[0165] Approximately 300 .mu.L of the purified poloxamer 407 at the
temperature of the OR (about 18.degree. C.) was instilled upstream
and approximately 100 .mu.L downstream into the coronary through
the arteriotomy site using a cannula. With the polymer gel in
place, any blood that accumulated in the stabilizer basin was
removed by syringe. In contrast to the dog experiments, the
arteriotomy opened again between 6.5 and 8.5 minutes and in each
case, approximately 100 .mu.L of the purified poloxamer 407 was
instilled upstream again. In two animals, a third application after
about 13 to 14 minutes, of approximately 100 .mu.L was needed to
provide the bloodless surgical field. Most of the blood collected
during the application of the purified poloxamer 407 was deemed to
stem from the snare holes, but blood volume collected was not
corrected for this in the gel experiments as well as the tape
experiments. After 15 minutes, the remaining blood was removed and
added to that previously collected to quantify total arteriotomy
blood loss for the 15 minutes with purified poloxamer 407 in place.
The order of vessel occlusion was reversed for two animals with the
gel first, followed by the tapes.
[0166] The volume of blood captured during the two 15 minute
periods, with and without internal vessel occlusion with purified
poloxamer 407, were compared and are shown in FIG. 2. The
application of purified poloxamer 407 reduces bleeding by
approximately 90% in the four animals.
[0167] The graft was sutured onto the arteriotomy with either the
gel present or the tapes utilized and after two additional hours,
fluoroscopy was used to evaluate patency of the graft. In three
pigs in which the evaluation could be performed, the grafts were
patent. Euthanasia was administered under anesthesia. A sample of
subtended myocardium was harvested and sent for histology to assess
for myocardial ischemia or early necrosis. Normal myocardium was
found by histological evaluation.
Incorporation by Reference
[0168] All of the U.S. patents and U.S. patent application
publications cited herein are hereby incorporated by reference.
Equivalents
[0169] Those skilled in the art will recognize, or be able to
ascertain using no more than routine experimentation, many
equivalents to the specific embodiments of the invention described
herein. Such equivalents are intended to be encompassed by the
following claims.
* * * * *