U.S. patent number RE35,192 [Application Number 08/319,148] was granted by the patent office on 1996-03-26 for post-surgical anesthesia at a continuous and progressively decreasing administration rate.
This patent grant is currently assigned to Phoenix Surgical Products, Inc.. Invention is credited to H. William Reese.
United States Patent |
RE35,192 |
Reese |
March 26, 1996 |
Post-surgical anesthesia at a continuous and progressively
decreasing administration rate
Abstract
A method of administering post-operative anesthesia directly to
the surgical site through a catheter introduced into the site
during the post-operative procedure. The flow of medication into
the catheter is regulated by a micro-bore cannula that insures
delivery at very small rates. The plunger of a spring-loaded
syringe creates the pressure that causes the medication to flow
through the cannula and catheter into the wound. Because of the
spring's nonlinear characteristics within the range of stroke of
the plunger, the pressure exerted on the liquid gradually decreases
with the expansion of the spring. By appropriately sizing the
spring and the inside diameter of the cannula, a device is
developed that administers the required dosages of anesthetic
continuously and at decreasing rates.
Inventors: |
Reese; H. William (Tempe,
AZ) |
Assignee: |
Phoenix Surgical Products, Inc.
(Peoria, AZ)
|
Family
ID: |
26760772 |
Appl.
No.: |
08/319,148 |
Filed: |
October 6, 1994 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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78632 |
Jun 21, 1993 |
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Reissue of: |
611976 |
Nov 13, 1990 |
05078679 |
Jan 7, 1992 |
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Current U.S.
Class: |
604/512; 604/121;
604/135; 604/93.01 |
Current CPC
Class: |
A61M
5/1454 (20130101) |
Current International
Class: |
A61M
5/145 (20060101); A61M 031/00 () |
Field of
Search: |
;604/49,50,51,131,134,135 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Weiss; John G.
Attorney, Agent or Firm: Durando; Antonio R. Weiss; Harry
M.
Parent Case Text
.Iadd.This application is a continuation of 08/078,632, filed Jun.
21, 1993, and is now abandoned, which is a reissue of 07/611,976,
filed Nov. 13, 1990, and is U.S. Pat. No. 5,078,679. .Iaddend.
Claims
What I claim as my invention is:
1. A method for the dispensation of post-surgical anesthesia at a
continuous and progressively decreasing administration rate,
comprising the following steps:
(a) providing a spring-loaded syringe, with sufficient capacity to
hold a predetermined amount of anesthetic medication as required
for the administration of post-surgical anesthesia, wherein the tip
of said spring-loaded syringe is attached to a segment of flexible
tubing ending with a luer-lock fitting;
(b) connecting an injection port to said spring-loaded syringe for
charging it with medication contained in a regular syringe by
injecting it into said injection port against the back pressure
exerted by the stopper of said spring-loaded syringe, wherein the
upstream branch of said injection port is attached to a segment of
flexible tubing ending with a luer-lock fitting cooperatively
engaged with the corresponding fitting attached to said
spring-loaded syringe;
(c) connecting one side of a flow controller downstream of said
injection port, said flow controller consisting of a micro-bore
cannula of specific dimensions to produce a desired pressure drop,
through which the medication is passed as a result of the pressure
exerted by said stopper of the spring-loaded syringe, wherein the
other side of said flow controller is connected to a segment of
flexible tubing ending with a luer-lock fitting;
(d) connecting one end of a catheter to the luer-lock fitting on
the downstream side of said flow controller;
(e) pushing a catheter placement needle, from the inside of a
surgical wound and under the skin, as far away from the site to be
medicated as possible, and then pushing it outside through the
skin;
(f) threading the end of said catheter through the needle and
pushing it through all the way to the surgical site;
(g) pulling said catheter placement needle out leaving the catheter
in place in the surgical site; and
(h) charging said spring-loaded syringe with medication through
said injection port and allowing it to flow through the system into
the surgical site for the required treatment period.
2. The method described in claim 1, wherein said spring-loaded
syringe has the capacity of 50 ml.
3. The method described in claim 2, wherein said spring-loaded
syringe exerts a pressure of approximately 12 psi when fully
charged with said anesthetic medication and a pressure of
approximately 5 psi with 5 ml remaining in the barrel.
4. The method described in claim 3, wherein said micro-bore cannula
in said flow controller is approximately 1/4 inch in length and
0.0016 inch in inside diameter.
5. The method described in claim 4, wherein said flexible tubing
consists of medical grade PVC tubing.
6. The method described in claim 5, wherein said catheter consists
of an 8 inch long 22 gauge catheter.
7. The method described in claim 6, wherein said catheter placement
needle consists of an 18 gauge hypodermic needle. .Iadd.
8. A method for the direct, low-flow-rate dispensation of
post-surgical analgesia nonsystematically, at a progressively
decreasing administration rate, into a cavity of a surgical site in
a patient for the localized relief of pain in that site only,
comprising the following steps:
(a) providing a spring-loaded syringe for dispensing analgesic
medication, said syringe having sufficient capacity to hold a
predetermined amount of analgesic medication as required for an
administration of post-surgical analgesia and being adapted for
administration at a progressively decreasing rate;
(b) providing a delivery means connected to said syringe for
delivering the analgesic medication directly into the surgical
site; and
(c) controlling the flow of analgesic medication into the cavity of
the surgical site from said syringe and through said delivery means
at a progressively decreasing rate not to exceed 25 ml per 24-hour
period for a required treatment period. .Iaddend. .Iadd.9. The
method described in claim 8, wherein said delivery means comprises
control means for regulating the flow rate of analgesic medication
being dispensed from said syringe. .Iaddend. .Iadd.10. The method
described in claim 9, wherein said control means for regulating the
flow rate of analgesic medication consists of a micro-bore cannula.
.Iaddend. .Iadd.11. The method described in claim 8, wherein said
syringe is capable of delivering the analgesic medication at a
continuous administration rate during the required treatment
period. .Iaddend. .Iadd.12. A method for the direct, low-flow-rate
dispensation of post-surgical analgesia nonsystematically, at a
progressively decreasing administration rate, into a cavity of a
surgical site in a patient for the localized relief of pain in that
site only, comprising the following steps:
(a) providing a first means for dispensing analgesic medication,
said first means having sufficient capacity to hold a predetermined
amount of analgesic medication as required for an administration of
post-surgical analgesia and being adapted for administration at a
progressively decreasing rate;
(b) providing a second means connected to said first means for
delivering the analgesic medication directly into the surgical
site; and
(c) controlling the flow of analgesic medication into the cavity of
the surgical site from said first means and through said second
means at a progressively decreasing rate not to exceed 25 ml per
24-hour period for a required treatment period;
wherein said step (b) is accomplished by providing a catheter
connected to said first means and a catheter placement needle; by
pushing the catheter placement needle inside a wound at a surgical
site so as to cause the needle to emerge from the skin of the
patient; by threading the end of said catheter through the needle
and placing it within the cavity of the surgical site; and by
pulling said catheter placement needle out leaving
the catheter in place in the surgical site. .Iaddend. .Iadd.13. The
method described in claim 12, wherein said second means comprises
means for regulating the flow rate of analgesic medication being
dispensed from
said first means. .Iaddend. .Iadd.14. The method described in claim
13, wherein said means for regulating the flow rate of analgesic
medication
consists of a micro-bore cannula. .Iaddend. .Iadd.15. A method for
the direct, low-flow-rate dispensation of post-surgical analgesia
nonsystematically, at a progressively decreasing administration
rate, into a cavity of a surgical site in a patient for the
localized relief of pain in that site only, comprising the
following steps:
(a) providing a spring-loaded syringe for dispensing analgesic
medication, said syringe having sufficient capacity to hold a
predetermined amount of analgesic medication as required for an
administration of post-surgical analgesia and being adapted for
administration at a progressively decreasing rate;
(b) providing a delivery means connected to said syringe for
delivering the analgesic medication directly into the surgical
site; and
(c) controlling the flow of analgesic medication into the cavity of
the surgical site from said syringe and through said delivery means
at a progressively decreasing rate. .Iaddend. .Iadd.16. A method
for the direct, low-flow-rate dispensation of post- surgical
analgesia nonsystematically, at a progressively decreasing
administration rate, into a cavity of a surgical site in a patient
for the localized relief of pain in that site only, comprising the
following steps:
(a) providing a first means for dispensing analgesic medication,
said first means having sufficient capacity to hold a predetermined
amount of analgesic medication as required for an administration of
post-surgical analgesia and being adapted for administration at a
progressively decreasing rate;
(b) providing a second means connected to said first means for
delivering the analgesic medication directly into the surgical
site; and
(c) controlling the flow of analgesic medication into the cavity of
the surgical site from said first means and through said second
means at a progressively decreasing rate for a required treatment
period;
wherein said step (b) is accomplished by providing a catheter
connected to said first means and a catheter placement needle; by
pushing the catheter placement needle inside a wound at a surgical
site so as to cause the needle to emerge from the skin of the
patient; by threading the end of said catheter through the needle
and placing it within the cavity of the surgical site; and by
pulling said catheter placement needle out leaving the catheter in
place in the surgical site. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is related in general to the field of drug infusions
and, in particular, to the area of administration of post-operative
anesthesia. The invention provides a novel technique and equipment
to inject liquid anesthetics directly into the surgical site on a
continuous basis.
2. Description of the Prior Art
Post-operative pain normally requires the injection of anesthetic
medication into the area affected by the surgical procedure in
order to alleviate the patient's discomfort and facilitate a
successful recovery. Typically, care providers inject a liquid
anesthetic directly into the surgical site for a number of days
after the operation. This procedure necessitates a new needle
puncture in an already sensitive area with each administration,
with the obvious result of pain exacerbation and an increased
potential for infection. Alternatively, post-operative pain can be
alleviated with the administration of narcotics, but this approach
is generally not favored because of their side effects.
When an anesthetic is administered locally, normally the dosage at
each injection is reduced over a period of a few days after the
operation because of the decreasing level of discomfort and the
corresponding smaller need for anesthesia. This requires that
accurate records be kept to avoid confusion concerning the type of
medication and dosages used at each time. Therefore, in addition to
the pain and trauma inflicted to the patient by the repeated needle
punctures, the potential for error is increased because of the
recurring human involvement. Thus, there is a need for an infusion
apparatus designed to administer the total dosage of anesthetic
required for post-operative treatment on a continuous and
progressively decreasing basis through a single injection site in
the surgical wound.
BRIEF SUMMARY OF THE INVENTION
One objective of this invention is the development of a device for
the administration of post-operative anesthesia locally and through
a single injection site. This is obtained by providing a catheter
that is introduced into the surgical wound and is used as the sole
channel for infusing the required amount of pain relieving
medication.
Another objective of the invention is an apparatus that dispenses
the medication on a continuous basis. Thus, this device involves a
spring-loaded syringe capable of holding the entire dosage of
anesthetic required to be infused during the course of treatment
and of delivering it continuously as a result of constant pressure
applied by a spring on the syringe plunger.
A further goal of the invention is the gradual decrease of the rate
of delivery of anesthetic according to a predetermined
administration schedule. Therefore, the rate of flow out of the
syringe is controlled by a specially designed length of micro-bore
tubing and a variable pressure spring that result in the desired
rate of delivery.
Yet another goal of the invention is a unit that can be set up as
part of the post-operative procedure and left in place during the
entire period of administration. To that end, the apparatus
includes a catheter placement needle to provide access to the
surgical site through a single procedure, and an injection port for
charging the spring-loaded syringe with the total dosage of
required medication.
A final objective is the easy and economical manufacture of the
device according to the above stated criteria. This is achieved by
using commercially available components and materials, modified
only to the extent necessary to fit the requirements of the
invention.
Therefore, according to these and other objectives, the present
invention describes an apparatus for administering post-operative
anesthesia directly to the surgical site through a catheter
introduced into the site during the post-operative procedure. The
flow of medication into the catheter is regulated by a micro-bore
cannula that insures delivery at very small rates. The plunger of a
spring-loaded syringe creates the pressure that causes the
medication to flow through the cannula and catheter into the wound.
Because of the spring's nonlinear characteristics within the range
of stroke of the plunger, the pressure exerted on the liquid
gradually decreases with the expansion of the spring. By
appropriately sizing the spring and the inside diameter of the
cannula, a device is developed that administers the required
dosages of anesthetic continuously and at decreasing rates.
Various other purposes and advantages of the invention will become
clear from its description in the specifications that follow and
from the novel features particularly pointed out in the appended
claims. Therefore, to the accomplishment of the objectives
described above, this invention consists of the features
hereinafter illustrated in the drawings, fully described in the
detailed description of the preferred embodiment and particularly
pointed out in the claims. However, such drawings and description
disclose but one of the various ways in which the invention may be
practiced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of the apparatus of this
invention as used to administer medication to a patient.
FIG. 2 is a cross-section of an elevational view of one embodiment
of the spring-loaded syringe shown in FIG. 1.
FIG. 3 is a representative plot of the cumulative volume of
medication administered by the apparatus of the invention as a
function of time.
DETAILED DESCRIPTION OF THE INVENTION
This invention consists of the application of simple mechanical
principles in combination with known structural components to
achieve a practical and economical design for an infusion device
with the properties described above. The main point of the
invention lies in the recognition of the advantages involved with
the continuous administration of post-operative anesthesia and the
fact that it can be achieved in an optimal manner by gradually
reducing the delivery rate according to a desired, predetermined
schedule.
Referring to the drawings, wherein like parts are designated
throughout with like numerals and symbols, FIG. 1 illustrates the
apparatus 10 of this invention with its several components
assembled for use. A spring-loaded syringe 20, integrally connected
through its tip 26 to standard medical tubing 31, is used both as
reservoir and pump. In the preferred embodiment of the invention, a
50 cc syringe is employed because that capacity corresponds with
the normal requirements of total anesthetic administration during
the post-operative period. As illustrated in more detail in FIG. 2,
the plunger 22 of the syringe is connected in working relationship
with a spring 30 that exerts pressure in the direction of
discharge. As the syringe is filled with medication by injection
through an apposite injection port 34, the stopper 23 of the
plunger 22 is pushed in an outward direction in the barrel 24, and
the spring 30 is compressed and loaded into a charged position for
exerting pressure on the liquid. When the outlet pressure of the
syringe is released, the spring pressure causes the medication to
flow out of the syringe continuously until the syringe becomes
empty at the end of the plunger's stroke.
According to basic principles of physics, the pressure exerted by
an ideal spring within its normal operating range is directly
proportional to its elastic force; this, in turn, is directly
proportional to the spring's linear compression. In practice,
therefore, the pressure exerted on the plunger's stopper decreases
approximately linearly as the spring 30 expands, producing a
progressively decreasing flow rate of medication out of the
syringe.
The medication tubing 31 attached to the syringe is equipped with a
luer-lock or similar fitting 32 for connection with the other
components of the invention. Directly downstream is an injection
port 34 mounted on a Y fitting, provided for use in the process of
charging the syringe 20 with medication, as mentioned above,
followed by a flow controller 36. The flow controller consists of a
micro-bore cannula of a specific inside diameter and length to
provide the necessary flow restriction and pressure drop for
producing, in cooperation with the syringe 20, the desired flow
rate of anesthetic to the patient. The flow controller 36 is
obviously placed downstream of the injection port 34 to avoid
interference with the process of charging the syringe. Through
another luer-lock or similar fitting, the flow controller 36 is
connected to a medication catheter 38 that is provided for
placement into the surgical site S. Finally, a hypodermic needle 40
is provided for use during the procedure of placing the catheter 38
into the site S through a puncture P in the skin of the
patient.
In order to determine the precise specifications of the spring 30
and of the micro-bore cannula contained in the flow controller 36,
experiments were conducted with medications currently used in
anesthesia. For example, the drugs marketed by Winthrop
Pharmaceuticals under the trademark "Marcaine" (0.25% HCl solution)
and by Astra Pharmaceutical Products, Inc. under the name
"Xylocane" (1% HCl solution) were tested over a three-day period of
administration. The syringe 20 was charged with 50 ml of
medication, well within the maximum recommended dosage for safety,
and various sizes of springs and cannulae were used in the
apparatus of the invention in order to determine experimentally
what combination would provide the required delivery rates. It was
found that a spring capable of producing an initial pressure of 12
psi, decreasing to 5 psi with 5 ml of liquid left in the syringe,
in combination with a cannula 1/4 inch long with an inside diameter
of 0.0016 inches, produces the desired clinical rate for these
drugs. Specifically, over a period of ten tests, the anesthetic was
delivered through the system at a rate of 23.4 ml (.+-.3.5 ml)
during the first 24 hour period, 14.1 ml (.+-.2.1 ml) during the
second 24 hour period, and 10.0 ml (.+-.1.5 ml) during the third 24
hour period. These rates are considered clinically optimal for
post-operative anesthesia. FIG. 3 illustrates in graphical form the
cumulative volume of medication administered to the patient in a
typical run.
Referring to the mode of operation of this invention, the following
steps are performed. The appropriate amount of medication is loaded
into the spring-loaded syringe 20 with a regular injection syringe
and needle through the port 34 according to standard safety
procedure to avoid air entrainment. The point of the hypodermic
needle 40 is pushed from inside the surgical wound S to penetrate
away from the site to be medicated, and then pushed outside through
the skin at a point P as far away from the site as possible. The
end of the catheter 38 is inserted into the needle and threaded
through it all the way to the surgical site, as illustrated in FIG.
1. Then, the needle is pulled out leaving the catheter in place in
the surgical site, carefully avoiding introducing it into the
epidural space. Finally, the syringe 20 is connected to the
catheter through the flow controller 36 for the delivery of the
medication. The catheter can safely remain in place for up to three
days, which is considered a normal period of post-operative
anesthetic treatment.
With the exception of the spring-loaded syringe, all the components
described above constitute standard medical equipment currently
available in commerce. For example, a standard injection port and
luer-lock fittings were used; the medication tubing was medical
grade flexible PVC tubing; the catheter was 8 inch long and 22
gauge; and the placement needle was a standard 18 gauge hypodermic
needle. The spring-loaded syringe was obtained by mounting a
standard spring in a regular syringe so that it produced the
necessary pressure against the plunger's stopper, as illustrated in
FIG. 2.
While the embodiment shown in the figures features the specific
shapes therein described, the invention can obviously take other
shapes with equivalent functionality and utility. In fact, any
shape for any of the components that retains the functional
characteristics described above provides an acceptable apparatus to
practice the invention. The capacity of the spring-loaded syringe
and the size of all other components can be varied in obvious ways
to produce different flow rates without affecting the scope of this
disclosure. Similarly, a variety of other components could be
introduced by one skilled in the art to fit the particular needs of
specific applications. Various changes in the details, steps and
materials that have been described may be made by those skilled in
the art within the principles and scope of the invention herein
illustrated and defined in the appended claims. Therefore, while
the present invention has been shown and described herein in what
is believed to be the most practical and preferred embodiment, it
is recognized that departures can be made therefrom within the
scope of the invention, which is therefore not to be limited to the
details disclosed herein but is to be accorded the full scope of
the claims so as to embrace any and all equivalent apparatus and
methods.
* * * * *