The Annals of Thoracic Surgery, Vol 42, 365-371, Copyright © 1986 by The Society of Thoracic Surgeons
Continuous measurement of intramyocardial pH: relative importance of hypothermia and cardioplegic perfusion pressure and temperature
TJ Takach, LR Glassman, AL Milewicz and RE Clark
The continuous measurement of intramyocardial pH was used to follow the
progression of ischemia and permit correlation to functional recovery.
Adequacy of myocardial preservation following 38 degrees C or 25 degrees C
global ischemia alone or with the administration of one or two doses of 38
degrees C, 25 degrees C, or 1 degree C crystalloid cardioplegia at aortic
root perfusion pressures of 90 mm Hg or 130 mm Hg was assessed. A new
miniature myocardial transducer incorporating fiberoptic technology and
dual pH and temperature-sensing capability was placed into the left
ventricular free wall and septum of 44 sheep undergoing ischemic arrest
during cardiopulmonary bypass. All groups underwent global ischemia until
myocardial pH was 6.8. An intramyocardial pH level of 6.8 reliably
correlated to similar levels of functional recovery in each group. Aortic
root perfusion pressure of 130 mm Hg provided enhanced myocardial
protection by increasing the total ischemic time (5 to 10 minutes) with one
(p less than 0.01) or two (p less than 0.001) doses of cardioplegic
solution until a given functional level of recovery was attained. Aortic
root perfusion pressure of 90 mm Hg provided no added benefit in total
ischemic time, rate of change of pH, or degree of recovery of function.
Hypothermic (25 degrees C) global ischemia alone enhanced myocardial
protection by providing increased time (p less than 0.01) until a given
functional level of recovery was attained with a slower rate of change of
pH (p less than 0.01) compared with normothermic (38 degrees C) global
ischemia alone.(ABSTRACT TRUNCATED AT 250 WORDS)
