U.S. patent application number 10/628866 was filed with the patent office on 2004-07-15 for systems and methods of ph tissue monitoring.
This patent application is currently assigned to E-Monitors, Inc.. Invention is credited to Khuri, Shukri F., Treanor, Patrick.
Application Number | 20040138542 10/628866 |
Document ID | / |
Family ID | 26834358 |
Filed Date | 2004-07-15 |
United States Patent
Application |
20040138542 |
Kind Code |
A1 |
Khuri, Shukri F. ; et
al. |
July 15, 2004 |
Systems and methods of pH tissue monitoring
Abstract
While ischemia or tissue acidosis, in cardiac tissue has been
measured, systems and methods to prevent and/or reverse tissue, and
in particular, cardiac acidosis were unknown. Surgeons did not know
how to reverse tissue acidosis once discovered. The present
invention relates to systems and/or methods of using tissue pH
measurements to diagnose ischemia and to gauge the conduct of an
operation, based on these pH measurements, so as to prevent and/or
reverse tissue ischemia/acidosis. The current invention provides
methods by which tissue acidosis can be corrected once
discovered.
Inventors: |
Khuri, Shukri F.; (Westwood,
MA) ; Treanor, Patrick; (Dedham, MA) |
Correspondence
Address: |
THOMAS O. HOOVER, ESQ.
BOWDITCH & DEWEY, LLP
161 Worcester Road
P.O. Box 9320
Framingham
MA
01701-9320
US
|
Assignee: |
E-Monitors, Inc.
Tewksbury
MA
|
Family ID: |
26834358 |
Appl. No.: |
10/628866 |
Filed: |
July 28, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10628866 |
Jul 28, 2003 |
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09580809 |
May 26, 2000 |
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6600941 |
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09580809 |
May 26, 2000 |
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09339081 |
Jun 23, 1999 |
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6567679 |
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60136502 |
May 28, 1999 |
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Current U.S.
Class: |
600/345 ; 604/65;
604/66; 604/67 |
Current CPC
Class: |
A61M 1/3664 20130101;
A61B 5/742 20130101; A61B 5/6848 20130101; A61B 5/1473 20130101;
A61B 5/413 20130101; A61B 5/14539 20130101; A61M 1/3613 20140204;
A61M 1/3621 20130101; A61B 5/1495 20130101; A61B 5/14542
20130101 |
Class at
Publication: |
600/345 ;
604/065; 604/066; 604/067 |
International
Class: |
A61B 005/05 |
Claims
What is claimed:
1. A method of effecting a change in a surgical procedure
comprising the steps of: contacting tissue of a patient with a pH
electrode; measuring the pH of the tissue with the pH electrode to
monitor the pH of the tissue during the surgical procedure;
determining if the tissue pH falls below a threshold level
indicative of acidosis; and determining the need for
revascularization of the tissue if the tissue pH measurement falls
below the threshold level indicative of acidosis.
2. The method of effecting a change in the surgical procedure of
claim 1 wherein the step of contacting tissue further comprises
inserting the pH electrode into the tissue.
3. The method of effecting a change in the surgical procedure of
claim 1 wherein the step of determining the need for
revascularization further comprises identifying specific segments
of the tissue requiring revascularization by at least one of
examining the onset of acidosis during the procedure and the
response of the tissue pH to atrial pacing.
4. The method of effecting a change in the surgical procedure of
claim 3 wherein the response to atrial pacing can be used during at
least one of an intra-operative duration and post-operative
duration.
5. The method of effecting a change in the surgical procedure of
claim 1 wherein the step of contacting the pH electrode to the
tissue of a patient is performed manually.
6. The method of effecting a change in the surgical procedure of
claim 1 wherein the step of contacting the pH electrode to the
tissue of a patient is performed by a percutaneous catheter.
7. The method of effecting a change in the surgical procedure of
claim 1 wherein the step of contacting the pH electrode to the
tissue of a patient is performed using one of a laparoscope, an
endoscope and a colonscope.
8. The method of effecting a change in the surgical procedure of
claim 1 wherein the tissue is myocardial tissue.
9. A method of effecting a change in a surgical procedure
comprising the steps of: contacting tissue of a patient with a pH
electrode; measuring the pH of the tissue with the pH electrode to
monitor the pH of the tissue during the surgical procedure;
determining if the tissue pH falls below a threshold level
indicative of acidosis; and changing the order of revascularization
of the tissue if the tissue pH measurement falls below the
threshold level indicative of acidosis.
10. The method of effecting a change in the surgical procedure of
claim 9 wherein the step of contacting tissue further comprises
inserting the pH electrode into the tissue.
11. The method of effecting a change in the surgical procedure of
claim 9 wherein the step of changing the order of revascularization
further comprises first revascularizing most ischemic segments of
the tissue.
12. The method of effecting a change in the surgical procedure of
claim 9 wherein the step of changing the order of revascularization
further comprises revascularizing most ischemic segments of
myocardium tissue to minimize the degree of acidosis during aortic
clamping.
13. The method of effecting a change in the surgical procedure of
claim 9 wherein the step of contacting the pH electrode to the
tissue of a patient is performed manually.
14. The method of effecting a change in the surgical procedure of
claim 9 wherein the step of contacting the pH electrode to the
tissue of a patient is performed by a percutaneous catheter.
15. The method of effecting a change in the surgical procedure of
claim 9 wherein the step of contacting the pH electrode to the
tissue of a patient is performed using one of a laparoscope, an
endoscope and a colonscope.
16. The method of effecting a change in the surgical procedure of
claim 9 wherein the tissue is myocardial tissue.
17. A method of determining a change in a surgical procedure
comprising the steps of: contacting tissue of a patient with a pH
electrode; measuring the pH of the tissue with the pH electrode to
monitor the pH of the tissue during the surgical procedure;
determining if the tissue pH falls below a threshold level
indicative of acidosis; and reducing a duration of ischemic time of
the tissue if the tissue pH measurement falls below the threshold
level indicative of acidosis.
18. The method of effecting a change in the surgical procedure of
claim 17 wherein the step of contacting tissue further comprises
inserting the pH electrode into the tissue.
19. The method of effecting a change in the surgical procedure of
claim 17 wherein the step of reducing the duration of ischemic time
further comprises altering the procedure such as by one of
shortening the procedure, changing the surgeon, and canceling the
procedure.
20. The method of effecting a change in the surgical procedure of
claim 17 wherein the step of contacting the pH electrode to the
tissue of a patient is performed manually.
21. The method of effecting a change in the surgical procedure of
claim 17 wherein the step of contacting the pH electrode to the
tissue of a patient is performed by a percutaneous catheter.
22. The method of effecting a change in the surgical procedure of
claim 17 wherein the step of contacting the pH electrode to the
tissue of a patient is performed using one of a laparoscope, an
endoscope and a colonscope.
23. The method of effecting a change in the surgical procedure of
claim 17 wherein the tissue is myocardial tissue.
24. A method of determining a change in a surgical procedure
comprising the steps of: contacting tissue of a patient with a pH
electrode; measuring the pH of the tissue with the pH electrode to
monitor the pH of the tissue during the surgical procedure;
determining if the tissue pH falls below a threshold level
indicative of acidosis; and delaying weaning from cardiopulmonary
bypass if the tissue pH measurement falls below the threshold level
indicative of acidosis.
25. The method of effecting a change in the surgical procedure of
claim 24 wherein the step of contacting tissue further comprises
inserting the pH electrode into the tissue.
26. The method of effecting a change in the surgical procedure of
claim 24 wherein the step of contacting the pH electrode to the
tissue of a patient is performed manually.
27. The method of effecting a change in the surgical procedure of
claim 24 wherein the step of contacting the pH electrode to the
tissue of a patient is performed by a percutaneous catheter.
28. The method of effecting a change in the surgical procedure of
claim 24 wherein the step of contacting the pH electrode to the
tissue of a patient is performed using one of a laparoscope, an
endoscope and a colonscope.
29. The method of effecting a change in the surgical procedure of
claim 24 wherein the tissue is myocardial tissue.
30. A method of controlling a fluid delivery system based on pH
data comprising the steps of: providing tissue pH data; determining
if selected tissue pH data falls below a threshold level indicative
of a tissue condition; and controlling fluid flow in response to
the determination.
31. The method of claim 30 further comprising the step of providing
a controller connected to the delivery system.
32. The method of claim 30 wherein the step of controlling delivery
of preservation fluid to a site further comprises the step of
altering the flow rate of the fluid.
33. The method of claim 30 wherein the step of controlling flow
further comprises the step of altering a temperature of a
preservation fluid.
34. The method of claim 30 wherein the step of controlling flow
further comprises the step of altering the site of delivery of the
fluid.
35. The method of claim 30 wherein the step of controlling flow
further comprises the step of directing the solution through a
valve.
36. The method of claim 30 wherein the method further comprises the
step of displaying changes in a procedure.
37. The method of claim 30 further comprising providing temperature
and fluid pressure data.
38. The method for dispersing cardioplegia within a specific
myocardial segment comprising: applying occlusive pressure to a
coronary artery proximal to the sight of insertion of a new vein
graft; and perfusing a cardioplegic solution through a proximal end
of the graft.
39. A method for preventing cell apoptosis comprising: providing a
pH electrode and monitor; inserting the pH electrode into a tissue
site; measuring tissue pH; and reversing tissue ischemia to prevent
cell apoptosis.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 09/580,809 filed on May 26, 2000, which is a
continuation-in-part of U.S. application Ser. No. 09/339,081 filed
on Jun. 23, 1999 which claims priority to U.S. Provisional
Application No. 60/136,502 filed May 28, 1999, the entire teachings
of the above applications being incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] It is well known in the art to determine the pH in body
fluids by using an electrode cell assembly and immersing the
measuring electrode into a sample of the bodily fluid. The pH is
known to be the symbol for the negative logarithm of the H.sup.+
ion concentration. The pH value of the blood indicates the level of
acidity of the blood. High blood acidity, which is reflected by a
low pH indicates that the organs of the body are not being provided
with enough oxygen, which can ultimately prove harmful.
[0003] It is also known in the art to measure tissue pH in
myocardial tissue. Measurement of pH in myocardial tissue has been
used to determine the presence of myocardial ischemia, as indicated
by tissue acidosis which is reflected by a decrease in pH. During
cardiac surgery, the aorta is cross clamped and the myocardium is
deprived of its blood and nutrient supply, creating the potential
for damage to the heart from ischemia. Ischemia can be diagnosed by
monitoring the pH of the myocardium which falls significantly and
becomes acidotic during ischemia.
[0004] There is an ongoing need, however, for further improvements
in methods for diagnosing and treating ischemic tissue.
SUMMARY OF THE INVENTION
[0005] While ischemia or tissue acidosis, in cardiac tissue has
been measured, systems and methods to prevent and/or reverse
tissue, and in particular, cardiac acidosis were unknown. Surgeons
did not know how to reverse tissue acidosis once discovered. The
present invention relates to systems and/or methods of using tissue
pH measurements to diagnose ischemia and to gauge the conduct of an
operation, based on these pH measurements, so as to prevent and/or
reverse tissue ischemia/acidosis. The current invention provides
methods by which tissue acidosis can be corrected once
discovered.
[0006] The present invention relates to pH-guided management of
tissue ischemia or the use of pH measurements of tissue as a system
for controlling diagnostic and/or surgical procedures. A preferred
embodiment of the invention relates specifically to an apparatus
and method which is applicable to patients undergoing cardiac
surgery. It employs a tissue electrode and monitor and comprises a
series of steps that, in a preferred embodiment, are aimed at
achieving a homogeneous distribution of cardioplegic solution
during aortic clamping, and at insuring adequate revascularization
of ischemic segments of the myocardium. The method using pH-guided
myocardial management guides the conduct of operations, prevents
damage to the heart, extends the safe period of oxygen deprivation,
and improves the outcome of patients undergoing heart surgery.
[0007] The use of the pH-guided myocardial management system to
identify ischemic segments of the myocardium can provide a user
with options for specific courses of conduct, both during and
after, the surgical procedure. These options include: effecting an
optimal delivery of preservation solutions to the heart to reduce
ischemia, assessing the adequacy of coronary revascularization
following a heart surgery procedure, identifying viable but
nonfunctioning heart muscle, prompting changes in the conduct of
the surgical procedure, monitoring the pH of the heart muscle
post-operatively and evaluating the efficacy of newer myocardial
protective agents.
[0008] There are several methods of delivery of a pH electrode,
used in pH-guided myocardial management, to a site of interest. The
electrode can be delivered manually by the user. The electrode can
also be delivered by a catheter through a percutaneous incision.
The electrode can also be delivered by an endoscope, a colonscope
or a laparoscope to a site of interest. Thus, in a preferred
embodiment of the invention, the method can be applied to other
tissue measurements such as brain tissue, kidney tissue,
musculo-cutaneous flaps or the small or large intestines. In
another embodiment, the pH of transplanted organs, such as liver or
kidney, can be measured to assist in the diagnosis and/or treatment
of rejection since acidosis is an early sign of rejection.
[0009] Other systems and methods can also be used to measure pH,
including, in certain applications, surface pH measurements,
magnetic resonance measurements, or optical methods using fiber
optic probes or endoscopes.
[0010] When a user has found that tissue acidosis is present at a
site of interest, the user can effect an optimal delivery of
preservation fluids, or cardioplegia fluids, to the heart to raise
the pH of the site. Several systems that provide optimal delivery
of the cardioplegia solutions to the site are available to the
user. These include: altering the flow rate of the preservation
fluid, altering the temperature of the fluid, altering the site of
delivery, repositioning the tip of the catheter, selectively
directing the preservation fluid through the manifold, applying
direct coronary artery pressure on the proximal portion of the
artery, occluding the left main coronary artery with a balloon
catheter, inflating the balloon of a retrograde coronary sinus
catheter, administering a bolus of cardioplegia through the orifice
of a right coronary artery and accelerating a surgical
procedure.
[0011] When a user has found that tissue acidosis is present at a
site of interest, the user can also prompt changes to the conduct
of the surgical procedure to raise the pH of the site. Several
alternatives for changing the surgical procedure are available to
the user. These include: determining the need for revascularization
of a specific segment of the myocardium, changing the order of
revascularization, providing for additional revascularization,
changing the operation or the surgeon to reduce ischemic time,
canceling an operation and delaying the weaning of a patient from
cardiopulmonary bypass.
[0012] The pH electrode itself can have a cable connected to a
silver wire where the silver wire is an Ag/AgCl (silver/silver
chloride) wire. The cable and wires are encased in a housing which
is encased in shrink tubing. The electrode has a glass stem which
houses the silver wire, a thermistor, a pH sensor, and a gelled
electrolyte. The electrode has a bendable joint which allows the
user to adjust the positioning of the electrode prior to or during
use and which facilitates electrode removal after chronic
insertion. The glass stem is pointed to allow direct insertion into
tissues. In a preferred embodiment, the glass stem is made of lead
glass.
[0013] The electrodes can be used in a probe that can be delivered
to a site within the human body using a catheter and/or endoscope.
The sensor can be connected to a data processing system such as a
personal computer that can be used to record and process data. The
computer can be programmed using a software module to control
system operation and indicate to the user the status of the patient
and changes in system status and operation. The system can also
prompt the surgeon as to indicated changes in a surgical procedure
in progress. The computer can be connected to a controller that
operates a fluid delivery system and various temperature and
pressure sensors can provide data for the monitoring system
regarding patient status.
[0014] The foregoing and other objects, features and advantages of
the invention will be apparent from the following more particular
description of preferred embodiments of the invention, as
illustrated in the accompanying drawings in which like reference
characters refer to the same parts throughout the different views.
The drawings are not necessarily to scale, emphasis instead being
placed upon illustrating the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 illustrates a method of using tissue pH to identify
ischemic segments of a myocardium and the options available to a
user to utilize this information and take an appropriate course of
action.
[0016] FIG. 2 illustrates the methods of delivery of a pH electrode
to cardiac tissue.
[0017] FIG. 3 illustrates a method of effecting an optimal delivery
of preservation solution to the heart during surgery.
[0018] FIG. 4 illustrates a method of using the pH electrode to
measure the condition of tissue and alter the conduct of an
operation involving the tissue.
[0019] FIG. 5 illustrates a sectional view of an embodiment of a pH
electrode.
[0020] FIG. 6 illustrates a turkey foot cardioplegia delivery
system and tools.
[0021] FIG. 7A shows a manifold cardioplegia delivery system and
tools attached to a heart.
[0022] FIG. 7B shows a cannula placed within the left main coronary
artery of the heart.
[0023] FIG. 8 shows a coronary sinus cannula connected to a venous
cannula.
DETAILED DESCRIPTION OF THE INVENTION
[0024] FIG. 1 illustrates a method of using tissue pH to identify
ischemic segments of the heart, which are regions of the heart
muscle that are not receiving an adequate blood and nutrient
supply, and the options available to a user to take advantage of
this information and pursue an appropriate course of action. A user
would first deliver a pH electrode to a patient's heart 10. The
user would then measure the tissue pH as displayed on a monitor 12
and determine whether or not there was acidosis present in the
tissue 14. If there is no tissue acidosis 16, the pH would be again
measured 12. In a preferred embodiment, the pH is continually
measured by the electrode with the pH measurements displayed on a
monitor. If acidosis existed in the tissue 18, however, the user
could use this information to take appropriate action such as, but
not limited to, the following:
[0025] A user can effect an optimal delivery of the preservation
solutions to the heart through one or more of a compendium of
specific interventions 20. To perform open heart surgery, the aorta
has to be clamped thus depriving the heart muscle from its blood,
nutrient, and oxygen supply. A preservation solution, often
referred to as a cardioplegic solution, is normally perfused into
the heart and its blood vessels to prevent time-dependent ischemic
damage. It has been shown that the measurement of tissue pH, which
reflects, in part, the washout of the hydrogen ion generated by the
metabolic processes, is a good indicator of the regional
distribution of the preservation solution. It has also been shown
this distribution to be markedly heterogenous and unpredictable,
with segments of the myocardial wall suffering from acidosis
because of failure of the cardioplegic solution to reach these
segments. The main objective of pH-guided myocardial management is
to prevent tissue acidosis in all the segments of the myocardium
throughout the course of open heart surgery. This is achieved by
insuring an adequate and a homogeneous delivery of the cardioplegic
solution and an adequate revascularization of ischemic segments of
the heart. These are achieved by maintenance of the myocardial pH
as near normal as possible, with normal pH ranging between 7.2 and
7.4.
[0026] A user can also assess the adequacy of coronary
revascularization following coronary artery bypass grafting,
balloon dilatation or intracoronary stenting 22. This functionality
employs the rate of washout of the hydrogen ion accumulating in the
tissues during ischemia as an indication of the magnitude of tissue
blood flow. Following restoration of flow through a newly
constructed aorto-coronary bypass graft, no change in the pH of a
myocardial segment subtended by that graft indicates inadequate
revascularization. On the other hand, a rise in the pH of more than
0.1 pH units indicates restoration of effective tissue flow to the
ischemic myocardium.
[0027] A user can also identify viable but non-functioning heart
muscle 24, known as hibernating myocardium, which improves its
function with adequate coronary revascularization. pH-guided
myocardial management has demonstrated that the ability of the
non-contractile myocardial wall segment to produce acid, i.e. to
exhibit tissue acidosis, is an indication of the viability and
reversibility of dysfunction in this segment. Hence the procedure
provides a tool with which the viability of the non-contractile
myocardial segment can be assessed.
[0028] A user can also prompt specific changes in the conduct of
the operation 26 after obtaining information regarding tissue pH.
These changes in operating procedure are outlined in greater detail
in FIG. 4.
[0029] A user can also monitor the acid-base status of the heart
muscle in the post-operative period 28 and identify impending
problems. This functionality allows the depiction of ischemic
events in the intensive care unit within the first 72 hours
postoperatively. This methodology is capable of continuous
monitoring of regional tissue metabolism and acid base balance in a
patient, post-surgery. A fall in the myocardial pH of more than 0.1
pH units in the face of a stable blood pH is indicative of
myocardial ischemia. The more severe the fall in the pH the more
the magnitude of the ischemic damage. This functionality is
achieved by implanting the electrodes in the myocardium at the time
of the operation and exteriorizing them through a special chest
tube. The electrodes are pulled out in the surgical intensive care
unit (SICU) after the monitoring is terminated by simply pulling on
them along with the chest tube which houses them.
[0030] The user can also evaluate the efficacy of newer myocardial
protective agents and methods in the prevention of tissue acidosis
and the improvement of patient outcomes 30. To improve myocardial
protection, a number of agents are being proposed as additions to
the cardioplegic solution, and new modalities for the
administration of cardioplegia are being sought. pH-guided
myocardial management provides a metabolic marker which can enable
the assessment of the efficacy of these new agents and modalities
in improving the degree of intraoperative protection, the hallmark
of which can be the degree of prevention of acidosis during the
period of aortic clamping. The variable employed to compare these
methods of myocardial protection is the integrated mean myocardial
pH during the period of aortic clamping. The higher the integrated
mean pH during this period, the better is the degree of myocardial
protection.
[0031] FIG. 2 illustrates various methods of delivery of a pH
electrode to cardiac tissue. A user can implant the pH electrode
using direct insertion 40. This can include opening the chest
cavity of a patient during a cardiac surgery procedure and placing
the electrode into the patient's cardiac tissue by hand. The user
can also insert the pH electrode by means of a catheter using a
percutaneous incision 42. A user can also insert the pH electrode
by using an endoscope, colonscope or laparoscope 44. The user can
then measure the pH of the tissue 46 and determine whether there is
acidosis in the tissue 48. If no acidosis is found 50, the pH of
the tissue can again be measured 46. If acidosis is found in the
tissue 52, the user can then take an appropriate course of action
54, as outlined in FIG. 1.
[0032] FIG. 3 illustrates a method of providing for an optimal
delivery of preservation solution to a heart during surgery. In
this method, a user can first measure cardiac tissue pH 60 and
determine whether there is acidosis in the tissue 62. If no
acidosis is found 64, the pH of the tissue can again be measured
62. In a preferred embodiment, the pH is continuously measured and
monitored. If acidosis is found in the tissue 66, the user can then
effect an optimal delivery of the preservation solutions to the
heart through one or more of a compendium of specific
interventions. Interventions to be used to effect an adequate and a
homogeneous delivery of the cardioplegic solution include, but are
not limited, to the following maneuvers:
[0033] The user can alter the flow rate of the preservation
solution 68 to provide an optimal delivery of the cardioplegia
solution. The perfusionist controls the flow rate of the
cardioplegic solution administered. pH-guided myocardial management
has demonstrated that patients and myocardial segments differ in
the flow rate necessary to prevent acidosis. Therefore, changing
the flow rate of the cardioplegia solution can alter and improve
tissue pH.
[0034] The user can also alter the temperature of the preservation
solution 70 to optimize solution delivery. Changes in myocardial
temperature, which can range widely in the course of cardiac
surgery, effect various degrees of vasoconstriction and
vasodilatation of the coronary vasculature. This, in turn, will
effect the distribution of the cardioplegic solution and also the
level of tissue acidosis. Avoidance of tissue acidosis can be
achieved either by cooling or by re-warming the cardioplegic
solution, depending on the effect of temperature on the regional
distribution of the cardioplegic solution. pH-guided myocardial
management has demonstrated that the effect of temperature on the
regional distribution of the cardioplegic solution is totally
unpredictable and, hence, continuous monitoring of myocardial
tissue pH allows the determination of the myocardial temperature
which is most likely to prevent myocardial acidosis. Opposite
effects on myocardial pH have been observed from patient to patient
with both cooling and rewarming. In general, however, giving warm
cardioplegia effected an improvement in tissue pH in most
patients.
[0035] To provide an optimal delivery of the solution, the user can
also alter the site of delivery of the cardioplegic solution 72.
The cardioplegic solution can be delivered through several sites:
antegrade through the aortic root, antegrade through the orifice of
the right and/or left main coronary arteries, antegrade through the
proximal ends of newly constructed grafts, and retrograde through
the coronary sinus. pH-guided myocardial management allows the
surgeon to choose the site or combination of sites of
administration which can best avoid regional acidosis.
[0036] The user can reposition the tip of the catheter through
which the cardioplegic solution is delivered 74 to optimize
delivery. This may need to be performed in patients with a very
short left main coronary artery when cardioplegia is administered
through the orifice of the left main. It can also be useful in
pulling back on a retrograde catheter which is pushed too far into
the coronary sinus.
[0037] The user can also selectively direct the cardioplegic
solution through a manifold so as to reduce the steal of the
solution 76. The cardioplegic solution can be delivered through a
manifold having several catheters radiating from a single source.
This arrangement of the manifold is known as a "turkey foot." When
the cardioplegic solution is administered through more than one of
these catheters simultaneously, there is a marked heterogeneity in
the distribution of the solution to the various myocardial segments
supplied by these catheters. The solution often moves
preferentially into the catheter supplying the myocardial segment
with least resistance, usually the myocardial segment with least
coronary artery disease. This is what is referred to as a "steal
phenomenon." Monitoring myocardial pH, which capitalizes on the
fact that the rate of washout of the hydrogen ion in tissue is
indicative of the magnitude of tissue flow, can determine which
segments of the myocardium are receiving the cardioplegic solution
and which segments are deprived of cardioplegia because of the
"steal" phenomenon. When steal is encountered, homogeneity of the
distribution of the cardioplegic solution can be achieved by
occluding the catheters responsible for the steal and by
specifically directing the flow only into the areas exhibiting
acidosis.
[0038] The user can also apply direct coronary artery pressure on
the proximal portion of the artery to distally direct cardioplegia
flow through a newly constructed graft 78. This pressure can force
the cardioplegia solution to an area with low pH, to lower tissue
acidosis in that area.
[0039] The user can perform a balloon catheter occlusion of the
orifice of the left main coronary artery during the delivery of
retrograde cardioplegia through the coronary sinus or through the
proximal ends of recently constructed saphenous vein grafts 80. The
balloon catheter occlusion of the left main coronary artery
prevents the steal phenomenon, where the solution follows the path
of least resistance, and forces the cardioplegia solution to an
area of low pH. This process can reverse acidosis of an area
showing a low pH.
[0040] The user can also inflate the balloon of a retrograde
coronary sinus catheter while the cardioplegic solution is being
administered antegrade 82. Normally, if cardioplegia is being
delivered antegrade and retrograde simultaneously, the balloon in
the coronary sinus is kept deflated. A more homogeneous
distribution of the cardioplegic solution can be achieved if the
balloon in the coronary sinus is kept inflated while the
cardioplegia is delivered simultaneously antegrade and
retrograde.
[0041] The user can also administer a bolus of cardioplegia through
the orifice of the right coronary artery when the latter is a
dominant, non-obstructed vessel 84. In the course of an open heart
operation in which the aortic root is open, cardioplegia can be
administered through the orifice of the right coronary artery in
addition to the orifice of the left coronary artery. This, however,
can be tedious and time consuming, hence it is not a common
practice. pH-guided myocardial management has shown that the
posterior left ventricular wall is more vulnerable to refractory
myocardial acidosis if the right coronary artery is dominant and no
cardioplegia is administered through it. Hence, if in the course of
pH-guided myocardial management, refractory acidosis is encountered
in the posterior wall, administering a bolus of cardioplegia
through the orifice of the right coronary artery, if the latter is
dominant, can insure adequate delivery of the cardioplegic solution
to the posterior wall and can reverse the acidosis.
[0042] A user can also accelerate the surgical procedure 86 when
tissue acidosis is present. By monitoring tissue acidosis, a user
can avoid either using his time wastefully or attempting
nonstandard or potentially ineffectual surgical procedures. Also,
in a few patients, less than 5%, there is no known method to
prevent tissue acidosis and the surgical procedure must be
accelerated. With the acceleration of a procedure, the aorta, which
is clamped during the surgery, is unclamped sooner than planned,
thus allowing oxygen rich blood to reach the heart muscle, thereby
reversing acidosis.
[0043] In the event that one of the described options, 68 through
86, fails to relieve the ischemic condition, as evidenced by the
display of tissue pH levels on the pH monitor, the user can use any
of the other described options to attempt to raise tissue pH.
[0044] FIG. 4 illustrates a method of using the pH electrode to
prompt specific changes in the conduct of an operation after
determining there is tissue acidosis. In this method, a user first
measures cardiac tissue pH 90 and determines whether there is
acidosis in the tissue 92. If no acidosis is found 94, the pH of
the tissue can again be continuously or periodically measured 90.
If acidosis is found in the tissue 96, the user can then change the
conduct of the procedure 98.
[0045] These changes can include, but are not limited, to the
following maneuvers. First, the determination of the need for the
revascularization of a specific segment of myocardium 100. The
ability to identify which specifically are the segments of the
myocardium that need revascularization can be lifesaving. Segments
requiring revascularization can be determined by either examining
the onset of regional acidosis in the course of an operation or the
response of the myocardial pH to atrial pacing. The response to
atrial pacing can be utilized intra-operatively, postoperatively in
the SICU, and in the cardiac catheterization laboratory.
[0046] The user can also change the order of revascularization.
pH-guided myocardial management allows the surgeon to revascularize
the most ischemic segments of the myocardium first so as to
minimize the degree of acidosis encountered in the course of aortic
clamping.
[0047] The user can also change the procedure by providing
additional revascularization of the heart 104. pH-guided myocardial
management involves identifying ischemic segments of the left
ventricular wall that require revascularization, often unplanned
preoperatively.
[0048] The user can also change the operation or the surgeon to
reduce the duration of the ischemic time 106. pH-guided myocardial
management allows for reductions in the magnitude of the planned
operation in several ways. When pH monitoring depicts a significant
amount of myocardial acidosis which cannot be corrected, the need
to reduce the ischemic time becomes more important than the
potential benefits of certain parts of the operation that can be
dispensed with, such as the construction of an additional graft. pH
monitoring also allows the surgeon to abandon a planned part of the
operation because it uncovers no real need for this part. In this
context, pH-guided myocardial management also plays a major value
in the teaching of residents because it provides the attending
surgeon with the information on what parts of the operation he/she
can give to the resident, and what part the attending surgeon can
be doing himself/herself, since residents, particularly early in
their training, can be fairly tardy in performing these
operations.
[0049] The user can also cancel an operation 108 if, based on the
pH measurements, the risk of the procedure is found to exceed the
benefit.
[0050] Lastly, the user can delay the weaning from cardiopulmonary
bypass until the oxygen debt, represented by residual acidosis
during reperfusion, is fully paid 110.
[0051] Weaning from cardiopulmonary bypass in the presence of
myocardial acidosis may cause the hemodynamics to deteriorate
postoperatively, often prompting the re-institution of
cardiopulmonary bypass. When the heart is subjected to significant
ischemia during the period of aortic clamping or reperfusion, a
significant amount of time may be needed until the ischemia
reverses to normal levels.
[0052] In the event that one of the described options, 100 through
106, fails to relieve the ischemic condition, as evidenced by the
display of tissue pH levels on the pH monitor, the user can use any
of these other described options to attempt to raise tissue pH.
[0053] FIG. 5 illustrates an embodiment of a pH electrode 136 used
to monitor tissue acidosis. The electrode 136 can have a cable 112
connected to a silver wire 114. In a preferred embodiment, the
silver wire 114 is an Ag/AgCl (silver/silver chloride) wire. In
another preferred embodiment, the cable 112 is connected to the
silver wire 114 by a platinum wire 116 passing through a glass seal
118. The cable 112 and wires 114, 116 are encased in a housing 120
which is encased in shrink tubing 122. The electrode 136 has a
glass stem 124 which houses the silver wire 114, a thermistor 126,
a pH sensor 128, and a gelled electrolyte 130. The electrode 136
can also have a suture groove 132 to allow the electrode 136 to be
secured to the site where it is used. The electrode 136 can also
have a bendable joint 134 which allows the user to adjust the
positioning of the electrode 136 prior to or during use. The glass
stem 124 is pointed to allow direct insertion into tissues. In a
preferred embodiment, the glass stem 124 is made of lead glass. The
electrode can be sterilized by ethylene oxide or gamma irradiation.
A pH electrode suitable for use with the invention is available
from Vascular Technology Inc., 175 Cabot Street, Lowell, Mass. This
particular electrode can be inserted into tissue to a depth of up
to 10 mm, has a diameter of 1 mm, and employs a pH sensor in the
distal 4 mm of the probe.
[0054] Tissue pH is an important clinical measurement. Local
acidosis, which can be measured as a distinct drop in pH, has been
associated with ischemia. Temperature is preferably measured
simultaneously with the pH to allow for the calibration and
temperature correction of the tissue pH measurement. Temperature
correction of the pH is important, particularly in procedures, such
as open-heart surgery, which require significant cooling. The pH
electrode uses combination pH/temperature sensors, each of which
contains a temperature-sensing element mounted inside the
pH-sensing sensor.
[0055] Glass pH electrodes are the method most commonly used to
obtain accurate clinical pH measurements. They consist of a hollow
glass sensor filled with electrolyte that is in turn in contact
with an internal reference wire. Due to the nature of the glass
used, an electric potential is developed across the glass. This
potential is proportional to the difference between the pH of the
analyte solution in contact with the exterior surface of the glass
and the essentially constant pH of the internal buffer
solution.
[0056] In order to make an electrical measurement, a complete
electric circuit must be formed. Therefore, a second electrical
contact with the analyte solution must be made. This is
accomplished through the use of a needle reference electrode. It
consists of a silver chloride needle in contact with a constant
molarity salt solution. The salt solution is placed in contact with
the analyte solution, i.e., the patient's tissue, using a suitable
isolation mechanism, in this case through the use of gelled salt
solution that has been placed in a flexible tube, the open end of
which is placed in contact with the patient.
[0057] The Nernst equation predicts that under constant
environmental conditions, the output of the glass pH electrode is
linear with pH. Therefore, the electrical output of the sensor can
be converted to pH by the use of a simple straight-line curve-fit.
This will require determining the electrical output of the
electrode at two different pH values, from which the slope and
offset constants for the straight-line equation can be calculated.
The commonly available standards buffers for pH electrode
calibration have pH values of 4, 7, and 10. The 4 and 7 buffers
have been chosen for use with this system. The 7 pH buffer was
chosen because the electrode's zero-potential point is near pH 7.
The 0.4 buffer was chosen because pH values of the greatest
interest lie somewhat below pH 7.
[0058] The theoretical sensitivity-the slope-of this type of
electrode is 59.16 mV/pH at 25.degree. C. For real electrodes, it
tends to be a little less, the value being slightly different from
one electrode to another and, for a given electrode, varying over
its useful life.
[0059] The zero potential point is defined, as that analyte pH
value for which the measured output voltage is zero, after
correcting for any difference in the salt concentrations of the
internal and reference solutions. The zero potential point should
occur, therefore, when the analyte pH value is the same as the pH
value of the pH sensor's internal buffer. If a measurement is
actually made under these conditions, however, a non-zero potential
will, in general, be measured. This occurs when the CI connection
that the sensor's internal reference wire is exposed to differs
from the concentration that the reference needle is exposed to, or
if both reference wires are not made of the same material. In this
system, the reference needle is immersed in a saturated KCl gel,
while the sensor's internal reference wire is exposed to an 0.87 M
concentration of KCl in the internal buffer. This difference
results in a measured potential of about +30 mV at 25.degree. C.
when the analyte has the same pH value as that of the internal
buffers, nominally 6.33 pH at 25.degree. C. Thus, in order to
measure the true zero potential point, it is necessary to correct
the measured voltage by subtracting 30 mV from it. The pH 7 buffer
is used during calibration for zero point calibration is the
closest readily available buffer value to 6.33.
[0060] Since there is some variation in output from the ideal
values as just described, both from sensor to sensor and over
extended periods of time for the same sensor, the pH sensors must
be calibrated prior to each use. This is accomplished automatically
during the calibration procedure by placing the sensors first in
the slope buffer (4.00 pH) and then in the zero potential point
buffer (7.00 pH). The microprocessor reads the output of the
sensors in mV, correcting for the salt differential, determines
when the readings are stable and then computes the slope and offset
calibration factors for each sensor. Both the slope and zero
potential point vary with temperature and are corrected for by the
monitor's software.
[0061] The pH electrode's combination pH/temperature sensor uses a
precision thermistor element to measure temperature. The thermistor
is one of the most common temperature measuring devices in use. It
consists of a small bead of metallic oxide semiconducting ceramic.
The material's electrical resistance varies inversely with
temperature in a non-linear manner.
[0062] To measure temperature, the thermistor is electrically
placed in series with a fixed resistor in the monitor that has
precisely known resistance. A voltage is applied across the series
combination and the voltage at the junction of the thermistor and
resistor is measured. This measured value, in conjunction with the
known values of the fixed resistor and of the applied voltage, is
used to calculate the resistance of the thermistor. The temperature
is then determined by means of a look-up table stored in the
microprocessor program. The thermistor sensors used with this
system are manufactured to a level of precision that makes
individual calibration by the user of the system unnecessary.
[0063] The pH electrode can be pre-calibrated and packaged such
that the tip of the electrode is sealed within a sleeve or a sleeve
pocket containing a pH 4.0 buffer. The sleeve pocket can be formed
of a plastic material and can have a 3 mm internal diameter. Prior
to its insertion in the patient, the sleeve pocket can be removed,
the electrode tip wiped dry with a gauze, and the electrode
inserted into a beaker containing a pH 7.0 buffer. The calibration
is completed at this point. Packaging the electrode within a pH 4.0
buffer allows the electrode to remain moist through its storage, a
factor which is necessary for proper calibration, and reduces the
steps required for electrode calibration to a single step. The
software in the electrode monitor can be modified to reflect the
single step calibration.
[0064] The monitor, to which the pH electrode, the reference
electrode, and thermistor are attached, processes the signals and
continually records and displays the following data at 20 second
intervals or less: 1) the tissue pH in pH units, 2) the tissue
hydrogen ion concentration [H.sup.+] in nmoles, 3) the tissue
temperature in .degree. C., 4) the pH corrected for 37.degree. C.,
and 5) the tissue hydrogen ion concentration [H.sup.+] is
calculated as the inverse log of pH. The correction for 37.degree.
C. is based on a factor of 0.017 pH units/.degree. C. which was
derived based on experiments performed in the inventor's
laboratory. In addition, the monitor allows for the calculation of
integrated mean pH, [H.sup.+], and temperature over a specific
period of time by signaling at the beginning and at the end of the
specified period. A slave monitor is attached to the unit and
placed in front of the surgeon providing a customized continuous
display of the data. The continuous real-time display of the data
allows for prompt institution of pH-guided myocardial management to
prevent or reverse myocardial tissue acidosis.
[0065] Several devices or tools can be used in pH guided myocardial
management during cardiac surgery and in the assessment of
myocardial viability. The maintenance and distribution of
cardioplegic solution to specific myocardial segments during
cardiac surgery can be achieved using several different devices and
approaches.
[0066] FIG. 6 illustrates a "turkey foot" cardioplegia delivery
system 140 (Medtronic, Grand Rapids, Mich.). The delivery system
140 in conjunction with the electrode can form a myocardial
management system. The system 140 can also include a data
processing system 160, such as a computer, and a controller 158.
The data processing system 160 can be programmed to receive
measured data 162, such as the status of the patient and changes in
system status. The data processing system 160 can be attached to a
fluid source of fluid delivery system 144. The data processing
system 160 can also be attached to the fluid source through the
controller 158. The controller 158 can operate the fluid delivery
system. The controller 158 can control the flow rate of a
preservation fluid or cardioplegia fluid delivered to a surgical
site. The controller 158 can also control the temperature of a
preservation solution and a delivery site of a preservation
solution. The system 140 has a plurality of controls 142 which can
be used to adjust and selectively administer the amount of
cardioplegia solution delivered from a source 144 to various
cardiac attachment sites. The system 140 can include an occluder or
valve 146 which controls the flow of the cardioplegic solution. The
system 140 includes several delivery devices attached between the
cardioplegia source 144 and various cardiac sites. These devices
allow the delivery of cardioplegic solution to their respective
cardiac sites. One device is a cannula 148 (Sarns Inc., Ann Arbor,
Mich.) which can be inserted in the aortic root. Another device is
a Spencer cannula 150 (Research Medical, Inc., Midvale, Utah) which
can be inserted within the orifice 156 of the left main coronary
artery. This insertion into the orifice 156 is shown in FIGS. 7A
and 7B. Another device is a malleable metallic catheter 152
(Medtronic, Grand Rapids, Mich.) which can be inserted within the
orifice of the right main coronary artery. The catheter 152 is also
shown in FIG. 7A in an uninserted state. Another device is a 14
gauge beaded needle (Randall Faichney Corp., Avon, Mass.) which can
be attached to the proximal end of a saphenous vein graft for the
delivery of cardioplegia. The attachment to the vein graft is also
shown in FIG. 7A.
[0067] Blocking the orifice of the left main coronary ostium with a
spherical catheter such as a Spencer cannula 150 (Research Medical,
Inc., Midvale Utah) or balloon tipped catheter such as a #3F
Fogerty Catheter (Ideas For Medicine, St. Petersburg, Fla.), while
providing cardioplegia through other sites of 140, can also be used
to redistribute cardioplegia solution during cardiac surgery. Also,
applying temporary occlusive pressure to a coronary artery proximal
to the site of insertion of a new vein graft while perfusing a
cardioplegic solution through the proximal end of the graft can
also be used to re-direct cardioplegic fluid during cardiac
surgery. Occlusive pressure can be maintained with a gauze "peanut"
at the tip of a Kelly clamp (Allegiance Healthcare Corp., McGaw
Park, Ill.).
[0068] A Guntrie balloon tipped cannula (Medtronic, Grand Rapids,
Mich.) can also be attached to the system 140 and inserted in the
coronary sinus for selective administration of cardioplegia in a
retrograde manner. The cannula 170 is illustrated in FIG. 8. In
this figure, it is illustrated attached through tubing 176 to the
venous cannual 178. This allows manipulating the pressure in the
coronary sinus to improve cardioplegia delivery to the tissues as
part of pH-guided myocardial management. The pressure can be
manipulated by inflating a coronary sinus balloon 172 with the
fluid orifice of the coronary sinus catheter closed, and delivering
the cardioplegia antegrade. The 1 mm tubing 176 connecting 170 to
178 creates back pressure which will improve delivery without
interfering with adequate antegrade cardioplegia flows. The opening
or closing of the fluid orifice of the coronary sinus catheter 170
can be controlled by a valve 184. The venous cannula 178 is
normally inserted in the course of cardiopulmonary bypass with its
tip 182 in the inferior vena cava and its more proximal orifice 180
in the right atrium.
[0069] Changing the tissue temperature by manipulating the
temperature of the cardioplegic solution using a water
heater/cooler, such as that manufactured by Sarns, Ann Arbor,
Mich., can aid in managing myocardial pH during cardiac surgery.
Also, changing the perfusion pressure of the cardioplegic solution
by changing the rate of cardioplegia flow using a cardioplegia
system such as an HE30 Gold cardioplegia system (Baxter
Corporation, Irvine, Calif.) can aid in managing myocardial pH
during cardiac surgery.
[0070] Tools can also be used for the assessment of myocardial
viability and the determination of the physiologic significance of
coronary stenosis. The tools can be used in either an operating
room or a cardiac catheterization lab.
[0071] In the operating room, pacing wires (Ethicon, Somerville,
N.J.) can be placed over the right atrium and connected to an
external pacemaker (Medtronic, Grand Rapids, Mich.). A pH electrode
can also be inserted into the myocardium. A fall in myocardial pH
in response to 5 minutes of rapid atrial pacing can indicate tissue
ischemia and also can indicate that the myocardial segment in which
the electrode is placed is viable.
[0072] In the cardiac catheterization laboratory, the pH electrode
can be mounted at the tip of a long 0.014 gauge wire and inserted
through a regular 6 french cardiac catheterization catheter such as
that manufactured by Cordis (Miami, Fla.). The catheter tip can be
positioned perpendicularly against the ventricular wall of the
segment subtended by the coronary artery being investigated and the
pH electrode pushed to penetrate into the subendocardium.
Preferably, the electrode is pushed to penetrate 5 mm into the
subendocardium. Pacing is achieved via a pacing wire advanced into
the right ventricle (Medtronic, Grand Rapids, Mich.) and attached
to an external pacemaker (Medtronic, Grand Rapids, Mich.). Again, a
fall in myocardial pH in response to 5 minutes of rapid arterial
pacing can indicate tissue ischemia.
[0073] While the pH electrodes and monitoring system have been
described for use in determining the ischemia of cardiac tissue,
the pH system and methods can be used in other types tissue as
well. The pH system can be used to monitor rejection in organ
transplantation, to assess mesenteric ischemia, to monitor and
assess brain blood flow and to monitor flaps in plastic
surgery.
[0074] The pH electrode can be used to monitor the kidney in the
course of and following kidney transplantation. The pH electrode
can be used in the monitoring of tissue perfusion to the kidney in
the course of major surgery and, in particular, during kidney
transplantation. The electrode is readily implantable in the kidney
in a manner similar to the heart, and a tissue pH level of 7.2 and
above indicates adequate tissue perfusion. Damage to the kidney,
particularly during excision of the kidney for the purpose of donor
related cardiac transplantation, can be detected and avoided, thus
insuring a better outcome of the donor related kidney
transplantation. Preservation of the kidney during transport prior
to transplantation can also be insured by monitoring and
maintaining the pH at normal levels. This can be achieved with
constant perfusion of the kidney with blood in a specially designed
apparatus for organ perfusion.
[0075] Following kidney transplantation, keeping the electrode in
the kidney throughout the immediate 48 hours post-operatively can
allow for monitoring initial ischemia and can allow for reversing
of this ischemia with operative interventions. Ischemia during this
period can herald a significantly bad outcome. Assessment of the
transplanted kidney, function and detection of its rejection can
also be performed by placing the electrode on a catheter and
passing it retrograde into the calyx of the kidney. Puncturing the
calyx of the kidney along with the kidney parenchyma, similar to
what was described above for the heart, can indicate impending or
actual rejection and, as such, would be indicative of adverse
outcome. Early detection of acidosis can prompt major treatment of
rejection, and thus can improve the outcome of kidney
transplantation.
[0076] Each electrode can be used also for the assessment of the
adequacy of the revascularization of the kidney in the course of
renal artery revascularization. The efficacy of the
revascularization of a critically stenod renal artery can be
determined intra-operatively in a manner similar to the efficacy of
the revascularization of the coronary arteries. Failure to reverse
acidosis with revascularization should prompt additional
intra-operative measures to reverse the acidosis, and hence, avoid
adverse outcome of revascularization. As in the heart, failure to
reverse the acidosis with revascularization is indicative of the
inadequacy of the revascularization process and provides a guide
for additional intra-operative management to improve the situation
and improve the outcome of the revascularization.
[0077] The pH electrode can also be used to monitor the liver
during and following liver transplantation. The pH electrode can be
inserted into the liver to provide important data similar to that
of the kidney, described above. The description of the use of the
electrode in the kidney is applicable to the liver in terms of the
use of the pH electrode in monitoring the intra-operative course,
identifying early rejection, and instituting measures to reverse
the rejection process.
[0078] The electrode can also be used in monitoring the periphery
in critical care. Insertion of the electrode in the subcutaneous
tissue of the periphery should provide information on the adequacy
of tissue perfusion. Acidosis measured at these sites, primarily in
the subcutaneous tissue of the distal half of the lower extremity,
can indicate an inadequate cardiac output, and can prompt the
institution of measures to improve cardiac output or tissue
perfusion. These measures can include pharmacologic manipulations
and/or insertion of an intra-aortic balloon (Arrow International,
Reading, Pa.) in the descending aorta, for example. Currently, only
measures of central hemodynamics are used to assess and treat low
cardiac output syndrome. Measuring the pH in the periphery provides
a more superior alternative because it provides a true measure of
tissue perfusion which is the ultimate goal in the maintenance of
an "adequate" cardiac output.
[0079] The electrode can also be used within the muscle and
subcutaneous tissue of flaps in plastic surgery. It has been
demonstrated that tissue acidosis with the pH electrode indicates
compromised viability of skin and subcutaneous flaps. The electrode
is placed post-operatively within the edge of the flap and the pH
is monitored up to three or four days post-operatively. A fall in
pH prompts an intra-operative intervention and a revision of the
flap to prevent its subsequent failure.
[0080] The pH electrode can also be used in the colon in the
assessment and treatment of intestinal ischemia. To assess and
reverse intestinal ischemia, the pH electrode can be placed on a
wire in a manner similar to that described for the heart during
cardiac catheterization above. This pH electrode-tipped wire can be
inserted through a colonscope, such as that manufactured by Olympus
Medical, Seattle, Wash., during regular colonoscopy into the distal
ileum. Intra-luminal pH in the ilium is a reliable measure of the
adequacy of the perfusion. Intra-luminal acidosis in the ilium
indicates intestinal ischemia, and can prompt maneuvers to either
reverse the ischemia or to prevent its adverse outcome. Knowledge
of intra-luminal pH in the ilium allows the initiation of operative
interventions, such as exploration of the abdomen with the possible
resection of intestine, for example, as well as pharmacologic
interventions to improve cardiac output and tissue perfusion.
[0081] The pH electrode can be used in other organs. In addition to
the organs mentioned above, tissue acidosis can be measured,
manipulated, and reversed by inserting the pH electrode, attached
to the pH monitoring system, in organs such as the brain, the
bladder, the diaphragm, and the small intestine.
[0082] Acidosis can prematurely trigger and accelerate cell
apoptosis, or programmed cell death. In the heart, apoptosis may
manifest in late adverse outcomes, mainly progressive heart
failure. During the course of open heart surgery, moderate to
severe acidosis is encountered, at least in one segment of the left
ventricle, in more than 50% of the patients. The prevention of the
onset of myocardial tissue acidosis by pH-guided myocardial
management in the course of open heart surgery reduces or
eliminates the potential of triggering apoptosis, and hence reduce
or eliminate the potential of late adverse postoperative
outcomes.
[0083] While this invention has been particularly shown and
described with references to preferred embodiments thereof, it will
be understood by those skilled in the art that various changes in
form and details may be made therein without departing from the
scope of the invention encompassed by the appended claims.
[0084] The claims should not be read as limited to the described
order or elements unless stated to that effect. Therefore, all
embodiments that come within the scope and spirit of the following
claims and equivalents thereto are claimed as the invention.
* * * * *