U.S. patent application number 11/000262 was filed with the patent office on 2005-05-05 for method and system for monitoring and controlling systemic and pulmonary circulation during a medical procedure.
This patent application is currently assigned to Medtronic, Inc.. Invention is credited to Hill, Michael R.S., Jahns, Scott E., Keogh, James R..
Application Number | 20050096707 11/000262 |
Document ID | / |
Family ID | 29420818 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050096707 |
Kind Code |
A1 |
Hill, Michael R.S. ; et
al. |
May 5, 2005 |
Method and system for monitoring and controlling systemic and
pulmonary circulation during a medical procedure
Abstract
A method of performing a medical procedure, such as surgery, is
provided. The system comprises a sensor to sense a biological
characteristic, such as a chemical, physical or physiological
characteristic of a bodily tissue or fluid. The method also
comprises a nerve stimulator in communication with the sensor to
inhibit beating of a heart when the sensor senses the biological
characteristic at a first value; and a cardiac stimulator in
communication with the sensor to stimulate beating of the heart
when the sensor senses the biological characteristic at a second
value.
Inventors: |
Hill, Michael R.S.;
(Minneapolis, MN) ; Jahns, Scott E.; (Hudson,
WI) ; Keogh, James R.; (Maplewood, MN) |
Correspondence
Address: |
JEFFREY HOHENSHELL
Medtronic, Inc.
Cardiac Surgery HQ
7601 Northland Drive
Brooklyn Park
MN
55428
US
|
Assignee: |
Medtronic, Inc.
|
Family ID: |
29420818 |
Appl. No.: |
11/000262 |
Filed: |
November 30, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11000262 |
Nov 30, 2004 |
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10421459 |
Apr 23, 2003 |
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10421459 |
Apr 23, 2003 |
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09669961 |
Sep 26, 2000 |
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Current U.S.
Class: |
607/17 |
Current CPC
Class: |
A61N 1/36114 20130101;
A61N 1/385 20130101 |
Class at
Publication: |
607/017 |
International
Class: |
A61N 001/365 |
Claims
1-8. (canceled)
9. A method for controlling a heart beat during a medical
procedure, comprising: sensing a first gas level in a body;
stimulating a first nerve to inhibit beating of a heart; performing
at least one step of the medical procedure; sensing a second gas
level while performing the medical procedure; stopping stimulation
of the first nerve to allow beating of the heart when the second
gas level is less than the initial gas level.
10. The method of claim 9 wherein the gas level is sensed for at
least one of the characteristics selected from the group consisting
of presence of oxygen, concentration of oxygen, presence of carbon
dioxide, and concentration of carbon dioxide.
11. The method of claim 9 further comprising stimulating the heart
with a cardiac stimulator to cause beating of the heart when the
second gas level is less than the first gas level.
12. The method of claim 9 wherein the first gas level and second
gas level are sensed in cerebral blood flow.
13. The method of claim 9 further comprising providing an alert
signal when the second value is less than the first value.
14. The method of claim 12 wherein the alert signal is selected
from the group consisting of: a visual signal, a flashing light, an
audible signal, and a beeping tone.
15. The method of claim 9 wherein the medical procedure is started
after sensing the first gas level, and wherein the second gas level
is sensed during the medical procedure.
16. A method for performing a medical procedure, comprising:
sensing a characteristic of a bodily tissue or fluid via a sensor
at a first value; sending a first signal related to the sensed
characteristic at a first value; modifying the beating of a heart
via a nerve stimulator in response to the first signal; performing
at least one step of the medical procedure; sensing the
characteristic via the sensor at a second value; sending a second
signal related to the sensed characteristic at a second value; and
modifying the beating of the heart via a cardiac stimulator in
response to the second signal.
17. The method of claim 16 wherein modifying the beating of the
heart via a nerve stimulator is performed automatically.
18. The method of claim 16 wherein modifying the beating of the
heart via a nerve stimulator is performed manually.
19. The method of claim 16 wherein modifying the beating of the
heart via a cardiac stimulator is performed automatically.
20. The method of claim 16 wherein modifying the beating of the
heart via a cardiac stimulator is performed manually.
21. The method of claim 16 further comprising the delivery of a
drug during the medical procedure.
22. The method of claim 21 wherein the drug is delivered via a drug
delivery means.
23. The method of claim 22 wherein the drug delivery means is
selected from the group consisting of a spray, a cream, an
ointment, a medicament, a pill, a patch, a catheter, a cannula, a
needle and syringe, a pump, and an iontophoretic drug delivery
device.
24. The method of claim 21 wherein the drug is selected from the
group consisting of a beta-blocker, a cholinergic agent, a
cholinesterase inhibitor, a calcium channel blocker, a sodium
channel blocker, a potassium channel agent, adenosine, an adenosine
receptor agonist, an adenosine deaminase inhibitor, dipyridamole, a
monoamine oxidase inhibitor, digoxin, digitalis, lignocaine, a
bradykinin agent, a serotoninergic agonist, an antiarrythmic agent,
a cardiac glycoside, a local anesthetic, atropine, a calcium
solution, an agent that promotes heart rate, an agent that promotes
heart contractions, dopamine, a catecholamine, an inotrope
glucagon, a hormone, forskolin, epinephrine, norepinephrine,
thyroid hormone, a phosphodiesterase inhibitor, prostacyclin,
prostaglandin and a methylxanthine.
25. The method of claim 21 wherein the drug is naturally occurring
or chemically synthesized.
26. The method of claim 16 wherein the nerve stimulator modifies
the beating of the heart by stimulating a vagal nerve.
27. The method of claim 16 wherein the nerve stimulator modifies
the beating of the heart by stimulating a carotid sinus nerve.
28. The method of claim 16 wherein the nerve stimulator modifies
the beating of the heart by stimulating a fat pad.
29. The method of claim 16 wherein the bodily fluid is blood.
30. The method of claim 16 wherein the bodily tissue is cardiac
tissue.
31. The method of claim 16 wherein the bodily tissue is a
nerve.
32. The method of claim 16 wherein the characteristic of a bodily
tissue or fluid is a chemical characteristic.
33. The method of claim 16 wherein the characteristic of a bodily
tissue or fluid is a physical characteristic.
34. The method of claim 16 wherein the characteristic of a bodily
tissue or fluid is a physiological characteristic.
35. The method of claim 16 wherein the characteristic of a bodily
tissue or fluid is a fluid flow characteristic.
36. The method of claim 16 wherein the characteristic of a bodily
tissue or fluid is a pressure characteristic.
37. The method of claim 16 wherein the characteristic of a bodily
tissue or fluid is a temperature characteristic.
38. The method of claim 16 wherein the characteristic of a bodily
tissue or fluid is an electrical characteristic.
39. The method of claim 16 wherein the characteristic of a bodily
tissue or fluid is a chemical concentration.
40. The method of claim 16 wherein the characteristic of a bodily
tissue or fluid is a protein or peptide.
41. The method of claim 16 wherein the characteristic of a bodily
tissue or fluid is a component of a metabolic process.
42. The method of claim 16 wherein the characteristic of a bodily
tissue or fluid is a gas.
43. The method of claim 42 wherein the gas is oxygen.
44. The method of claim 42 wherein the gas is carbon dioxide.
45. The method of claim 16 wherein the sensor is selected from the
group consisting of an imaging system, an electrical sensor, a
chemical sensor, an electromagnetic interference sensor, an
electrochemical sensor, a pressure sensor, a sound wave sensor, a
magnetic sensor, an ultraviolet sensor, a visible light sensor, an
infrared sensor, a radiation sensor, a flow sensor, a temperature
sensor, a gas sensor, an optical sensor, a pH sensor, a
potentiometric sensor, a fluorescence sensor and a biosensor.
46. The method of claim 16 wherein the nerve stimulator comprises
one or more electrodes.
47. The method of claim 46 wherein the electrodes are selected from
the group consisting of nerve stimulation electrodes, endotracheal
electrodes, endoesophageal electrodes, intravascular electrodes,
transcutaneous electrodes, intracutaneous electrodes, balloon-type
electrodes, basket-type electrodes, umbrella-type electrodes,
tape-type electrodes, suction-type electrodes, screw-type
electrodes, barb-type electrodes, bipolar electrodes, monopolar
electrodes, metal electrodes, wire electrodes, patch electrodes,
cuff electrodes, clip electrodes, needle electrodes and probe
electrodes.
48. The method of claim 16 wherein the cardiac stimulator comprises
one or more electrodes.
49. The method of claim 48 wherein the electrodes are selected from
the group consisting of cardiac stimulation electrodes, clip
electrodes, needle electrodes, probe electrodes, pacing electrodes,
epicardial electrodes, patch electrodes, intravascular electrodes,
balloon-type electrodes, basket-type electrodes, tape-type
electrodes, umbrella-type electrodes, suction-type electrodes,
endotracheal electrodes, endoesophageal electrodes, transcutaneous
electrodes, intracutaneous electrodes, screw-type electrodes,
barb-type electrodes, bipolar electrodes, monopolar electrodes,
metal electrodes, wire electrodes and cuff electrodes.
50. The method of claim 16 further comprising controlling a
patients breathing via a breathing regulator.
51. The method of claim 50 wherein the breathing regulator
stimulates a phrenic nerve.
52. The method of claim 50 wherein the breathing regulator controls
a respirator.
53. The method of claim 50 wherein the breathing regulator
comprises one or more electrodes.
54. The method of claim 53 wherein the electrodes are selected from
the group consisting of nerve stimulation electrodes, endotracheal
electrodes, endoesophageal electrodes, intravascular electrodes,
transcutaneous electrodes, intracutaneous electrodes, balloon-type
electrodes, basket-type electrodes, umbrella-type electrodes,
suction-type electrodes, screw-type electrodes, tape-type
electrodes, barb-type electrodes, bipolar electrodes, monopolar
electrodes, metal electrodes, wire electrodes, patch electrodes,
cuff electrodes, clip electrodes, needle electrodes and probe
electrodes.
55. The method of claim 16 wherein the medical procedure is
selected from the group consisting of a surgical procedure, a
non-surgical procedure, a fluoroscopic procedure, a cardiac
procedure, a vascular procedure, a neurosurgical procedure, an
electrophysiology procedure, a diagnostic procedure, a therapeutic
procedure, an ablation procedure, an endovascular procedure, a
liver procedure, a spleen procedure, a pulmonary procedure, an
aneurysm repair, an imaging procedure, a CAT scan procedure, a MRI
procedure, a pharmacological therapy, a drug delivery procedure, a
biological delivery procedure, a genetic therapy, a cellular
therapy, a cancer therapy, a radiation therapy, a transplantation
procedure, a coronary angioplasty procedure, a stent delivery
procedure, an atherectomy procedure, a procedure that requires
precise control of cardiac motion, a procedure that requires
precise control of bleeding, a non-invasive procedure, a minimally
invasive procedure, an invasive procedure, a port-access procedure,
an endoscopic procedure, a sternotomy procedure, a thoracotomy
procedure and a robotic procedure.
56. A method for performing a medical procedure, comprising:
sensing a first level of a biological characteristic in a body;
stimulating a nerve to inhibit beating of a heart; performing at
least one step of the medical procedure; sensing a second level of
the biological characteristic while performing the medical
procedure; stopping stimulation of the nerve to allow beating of
the heart when the second level differs from the first level by a
selective amount.
57. The method of claim 56 wherein the biological characteristic is
a chemical characteristic.
58. The method of claim 56 wherein the biological characteristic is
a physical characteristic.
59. The method of claim 56 wherein the biological characteristic is
a physiological characteristic.
60. The method of claim 56 wherein the biological characteristic is
a fluid flow characteristic.
61. The method of claim 56 wherein the biological characteristic is
a pressure characteristic.
62. The method of claim 56 wherein the biological characteristic is
a temperature characteristic.
63. The method of claim 56 wherein the biological characteristic is
an electrical characteristic.
64. The method of claim 56 wherein the biological characteristic is
a chemical concentration.
65. The method of claim 56 wherein the biological characteristic is
a protein or peptide.
66. The method of claim 56 wherein the biological characteristic is
a component of a metabolic process.
67. The method of claim 56 wherein the biological characteristic is
a gas.
Description
PRIORITY
[0001] Applicants claim priority to co-pending U.S. patent
application Ser. No. 09/669,961 filed Sep. 26, 2000.
FIELD OF THE INVENTION
[0002] This invention relates to methods and systems for performing
a medical procedure, especially procedures during which it is
necessary to adjust the beating of the heart in order to allow the
medical procedure to be performed on the heart or another organ.
More particularly, this invention relates to methods and systems
for monitoring and controlling one or more physiological and/or
chemical parameters of a fluid such as blood or oxygen in the
systemic and/or pulmonary circulatory systems during such a medical
procedure.
BACKGROUND OF THE INVENTION
[0003] The current leading cause of death in the United States is
coronary artery disease in which the coronary arteries are blocked
by atherosclerotic plaques or deposits of fat. The typical
treatment to relieve a partially or fully blocked coronary artery
is coronary artery bypass graph (CABG) surgery.
[0004] CABG surgery, also known as "heart bypass" surgery,
generally entails using a graph to bypass the coronary obstruction.
The procedure is generally lengthy, traumatic and subject to
patient risks. Among the risk factors involved is the use of a
cardiopulmonary bypass (CPB) circuit, also known as a "heart-lung
machine", to pump blood and oxygenate the blood so that the
patients heart may be stopped during the surgery.
[0005] Conventional CABG procedures are typically conducted on a
stopped heart while the patient is on a (CPB) circuit. A stopped
heart and a CPB circuit enables a surgeon to work in a bloodless,
still operative field. However, there a number of problems
associated with CABG procedures performed while on CPB including
the initiation of a systemic inflammatory response due to
interactions of blood elements with the artificial material
surfaces of the CPB circuit and global myocardial ischemia due to
cardioplegic cardiac arrest. For these reasons, avoiding the use of
CPB or cardioplegic cardiac arrest may help minimize post-operative
complications.
[0006] One method, as disclosed in U.S. Pat. No. 5,651,378 to
Matheny and Taylor and in U.S. Pat. No. 5,913,876 to Taylor et al.,
for facilitating coronary bypass surgery on a beating heart and
thereby avoid the use of CPB and cardioplegic cardiac arrest
includes stimulating the vagal nerve electrically in order to
temporarily stop or substantially reduce the beating of the heart.
This may be followed by pacing the heart to start its beating.
[0007] Another method, as disclosed in two published PCT
applications, WO 99/09971 and WO 99/09973, both to Puskas, involves
stopping the beating of the heart during coronary bypass surgery
using electrical stimulation of the vagal nerve in combination with
administration of drugs. Another method, as disclosed in U.S. Pat.
No. 6,060,454 to Duhaylongsod, involves stopping the beating of the
heart during coronary bypass surgery via the local delivery of
drugs to the heart.
[0008] Although it is desirable to stop the heart for a period of
time in order to allow the surgeon to accomplish a required task
without interference from heart movement, i.e. a motionless
operative field, it is undesirable to have the heart stopped for
too long a period of time since the body needs, among other things,
constant supply of oxygen. In fact it is particularly important to
maintain sufficient blood flow, and therefore oxygen flow, to the
brain. A system for sensing biological parameters, such as the
amount of blood flow or oxygen flow to the brain, could help
determine whether these parameters are sufficient during a medical
procedure.
[0009] It would be desirable to provide a method for controllably
stopping or slowing the heart intermittently in order to control
blood flow in the systemic and/or pulmonary circulatory systems
during a medical procedure.
[0010] Additionally, it would be desirable to provide a means for
monitoring one or more chemical, physical or physiological
characteristics of a bodily tissue or fluid during the
procedure.
[0011] Additionally, it would be desirable to provide a method for
controllably stopping or slowing the heart intermittently for
diagnostic or therapeutic purposes.
[0012] Additionally, it would, be desirable to provide a method for
controllably stopping or slowing the heart intermittently in order
to perform surgery on the heart or another organ.
SUMMARY OF THE INVENTION
[0013] One aspect of the present invention provides a system for
performing a medical procedure. The system includes a sensor to
sense a biological characteristic, a nerve stimulator to inhibit
beating of a heart when the sensor senses the biological
characteristic at a first value and a cardiac stimulator to
stimulate beating of the heart when the sensor senses the
biological characteristic at a second value.
[0014] The biological characteristic maybe a chemical
characteristic of a tissue, a chemical characteristic of a fluid, a
physical characteristic of a tissue, a physical characteristic of a
fluid, a physiological characteristic of a tissue, and a
physiological characteristic of a fluid. The biological
characteristic may be a characteristic of a body component such as
the blood, blood, cardiac tissue, or a nerve. The biological
characteristic may be fluid flow, fluid pressure, mechanical
pressure, temperature, electrical current, chemical concentration,
presence of a protein, concentration of a protein, presence of a
peptide, concentration of a peptide, a metabolic process, presence
of a gas, concentration of a gas, presence of oxygen, concentration
of oxygen, presence of carbon dioxide, concentration of carbon
dioxide.
[0015] The system may also include drug delivery means such as a
spray, a cream, an ointment, a medicament, a pill, a patch, a
catheter, a cannula, a needle and syringe, a pump, and an
iontophoretic drug delivery device to deliver at least one drug
during the procedure. The drug may be a beta-blocker, a cholinergic
agent, a cholinesterase inhibitor, a calcium channel blocker, a
sodium, channel blocker, a potassium channel agent, adenosine, an
adenosine, receptor agonist, an adenosine deaminase inhibitor,
dipyridamole, a monoamine oxidase inhibitor, digoxin, digitalis,
lignocaine, a bradykinin agent, a serotoninergic agonist, an
antiarrythmic agent, a cardiac glycoside, a local anesthetic,
atropine, a calcium solution, an agent that promotes heart rate, an
agent that promotes heart contractions, dopamine, a catecholamine,
an inotrope glucagon, a hormoone, forskolin, epinephrine,
norepinephrine, thyroid hormone, a phosphodiesterase inhibitor
prostacyclin, prostagiandin and a methylxanthine. The drug may be
naturally occurring or chemically syrithesized.
[0016] The nerve stimulator may stimulate a nerve such as a vagal
nerve, a carotid sinus nerve, a fat pad. The nerve stimulation may
be stopped automatically when the sensor senses the biblogical
characteristic at the second value. Cardiac stimulation may begin
automatically when the sensor senses the biological characteristic
at the second value. The nerve stimulator may be, for example, one
or more electrodes, such as nerve stimulation electrodes,
endotracheal electrodes, endoesophageal electrodes, intravascular
electrodes, transcutaneous electrodes, intracutaneous electrodes,
balloon-type electrodes, basket-type electrodes, umbrella-type
electrodes, tape-type electrodes, suction-type electrodes,
screw-type electrodes, barb-type electrodes, bipolar electrodes,
monopolar electrodes, metal electrodes, wire electrodes, patch
electrodes, cuff electrodes, clip electrodes, needle electrodes and
probe electrodes.
[0017] The sensor may be an imaging system, an electrical sensor, a
chemical sensor, an electromagnetic interference sensor, an
electrochemical sensor, a pressure sensor, a sound wave sensor, a
magnetic sensor, an ultraviolet sensor, a visible light sensor, an
infrared sensor, a radiation sensor, a flow sensor, a temperature
sensor, a gas sensor, an optical sensor, a pH sensor, a
potentiometric sensor, a fluorescence sensor and a biosensor.
[0018] The cardiac stimulator may be, for example, one or more
electrodes, such as cardiac stimulation electrodes, clip
electrodes, needle electrodes, probe electrodes, pacing electrodes,
epicardial electrodes, patch electrode intravascular electrodes,
balloon-type electrodes basket-type electrodes, tape-type
electrodes, umbrella type electrodes, suction-type electrodes,
endotracheal electrodes, endoesophageal electrodes, transcutaneous
electrodes, intracutaneous electrodes, screw-type electrodes,
barb-type electrodes, bipolar electrodes, monopolar electrodes,
metal electrodes, wire electrodes and cuff electrodes.
[0019] The system may also include a breathing regulator, which may
control a respirator. The breathing regulator may stimulate a
phrenic nerve. The breathing regulator may be, for example, one or
more electrodes such as nerve stimulation electrodes, endotracheal
electrodes, endoesophageal electrodes, intravascular electrodes,
transcutaneous electrodes, intracutaneous electrodes, balloon-type
electrodes, basket-type electrodes, umbrella-type electrodes,
suction-type electrodes, screw-type electrodes, tape-type
electrodes, barb-type electrodes, bipolar electrodes, monopolar
electrodes, metal electrodes, wire-electrodes, patch electrodes,
cuff electrodes, clip electrodes, needle electrodes and probe
electrodes.
[0020] The medical procedure may be a surgical procedure, a
non-surgical procedures, a fluoroscopic procedure, a cardiac
procedure, a vascular procedure, a neurosurgical procedure, an
electrophysiological procedure, a diagnostic procedure, a
therapeutic procedure, an ablation procedure, an endovascular
procedure, a liver procedure, a spleen procedure, a pulmonary
procedure, an aneurysm repair, an imaging procedure, a CAT scan
procedure, a MRI procedure, a pharmacological therapy, a drug
delivery procedure, a biological delivery procedure, a genetic
therapy, a cellular therapy, a cancer therapy, a radiation therapy,
a transplantation procedure, a coronary angioplasty procedure, a
stent delivery procedure, an atherectomy procedure, a procedure
that requires precise control of cardiac motion, a procedure that
requires precise control of bleeding, a non-invasive procedure, a
minimally invasive procedure, an invasive procedure, a port-access
procedure, an endoscopic procedure, a sternotomy procedure, a
thoracotomy procedure and a robotic procedure.
[0021] Another aspect of the present invention provides a method
for performing a medical procedure. A biological characteristic is
sensed at a first value and a first signal related to the sensed
biological characteristic is sent. Beating of a heart is inhibited
in response to the first signal. The medical procedure is then
performed. The biological characteristic is then sensed at a second
value and a second signal related to the sensed biological
characteristic at the second value is sent. Beating of the heart is
stimulated in response to the second signal.
[0022] Beating of the heart may be inhibited automatically in
response to the first signal. Beating of the heart may be
stimulated automatically in response to the second signal. At last
one drug may be delivered during the medical procedure. A nerve may
be stimulated to inhibit beating of the heart. Breathing may be
stopped while beating of the heart is inhibited. Breathing may be
stopped automatically.
[0023] The biological characteristic may be a characteristic of
blood, a characteristic of cardiac tissue, a characteristic of a
nerve, a fluid flow characteristic, a pressure characteristic, a
temperature characteristic, an electrical characteristic, a
chemical concentration, a presence of a protein, a concentration of
a protein, a presence of a peptide, a component of a metabolic
process, a presence of a gas, a concentration of a gas, a presence
of oxygen, a concentration of oxygen, a presence of carbon dioxide,
a concentration of carbon dioxide, a chemical characteristic, a
physical characteristic, and a physiological characteristic.
[0024] Another aspect of the present invention provides a device
for performing a medical procedure. The device includes a
processor, a sensor to sense a biological characteristic and at
least one nerve stimulation electrode. The processor receives a
signal from the sensor and adjusts output from the nerve
stimulation electrode in response to the signal.
[0025] The sensor may be an imaging system, an electrical sensor, a
chemical sensor, an electromagnetic interference sensor, an
electrochemical sensor, a pressure sensor, a sound wave sensor, a
magnetic sensor, an ultraviolet sensor, a visible light sensor, an
infrared sensor, a radiation sensor, a flow sensor, a temperature
sensor, a gas sensor, an optical sensor, a pH sensor, a
potentiometric sensor, a fluorescence sensor and a biosensor.
[0026] The nerve stimulation electrode may be one or more
electrodes, such as endotracheal electrodes, endoesophageal
electrodes, intravascular electrodes, transcutaneous electrodes,
intracutaneous electrodes, balloon-type electrodes, basket-type
electrodes, umbrella-type electrodes, tape-type electrodes,
suction-type electrodes, screw-type electrodes, barb-type
electrodes, bipolar electrodes, monopolar electrodes, metal
electrodes, wire electrodes, patch electrodes, cuff electrodes,
clip electrodes, needle electrodes and probe electrodes.
[0027] The device may also include a cardiac stimulation electrode
to stimulate beating of the heart. The processor receives a signal
from the sensor and adjusts output from the cardiac stimulation
electrode in response to the signal. The cardiac electrode may be,
for example, one or more electrodes such as clip electrodes, needle
electrodes, probe electrodes, pacing electrodes, epicardial
electrodes, patch electrodes, intravascular electrodes,
balloon-type electrodes, basket-type electrodes, tape-type
electrodes, umbrella-type electrodes, suction-type electrodes,
endotracheal electrodes, endoesophageal electrodes, transcutaneous
electrodes, intracutaneous electrodes, screw-type electrodes,
barb-type electrodes bipolar electrodes, monopolar electrodes,
metal electrodes, wire electrodes and cuff electrodes.
[0028] The device may also include a breathing regulation electrode
for controlling breathing. The processor adjusts the output from
the breathing regulation electrode in response to the signal. The
breathing regulation electrode may be, for example, one or more
electrodes such as nerve stimulation electrodes, endotracheal
electrodes, endoesophageal electrodes, intravascular electrodes,
transcutaneous electrodes, intracutaneous electrodes, balloon-type
electrodes; basket-type electrodes, umbrella-type electrodes,
suction-type electrodes, screw-type electrodes, tape-type
electrodes, barb-type electrodes, bipolar electrodes, monopolar
electrodes, metal electrodes, wire electrodes, patch electrodes,
cuff electrodes; clip electrodes, needle electrodes and probe
electrodes.
[0029] The device may also include a drug pump for delivering at
least one drug. The processor adjusts the output of the drug. The
drug may be, for example, a beta-blocker, a cholinergic agent, a
cholinesterase inhibitor, a calcium channel blocker, a sodium
channel-blocker, a potassium channel agent, adenosine, an adenosine
receptor agonist, an adenosine deamrinase inhibitor, dipyridamole,
a monoamine oxidase inhibitor, digoxin, digitalis, lignocaine, a
bradykinin agent, a serotoninergic agonist, an antiarrythmic agent,
a cardiac glycoside, a local anesthetic, atropine, a calcium
solution, an agent that promotes heart rate, an, agent that
promotes heart contractions, dopamine, catecholamine, an inotrope
glucagon, a hormone, forskolin, epinephrine norepinephrine, thyroid
hormone, a phosphodiesterase inhibitor, prostacyclin, prostaglandin
and a methylxanthine.
[0030] The foregoing, and other, features and advantages of the
invention will become further apparent from the following detailed
description of the presently preferred embodiments, read in
conjunction with the accompanying drawings. The detailed
description and drawings are merely illustrative of the invention
rather than limiting, the scope of the invention being defined by
the appended claims in equivalence thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a schematic view of one embodiment of a system for
monitoring at least one chemical, physical or physiological
characteristic during a medical procedure in accordance with the
present invention;
[0032] FIG. 2 is a schematic view of one embodiment of a medical
device in accordance with the present invention;
[0033] FIG. 3 is a flow diagram of one embodiment of a method of
performing a medical procedure in accordance with the present
invention; and
[0034] FIG. 4 is a timeline view of one embodiment of a system for
monitoring at least one chemical, physical or physiological
characteristic during a medical procedure in accordance with the
present invention.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0035] FIG. 1 shows a schematic view of one embodiment of a system
for performing a medical procedure in accordance with the present
invention at 100. System 100 comprises a sensor 5, a nerve
stimulator 10, and a cardiac stimulator 20. System 100 may also
feature a controller 30 and a breathing regulator 40.
[0036] Sensor 5 may be any suitable blood gas sensor for measuring
the concentration or saturation of a gas in the blood stream. For
example, sensor 5 may be a sensor for measuring the concentration
or saturation of oxygen or carbon dioxide in the blood.
Alternatively, sensor 5 may be any suitable sensor for measuring
blood pressure or flow, for example a Doppler ultrasound sensor
system, or a sensor for measuring hematocrit (HCT) levels.
[0037] Alternatively sensor 5 may be a biosensor, for example,
comprising an Immobilized biocatalyst, enzyme, immunoglobulin,
bacterial, mammalian or plant tissue, cell and/or subcellular
fraction of a cell. For example, the tip of a biosensor may
comprise a mitochondrial fraction of a cell, thereby providing the
sensor with a specific biocatalytic activity.
[0038] Sensor 5 may be based on potentiometric technology or fiber
optic technology. For example, the sensor may comprise a
potentiometric or fiber optic transducer. An optical sensor may be
based on either an absorbance or fluorescence measurement and may
include an UV, a visible or an IR light source.
[0039] Sensor 5 may be used to detect naturally detectable
properties representative of one or more characteristics, e.g.,
chemical, physical or physiological, of a patients bodily tissues
or fluids. For example, naturally detectable properties of patients
bodily tissues or fluids may include pH, fluid, flow, electrical
current, temperature pressure, components of metabolic processes,
chemical concentrations, for example, the absence or presence of
specific peptides, proteins, enzymes, gases, ions, etc.
[0040] Sensor 5 may include one or more imaging systems, camera
systems operating in UV, visible, or IR range; electrical sensors;
voltage sensors; current sensors; piezoelectric sensors;
electromagnetic interference (EMI) sensors; photographic plates,
polymer-metal sensors; charge-coupled devices (CCDs); photo diode
arrays; chemical sensors, electrochemical sensors; pressure
sensors, sound wave sensors; magnetic sensors; UV light sensors;
visible light sensors; IR light sensors; radiation sensors; flow
sensors; temperature sensors; or any other appropriate or suitable
sensor. Sensor 5 may be a continuous, in-line monitoring system or
it may be attached to an extracorporeal device.
[0041] In one embodiment of the invention, sensor 5 may be a
cerebral blood flow sensor, in which case, the sensor may be placed
in any suitable manner for sensing cerebral blood flow. For
example, sensor 5 may be inserted between the skull and the dura of
the brain. Alternatively, sensor 5 may be placed in the patients
neck. For example, at least a portion of sensor 5 may be placed in
an artery, such as the carotid artery. Such a placement would allow
measurement of blood as it flows to the brain. Alternatively,
sensor 5 may be placed in a vein, such as the jugular vein. This
placement would allow measurement of blood as it flows from the
brain.
[0042] In the case of blood oxygen saturation sensing, a certain
level of oxygen generally remains in the blood as it flows from the
brain. This level may be established by measuring the patients
oxygen prior to surgery. If blood measured by sensor 5 in the vein
has oxygen below the established level, the brain is consuming all
or most of the oxygen flowing to it and probably requires
additional oxygen. Other suitable placements of sensor 5 may be
possible. Sensor 5 may be used to alert a surgeon to changes in the
patients circulatory, system.
[0043] System 100 may also include a nerve stimulator 10. In one
embodiment, the nerve stimulator 10 may be used to electrically
manipulate cardiac rhythm by stimulating the vagus nerve. This
vagal stimulation may produce asystole (slowing or stopping of the
hearts beating.) Once this induced asystole is stopped, i.e. once
the vagal stimulation is stopped, the heart may be allowed to
return to its usual cardiac rhythm. Alternatively, the heart may be
paced with an electrical pacing system, thereby maintaining a
normal cardiaic output. Vagal stimulation, alone or in combination
with electrical pacing, may be used selectively and intermittently
to allow a surgeon to perform a medical procedure during
intermittent periods of asystole.
[0044] It is known that stimulation of the vagus nerve can reduce
the sinus rate, as well as prolong AV conduction time or if
stimulation energies are high enough, induce AV node block. Use of
vagal nerve stimulation to treat supraventricular arrhythmias and
angina pectoris is disclosed in the article "Vagal Tuning" by
Bilgutay et al., Journal of Thoracic and Cardiovascular Surgery,
Vol. 56, No. 1, July, 1968, pp. 71-82. It is also known that
stimulation of the carotid sinus nerve produces a similar result,
as disclosed in the article "Carotid Sinus Nerve Stimulation in the
Treatment of Angina. Pectoris and Supraventricular Tachycardia" by
Braunwald et al., published in California Medicine, Vol. 112, pp.
41-50, March, 1970.
[0045] As set forth in "Functional Anatomy of the Cardiac Efferent
Innervation" by Randall et al., in Neurocardiology, edited by
Kulbertus et al, Futura Publishing Co., 1988, direct surgical
excision of the fat pad associated with the SA node affects the
functioning of the SA node without Significantly affecting the AV
node. Similarly, excision of the fat pad associated with the AV
node affects functioning of the AV node without significantly
affecting the SA node.
[0046] As set forth in the article "Parasympathetic Postganglionic
Pathways to the Sinoatrial Node", Bluemel et al., Am. J. Physiol.
259, (Heart Circ. Physiol. 28). H1504-H1511, 1990, stimulation of
the fat pad associated with the SA node results in slowing of the
sinus rate without the accompanying prolongation of AV conduction
time which normally results from vagal nerve stimulation. The
article also indicates that stimulation of the fat pad associated
with the AV node is believed to produce corresponding effects
limited to the AV node, i.e., extension of the AV conduction time
without concurrent slowing of the sinus rate.
[0047] As set forth in the article "Neural Effects on Sinus Rate
and Atrial Ventricular Conduction Produced by Electrical
Stimulation From a Transvenous Electrode Catheter in the Canine
Right Pulmonary Artery" by Cooper et al., published in Circulation
Research, Vol. 46, No. 1, January, 1980, pp. 48-57, the fat pads
associated with both the AV node and the SA node may be stimulated
by means of electrodes located in the right pulmonary artery. The
results obtained include-both a depression of the sinus rate and a
prolongation of the AV conduction time in response to continuous
stimulation at 2-80 Hz at up to 50 ma.
[0048] Generally in healthy individuals, the SA node functions as
the pacemaker. Normal heart rhythm associated with the SA node is
typically referred to as sinus rhythm. When the SA node fails, the
AV node generally takes over creating a heart rate of approximately
35 to 60 beats per minute. Heart rhythm associated with the AV node
is typically referred to as nodal rhythm. When the AV node itself
is blocked or injured, a new seven slower pacemaker site may form
at the junction of the AV node and the His bundle. Heart rhythm
associated with this junction is typically referred to as
junctional, escape rhythm. When this junction site is inhibited,
the Purkinje fibers in the His bundle or below may act as a
pacemaker creating a heart rate of approximately 30 beats per
minute. Heart rhythm associated with the Purkinje fibers is
typically referred to as idioventricular rhythm.
[0049] In one embodiment of the present invention, nerve stimulator
10 may be used to electrically manipulate cardiac rhythm by
stimulating the carotid sinus nerve, the fat pad associated with
the SA node, the fat pad associated with the AV node, the junction
of the AV node and the His bundle and/or the Purkinje fibers.
[0050] In one embodiment of the present invention, nerve stimulator
10 is used alone or in combination with other heart rate inhibiting
agents to temporarily stop or slow the beating heart, thereby
eliminating or reducing heart motion and/or blood flow during a
medical procedure. For example, the present invention may be used
to eliminate or reduce motion in the anastomosis field during CABG
Procedures such that a facilitated anastomosis procedure may be
performed; safely and effectively. The number of occasions that the
vagal nerve may be stimulated depends on the type of medical
procedure to be performed. Likewise, the type of medical procedure
to be performed will dictate the duration of the individual
electrical stimulations.
[0051] Nerve stimulator 10 may be powered by AC current, DC current
or it may be battery powered either by a disposable or rechargeable
battery. Nerve stimulator 10 may be configured to synchronize
activation and deactivation of breathing regulator 40 with vagal
stimulation, thereby minimizing or eliminating unwanted heart and
chest motion associated with the patients breathing. Nerve
stimulator 10 may comprise a surgeon controlled switch box. A
switch may be incorporated in or on one of the surgeons
instruments, such as surgical site retractor, or any other location
easily and quickly accessed by the surgeon for regulation of the
nerve stimulator by the surgeon. The switch may be, for example, a
hand switch, a footswitch, or a voice-activated switch comprising
voice-recognition technologies.
[0052] A visual and/or audible signal used to alert a surgeon to
the completion or resumption of vagal nerve stimulation may be
incorporated into nerve stimulator 10. For example, a beeping tone
or flashing light that increases in frequency as the nerve
stimulation period should end or begin may be used.
[0053] Nerve stimulator 10 may be slaved to cardiac stimulator 20
or cardiac stimulator 20 may be slaved to nerve-stimulator 10. For
example, the output of cardiac stimulator 20 may be off whenever
the output of nerve stimulator 10 is on. Software controlling
cardiac stimulator 20 may be designed to automatically commence
cardiac pacing if the heart does not resume beating within a
pre-determined interval after cessation of vagal nerve stimulation.
In addition, the software controlling nerve stimulator 10 may be
designed to automatically stop vagal nerve stimulation if the heart
has been stopped for to long. For example, a predetermined time
interval may be set to automatically stop vagal stimulation. In one
embodiment of the invention, if sensor 5 of the present invention
indicates that not enough blood is flowing to the brain, vagal
stimulation may be stopped, thereby allowing the heart to beat
again.
[0054] In another embodiment it may be necessary to use cardiac
stimulator 20 to actively stimulate the heart into beating again.
For example in one embodiment of the present invention, sensor 5
may indicate that not enough, blood is flowing to the brain causing
nerve stimulator 10 to be automatically turned off and cardiac
stimulator 20 to be automatically turned on. Alternatively, the
surgeon may turn on cardiac stimulator 20 to begin stimulation.
[0055] Just like nerve stimulator 10, cardiac stimulator 20 may be
intermittently stopped and, started to allows the surgeon to
perform individual steps of a medical procedure.
[0056] Cardiac stimulator 20 may be a conventional ventricular
demand pacer or dual chamber (atrial-ventricular) pacer. Cardiac
stimulator 20 may be powered by AC current, DC current or it may be
battery powered either by a disposable or re-chargeable battery.
Cardiac stimulator 20 may be configured to synchronize activation
and deactivation of breathing regulator 40 with pacing, thereby
minimizing or eliminating unwanted heart and chest motion
associated with the patients breathing.
[0057] Cardiac stimulator 20 may be any conventional pacing device
suitable for ventricular demand pacing and having leads
electrically coupled to a switch box. Cardiac stimulator 20 may be
combined in a single unit with a switch box. A switch may be
incorporated in or on one of the surgeon's instruments, such as
surgical site retractor, or any other location easily and quickly
accessed by the surgeon for regulation of the cardiac stimulator by
the surgeon. The switch may be, for example, a hand switch, a
foot-switch, or a voice-activated switch comprising
voice-recognition technologies. A single switch may be used to
regulate both cardiac stimulator 20 and nerve stimulator 10.
[0058] A visual and/or audible signal used to prepare a surgeon for
the resumption of pacing may be incorporated into cardiac
stimulator 20. For example, a beeping tone or flashing light that
increases in frequency as the pacing period ends may be used. A
single signaling method or device may be used for both cardiac
stimulator 20 and nerve stimulator 10.
[0059] Sensor 5, nerve stimulator 10 and/or cardiac stimulator 20
may be slaved to a robotic system or a robotic system may be slaved
to sensor 5, nerve stimulator 10 and/or cardiac stimulator 20.
Breathing regulator 40 and other components may also be slaved to
such a system. Computer and voice-controlled robotic systems that
position and maneuver endoscopes and/or other surgical instruments
for performing microsurgical procedures such as anastomoses through
small incisions may be used by a surgeon to perform precise and
delicate maneuvers. These robotic systems may allow a surgeon to
perform a variety of microsurgical procedures-including endoscopic
CABG. Endoscopic CABG may allow multiple occluded coronary arteries
to be bypassed without a thoracotomy or mini-thoracotomy. Heart
valve repair and replacement may also be other surgical
applications for these robotic systems. In general, robotic systems
may include head-mounted displays, which integrate 3-D
visualization of surgical anatomy and related diagnostic and
monitoring data, miniature high resolution 2-D and 3-D digital
cameras, a computer, a high power light source and a standard video
monitor.
[0060] System 100 may also include a breathing regulator 40. In one
embodiment, the breathing regulator 40 may be used to stimulate the
phrenic nerve in order to provide a diaphragmatic pacemaker.
Breathing regulator 40 may comprise one or more electrodes for
supplying electrical current to the phrenic nerve to control
breathing during vagal and/or cardiac stimulation and/or
destimulation. Electrodes used to stimulate the phrenic nerve may
be, for example, non-invasive, e.g., clips, or invasive, e.g.,
needles or probes. The application of an electrical stimulus to the
phrenic nerve may include, but is not limited to bipolar and/or
monopolar techniques. Different electrode positions are accessible
through various access openings, for example, in the cervical or
thorax regions. Nerve stimulation electrodes may be positioned
through a thoracotomy, sternotomy, endoscopically through a
percutaneous port, through a stab wound or puncture, through a
small incision, placed on the skin or in combinations thereof. The
present invention may include various electrodes, catheters and
electrode catheters suitable for phrenic nerve stimulation to
control breathing.
[0061] Phrenic nerve stimulation electrodes may be intravascular,
patch-type, balloon-type, basket-type, umbrella-type, tape-type,
cuff-type, suction-type, screwy-type, barb-type, bipolar,
monopolar, metal, wire, endotracheal, endoesophageal intravascular,
transcutaneous or intracutaneous electrodes. Guided or steerable
catheter devices comprising electrodes may be used alone- or in
combination with the nerve stimulation electrodes. For example, a
catheter comprising one or more wire, metal strips or metal foil
electrodes or electrode arrays may be used. The catheter may
comprise, for example, a balloon, which may be inflated with air or
liquid to press the electrodes firmly against a vessel wall that
lays adjacent the phrenic nerve.
[0062] Phrenic nerve stimulation electrodes may be oriented in any
fashion along the catheter device, including longitudinally or
transversely. Various techniques such as ultrasound, fluoroscopy
and echocardiography may be used to facilitate positioning of the
electrodes. If desired or necessary, avoidance of obstruction of
blood flow may be achieved with notched catheter designs or with
catheters which incorporate one or more tunnels or passageways.
[0063] In another embodiment, breathing regulator 40 may comprise a
connector, which interfaces with a patients respirator, and sends a
logic signal to activate or deactivate the respirator to control
breathing during vagal and/or cardiac stimulation and/or
destimulation.
[0064] FIG. 2 shows one embodiment of the present invention at 200.
In this embodiment, the elements named above may be combined or
connected to a control unit along with other components. Unit 200
may be used to coordinate the various elements.
[0065] Unit 200 may incorporate a controller as described above or
any suitable processor 230. For example, the processor may process
sensed blood information from sensor 205. The controller may store
and/or process such information before, during and/or after a
medical procedure. For example, the patients oxygen concentration
or blood pressure may be sensed, stored and processed prior to and
during surgery.
[0066] Unit 200 may also incorporate a nerve stimulator. For
example, FIG. 2 shows an electrode for nerve stimulation at 210.
Electrodes used to stimulate a nerve such as the vagal nerve may
be, for example, non-invasive, e.g., clips, or invasive, e.g.,
needles or probes. The application of an electrical stimulus to the
right or left vagal nerve may include, but is not limited to
bipolar and/or monopolar techniques. Different electrode positions
are accessible through various access openings, for example, in the
cervical or thorax regions. Nerve stimulation electrodes 210 may be
positioned through a thoracotomy, sternotomy, endoscopically
through a percutaneous port, through a stab wound or puncture,
through a small incision in the neck or chest, through the internal
jugular vein, the esophagus, the trachea, placed on the skin or in
combinations thereof. Electrical stimulation may be carried out on
the right vagal nerve, the left vagal nerve or to both nerves
simultaneously or sequentially. The present invention may include
various electrodes, catheters and electrode catheters suitable for
vagal nerve stimulation to temporarily stop or slow the beating
heart alone or in combination with other heart rate inhibiting
agents.
[0067] Nerve stimulation electrodes 210 may be endotracheal,
endoesophageal, intravascular, transcutaneous, intracutaneous,
patch-type, balloon-type, cuff-type; basket-type, umbrella-type,
tape-type, screw-type, barb-type, metal, wire, or suction-type
electrodes. Guided or steerable catheter devices comprising
electrodes may be used alone or in combination with the nerve
stimulation electrodes 210. For example, a catheter comprising one
or more wire, metal strips or metal foil electrodes or electrode
arrays maybe inserted into the internal jugular vein to make
electrical contact with the wall of the internal jugular vein, and
thus stimulate the vagal nerve adjacent to the internal jugular
vein. Access to the internal jugular vein may be via, for example,
the right atrium, the right atrial appendage, the inferior vena
cava or the superior vena cava. The catheter may comprise, for
example, a balloon, which may be inflated with air or liquid to
press the electrodes firmly against the vessel wall. Similar
techniques may be performed by insertion of a catheter type device
into the trachea or esophagus. Additionally tracheal tubes and
esophageal tubes comprising electrodes may be used.
[0068] Nerve stimulation electrodes 210 may be oriented in any
fashion along the catheter device, including longitudinally or
transversely. Various techniques such as ultrasound, fluoroscopy
and echocardiography may be used to facilitate positioning of the
electrodes. If desired or necessary, avoidance of obstruction of
blood flow may be achieved with notched catheter designs or with
catheters which incorporate one or more tunnels or passageways.
[0069] In one embodiment of the present invention the location of
the electrodes 210 is chosen to elicit maximum bradycardia
effectiveness while minimizing current spread to adjacent tissues
and vessels and to prevent the induction of post stimulation
tachycardia. Furthermore, a non-conductive material such as
configurations to shield them from the surrounding tissues and
vessels, while exposing their confronting edges and surfaces for
positive contact with the vagal nerve or selected tissues.
[0070] Unit 200 may also incorporate a cardiac stimulator. For
example, FIG. 2 shows a electrode for stimulation of the heart at
220. Cardiac electrodes 220 used to stimulate the heart may be, for
example, non-invasive, e.g., clips, or invasive, e.g. needles or
probes. Electrodes 220 may be positioned through a thoracotomy,
sternotomy, endoscopically through a peutaneous port, through a
stab wound or puncture, through a small incision in the chest,
placed on the chest or in combinations thereof. The present
invention may also use various electrodes, catheters and electrode
catheters and to pacing the heart, e.g., epicardial, patch-type,
intravascular, balloon-type, basket-type, umbrella-type tape-type
electrodes, suction-type, pacing electrodes, endotracheal
electrodes, endoesophageal electrodes, transcutaneous electrodes,
intracutaneous electrodes, screw-type electrodes, barb-type
electrodes, bipolar electrodes, monopolar electrodes, metal
electrodes, wire electrodes and cuff electrodes, Guided or
steerable catheter devices comprising electrodes may be used alone
or in combination with the electrodes. Controller 230 may be used
to gather information from nerve stimulation electrodes 210 and
cardiac stimulation electrodes 220. Controller 230 may also be used
to control the stimulation levels and stimulation duration from
nerve stimulation electrodes 210 and cardiac stimulation electrodes
220. Controller 230 may also gather and process information from
sensor 205. This information may be used to adjust-stimulation
levels and stimulation times from nerve stimulation electrodes 210
and cardiac stimulation electrodes 220.
[0071] Unit 200 may incorporate one or more switches to facilitate
regulation of the various components by the surgeon. One example of
such a switch is shown as foot pedal 250. The switch may also be,
for example, a hand switch, or a voice-activated switch comprising
voice-recognition technologies. The switch may be incorporated in
or on one of the surgeons instruments, such as surgical site
retractor, or any other location easily and quickly accessed by the
surgeon. Unit 200 may also include a display 260. Unit 200 may also
include other means of indicating the status of various components
to the surgeon such as a numerical display, gauges, a monitor
display or audio feedback. Unit 200 may also include one or more
visual and/or audible signals used to prepare a surgeon for the
start or stop of nerve stimulation and/or cardiac stimulation.
[0072] FIG. 3 shows a flow diagram of one embodiment of the present
invention. The patient is prepared for a medical procedure at 500.
Once the patient is prepared, the initial state of cerebral blood
circulation is measured (Block 505). Such measurements may include
for example blood flow, oxygen concentration, carbon dioxide
concentration, etc. The initial state of cerebral blood circulation
is then used as a gauge to compare with the state of cerebral blood
circulation during the procedure.
[0073] At Block 510, a nerve that controls the beating of the heart
is stimulated. Such a nerve may be for example a vagal nerve. At
Block 510, one or more of a variety of pharmacological agents or
drugs may be delivered. These drugs may produce reversible asystole
of a heart while maintaining the ability of the heart to be
electrically paced.
[0074] A variety of pharmacological agents or drugs may also be
delivered at other times during the procedure 500. These drugs may
also produce reversible asystole of a heart while maintaining the
ability of the heart to be electrically paced. Other drugs may be
administered for a variety of functions and purposes as described
below. Drugs may be delivered at any appropriate time during the
medical procedure, for example, at the beginning of the procedure,
intermittently during the procedure, continuously during the
procedure or following the procedure.
[0075] Drugs, drug formulations or compositions suitable for
administration to a patient during a medical procedure may include
a pharmaceutically acceptable carrier or solution in an appropriate
dosage. There are a number of pharmaceutically acceptable carriers
that may be used for delivery of various drugs, for example, via
direct injection, oral delivery suppository delivery, transdermal
delivery, epicardial delivery and/or inhalation delivery.
Pharmaceutically acceptable carriers include a number of solutions,
preferably sterile, for example, water, saline. Ringers solution
and/or sugar solutions such as dextrose in water or saline. Other
possible carriers that may be used include sodium citrate, citric
acid, amino acids, lactate, mannitol, maltose, glycerol, sucrose,
ammonium chloride, sodium chloride, potassium chloride, calcium
chloride, sodium lactate, and/or sodium bicarbonate. Carrier
solutions may or may not be buffered.
[0076] Drug formulations or compositions may include antioxidants
or preservatives such as ascorbic acid. They may also be in a
pharmaceutically acceptable form for parenteral administration, for
example to the cardiovascular system, or directly to the heart,
such as intracoronary infusion or injection. Drug formulations or
compositions may comprise agents that provide a synergistic effect
when administered together. A synergistic effect between two or
more drugs or agents may reduce the amount that normally is
required for therapeutic delivery of an individual drug or agent.
Two or more drugs may be administered, for example, sequentially or
simultaneously. Drugs may be administered via one or more bolus
injections and/or infusions or combinations thereof. The injections
and/or infusions may be continuous or intermittent. Drugs may be
administered, for example, systemically or locally, for example, to
the heart, to a coronary artery and/or vein, to a pulmonary artery
and/or vein, to the right atrium and/or ventricle, to the left
atrium and/or ventricle to the aorta, to the AV node, to the SA
node, to a nerve and/or to the coronary sinus. Drugs may be
administered or delivered via intravenous, intracoronary and/or
intraventricular administration in a suitable carrier. Examples of
arteries that may be used to deliver drugs to the AV node include
the AV node artery, the right coronary artery, the right descending
coronary artery, the left coronary artery, the let anterior
descending coronary artery and Kugel's artery. Drugs may be
delivered systemically, for example, via oral, transdermal,
intranasal suppository or inhalation methods. Drugs also may be
delivered via a pill, a spray, a cream, an ointment or a medicament
formulation.
[0077] Drugs may be delivered via a drug delivery device that may
comprise a catheter, such as a drug delivery catheter or a guide
catheter, a patch, such as a transepicardial patch that slowly
releases drugs directly into the myocardium, a cannula, a pump
and/or a hypodermic needle and syringe assembly. A drug delivery
catheter may include an expandable member, e.g., a low-pressure
balloon, and a shaft having a distal portion, wherein the
expandable member is disposed along the distal portion. A catheter
for drug delivery may comprise one or more lumens and may be
delivered endovascularly via insertion into a blood vessel, e.g.,
an artery such as a femoral, radial, subclavian or coronary artery.
The catheter can be guided into a desired position using various
guidance techniques, e.g., flouroscopic guidance and/or a guiding
catheter or guide wire techniques. Drugs may be delivered via an
iontophoretic drug delivery device placed on the heart. In general,
the delivery of ionized drugs may be enhanced via a small current
applied across two electrodes. Positive ions may be introduced into
the tissues from the positive pole, or negative ions from the
negative pole. The use of iontophoresis may markedly facilitate the
transport of certain ionized drug molecules. For example, lidocaine
hydrochloride may be applied to the heart via a drug patch
comprising the drug. A positive electrode could be placed over the
patch and current passed. The negative electrode would contact the
heart or other body part at some desired distance point to complete
the circuit. One or more of the electrodes may also be used as
nerve stimulation electrodes 210 or as cardiac stimulation
electrodes 220.
[0078] The two divisions of the autonomic nervous system that
regulate the heart have opposite functions. First, the adrenergic
or sympathetic nervous system increases heart rate by releasing
epinephrine and norepinephrine. Second, the parasympathetic system
also known as the cholinergic nervous system or the vagal nervous
system decreases heart rate by releasing acetylcholine.
Catecholamines such as norepinephrine (also called noradrenaline)
and epinephrine (also called adrenaline) are agonists for
beta-adrenergic receptors. An agonist is a stimulant biomolecule or
agent that binds to a receptor.
[0079] Beta-adrenergic receptor blocking agents compete with
beta-adrenergic receptor stimulating agents for available
beta-receptor sites. When access to beta-receptor sites are blocked
by receptor blocking agents, also known as beta-adrenergic
blockade, the chronotropic or heart rate, inotropic or
contractility, and vasodilator responses to receptor stimulating
agents are decreased proportionately. Therefore, beta-adrenergic
receptor blocking agents are agents that are capable of blocking
beta-adrenergic receptor sites.
[0080] Since beta-adrenergic receptors are concerned with
contractility and heart rate, stimulation of beta-adrenergic
receptors, in general, increases heart rate, the contractility of
the heart and the rate of conductor of electrical impulses through
the AV node and the conduction system.
[0081] Drugs, drug formulations and/or drug compositions that may
be used according to this invention may include any naturally
occurring or chemically synthesized (synthetic analogues)
beta-adrenergic receptor blocking agents. Beta-adrenergic receptor
or .quadrature.-adrenegic blocking agents are also known as
beta-blockers or .quadrature.-blockers and as class II
antiarrhythmics.
[0082] The term "beta-blocker" appearing herein may refer to one or
more agents that antagonize the effects of beta-stimulating
catecholamines by blocking the catecholamines ines from binding to
the beta-receptors. Examples of beta-blockers include, but are not
limited to a acebutolol, alprenolol, atenolol, betantolol,
betaxolol, becantolol, bisoprolol, carterolol, celiprblol,
chlorthalidone, esmolol, labetalol, metoprolol, nadolol,
penbutolol, pindolol, propranolol, oxprenolol, sotalol, teratolo,
timolol and combinations, mixtures and salts thereof.
[0083] The effects of administered beta-blockers may be reversed by
administration of beta-receptor agonists, e.g., dobutamine or
isoproterenol.
[0084] The parasympathetic or cholinergic system participates in
control of heart rate via the sinoatrial (SA) node, where it
reduces heart rate. Other cholinergic effects include inhibition of
the AV node and an inhibitory effect on contractile force. The
cholinergic system acts through the vagal nerve to release
acetylcholine, which, in turn, stimulates cholinergic receptors.
Cholinergic receptors are also known as muscarinic receptors.
Stimulation of the cholinergic receptors decreases the formation of
CAMP. Stimulation of cholinergic receptors generally has an
opposite effect on heart rate compared to stimulation of
beta-adrenergic receptors. For example, beta-adrenergic stimulation
increases heart rate, whereas cholinergic stimulation decreases it.
When vagal tone is high and adrenergic tone is low, there is a
marked slowing, of the heart (sinus bradycardia). Acetylcholine
effectively reduces the amplitude, rate of increase and duration of
the SA node action potential. During vagal nerve stimulation, the
SA node does not arrest. Rather, pacemaker function may shift to
cells that fire at a slower rate. In addition, acetylcholine may
help open certain potassium channels thereby creating an outward
flow of potassium ions and hyperpolarization. Acetylcholine also
slows conduction through the AV node.
[0085] Drugs, drug formulations and/or drug compositions that may
be used according to this invention may include any naturally
occurring or chemically synthesized (synthetic analogues)
cholinergic agent. The term "cholinergic agent" appearing herein
may refer to one or more cholinergic receptor modulators, or
agonists. Examples of cholinergic agents include, but are not
limited to, acetylcholine, carbachol (carbamyl choline chloride),
bethanechol, methacholine, arecoline, norarecoline and
combinations, mixtures and/or salts thereof.
[0086] Drugs, drug formulations and/or drug compositons that may be
used according to this invention may include any naturally
occurring or chemically synthesized cholinesterase inhibitor. The
term "cholinesterase inhibitor" appearing herein may refer to one
or more agents that prolong the action of acetylcholine by
inhibiting its destruction or hydrolysis by cholinesterase.
Cholinesterase inhibitors are also known as acetylcholinesterase
inhibitors. Examples of cholinesterase inhibitors include, but are
not limited to, edrophonium, neostigmine, neostigmine
methylsulfate; pyridostigmine, tacrine and combinations, mixtures
and/or salts thereof.
[0087] There are ion-selective channels within certain cell
membranes. These ion selective channels include calcium channels,
sodium channels and/or potassium channels. Therefore, other drugs,
drug formulations and/or drug compositions that may be used
according to this invention may include any naturally occurring or
chemically synthesized calcium channel blocker. Calcium channel
blockers inhibit the inward flux of calcium ions across cell
membranes of arterial smooth muscle cells and myocardial cells.
Therefore, the term "calcium channel blocker" appearing herein may
refer to one or more agents that inhibit or block the flow of
calcium ions across a cell membrane. The calcium channel is
generally concerned with the triggering of the contractile cycle.
Calcium channel, blockers are also known as calcium ion influx
inhibitors, slow channel blockers, calcium ion antagonists, calcium
channel antagonist drugs and as class IV antiarrhythmics. A
commonly used calcium channel blocker is verapamil.
[0088] Administration of a calcium channel blocker, e.g.,
verapamil, generally prolongs the effective refractory period
within the AV node and slows AV conduction in a rate-related
manner, since the electrical activity through the AV node depends
significantly upon the influx of calcium ions through the slow
channel. A calcium channel blocker has the ability to slow a
patients heart rate, as well as produce AV block. Examples of
calcium channel blockers include, but are not limited to,
amiloride, amlodipine, bepridil, diltiazem, felodipine, isradipine,
mibefradil, nicardipine, nifedipine (dihydropyridines), nickel,
nimodinpine, nisoldipine, nitric oxide (NO), norverapamil and
veraparhil and combinations, mixtures and/or salts thereof.
Verapamil and diltiazem are very effective at inhibiting the AV
node, whereas drugs of the nifedipine family have a lesser
inhibitory effect on the AV node. Nitric oxide (NO) indirectly
promotes calcium channel closure. NO may be used to inhibit
contraction. NO may also be used to inhibit sympathetic outflow,
lessen the release of norepinephrine, cause vasodilation, decrease
heart rate and decrease contractility. In the SA node, cholinergic
stimulation leads to formation of NO.
[0089] Other drugs, drug formulations and/or drug compositions that
may be used according to this invention may include any naturally
occurring or chemically synthesized sodium channel blocker. Sodium
channel blockers are also known as sodium channel inhibitors,
sodium channel blocking agents, rapid channel blockers or rapid
channel inhibitors. Antiarrhythmic agents that inhibit or block the
sodium channel are known as class I antiarrhythmics, examples
include, but are not limited to, quinidine and quinidine-like
agents, lidocaine and lidocaine-like agents, tetrodotoxin,
encainide, flecainid and combinatons, mixtures and/or salts
thereof. Therefore, the term "sodium channel blocker" appearing
herein may refer to one or more agents that inhibit or block the
flow of sodium ions across a cell membrane or remove the potential
difference across a cell membrane. For example, the sodium channel
may also be totally inhibited by increasing the extracellular
potassium levels to depolarizing hyperkalemic values, which remove
the potential difference across the cell membrane. The result is
inhibition of cardiac contraction with cardiac arrest
(cardioplegia). The opening of the sodium-channel (influx of
sodium) is for swift conduction of the electrical impulse
throughout the heart.
[0090] Other drugs, drug formulations and/or drug compositions that
may be used according to this invention may include any naturally
occurring or chemically synthesized potassium channel agent. The
term "potassium channel agent" appearing herein may refer to one or
more agents that impact the flow of potassium ions across the cell
membrane. There are two major types of potassium channels. The
first type of channel is voltage-gated and the second type is
ligand-gated. Acetylcholine-activated potassium channels, which are
ligand-gated channels, open in response to vagal stimulation and
the release of acetylcholine. Opening of the potassium channel
causes hyperpolarization, which decreases the rate at which the
activation threshold is reached. Adenosine is one example of a
potassium channel opener. Adenosine slows conduction through the AV
node. Adenosine, a breakdown product of adenosine triphosphate
inhibits the AV node and atria. In, atrial tissue, adenosine causes
the shortening of the action potential duration and causes
hyperpolarization. In the AV node, adenosine has similar effects
and also decreases the action potential amplitude and the rate of
increase of the action potential. Adenosine is also a direct
vasodilator by its actions on the adenosine receptor on vascular
smooth muscle cells. In addition, adenosine acts as a negative
neuromodulator, thereby inhibiting release of norepinephrine. Class
III antiarrhythmic agents also known as potassium channel
inhibitors lengthen the action potential duration and
refractoriness by blocking the outward potassium channel to prolong
the action potential. Amiodarone and d-sotalol are both examples of
class III antiarrhythmic agents.
[0091] Potassium is the most common component in cardioplegic
solutions. High extracellular potassium levels reduce the membrane
resting potential. Opening of the sodium channel, which normally
allows rapid sodium influx during the upstroke of the action
potential, is therefore inactivated because of a reduction in the
membrane resting potential. The present invention may be combined
with conventional CPB, the induced asystole as described by this
invention may serve as a substitute for conventional cardioplegic
arrest. For example, the combination of drugs and vagal stimulation
may be used as a cardioplegic agent in a variety of medical
procedures.
[0092] Drugs, drug formulations and/or drug compositions that may
be used during according to this invention may comprise one or more
of any naturally occurring or chemically synthesized beta-blocker,
cholinergic agent, cholinesterase inhibitor, calcium channel
blocker, sodium channel blocker, potassium channel agent,
adenosine, adenosine receptor agonist, adenosine deaminase
inhibitor, dipyridamole, monoamine oxidase inhibitor, digoxin,
digitalis, lignocaine, bradykinin agents, serotoninergic agonist,
antiarrythmic agents, cardiac glycosides, local anesthetics and
combinations or mixtures thereof. Digitalis and digoxin both
inhibit the sodium pump. Digitalis is a natural inotrope derived
from plant material, while digoxin is a synthesized inotrope.
Dipyridamole inhibits adenosine deaminase, which breaks down
adenosine. Drugs, drug formulations and/or drug compositions
capable of reversibly suppressing autonomous electrical conduction
at the SA and/or AV node, while still allowing the heart to be
electrically paced to maintain cardiac output may be used according
to this invention.
[0093] In one embodiment, thee cardiac asystole produced in
accordance with the resent invention is reversible e.g., chemically
such as by the administration of atropine or by natural forces.
Beta-adrenergic stimulation or administration of calcium solutions
may be used to reverse the effects of a calcium channel blocker
such as verapamil. Agents that promote heart rate and/or
contraction may be used in a preferred embodiment of the present
invention. For example, dopamine, a natural catbcliplamine, is
known to increase contractility. Positive inotropes are agents that
specifically increase the force of contraction of the heart.
Glucagon, a naturally occurring hormone, is known to increase heart
rate and contractility. Glucagon may be used to reverse the effects
of a beta-blocker since its effects bypass the beta receptor.
Forskolin is known to increase heart rate and contractility. As
mentioned earlier epinephrine and norepiriephrine naturally
increase heart rate and contractility. Thyroid hormone,
phosphodiesterase inhibitors and prostacyclin, a prostaglandin are
also known, to increase heart rate and contractility. In addition,
methylxanthines are known to prevent adenosine from interacting
with its cell receptors.
[0094] Typically, vagal nerve stimulation prevents the heart from
contracting. This non-contraction must then be followed by periods.
Without vagal nerve stimulation during which the heart is allowed
to contract, and blood flow is restored throughout the body. At
block 517, the state of cerebral blood circulation may be
monitored. This monitoring may occur at specific points during the
procedure, for example, as shown at block 517. Alternatively,
monitoring may occur continuously. If cerebral blood circulation is
sufficient, then all or a portion of the medical procedure may be
carried out (Block 520). However, if the state of cerebral blood
circulation is not sufficient, then a signal may indicate that the
state of blood circulation to the brain is insufficient. If the
sensor indicates that the state of blood circulation is
insufficient, the surgeon may proceed to block 530, where the nerve
stimulation is ceased an the heart is allowed to contract. The
cardiac stimulator may be used to cause the heart to contract.
Alternatively, unit 200 may automatically proceed to Block 530 to
cease nerve stimulation. In addition, Unit 200 may automatically
begin cardiac stimulation.
[0095] The state of cerebral blood circulation sensed by sensor 5
may be communicated to the surgeon by a number of suitable means.
For example, the ambient blood flow may be indicated on a display
or monitor. A visual or audio signal may indicate when the level of
cerebral blood flow reaches a certain level, e.g. when blood flow
is insufficient. Alternatively, the system of the present invention
may "lock" the controls of the vagal stimulator in an "off" state
when cerebral blood flow reaches a predetermined condition, thereby
indicating that blood flow is insufficient. The system may then
release the controls when the state of cerebral blood circulation
sensed by the sensor is again sufficient.
[0096] Additionally, the amount of vagal nerve stimulation used may
be adjusted based on the output of the sensor 5. For example, the
level of stimulation may be lowered or the duration of stimulation
may be lowered if the sensor indicates that cerebral blood
circulation at 517 is insufficient. This adjustment may be
automatic or may be controlled by the surgeon.
[0097] At Block 520, a medical procedure may be performed or begun.
Such a procedure may be for example surgery on the heart.
Alternatively, the procedure may be surgery performed on another
organ of the body.
[0098] The term "medical procedure" may mean any one or more
medical or surgical procedures such as, for example cardiac
surgery, performed with or without cardiopulmonary bypass (CPB)
circuits, heart valve repair, heart valve replacement, MAZE
procedures, transmyocardial revascularization (TMR), CABG
procedures, anastomosis procedures, non-surgical procedures,
fluoroscpic procedures, beating heart surgery, vascular surgery,
neurosurgery, brain surgery, electrophysiology procedures
diagnostic and therapeutic procedures, ablation procedures,
ablation of arrhythmias, endovascular procedures, treatment of the
liver, spleen, heart, lungs, and major blood vessels, aneurysm
repair, imaging procedures of the heart and great vessels, CAT
scans or MRI procedures, pharmacological therapies, drug delivery
procedures, gene therapies, cellular therapies, cancer therapies,
radiation therapies, genetic, cellular, tissue and/or organ
manipulation or transplantation procedures, coronary angioplasty
procedures, placement or delivery of coated or noncoated stents,
atherectomy procedures, atherosclerotic plaque manipulation and/or
removal procedures, procedures where bleeding needs to be precisely
controlled, procedures that require precise control of cardiac
motion and/or bleeding.
[0099] When the medical procedure comprises one or more medical
devices, e.g., coated stents, these devices may be coated with one
or more radioactive materials and/or biological agents such as, for
example, an anticoagulant agent, an antithrombotic agent, a
clotting agent, a platelet agent, an anti-inflammatory agent an
antibody, an antigen, an immunoglobulin, a defense agent, an
enzyme, a hormone, a growth factor, a neurotransmitter, a cytokine,
a blood agent, a regulatory agent, a transport agent, a fibrous
agent, a protein, a peptide, a proteoglycan, a toxin, an antibiotic
agent, an antibacterial agent, an antimicrobial agent, a bacterial
agent or component, hyaluronic acid a polysaccharide, a
carbohydrate, a fatty acid, a catalyst, a drug, a vitamin, a DNA
segment, a RNA segment, a nucleic acid, a lectin, an antiviral
agent, a viral agent or component, a genetic agent, a ligand and a
dye (which acts as a biological ligand). Biological agents may be
found in nature (naturally occurring) or may be chemically
synthesized.
[0100] The medical procedure may be non-invasive, minimally
invasive and/or invasive. The medical procedure-may entail a
port-access approach, a partially or totally endoscopic approach, a
sternotomy approach or a thoracotomy approach. The medical
procedure may include the use of various mechanical stabilization
devices or techniques as well as various robotic or imaging
systems.
[0101] In one method, the heart may be temporarily slowed or
intermittently stopped for short periods of time to permit the
surgeon to accomplish the required surgical task and yet still
allow the heart itself to supply blood circulation to the body. For
example, stimulation of the vagus nerve in order to temporarily and
intermittently slow or stop the heart is described in U.S. Pat. No.
6,006,134 entitled "Method and Device for Electronically
Controlling the Beating of a Heart Using Venous Electrical
Stimulation of Nerve Fibers", Dec. 21, 1999, to Hill and Junkman.
This patent is assigned to Medtronic, Inc. and is incorporated
herein by reference.
[0102] During this medical procedure, the state of cerebral blood
circulation may be monitored constantly or intermittently as
described above. An assessment, for example, of the amount of blood
flowing to the brain may again be taken at block 525. If the state
of cerebral blood circulation is sufficient the physician may
continue with the medical procedure that is in progress. However,
if the state of cerebral blood circulation is not sufficient, then
the sensor 5 may indicate that blood circulation to the brain is
insufficient. If the sensor indicates that blood circulation is
insufficient, the surgeon may proceed to Block 530, where the nerve
stimulation is ceased. The heart will therefore be allowed to
contract and thus blood will again be allowed to flow to the brain
and vital organs. The cardiac stimulator maybe used to cause the
heart to contract. Alternatively, unit 200 may automatically
proceed to Block 530 to cease nerve stimulation. In addition, Unit
200 may automatically begin cardiac stimulation. Additionally the
amount of vagal nerve stimulation used may be adjusted based on the
output of the sensor 5. For example, the level of stimulation may
be lowered or the duration of stimulation may be lowered if the
sensor indicates that cerebral blood circulation at 525 is
insufficient.
[0103] After a time, the medical procedure or one phase of the
procedure is completed at 520. After some phase of the medical
procedure is performed, cardiac contractions are allowed to occur
(Block 530). Cardiac contractions may need to occur intermittently
during the procedure to ensure adequate blood flow. In one
embodiment, the stimulation from the nerve stimulator 10 is stopped
or slowed enough to allow the heart to contract. For example, the
vagal nerve stimulation is removed, thereby allowing cardiac
contractions to occur.
[0104] In another embodiment, the heart may be stimulated to ensure
that cardiac contractions occur (Block 535). For example, cardiac
stimulator 20 may be used to apply pacing pulses to the heart to
encourage the heart to contract normally. In particular, the pacing
pulses may be applied to the ventricle as is well known in the
field. Additionally, the amount of cardiac stimulation used may be
adjusted based on the output of the sensor 5. For example, the
level of stimulation may, be increased or the duration of
stimulation may be increased if the sensor indicates that cerebral
blood circulation at 525 is insufficient.
[0105] The present invention permits the heart to be stilled or
quiescent for selected and controllable periods of time in order to
permit a medical procedure to be performed. While such a period of
stillness or quiescence is desired, it must not last too long,
otherwise insufficient blood and oxygen is delivered to organs.
Thus, it is necessary to have the periods when the heart is beating
(Blocks 530, 535).
[0106] The state of cerebral blood circulation, for example, sensed
by sensor 5 while the heart is beating may be communicated to the
surgeon by a number of suitable means. For example, ambient blood
flow may be indicated on a display or monitor. A visual or audio
signal may indicate when the level of cerebral blood flow reaches a
certain level, e.g. when blood flow is insufficient. Alternatively,
the system of the present invention may "lock" the controls of the
cardiac stimulator in an "on" state when the state of cerebral
blood circulation reaches a predetermined condition, thereby
indicating that blood circulation is insufficient. The system may
then release the controls when the state of blood circulation
sensed by the sensor is again sufficient.
[0107] If additional medical procedures or additional stages of
medical procedures need to be performed, the heart may again be
stilled using the methods of stilling the heart described above.
Therefore from Block 530 or Block 535, the method may be repeated
(as in the loop designated by 540). For example, the heart may
again be prevented from contracting by stimulation of the vagal
nerve (510). Additional drugs may be delivered or the drugs
previously administered may continue to be administered.
[0108] This cycle may be repeated until the procedure, such as the
surgery, is completed. As the cycle continues sensor 5 enables
monitoring of the state of blood circulation and, if necessary,
appropriate adjustment of nerve stimulation and cardiac stimulation
to ensure sufficient blood circulation.
[0109] For example, the surgical procedure at 520 may require
several stitches to be made by the surgeon. The surgeon may
stimulate the vagal nerve, at 510 to stop the heart. Then the
surgeon may make the first stitch at 520. The surgeon may then
reduce or halt stimulation at 530 and allow the heart to contract.
The surgeon may also pace the heart at 535. Then at 540, the
surgeon may return to 510 to inhibit contractions of the heart. At
520, the surgeon will then make the second stitch. This process may
be repeated (the loop designated by 540 may be repeated) until all
the required stitches have been made. Meanwhile, the state of blood
circulation is monitored continuously or, for example at Blocks 517
and 525 by sensor 5. The procedure may proceed uninterrupted if the
state of blood circulation remains sufficient.
[0110] If required, after the procedure is completed, step 535 may
be performed until the heart is beating normally. Step 545 may be
continued until, the physician is satisfied that the heart is
beating normally and the state of blood circulation has reached an
acceptable level.
[0111] FIG. 4 is a timeline showing the relationship of a sensor, a
nerve stimulator and a cardiac stimulator in one embodiment of the
present invention.
[0112] Point 610 indicates a point before the medical procedure has
begun. At this point 610, both nerve stimulation and cardiac
stimulation are off. At point 610, the heart is beating regularly.
The patients state of cerebral blood circulation, for example, may
be measured by sensor 5 at point 610. Thus sensor 5 may be turned
on at point 610.
[0113] Then nerve stimulation is turned on to inhibit beating of
the heart. During phase 601, the vagal nerve stimulation is on and
the cardiac stimulation is off. This is the condition of the two
types of stimulation at step 520 described above. In one
embodiment, shown in FIG. 3 sensor 5 is on throughout the entire
procedure. Alternatively, sensor 5 may be turned on during phase
601 to check the state of cerebral blood circulation (as described
at Block 517).
[0114] Point 611 is a representative point during phase 601. At
point 611 the contractions of the heart are stilled or
substantially slowed. Also, at point 611, the current state of
cerebral blood-circulation may be determined (as described at
Blocks 517 and 525). If the state of cerebral blood circulation at
point 611 is sufficient, then the medical procedure can proceed (as
described at Block 520). However, if the state of cerebral blood
circulation is not sufficient at point 611, sensor 5 may provide a
signal indicating that the state of cerebral blood circulation is
insufficient. The surgeon may then proceed immediately to phase
602. Alternatively, control unit 200 may automatically proceed to
phase 602 after providing the signal.
[0115] Additionally, the amount of vagal stimulation used may be
adjusted based on the output of the sensor 5. For example, the
level of stimulation may be decreased or the duration of
stimulation may be decreased if the sensor indicates that the state
of blood circulation, at point 611 is insufficient.
[0116] During phase 602 the vagal stimulation is turned off (as
described at step 530) and the cardiac stimulation may be turned on
(as described at 535). Point 612 is a representative point during
phase 602. At point 612, the contractions are allowed and/or may be
induced. In one embodiment, sensor 5 is still on during phase 602.
Alternatively, sensor 5 may be turned on during phase 602 to check
the state of blood circulation to the brain.
[0117] Additionally, the amount of cardiac stimulation used may be
adjusted based on the output of the sensor 5. For example, the
level of stimulation may be increased or the duration of
stimulation may be increased if the sensor indicates that cerebral
blood circulation at point 612 is insufficient.
[0118] During phase 603, the vagal nerve stimulation is again
turned on and the cardiac stimulation is turned off. Also, during
phase 603, sensor 5 may still be on. The amount or duration of
vagal stimulation during phase 603 may be different than the amount
or duration of vagal stimulation during phase 601, based on the
data gathered from sensor 5 during phase 601. Alternatively, the
current state of cerebral blood circulation may again be determined
during phase 603 (as described at Block 525). Point 613 is a
representative point during phase 603. If the state of blood
circulation at point 613 is sufficient, then the medical procedure
can proceed (as described in step 520). However, if the state of
blood circulation is not sufficient at point 611, sensor 5 may
provide a signal indicating that blood circulation is insufficient.
The surgeon may then proceed immediately to phase 602.
Alternatively control unit 200 may automatically proceed to phase
602 after providing the signal. Additionally, the amount of vagal
stimulation used may again be adjusted based on the output of the
sensor 5.
[0119] During phase 604 the vagal stimulation is again turned off
and the cardiac stimulation may again be turned on. The amount or
duration of cardiac stimulation during phase 604 may be different
than the amount or duration of cardiac stimulation during phase
602, based on the data gathered from sensor 5 during the previous
phases.
[0120] The method of the present invention may be repeated as
necessary until a point is reached, represented by point 615, when
the necessary medical procedures are completed. At this point 615,
nerve stimulation is off although cardiac stimulation may be left
on in order to pace the heart to its normal rhythm. At point 615,
the state of cerebral blood circulation may be checked for a final
time (as described at 545).
[0121] It will be appreciated by those skilled in the art that
while the invention has been described above in connection with
particular embodiments and examples, the invention is not
necessarily so limited, and that numerous other embodiments
examples, uses, modifications and departures from the embodiments,
examples and uses are intended to be encompassed by the claims
attached hereto.
* * * * *