U.S. patent application number 10/059850 was filed with the patent office on 2002-07-04 for subcutaneously implanted cannula and method for arterial access.
This patent application is currently assigned to VascA, Inc.. Invention is credited to Brugger, James M., Burbank, Jeffrey H., Finch, Charles D. JR., Kuiper, Hendrik E..
Application Number | 20020087127 10/059850 |
Document ID | / |
Family ID | 27391645 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020087127 |
Kind Code |
A1 |
Finch, Charles D. JR. ; et
al. |
July 4, 2002 |
Subcutaneously implanted cannula and method for arterial access
Abstract
A catheter with valve for implantation in a vascular structure
of a living being. The catheter is in the general shape of a "T"
with the top of the "T" implanted within the lumen of a vascular
structure, and the leg of the "T" extending out of the vascular
structure through an incision in the vascular structure. The lumen
of the implanted portion of the catheter completely occupies the
lumen of the vascular structure, causing all blood flow through the
vascular structure to be directed through the implanted portion of
the catheter. A valve is placed in the wall of the implanted
portion of the catheter which opens into the lumen of the leg of
the "T" of the catheter upon application of sufficient differential
pressure between the lumens of the two portions of the catheter.
The leg of the "T" is connected to the side wall of the implant
portion of the catheter at an angle, such that the axis of the
lumen of the leg of the "T" intersects the axis of the lumen of the
implanted portion of the catheter at approximately a 45 degree
angle.
Inventors: |
Finch, Charles D. JR.;
(Clinton, MS) ; Kuiper, Hendrik E.; (Edwards,
MS) ; Burbank, Jeffrey H.; (Boxford, MA) ;
Brugger, James M.; (Newburyport, MA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
VascA, Inc.
Highwood Office & Research Park 3 Highwood Drive
Tewksbury
MA
01876
|
Family ID: |
27391645 |
Appl. No.: |
10/059850 |
Filed: |
January 28, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10059850 |
Jan 28, 2002 |
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09472593 |
Dec 27, 1999 |
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09472593 |
Dec 27, 1999 |
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08724948 |
Oct 2, 1996 |
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6053901 |
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08724948 |
Oct 2, 1996 |
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08539105 |
Oct 4, 1995 |
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5807356 |
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08539105 |
Oct 4, 1995 |
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08183151 |
Jan 18, 1994 |
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5562617 |
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Current U.S.
Class: |
604/284 |
Current CPC
Class: |
A61M 39/0208 20130101;
A61F 2/064 20130101; A61M 2039/0211 20130101 |
Class at
Publication: |
604/284 |
International
Class: |
A61M 025/00 |
Claims
What is claimed is:
1. An arterial cannula comprising: a tubular body having a first
end, a second end; and a lumen therebetween, wherein the tubular
body is adapted to be implanted within an arterial lumen; and a
tubular access leg having a first end connected to the tubular body
at a junction, a second end, and a lumen therebetween, wherein the
access tube lumen is fluidly coupled to the tubular body lumen at
the junction.
2. An arterial cannula as in claim 1, wherein the tubular body has
a length in the range from 10 mm to 50 mm and an outer diameter in
the range from 3 mm to 10 mm.
3. An arterial cannula as in claim 1, wherein the access leg has a
length in the range from 25 mm to 700 mm and an outer diameter in
the range from 3 mm to 10 mm.
4. An arterial cannula as in claim 1, wherein at least a portion of
the access leg is sufficiently compliant so that no substantial
forces may be transmitted to the tubular body through the access
leg.
5. An arterial cannula as in claim 4, wherein at least a portion of
the access leg adjacent to the tubular body has a bending stiffness
which is less than that of the adjacent tubular body.
6. An arterial cannula as in claim 5, wherein said portion of the
access leg has a hoop strength sufficient to withstand an internal
pressure of -250 mmHg.
7. An arterial cannula as in claim 1, wherein the tubular body is
circumferentially reinforced.
8. An arterial cannula as in claim 7, wherein the circumferential
reinforcement comprises a helical wire or circumferential
corrugation.
9. An arterial cannula as in claim 7, wherein the access leg is
circumferentially reinforced.
10. An arterial cannula as in claim 9, wherein the circumferential
reinforcement comprises a helical wire or circumferential
corrugation.
11. An arterial cannula as in claim 1, further comprising a
pressure-responsive valve at the junction, said valve inhibiting
blood flow across the junction in the absence of a pressure
differential thereacross.
12. An arterial cannula as in claim 11, wherein the valve is
incorporated in the tubular body so that no structure of the valve
intrudes into the vascular lumen.
13. An arterial catheter as in claim 12, wherein the valve is a
slit valve formed in the tubular body at the junction.
14. A method for implanting an arterial access cannula within a
lumen of an artery, said method comprising: surgically exposing the
artery; making an incision in a wall of the artery; introducing a
tubular body of the access cannula through the incision and into
the lumen of the artery so that a lumen of the tubular body is
evenly aligned with the arterial lumen and an access leg of the
cannula is aligned through the incision; and closing the incision
and securing the tubular body within the arterial lumen.
15. A method as in claim 14, wherein the artery is selected from
the group consisting of the proximal ulnar, proximal radial,
brachial artery, axillary artery, subclavian artery and synthetic
arteries.
16. A method as in claim 14, wherein the lumen of the tubular body
is selected to have a cross-sectional dimension substantially equal
to that of the blood vessel.
17. A method as in claim 16, further comprising the steps of
determining a cross-sectional dimension of the artery and selecting
a tubular body having a cross-sectional dimension substantially
equal to that of the arterial lumen.
18. A method as in claim 14, wherein the tubular body has an outer
diameter in the range from 10 mm to 50 mm and a length in the range
from 3 mm to 10 mm.
19. A method as in claim 14, further comprising subcutaneously
introducing an arterial port wherein the arterial port is connected
or connectable to the access leg of the arterial access
cannula.
20. A method as in claim 19, wherein the arterial port is
introduced through the incision.
21. A method as in claim 19, wherein the arterial port is
introduced through a separate incision remote from the first
incision, and thereafter connected to the access leg of the
arterial access cannula.
22. A method as in claim 14, further comprising surgically exposing
a vein; introducing a venous cannula through the wall of the vein;
and introducing a venous port subcutaneously, wherein the venous
port is connected or connectable to the venous catheter.
23. A method as in claim 22, wherein the venous cannula and the
venous port are introduced through a single incision.
24. A method as in claim 22, wherein the venous cannula and the
venous port are introduced through separate incisions and
thereafter connected.
25. A cannula comprising: a tubular body having a first end, a
second end, and a lumen therebetween; a tubular access leg having a
first end connected to the tubular body at a junction; and a
pressure-responsive valve at the junction, said valve inhibiting
fluid flow across the valve in the absence of a pressure
differential thereacross.
26. A cannula as in claim 25, wherein the tubular body has a length
in the range from 10 mm to 50 mm and an outer diameter in the range
from 3 mm to 10 mm.
27. A cannula as in claim 26, wherein the access leg has a length
in the range from 25 mm to 700 mm and an outer diameter in the
range from 3 mm to 10 mm.
28. A cannula as in claim 25, wherein at least a portion of the
access leg is sufficiently compliant so that no substantial forces
may be transmitted to the tubular body through the access leg.
29. A cannula as in claim 28, wherein at least a portion of the
access leg adjacent to the tubular body has a bending stiffness
which is less than that of the adjacent tubular body.
30. A cannula as in claim 29, wherein said portion of the access
leg has a hoop strength sufficient to withstand an internal
pressure of -250 mnmHg.
31. A cannula as in claim 25, wherein the tubular body is
circumferentially reinforced.
32. A cannula as in claim 31, wherein the circumferential
reinforcement comprises a helical wire or circumferential
corrugation.
33. A cannula as in claim 31, wherein the access leg is
circumferentially reinforced.
34. A cannula as in claim 33, wherein the circumferential
reinforcement comprises a helical wire or circumferential
corrugation.
35. A cannula as in claim 25, further comprising a
pressure-responsive valve at the junction, said valve inhibiting
blood flow across the junction in the absence of a pressure
differential thereacross.
36. A cannula as in claim 35, wherein the valve is incorporated in
the tubular body so that no structure of the valve intrudes into
the vascular lumen.
37. A cannula as in claim 36, wherein the valve is a slit valve
formed in the tubular body at the junction.
38. A cannula as in claim 25, wherein the tubular body is adapted
to be implanted in a blood vessel.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a division from co-pending
application Ser. No. 09/472,593 (Attorney Docket No. 017742-000430)
filed Dec. 27, 1999, which was a continuation of application Ser.
No. 08/724,948 (Attorney Docket No. 017742-000410) filed Oct. 2,
1996, now U.S. Pat. No. 5,807,356, which is a continuation-in-part
of application Ser. No. 08/539,105 (Attorney Docket No.
017742-000400), filed on Oct. 4, 1995, which was a
continuation-in-part of application Ser. No. 08/183,151 (Attorney
Docket No. 017742-000200), filed on Jan. 18, 1994, now U.S. Pat.
No. 5,562,617, the full disclosures of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. The Field of Invention.
[0003] The present invention relates to subcutaneously implanted
cannulas used to access the body's circulation. More particularly,
this invention provides a cannula and method for establishing
intermittent vascular access using an implanted cannula in the
general shape of a "T".
[0004] The advent of hemodialysis for the treatment of end-stage
renal disease has prompted the development of many vascular access
devices for the purpose of acquiring and returning large quantities
of blood for passage through an extracorporeal circuit during
hemodialysis procedure. Available devices have generally relied on
the use of either indwelling venous catheters or flow through shunt
devices which create an artificial fistula between an artery and
vein.
[0005] Venous catheters are limited by relatively poor draw flows
and by their tendency to be irritative resulting in vessel
stenosis, thrombosis, and occasionally vessel perforation. They
frequently fail because of infection, weakness in the vessel wall,
poor catheter position, and/or thrombus formation in the catheter
lumen. Shunt devices which create a fistulous blood flow between an
artery and a vein have been the mainstay of modern vascular access
for dialysis but are similarly problematic. Installation of these
"shunts" is an extensive surgical procedure resulting in
significant tissue trauma and pain. Once in place, the shunts
result in additional cardiac output needs with as much as one-fifth
of the cardiac output (approximately 1000 ml per minute) required
for adequate function. In addition, the transfer of the arterial
pressure wave results in damage to the vein at the point of
anastomosis with the shunt and can result in intimal hyperplasia
and subsequent thrombosis and shunt occlusion. When such occlusion
occurs, another vein segment must be used for shunt revision, and
exhaustion of available sites is distressingly common and can be
fatal. Repeated punctures of the wall of the shunt often result in
eventual failure and require additional surgery to repair or
replace the shunt. The expense in terms of both health care dollars
and human misery is enormous.
[0006] Each of the available access technologies mentioned thus far
are also complicated by the possibility of recirculation of blood
already passed through the extracorporeal circuit resulting in the
loss of treatment efficiency. The harm done to patients by the
"recirculation syndrome" is insidious and at times undetected until
great harm has been done.
[0007] Indwelling catheters which occupy only a portion of the
vessel lumen are subject to movement within the vessel, which can
cause irritation or even vessel perforation. Further, catheters
which occupy only a portion of the vessel lumen, and which are
inserted or threaded through the lumen for substantial distances
tend to disrupt the normal flow of blood through the vascular
structure, altering the hemodynamics of the blood flow in a manner
which can damage the vessel, the components of the blood, and which
can encourage thrombosis. Such catheters are generally unsuitable
for long term implantation in arteries.
[0008] What is needed is a cannula that can be implanted within an
artery and that will cause minimal disruption of blood flow through
the lumen of the artery during use and nonuse of the cannula, which
does not cause vessel stenosis, thrombosis, or vessel perforation,
which is capable of handling large quantities of blood, and which
will retain its usefulness for a long period of time after
implantation.
[0009] 2. Description of the Background Art.
[0010] Vascular access employing indwelling catheters is described
in a number of patents and publications including U.S. Pat. Nos.
3,888,249; 4,543,088; 4,634,422; 4,673,394; 4,685,905; 4,692,146;
4,695,273; 4,704,103; 4,705,501; 4,772,270; 4,846,806; 5,053,613;
5,057,084; 5,100,392; 5,167,638; 5,108,365; 5,226,879; 5,263,930;
5,281,199; 5,306,255; 5,318,545; 5,324,518; 5,336,194; 5,350,360;
5,360,407; 5,399,168; 5,417,656; 5,476;451; 5,503,630; 5,520,643;
5,527,277; and 5,527,278; and EP 228 532; and Wigness et al. (1982)
paper entitled "Biodirectional Implantable Vascular Access
Modality" presented at the Meeting of the American Society for
Artificial Internal Organs, Apr. 14-16, 1982, Chicago, Ill.
[0011] Catheters having distal valves are described in a number of
patents including U.S. Pat. Nos. 274,447; 3,331,371; 3,888,249;
4,549,879; 4,657,536; 4,671,796; 4,701,166; 4,705,501; 4,759,752;
4,846,806; 4,973,319; 5,030,710; 5,112,301; 5,156,600; and
5,224,978.
[0012] Implantable dialysis connection parts are described in a
number of patents including U.S. Pat. Nos. 4,692,146; 4,892,518;
5,041,098; 5,180,365; and 5,350,360.
BRIEF SUMMARY OF THE INVENTION
[0013] The present invention provides improved implantable vascular
cannulas which are particularly useful for providing long-term
access to the arterial vasculature, including both native arteries
and artificial arterial lumens (such as an arteriovenous (AV) shunt
or an arterial graft. The cannulas of the present invention
comprise a tubular body which is implantable within an arterial
lumen and an access leg having one end attached to a side wall of
the tubular body. Both the tubular body and the access leg have
lumens therethrough, with the lumen of the tubular body being
configured to receive the entire blood flow of the arterial lumen
in which it is implanted. The access leg, which is attached to the
tubular body in a generally T-shaped configuration, thus provides
for access into the lumen of the tubular body for either
withdrawing blood (e.g. for hemodialysis or other extra- corporeal
treatment) or for introducing drugs or other media into the
arterial blood flow.
[0014] The arterial access cannula may be implanted either
subcutaneously or transcutaneously. By transcutaneous, it is meant
that a portion of the access leg will pass outwardly through the
patient's skin to permit direct arterial access using external drug
pumps, syringes, or other equipment. It will be appreciated, of
course, that a hemostasis valve must be provided on the access leg
to prevent uncontrolled blood loss. Usually, any transcutaneous use
of the cannula of the present invention will be only for a short
time.
[0015] More usually, the cannula of the present invention will be
intended for subcutaneous use. In that case, an access port is
connected to the open end of the access leg and is also
subcutaneously implanted beneath the patient's skin. The access
port will be suitable for attachment to needles, tubes, catheters,
and other devices which may be percutaneously introduced into the
access port to provide a desired external connection. An example of
an access port comprises a chamber having a penetrable membrane on
one side thereof. Temporary access to the chamber is formed by
penetrating the needle, tube, or catheter through the penetrable
membrane.
[0016] In all cases, the T-configured arterial cannula of the
present invention is an improvement over prior indwelling catheters
in a number of respects. The tubular body is firmly anchored within
the artery and not subject to being moved or dislodged by blood
flow. Thus, trauma to the arterial wall from movement of the
cannula is significantly lessened. Moreover, by assuring that the
lumen of the tubular body has a cross-sectional shape and
dimensions which closely match those of the arterial lumen, smooth
blood flow through the cannula can be enhanced while the risk of
thrombus formation is substantially reduced.
[0017] In a preferred construction, the arterial cannula will
include an isolation valve, at or near the junction between the
access leg and the tubular body. The isolation valve can be any
type of valve that closes or inhibits flow between the tubular body
lumen and the access leg lumen in the absence of a pressure drop
therebetween. Thus, when blood is not being withdrawn and/or when
drugs or other media are not being introduced, the isolation valve
will close and isolate the lumen of the access leg from arterial
blood flow. Such isolation is a significant advantage since it
reduces the risk of thrombus formation within the access leg and
thrombus release into the arterial lumen. Often, it will be
desirable to flush the lumen of the access leg with an
anti-coagulant fluid after each use. The removal of static blood
and the placement of the anti-coagulant fluid further decreases the
risk of thrombus formation and release. The isolation valve may be
in a variety of forms, including slit valves, flap valves, ball
valves, and may further be configured to provide for one-way or
bi-direction flow. For example, in the case of arterial cannulas
used for withdrawing blood, it will often be advantageous to have a
one-way isolation valve which permits blood flow from the tubular
body into the access leg, but inhibits reverse flow of any
materials from the access leg into the lumen. In the case of drug
and other infusions into the artery, it may be desirable to provide
a one-way isolation valve which permits such introduction, but
prevents reflux of blood into the access leg. A particularly
preferred valve is a slit valve formed into the wall of the tubular
body, as illustrated in detail hereinafter. When such a slit valve
is closed, the inner profile of the tubular body lumen will be
substantially smooth and free from discontinuities caused by the
valve.
[0018] The arterial cannula may be formed from any one or a
combination of a variety of biocompatible materials. By
biocompatible, it is meant that the material(s) will be suitable
for a long term implantation within patient vasculature and tissue
and will be free from immunogenicity and inflammatory response.
Usually, the cannula will be formed in whole or in part from an
organic polymer, such as silicone rubber, polyethylenes,
polyurethanes, polyvinylchloride, polytetrafluoroethylene (PTFE),
polysulfone, or the like. Portions of the cannula may be
reinforced, for example the access leg may include circumferential
reinforcement to enhance its hoop strength without significantly
diminishing flexibility. Such reinforcement may take the form of a
helical wire or ribbon, axially spaced-apart hoops, or the like.
Preferably, the reinforcement may be achieved by molding the access
leg to incorporate circumferential corrugation, i.e. a plurality of
axially spaced-apart circumferential ribs along all or a portion of
its lengths. In all cases, it is desirable that the internal lumen
of the access leg and the tubular body remain as smooth as possible
to avoid disturbances to blood flow.
[0019] The tubular body of the arterial cannula will have
dimensions compatible with implantation within a variety of
arteries, including both native (natural) arteries and implanted
synthetic arteries. The most common native arteries in which the
cannulas may be implanted include the proximal ulnar, proximal
radial, brachial artery, axillary artery, and subdlavian artery.
Implanted synthetic arteries include bypasses, shunts (e.g. AV
shunts), arterial grafts, and the like. Both native arteries and
implanted synthetic arteries have lumens, and reference to
"arterial lumens" herein is intended to refer to both such
lumens.
[0020] Generally, the length of the tubular body will be in the
range from 10 mm to 50 mm and the outer diameter will be in the
range from 3 mm to 10 mm. The diameter of the lumen of the tubular
body will generally be in the range from 1 mm to 8 mm. The access
leg will usually have a length in the range from 25 mm to 700 mm
and an outer diameter in the range from 3 mm to 10 mm. The lumen
diameter of the access leg will generally be in the range from 2 mm
to 8 mm.
[0021] In a preferred aspect of the present invention, at least a
portion of the access leg of the arterial cannula will be
sufficiently compliant so that substantially no forces are
transmitted from the access leg back into the tubular body. For
proper functioning of the arterial cannula, it is important that
the tubular body remain properly aligned within the arterial lumen.
This can be achieved by fabricating at least a portion of the
access leg adjacent to the tubular body to have a low bending
stiffness. The hoop strength of the access tube, in contrast,
should remain relatively high, being at least sufficient to
maintain patency of its lumen at internal pressures below -250
mmHg, preferably below -400 mmHg. Use of the helical reinforcement
designs described above helps assure that the access leg can be
sufficiently flexible while retaining sufficient strength.
[0022] In a first specific aspect of the present invention, a
system for performing extracorporeal blood treatment comprises an
arterial cannula as described above in combination with a venous
cannula which is implantable within a venous lumen. The venous
cannula will also comprise an access leg, but will usually be in
the form of a conventional in-dwelling catheter or a distal portion
of the cannula as within the venous lumen in a generally free or
unrestricted manner. The use of conventional in-dwelling cannula in
the venous vasculature is not problematic. Usually, both the
arterial cannula and the venous cannula of the systems of the
present invention will further include access ports intended to be
connected to catheters for completing an extracorporeal circuit.
Such access ports may be of generally conventional construction and
may be connected to extracorporeal treatment circuits in a general
conventional manner.
[0023] In another aspect, the present invention comprises a method
for implanting an arterial access cannula within the lumen of an
artery. The method comprises surgically exposing the artery and
making an incision in its wall. The tubular body of the access
channel is introduced through the incision and into the lumen of
the artery. The lumen of the tubular body will be evenly
circumferentially aligned with the arterial lumen, and the incision
then closed. In some instances, the tubular body will have flared
portions at either end, and the flared portions can optionally be
tied within the artery to further anchor the cannula therein. The
method may further comprise an initial step of determining a
cross-sectional dimension of the artery and selecting a tubular
body having a cross-section dimension substantially equal to that
of the arterial lumen. The method may still further comprise
subcutaneously introducing an arterial port, where the arterial
port is connected or connectable to the access leg of the arterial
access cannula. The arterial port may be introduced through the
same incision as the arterial cannula. Alternatively, the arterial
port may be introduced through a second incision formed remotely
from the first incision, and the port thereafter connected to the
access leg by forming a subcutaneous path between the two.
[0024] The method may still further comprise introducing a venous
cannula by surgically exposing a vein, and introducing the venous
cannula therethrough. The venous port may then be introduced,
either through the same or a different surgical incision, in order
to form a desired subcutaneous access assembly. By having
introduced both an arterial cannula and a venous cannula, the
patient is ready for access to hemodialysis or a variety of other
extracorporeal treatment modalities.
[0025] In still further aspects of the present invention, methods
are provided for performing extracorporeal blood treatment by
percutaneously attaching a first catheter to an access leg of a
subcutaneously implanted arterial cannula having a tubular body
disposed within an arterial lumen. A second catheter is then
percutaneously attached to a subcutaneously implanted venous access
catheter, and blood may be circulated from the first catheter
through an extracorporeal circuit to the second catheter. The first
and/or second catheters are typically percutaneously penetrated to
connect to the access leg, e.g. by penetrating a needle or
needle-introduced catheter through a membrane of a conventional
access port. The extracorporeal circuit may be hemodialysis, and
the method may further comprise stopping blood circulation and
filling at least the access leg of the arterial cannula with an
anti-coagulant fluid.
[0026] In still a further aspect of the present invention, a method
for administering a fluid medium into an artery comprises
percutaneously attaching a needle or needle-introduced catheter to
an access leg of a subcutaneously implanted arterial cannula having
a tubular body implanted within the arterial lumen. The fluid
medium is then infused through the needle or catheter into the
access leg and from there into the lumen of the tubular body. The
fluid medium will usually be a medication, but could also be a
diagnostic or other conventional agent introduced to arterial blood
flow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 shows a perspective view of the preferred embodiment
of the present invention implanted within a vascular structure.
[0028] FIG. 2 shows a cross-sectional view of the preferred
embodiment of the present invention.
[0029] FIG. 3 shows a cross-sectional view of the valve of the
preferred embodiment of the present invention in the closed
position.
[0030] FIG. 4 shows a cross-sectional view of the valve of the
preferred embodiment of the present invention in the open
position.
[0031] FIGS. 5 and 6 are top and side elevational views,
respectively, of a percutaneous access port which may be utilized
with either the arterial cannula or venous cannula of the present
invention.
[0032] FIG. 7 is a cross-sectional view taken along line 7-7 of
FIG. 5.
[0033] FIG. 8 is a cross-sectional view taken along line 8-8 of
FIG. 5.
[0034] FIG. 9 is an isometric view of a second embodiment of an
arterial cannula constructed in accordance with the principles of
the present invention.
[0035] FIG. 10 is a detailed view of the tubular body of the
cannula of FIG. 9 shown in partial cross-section.
[0036] FIG. 11 illustrates subcutaneous implantation of the
arterial cannula of FIG. 9 in tissue.
DETAILED DESCRIPTION OF THE INVENTION
[0037] Referring to FIG. 1 there is depicted an arterial cannula 10
constructed in accordance with the principles of the present
invention implanted within an arterial lumen 20. The cannula is
shaped generally like a "T" and is comprised of two primary
sections; the tubular body 25 and the access leg 30. The
intravascular tube 25 is an elongated tube having a single lumen
26, open on both ends. When implanted within the lumen 20, the
tubular body 25 will have an upstream end 27, and a downstream end
28, determined by the direction of blood flow in the vascular
structure 20. In FIG. 1 the direction of blood flow is indicated by
the arrow 21. The cannula however, can be implanted in either
orientation.
[0038] The access leg 30 is an elongated tube having a single lumen
31. A distal end 32 of the access leg 30 is connected to the
tubular body 25, generally near the mid-point thereof. The access
leg 30 may extend from the tubular body 25 at any angle, including
a 90 degree angle, but it is preferred that the access leg 30 of
the cannula 10 extend from the tubular body 25 in a direction which
is inclined toward the upstream end 27 of the tubular body 25. The
angle formed between the access leg 30 and the upstream end 27 of
the tubular body 25 is an acute angle. The angle formed between the
access leg 30 and the downstream end 28 of the intravascular tube
25 is an obtuse angle. A preferred angle between the access leg 30
and the upstream end 27 of the tubular body 25 is between
30.degree. and 60.degree., usually being approximately 45
degrees.
[0039] A valve 40 is preferably located at the point of connection
between the distal end 32 of the access leg 30 and the tubular body
25. The preferred valve 40 is a slit valve. Such valves are well
known in the art. As best shown in FIG. 3, the slit valve is
comprised of a membrane 41 which has a slit 42 extending partially
across the membrane 41 and completely through the membrane 41. The
membrane 41 acts to prevent fluid flow through the lumen 31 of the
access leg 30, except when adequate differential pressure exists on
opposite sides of the membrane 41 to cause the slit 42 to open, as
is shown in FIG. 4. The membrane 41 is located such that the side
of the membrane 41 located towards the vascular structure is
essentially flush with the inner wall of the intravascular tube 25.
When the catheter 10 is not in use, the membrane 41 of the valve 40
and the inner surface of the tubular body 25 form a continuous tube
that has minimal impact on normal blood flow through the arterial
lumen.
[0040] In the preferred embodiment, the membrane 41 is comprised of
a portion of the side wall of the tubular body 25. To create the
valve 40, a slit 42 is cut in the side wall of the tubular body 25
to correspond to the point of connection of the access leg 30. In
this manner, when the valve is closed, the inner surface of the
tubular body 25 is a continuous smooth surface which has minimal
impact on normal blood flow. When the valve 40 opens, fluid flow
between the lumen 31 and the access leg 30 and the lumen 26 of the
intravascular tube 25 occurs.
[0041] The outer circumference of the tubular body 25 is provided
with expanded barbs 29 to hold cannula 10 in place within the
vascular structure 20. One each of these expanded barbs 29 may be
placed proximate the upstream end 27 and proximate the downstream
end 28 of the tubular body 25. The expanded barbs 29 have an
enlarged outer circumference which tends to slightly distend the
wall of the arterial lumen 20, providing a snug fit, but not
preventing the continued viability of the arterial wall. Additional
areas of expanded outer diameter (not shown) may be spaced along
the outer surface of the tubular body 25. The fit between the
arterial wall and the tubular body 25 must be of sufficient
tightness to prevent passage of blood between the arterial wall and
the outer surface of the tubular body 25. Optionally, it may be
possible to place ties or clamps (not shown) about the outer wall
of the artery adjacent to the expanded barbs 29 to hold the cannula
10 in place. All blood flowing through the arterial lumen should
pass through the lumen 26 of the tubular member 25.
[0042] In use, the proximal end 33 of the access leg 30 of the
cannula 10 may be connected to a subcutaneous port, or may extend
transcutaneously (i.e. through the skin).
[0043] The cannula 10 is suitable for use with any device requiring
or facilitating intermittent vascular access. The cannula 10 of the
present invention is particularly useful for arterial access in
hemodialysis, since such treatment requires large quantity blood
flow, and requires relatively frequent vascular access over a long
period of time. For such use two cannulas 10 may be surgically
implanted. One of the devices is implanted in an artery. The other
device is implanted in a vein. Usually, however, a conventional
in-dwelling catheter will be used for the venous access since vein
access is easier to establish. In this manner both the venous and
arterial circulations are accessed separately, without fistulous
communication. Current use of shunts, which create a fistulous
connection between artery and vein, not only involve a more
extensive surgical procedure, but are fraught with problems
including increased cardiac output requirements, damage to the vein
due to arterial pressure waves, and frequent shunt occlusion or
thrombosis.
[0044] During hemodialysis, blood is removed from the arterial
cannula 10 implanted in an artery and is subjected to the
extracorporeal dialysis circuit. Removal occurs by reducing the
pressure in the access leg 30 of the cannula 10, until the slit
valve 40 opens, and blood flows from the tubular body 25 into the
access leg 30. The treated blood is returned to a cannula implanted
in a vein. At the completion of the dialysis treatment of the
access leg 30 of cannula 10 is filled with anti-coagulant fluid, to
discourage thrombosis and occlusion of the access legs 30. A
similar process may be used for apheresis or exchange transfusion
procedures. Additionally, a single arterial cannula 10 may be used
for frequent administration of medication into artery or vein, or
for large volume fluid infusions.
[0045] Surgical implantation of the arterial cannula 10 is a
straight forward procedure. The chosen artery is located and
isolated, and a small incision is made in the luminal wall. The
tubular body 25 of the cannula 10 is inserted into the incision,
with the access leg 30 extending out of the lumen through the
incision. The incision is then sutured to provide a snug fit around
the access leg 30. The proximal end 33 of access leg 30 of the
cannula 10 is then attached to a subcutaneous port (described
hereinafter) or other device requiring intermittent vascular
access.
[0046] Materials of construction well known in the art may be used
for the manufacture of the cannula 10. However, it is important
that the tubular body 25 be particularly biocompatible with the
arterial wall 20, since it is intended that the wall in contact
with the cannula 10 remain viable. Since the cannula 10, unlike
most prior art catheters, is not designed to be pushed or threaded
some distance into a blood vessel, the access tube of the cannula
may be comprised of relatively flexible material. This may be
accomplished by including a spring or other reinforcement element
(not shown) within the walls of the cannula 10 to maintain hoop
strength. The materials of construction of the tubular body should
be of sufficient rigidity to maintain the preferred angle between
the access leg 30 and the tubular body. The dimensions of the
catheter 10 depend upon the size of the vascular structure 20 to be
accessed. Typically the outer diameter of the tubular body 25 will
be between 3 and 10 mm, with a wall thickness of approximately 0.5
to 1 mm, yielding a lumen 26 diameter of between 1 and 8 mm. A
typical length of the tubular body 25 from upstream end 27 to
downstream end 28 is between 10 and 50 mm. The maximum diameter of
the outer surface of the expanded barbs 29 is approximately 30
percent greater than the diameter of the tubular body 25 where no
expanded barb 29 is present. The length and flexibility of the
access leg can vary depending upon the use of the catheter 10. For
use with subcutaneous ports an access leg 30 length of
approximately 25 mm to 700 mm, usually about 100 mm is generally
sufficient.
[0047] Referring now to FIGS. 5-8, an exemplary implantable port
100 will be described. The implantable port 100 may be used with
either the arterial cannula 10 described above, or with more
conventional in-dwelling cannula which may be used in systems for
venous access, as described in more detail hereinafter. The port
100 includes a single hematologic chamber 125, where the base and
sides are formed by a circumferential wall 126. The port 100
further includes wall 126 and a cover 120 which holds a replaceable
diaphragm 127 in place. The cover 120 is removable to allow
replacement of the diaphragm 127 if needed. A base 129 of the port
100 comprises a flange having apertures 130 which permit fastening
of the port to underlying tissue, typically using sutures. A
connector 128 open to one end of the chamber 125 is connectable to
the free end of access leg 30 which forms part of the arterial
cannula 10 described above.
[0048] Referring now to FIGS. 9 and 10, an alternative embodiment
of an arterial cannula 200 constructed in accordance with the
principles of the present invention will be described. The cannula
200 includes both a tubular body 202 and an access leg 204. The
access leg 204 comprises a portion adjacent to the tubular body 202
including a plurality of circumferential ribs or corrugations 206
which provides substantial hoop strength to the leg without
diminishing the desired flexibility. The remainder of the access
leg 204 comprises larger sections 208, with the distal end 210
being suitable for attachment to the vascular port 100 at connector
128, as described previously.
[0049] The tubular body 202 comprises a molded insert 230 including
a main body portion 32 and a branch portion 234. An isolation valve
36 is formed at the end of branch 234, generally as described above
with previous embodiments. Tubular body 202 is connected to the
adjacent end of the access leg 206 by over molding an exterior body
238. Usually, a titanium tube 240 is placed within the junction
between the end of access leg 206 and the end of branch portion
234. The tube may be titanium or other biocompatible metal. The
insert 230 is typically formed from a relatively soft material,
such as 40D to 50D silicone rubber. The outer portion 238 of the
tubular body 202 is formed from a similar material, such as 50 D
silicone rubber. The access tube may be also formed from silicone
having a hardness of 40D to 50D. Conventional molding techniques
may be used to form all these parts.
[0050] Referring now to FIG. 11, the tubular body 202 of the
arterial cannula 200 may be implanted within an artery A by first
surgically exposing the artery and thereafter forming an incision
in the side of the artery. The tubular body 202 is the introduced
through the incision, and the incision sutured to hold the body
within the arterial lumen. The access leg 204 is then moved to a
location where the arterial port 100 is to be implanted. Note that
the entire assembly of the arterial cannula 200 and arterial port
100 may be implanted together within a single incision.
Alternatively, the arterial cannula 200 and the arterial port 100
may be separately implanted, with the access leg 204 being
separately positioned therebetween.
[0051] Although the foregoing invention has been described in some
detail by way of illustration and example, for purposes of clarity
of understanding, it will be obvious that certain changes and
modifications may be practiced within the scope of the appended
claims.
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