Continuous measurement of intramyocardial pH: correlation to functional recovery following normothermic and hypothermic global ischemia.
The continuous measurement of intramyocardial pH was used to follow the progression of ischemia and was correlated to the recovery of left ventricular function following normothermic (38 degrees C) and hypothermic (25 degrees C) global ischemia. New miniature myocardial transducers, which incorporate fiberoptic technology and dual pH- and temperature-sensing capability, were placed into the left ventricular free wall and septum of 52 sheep undergoing cardiopulmonary bypass. Left ventricular stroke work as a function of mean left atrial pressure curves were generated before and after cardiopulmonary bypass by volume loading with whole blood. Functional recovery was determined by the ratio of the integrals of the preischemic and postischemic function curves. Control sheep (N = 11) did not undergo ischemia. Three groups (N = 41) underwent aortic cross-clamping until pH reached 7.0, 6.8, or 6.6. The preischemic myocardial pH averaged 7.42 +/- 0.01. Following both normothermic and hypothermic global ischemia, no significant difference was demonstrated in recovery of function between control (pH 7.4) and pH 7.0 groups at either temperature. However, recovery of function of the pH 6.8 and pH 6.6 groups was significantly decreased (p less than 0.01) versus control and pH 7.0 groups at both temperatures. No significant difference in recovery of function was demonstrated at any pH level when normothermic versus hypothermic groups were compared. However, hypothermia provided increased time (p less than 0.001) before each level of function was reached with a slower rate of change of pH (p less than 0.01) compared with the corresponding same pH group in sheep undergoing normothermic (38 degrees C) cardiopulmonary bypass.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D001831:Body Temperature; D002315:Cardiopulmonary Bypass; D004195:Disease Models, Animal; D005069:Evaluation Studies as Topic; D005260:Female; D006324:Heart Arrest, Induced; D006863:Hydrogen-Ion Concentration; D007036:Hypothermia, Induced; D007430:Intraoperative Care; D008297:Male; D008722:Methods; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism*; D012756:Sheep; D013318:Stroke Volume; D013997:Time Factors; D014159:Transducers