Ann Thorac Surg 1994;57:512-514
© 1994 The Society of Thoracic Surgeons
Continuous measurement of intramyocardial pH: Relative importance of hypotliermia and cardioplegic perfusion pressure and temperature
Richard E. Clark, M.D.*
Cardiovascular/Pulmonary Research Center, Allegheny-Singer Research Institute, Pittsburgh, Pennsylvania, USA
* Address reprint requests to Dr Clark, Cardiovascular/Pulmonary Research Center, Allegheny-Singer Research Institute, 320 E North St, Pittsburgh, PA 15212-9986.
The continuous measurement of intramyoordial pH was used id follow the progression of ischemia enyocardiat preservation following 38dgC or 25dgC global ischemia alone or with the administration or one or two doses of 38dgC, 25dgC, or 1dgC crystalloid cardioplegiaal aortic root perfusion pressures of 90 mm Hg or 130 mm Hg was assessed. A new miniature myocardial transducer incorporating fiberoptic technology met dual pH and temperalure-sensing capability was placed into the left ventricular free wall and septum of 44 sheep undergoing ischemic went 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 prressure of 130 mm Hg provided enhanced myocardial protection by increasing the total ischemial time (5 to 10 minutes) with one (p < 0.01) or two (p < 0.00) doses of cardioplegic solution until a given functional level of recovery was attained. Aortic 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. Hypolhemik (25 °C) global ischemia alone enhanced myocardial protection by providing increased time (p 0.01) until a given functional level of recovery was attained with a slower rate of change of pH (p < 0.01) compared wilh nomothermic (38°C) global ischemia alone. Very cold (1°C) cardioplegia during hypothermic (25°C) global ischemia generally enhanced myocardial protection by providing increased time (92 minutes) until a myocadiol pH value of 6.8 was attained. It is concluded that continuous measurement of inlestitial myocardial pH and temperature is a practical and useful method for assessment of the adequacy of myocardial protective methods and solutions.
Copyright © 1994 by The Society of Thoracic Surgeons.