U.S. patent application number 09/401734 was filed with the patent office on 2002-07-04 for methods and devices for maintaining cardiopulmonary bypass and arresting a patient's heart.
Invention is credited to FAN, SYLVIA W., ROBERTS, CRAIG P., TOOMASIAN, JOHN M..
Application Number | 20020087107 09/401734 |
Document ID | / |
Family ID | 25146969 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020087107 |
Kind Code |
A1 |
ROBERTS, CRAIG P. ; et
al. |
July 4, 2002 |
METHODS AND DEVICES FOR MAINTAINING CARDIOPULMONARY BYPASS AND
ARRESTING A PATIENT'S HEART
Abstract
An endovascular system for arresting a patient's heart and
maintaining the patient on cardiopulmonary bypass. A venous
cannula, venting catheter and an aortic occlusion device are all
coupled together so that the blood drawn into each of these
catheters may be fed to a pump. A manifold has valves which control
flows through the venous cannula, venting catheter and aortic
occlusion device. A blood storage element is also provided so that
the amount of blood in the perfusion circuit may be varied if
necessary. The blood storage element is preferably positioned in
parallel with the pump so that the pump may be used to add and
remove blood to and from the blood storage element.
Inventors: |
ROBERTS, CRAIG P.; (LAGUNA
NIGUEL, CA) ; TOOMASIAN, JOHN M.; (MENLO PARK,
CA) ; FAN, SYLVIA W.; (SAN FRACISCO, CA) |
Correspondence
Address: |
JENS HOEKENDIJK
Hoekendijk & Lynch LLP
P.O. Box 4787
Burlingame
CA
94011-4787
US
|
Family ID: |
25146969 |
Appl. No.: |
09/401734 |
Filed: |
September 23, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09401734 |
Sep 23, 1999 |
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08789223 |
Jan 24, 1997 |
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5957879 |
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Current U.S.
Class: |
604/5.01 ;
604/35; 604/6.11; 604/6.16 |
Current CPC
Class: |
A61M 2205/12 20130101;
A61M 2202/047 20130101; Y10S 128/03 20130101; A61M 25/0021
20130101; A61M 25/0032 20130101; A61M 2025/0004 20130101; A61M
25/007 20130101; A61M 1/3667 20140204; A61M 2025/0031 20130101;
A61M 2210/125 20130101; A61M 1/3613 20140204 |
Class at
Publication: |
604/5.01 ;
604/6.11; 604/6.16; 604/35 |
International
Class: |
A61M 037/00; A61M
001/00 |
Claims
What is claimed is:
1. A method of withdrawing blood from a patient for use with a
cardiopulmonary bypass system, comprising the steps of: providing a
venous cannula and a venting catheter, the venous cannula having a
lumen and at least one opening in fluid communication with the
lumen, the venting catheter also having a venting lumen with at
least one opening in fluid communication with the venting lumen;
inserting the venous cannula into a vein of a patient; passing the
venting catheter through the patient's tricuspid and pulmonary
valves; coupling the venous catheter and the venous cannula to a
pump; and withdrawing blood from the patient through the lumen of
the venous cannula and the venting lumen of the venting catheter
using the pump.
2. The method of claim 1, further comprising the step of: inserting
an arterial cannula into an artery of the patient, the arterial
cannula having a lumen; coupling the lumen of the arterial cannula
to an outlet of the pump; and returning the blood to the patient
through the lumen of the arterial cannula using the pump.
3. The method of claim 2, further comprising the step of: fluidly
coupling a blood storage element to the outlet of the pump; and
selectively changing a volume of blood in the blood storage
element.
4. The method of claim 1, wherein: the providing step is carried
out with the pump being a centrifugal pump.
5. The method of claim 1, further comprising: inserting an aortic
occlusion device into the patient; passing the aortic occlusion
device through the patient so that an occluding member on the
aortic occlusion device is positioned in the ascending aorta;
expanding the occluding member so that the ascending aorta is
occluded; delivering cardioplegic fluid through a lumen in the
aortic occlusion device; coupling the lumen of the aortic occlusion
device to the pump; and venting blood from the patient through the
lumen in the aortic occlusion device using the pump.
6. A method of withdrawing and returning blood to a patient
supported by a cardiopulmonary bypass system, comprising the steps
of: passing a first lumen and a second lumen through an opening in
a patient's artery, the first lumen having an occluding member
mounted thereto, the occluding member being movable between a
collapsed condition and an expanded condition; inserting a venous
cannula into a vein of the patient; coupling the venous cannula to
a venous line; withdrawing blood from the patient through the
venous cannula and the venous line; returning the blood to the
patient through an arterial line coupled to the second lumen;
positioning the occluding member in the patient's ascending aorta;
expanding the occluding member to occlude the patient's ascending
aorta delivering cardioplegic fluid through the first lumen to
thereby arrest the patient's heart; providing a blood storage
element having an inlet and an outlet; fluidly coupling the inlet
of the blood storage element to the arterial line; and selectively
changing a volume of blood in the blood storage element.
7. The method of claim 6, further comprising the step of: providing
a venting catheter; passing the venting catheter through the
patient's tricuspid and pulmonary valves; and withdrawing blood
from the patient using the venting catheter.
8. The method of claim 6, further comprising the steps of: coupling
the outlet of the blood storage element to the venous line.
9. The method of claim 8, wherein: the withdrawing step is carried
out with the venous cannula being coupled to a pump.
10. The method of claim 6, wherein: the providing step is carried
out with the first lumen and second lumen being carried by a single
device.
11. The method of claim 6, wherein: the passing step is carried out
with the first lumen being slidable relative to the second
lumen.
12. An endovascular bypass system, comprising: an aortic occlusion
device having a lumen and an occluding member, the occluding member
being sized and configured to occlude a patient's ascending aorta;
a venous cannula having a lumen for withdrawing blood from the
patient; a manifold having first and second valves and first and
second valve controls for controlling the first and second valves;
a vent line extending between the lumen of the aortic occlusion
device to the manifold; and a venous line extending from the venous
cannula to the manifold; the first and second valves being
positioned to regulate flows through the first and second lines,
respectively.
13. The endovascular bypass system of claim 12, further comprising:
a pump having an inlet and an outlet; and an exit line which
receives blood passing through the first and second valves, the
exit line being fluidly coupled to the pump inlet.
14. The endovascular bypass system of claim 12, further comprising:
an arterial cannula having a lumen for returning oxygenated blood
to the patient; an arterial line extending from the pump outlet to
the lumen of the arterial cannula; and a blood storage device
having an inlet line and an outlet line, the inlet line being
coupled to the arterial line.
15. The endovascular bypass system of claim 14, wherein: the outlet
line of the blood storage element is coupled to the manifold; and
the manifold having a third valve and a third valve controller for
controlling the third valve, the third valve being positioned to
regulate blood flow through the outlet line of the blood storage
element.
16. The endovascular bypass system of claim 12, further comprising:
a bridge line extending between the arterial line and the second
conduit.
17. A method of arresting a patient's heart and maintaining bypass
support, comprising the steps of: inserting a venous cannula into a
vein of a patient; coupling the venous cannula to an inlet of a
pump, the pump having an outlet; withdrawing blood from the patient
through the venous cannula using the pump; fluidly coupling the
outlet of the pump to an arterial cannula through an arterial line;
returning blood to the patient through the arterial cannula;
inserting an aortic occlusion device through an artery of the
patient, the aortic occlusion device having an occluding member;
expanding the occluding member in the patient's ascending aorta
thereby occluding the ascending aorta; delivering cardioplegic
fluid to the ascending aorta through a lumen in the aortic
occlusion device; and coupling the lumen of the aortic occlusion
device to the pump intake.
18. The method of claim 17, wherein: the blood returning step is
carried out with the aortic occlusion device passing through the
arterial cannula.
19. The method of claim 17, wherein: the arterial cannula and
aortic occlusion device are integrally formed.
20. The method of claim 17, further comprising: fluidly coupling
the venous cannula and the arterial cannula with a bridge.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of co-pending application
Ser. No. 08/789,223, filed Jan. 24, 1997, the complete disclosure
of all of which is hereby incorporated herein by reference for all
purposes.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to systems for arresting a
patient's heart and maintaining a patient on cardiopulmonary
bypass. Such systems are used when performing surgical procedures,
such as coronary artery bypass grafting, on an arrested heart.
[0003] In conventional open-heart surgery, the patient's breast
bone is sawed open, the chest is spread apart, and the heart is
accessed through the large opening created in the patient's chest.
The patient is placed on cardiopulmonary bypass and the patient's
heart is then arrested using catheters and cannulae which are
inserted directly into the large arteries and veins attached to the
heart through the large opening in the chest. The arterial cannula
typically passes through the wall of the ascending aorta and a
cross-clamp is applied to the ascending aorta to isolate the
coronary arteries from the remainder of the arterial system. A
venous cannula passes through the right atrium for withdrawing
blood from the patient.
[0004] Recent developments in cardiac surgery have enabled surgeons
to perform coronary artery bypass grafting and valve repair and
replacement procedures without creating a large opening in the
patient's chest. These developments have significantly reduced
trauma to the patient by eliminating the need for sawing open the
breast bone and opening the patient's chest. Such procedures are
disclosed in U.S. Pat. Nos. 5,452,733 and 5,571,215 which are
hereby incorporated by reference.
[0005] In order to perform such surgical procedures, the patient's
heart must be arrested and the patient placed on cardiopulmonary
bypass without direct access to the heart. Catheters and cannulae
for arresting the patient's heart and establishing bypass without
requiring direct access to the patient's heart are disclosed in
U.S. Pat. Nos. 5,584,803 and 5,558,644 which are hereby
incorporated by reference.
[0006] The systems described in U.S. Pat. Nos. 5,584,803 and
5,558,644 include an aortic occlusion device which has a balloon to
occlude the ascending aorta and a lumen to deliver cardioplegic
fluid for arresting the patient's heart. The aortic occlusion
device replaces the conventional external cross-clamp and
advantageously reduces the amount of displacement and distortion of
the aorta. Minimizing distortion of the aorta may reduce the amount
of emboli released and, therefore, may reduce stroke incidents.
[0007] A venous cannula withdraws blood from the patient and blood
is returned to the patient through an arterial cannula which is
placed at a peripheral artery such as the femoral artery. In a
preferred embodiment, the aortic occlusion device passes through
the arterial cannula thereby minimizing the number of penetrations
in the patients vascular system.
[0008] The systems described in U.S. Pat. Nos. 5,584,803 and
5,558,644 also include an endovascular coronary sinus catheter for
retrograde perfusion of a cardioplegic agent, preferably blood
cardioplegia, via the coronary sinus. The coronary sinus catheter
preferably passes through the internal jugular vein and has an
inflatable balloon for occluding the coronary sinus. An
endovascular venting catheter extends through the tricuspid and
pulmonary valves for venting the pulmonary artery.
[0009] Although the endovascular bypass system has performed
admirably and has enabled surgeons to perform less invasive cardiac
procedures, the extracorporeal bypass circuit which couples the
catheters and cannulae to the cardiopulmonary bypass elements may
be optimized.
[0010] Thus, a specific object of the present invention is to
provide an extracorporeal flow circuit for use with endovascular
cardiopulmonary bypass systems.
SUMMARY OF THE INVENTION
[0011] In accordance with the present invention, methods and
devices for maintaining cardiopulmonary bypass support and
arresting the patient's heart are provided.
[0012] In a first aspect of the invention, a method of withdrawing
blood from a patient and arresting the patient's heart is provided.
An aortic occlusion device has an occluding member, a lumen and
first and second branches coupled to the lumen. The first branch is
coupled to a source of cardioplegic fluid, preferably blood
cardioplegia, and the second branch is coupled to a pump,
preferably a non-occlusive pump such as a centrifugal pump. A
venous cannula is also coupled to the pump for withdrawing blood
from the patient. The aortic occlusion device is then inserted into
the patient so that the occluding member is positioned in the
ascending aorta. The occluding member is then expanded to occlude
the ascending aorta and cardioplegic fluid is delivered through the
lumen in the aortic occlusion device to arrest the patient's heart.
An advantage of the present invention is that a single pump is used
for withdrawing blood through the venous cannula and the aortic
occlusion device. The single pump reduces the complexity of
multi-pump systems.
[0013] In another aspect of the present invention, another method
of withdrawing blood from the patient is provided. A venting
catheter is passed through the patient's tricuspid and pulmonary
valves and a venous cannula is positioned in an artery of the
patient. The venting catheter and venous cannula are both coupled
to a pump, preferably a non-occlusive pump such as a centrifugal
pump. An advantage of coupling the venous cannula and venting
catheter to the same pump is that the system becomes
self-regulating in that blood is withdrawn through the venous
cannula when low flows are achieved through the vent catheter.
[0014] In yet another aspect of the invention, a method of
withdrawing and returning blood to a patient supported by a bypass
system is provided. A venous cannula is inserted into the venous
system for withdrawing blood from the patient and an arterial
cannula is inserted into the arterial system for returning blood to
the patient. A venous line is coupled to the venous cannula and
blood is withdrawn from the patient through the venous cannula and
venous line. The venous cannula directs the blood to at least one
pump which then pumps the blood through an arterial line to the
arterial cannula. A blood storage element is coupled to the
arterial line and is used to change the amount of blood in the
perfusion circuit as needed. In a preferred aspect of the method,
an outlet of the blood storage element is coupled to the venous
line so that the blood storage element is in parallel with the
pump. In another preferred aspect of the invention, the first and
second lumens are slidably coupled together. The blood storage
element advantageously permits the perfusionist to actively adjust
the amount of blood in the perfusion circuit by withdrawing or
adding blood to the blood storage element using the pump.
[0015] These and other aspects of the invention will become
apparent from the following description of the preferred
embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows a system for arresting a patient's heart and
maintaining bypass support according to the present invention.
[0017] FIG. 2 is a cross-sectional view of an aortic occlusion
device and an arterial cannula around line A-A of FIG. 1.
[0018] FIG. 3 is a cross-sectional view of a coronary sinus
catheter about line B-B of FIG. 1.
[0019] FIG. 4 shows a venous cannula and a venting catheter
extending therethrough.
[0020] FIG. 5 is a cross-sectional view of the venous cannula and
venting catheter of FIG. 4 about line C-C.
[0021] FIG. 6 shows a flow directing catheter used to direct the
venting catheter.
[0022] FIG. 7 is a cross-sectional view of the flow directing
catheter and venting catheter of FIG. 6 about line D-D.
[0023] FIG. 8 shows the distal tip of another preferred venting
catheter.
[0024] FIG. 9 is a cross-sectional view of the venting catheter of
FIG. 8 about line E-E.
[0025] FIG. 10 shows an obturator for use with the venting
catheters of FIGS. 4-9.
[0026] FIG. 11 shows another system for arresting a patient's heart
and maintaining bypass support according to the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Referring to FIG. 1, a cardiopulmonary bypass system
according to the present invention is shown. The cardiopulmonary
bypass system includes an aortic occlusion device 2, an
endovascular coronary sinus catheter 4, and an endovascular venting
catheter 6. Blood is withdrawn from the patient through a venous
cannula 8 and returned to the patient through an arterial cannula
10. The description of the invention begins with a discussion of
the various catheters 2, 4, 6 and cannulae 8, 10 of a preferred
endovascular catheter and cannula system. Although the following
describes a preferred endovascular system, other systems may be
used without departing from the scope of the invention.
[0028] The aortic occlusion device 2 preferably passes through the
femoral artery or subclavian artery and into the ascending aorta.
The catheter 2 has an occluding member 12, which is preferably a
balloon, for occluding the ascending aorta. Referring to the
cross-sectional view of FIG. 2, the aortic occlusion device 2 has a
first lumen 14 having an outlet distal to the occluding member 12
for delivering cardioplegic fluid to arrest the patient's heart. A
second lumen 16 is coupled to a pressure monitor 13 to monitor
pressure distal to the occluding member 12 and a third lumen 18 is
coupled to a syringe 15 for delivering inflation fluid to the
occluding member 12. A member 20, which is wound in a helical
manner, reinforces the catheter 2. The second lumen 16 may be
eliminated by monitoring pressure through the first lumen 14 or by
providing a pressure transducer. The first lumen 14 of the aortic
occlusion device 2 is fluidly coupled to a first branch 21 (see
FIG. 1), which is used for perfusing cardioplegic fluid, and a
second branch 23 (see FIG. 1), which is used for venting blood from
the heart as will be described below. Aortic occlusion devices are
described in U.S. Pat. Nos. 5,584,803, 5,478,309, and 5,433,700 and
U.S. patent application Ser. No. 08/782,113, entitled "Muti-Lumen
Catheter and Method of Manufacture," filed Jan. 13, 1997, by
inventors Timothy Corvi and John Stevens, which are all hereby
incorporated by reference.
[0029] Still referring to FIG. 2, the aortic occlusion device 2
preferably passes through a lumen 25 in the arterial cannula 10 in
the manner described in U.S. Pat. Nos. 5,584,803 and 5,478,309
which are hereby incorporated by reference. The arterial cannula 10
also has a reinforcing member 27 wound in a helical manner and a
preferred arterial cannula 10 is described in U.S. patent
application Ser. No. 08/749,683, entitled "Cannula and Method of
Manufacture and Use," filed Nov. 15, 1996, by inventor David Snow,
which is also hereby incorporated by reference. The aortic
occlusion device 2 and the arterial cannula 10 may also be coupled
together into a single, multi-channel catheter as described in U.S.
Pat. No. 5,312,344, however, it is preferred to separate the aortic
occlusion device 2 from the arterial cannula 10 for a number of
reasons such as being able to replace the aortic occlusion device 2
without taking the patient off cardiopulmonary bypass. The aortic
occlusion device 2 may also pass through a puncture in the
ascending or descending aorta similar to the blood vessel occlusion
trocar disclosed in U.S. Pat. No. 5,499,996.
[0030] The coronary sinus catheter 4 is used for retrograde
delivery of cardioplegic fluid via the coronary sinus. Thus, both
antegrade and retrograde delivery of cardioplegic fluid are
provided with the aortic occlusion device 2 providing antegrade
perfusion and the coronary sinus catheter 4 providing retrograde
perfusion. The coronary sinus catheter 4 preferably passes through
the internal jugular vein, through the right atrium and into the
coronary sinus. An occluding member 22, which is preferably a
balloon, is used to occlude the coronary sinus. Referring to the
cross-sectional view of FIG. 3, a first lumen 24 is used for
infusing cardioplegic fluid, preferably blood cardioplege, a second
lumen 26 is coupled to a pressure monitor 13 and a third lumen 28
is coupled to a syringe 15 for inflating the occluding member 22.
The first and second lumens 24, 26 have outlets distal to the
occluding member 22 for infusing cardioplege distal to the
occluding member 22 and for measuring pressure distal to the
occluding member 22. Endovascular coronary sinus catheters are
disclosed in U.S. Pat. No. 5,558,644 which is hereby incorporated
by reference.
[0031] The venting catheter 6 preferably extends through the
internal jugular vein, through the right atrium, and through the
tricuspid and pulmonary valves so that a distal tip 28 is in the
pulmonary artery. The venting catheter 6 is used to decompress the
heart through the pulmonary vasculature and to aid the venous
cannula 8 in withdrawing blood from the patient. An advantage of
the venting catheter 6 is that it partially opens the pulmonary and
tricuspid valves to enhance blood removal through the venous
cannula 8. The venting catheter 6 can also be used as a diagnostic
tool in that high flows through the venting catheter 6 may indicate
a problem with the venous cannula 8 such as improper placement. A
further description of the venting catheter 6 is provided below in
connection with the description of FIGS. 8 and 9. Although it is
preferred to provide a venting catheter 6, venting of the pulmonary
artery may also be accomplished using trocar, needle or the like
which penetrates the wall of the pulmonary artery. Aortic occlusion
devices, coronary sinus catheters, venting catheters, and arterial
and venous cannulae may be purchased from Heartport, Inc. of
Redwood City, Calif.
[0032] Referring to FIGS. 4 and 5, another venting catheter 6A and
venous cannula 8A are shown. The venting catheter 6A extends
through the venous cannula 8A thereby eliminating the need for an
independent access site for the venting catheter 6A. The venous
cannula 8A has a lumen 32 which receives the venting catheter 6A
and a hemostasis valve (not shown) which seals the area between the
venting catheter 6A and venous cannula 8A. The venous cannula 8A
also preferably has an opening 30 through which the venting
catheter 6A extends. Venous blood is withdrawn through openings 33
and pass through a line (not shown) connected to a barbed connector
34. The venting catheter 6A has a lumen 31 and openings 33 at a
distal end for withdrawing blood from the pulmonary artery.
Referring to FIGS. 6 and 7, a flow-directing catheter 36 having a
flow-directing element 38, such as a balloon, may be used to help
position the venting catheter 6A. The flow-directing catheter 36
has a first lumen 37 and a second lumen 39 with one of the lumens
being used to inflate the flow-directing element 38 and the other
lumen either receiving a guidewire or being used for pressure
measurement. Referring to FIG. 10, a specialized obturator 41
having an angled tip 43 is used to direct the venting catheter 6,
6A through the opening 30 in the venous cannula 8A.
[0033] Referring to FIGS. 1, 8 and 9, the venting catheter 6 has a
flow-directing element 40, such as a balloon, for directing the
venting catheter 6B through the tricuspid and pulmonary valves. The
venting catheter 6 has a first lumen 42 for venting blood from the
pulmonary artery, a second lumen 44 for monitoring pressure with
the pressure monitor 13 or receiving a guidewire, and a third lumen
46 coupled to syringe 15 for inflating the flow-directing element
40. The catheter may also have a shaped distal portion which is
configured to direct the distal tip through the tricuspid and
pulmonary valves.
[0034] Referring again to FIG. 1, the aortic occlusion device 2 and
coronary sinus catheter 4 are both coupled to a source of
cardioplegic fluid 48. A preferred cardioplegic fluid is blood
cardioplegia which contains a mixture of cardioplegic agent and
blood. Blood is withdrawn from the extracorporeal bypass circuit,
which will be described in greater detail below, combined with the
cardioplegic agent, and delivered to the catheters with a roller
pump 50. A manifold 52 having valve operators 53, 55 regulates the
flow rate of cardioplegic fluid through cardioplege feed lines 54,
56 leading to the catheters 2, 4.
[0035] The pressure of the cardioplegic fluid being delivered to
the patient's vascular system is measured to prevent overpressure.
Pressure monitoring is particularly important when infusing the
cardioplegic solution since overpressure can damage the blood and
coronary vessels and can increase oxygen demand by distending the
heart. As mentioned above, the aortic occlusion device 2, coronary
sinus catheter 4 and venting catheter 6 all include lumens for
pressure monitoring. A pressure monitor 58 also measures the
delivery pressure of the cardioplege solution. The system may also
include pressure alarms (not shown) which provide visual or audible
signals when high or low pressure limits are reached.
[0036] The endovascular cardiopulmonary bypass system described
above withdraws blood from the patient through the venous cannula
8, venting catheter 6 and aortic occlusion device 2. The venous
cannula 8 and venting catheter 6 are generally withdrawing blood
throughout the bypass procedure while venting through the aortic
occlusion device 2 is intermittent. In many conventional perfusion
circuits, a number of pumps, typically roller pumps, would be used
to accomplish these tasks. In accordance with the present
invention, a single pump 60, preferably a centrifugal pump, is used
to perform at least two, and preferably all three, of these tasks.
It is preferred to use a centrifugal pump rather than a roller pump
since roller pumps are positive displacement pumps which can create
dangerously high negative and positive pressures. If a roller pump
is used, it is preferred to provide a pressure relief valve or a
pressure alarm to prevent overpressure. Another advantage of using
the single pump 60 is ease of operation since the user must
concentrate on only one pump rather than three or more. A pump
controller 61 is used to control the pump. Preferred pumps include
the Delphin by Sarns, the Lifestream by Bard, and the Biomedicus by
Medtronic.
[0037] The amount of blood being withdrawn through the catheters 2,
6 and cannula 8 is regulated by valves 62, 64, 66 on a manifold 68.
The manifold 68 receives blood through a venous line 70 from the
venous cannula 8, a line 72 from the venting catheter 6, and a vent
line 74 from the aortic occlusion device 2. The vent line 74
extends from the second branch 23 of the aortic occlusion device 2
which is fluidly coupled to the first lumen 14. The valves 62, 64,
66 regulate flows through the aortic occlusion device 2, venous
cannula 8 and venting catheter 6, respectively. The manifold 68 is
preferably provided together with the various lines and catheters
already connected together in a sterilized package. The lines 70,
72, 74 all merge into a common line 76 which has a connector 78 for
connecting to a pump inlet 80. Thus, an advantage of the present
system is that only one connection is required to couple the
catheters and cannula to the pump inlet 80 after the catheters and
cannulae are removed from the sterilized packaging. The present
invention provides clear advantages over conventional perfusion
circuits by eliminating the number of connections between
catheters, cannulae and the various pumps thereby reducing the
set-up time.
[0038] After passing through the pump 60, blood passes through a
pump outlet 82 and into an arterial line 84. The arterial line 84
passes through an oxygentor/heat exchanger 86, which is preferably
a membrane-type oxygenator/heat exchanger, and through a
filter/bubble trap 88 and is returned to the patient through the
arterial cannula 10. Preferred oxygenator/heat exchangers 86
include the Affinity by Avecor and the Maxima by Medtronic. The
filter/bubble trap 88 may be dispensed with if the oxygenator/heat
exchanger 86 is capable of performing the functions of the
filter/bubble trap 88. If a separate filter/bubble trap 88 is used
preferred filter/bubble traps include the H-690 by Bard and the
AF1040D by Baxter.
[0039] Another advantage of the present system is that the system
is closed and does not have an air/blood contact surface which
generally occurs when using open cardiotomy reservoirs. Reducing or
eliminating air/blood contact advantageously reduces complement
activation and other humoral mediated response mechanisms. Another
benefit of the present invention is a reduced priming volume as
compared to conventional systems having open cardiotomy reservoirs.
A reduced priming volume will reduce hemodilution and will result
in higher hematocrits and, thus, more oxygen carrying capacity and
buffering capability. A reduction in blood clotting factor dilution
may also reduce bleeding complications.
[0040] Fluctuations in the volume of blood handled by the perfusion
system are accommodated with a blood storage element 90. When a
patient is on cardiopulmonary bypass, the volume of blood in the
extracorporeal circuit may increase or decrease throughout the
procedure. For example, blood in the circuit may be lost to field
suction or blood may be added to the circuit when it is desired to
reduce the blood volume in the patient. The blood storage element
90 provides the perfusionist with the flexibility to change the
blood volume in the perfusion circuit for these and other purposes.
The blood storage element 90 may be any type of storage element 90
and is preferably a collapsible bag such as the BMR 1900 by
Baxter.
[0041] The blood storage element 90 is preferably configured in
parallel with the pump 60, however, it may also be configured in
series with the pump 60. Valves 92, 94 and valve 96, which is
preferably mounted to the manifold 68, regulate flow through the
blood storage element 90. Although valves 92, 94, 96 are preferred,
clamps may also be used instead of valves, however, valves 92, 94,
96 are preferred so that the flow rate into and out of the blood
storage element 90 may be regulated. The valves 92, 94, 96 are
particularly useful for providing a low, continuous flow through
the blood storage element to minimize clotting of stagnant blood. A
syringe 98 filled with heparin may also provided to reduce clotting
in the blood storage element 90. Furthermore, the entire perfusion
circuit and all of the catheters and cannulae disclosed herein may
be coated with a biocompatible coating, such as Duraflo II by
Baxter or Cameda by Medtronic, to reduce clotting and damage to the
blood.
[0042] A field suction device 100, for clearing the surgical field
of blood, is coupled to a conventional cardiotomy reservoir 102. An
IV bag 104 is also coupled to the cardiotomy reservoir 102 and a
regulated wall vacuum 106 is used to draw fluid into the cardiotomy
reservoir 102. A make-up line 108 leads from the cardiotomy
resesrvoir 102 to the common line 76 and is used to draw blood into
the perfusion system if required. Another source of blood 110 and a
filter 111 are coupled to the common line 76 to add blood to the
perfusion circuit, if required, or to prime the system.
[0043] A bridge line 112 extends between the arterial line 84 and
venous line 70 for recirculating blood through the perfusion
circuit and bypassing the patient. Clamps 114, 116 are closed to
isolate the patient from the perfusion circuit and clamp 118 is
opened to isolate the patient and recirculate blood in the
perfusion circuit. The bridge line 112 is particularly useful in
removing air from the perfusion circuit. If air is introduced in
the circuit, clamps 114, 116 are closed, thereby isolating the
patient from the circuit, and clamp 118 is opened to permit
circulation of blood in the perfusion circuit. Blood is then
circulated through the circuit until the air is removed through the
oxygenator/heat exchanger 86 and bubble trap/filter 88. Clamp 118
may also have a partially open position so that a small flow of
blood passes through the clamp 118 to reduce clotting of stagnant
blood in the bridge line 112.
[0044] Referring to FIG. 11, another preferred bypass circuit is
shown with like reference numerals referring to like structures.
The bypass circuit has the venting catheter 6A extending through
the venous cannula 8A, as described above, which advantageously
reduces the number of openings in the patient's vascular
system.
[0045] While the above is a preferred description of the invention,
various alternatives, modifications and equivalents may be used
without departing from the scope of the invention. For example, the
occluding members can be an expandable member other than a balloon,
the blood storage element and the bridge line may be dispensed
with, and the access sites for the various catheters and cannulae
may be from any other suitable vein or artery. Furthermore, the
term "fluidly coupled" as used herein does not require a direct
connection but, rather, a fluid communication between elements
which may be through pipes, hoses, filters, valve and the like.
Therefore, the above description should not be taken as limiting
the scope of the invention which is defined by the claims.
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