title: The relative importance of alkalinity, temperature, and the washout effect of bicarbonate-buffered, multidose cardioplegic solution.
abstract: Recent experimental and clinical studies from our institution have shown that the administration of cold, bicarbonate-buffered, hyperkalemic crystalloid cardioplegic solution resulted in a significant rise in intramyocardial pH. This rise could theoretically be caused by (1) the alkalinity of the solution administered (pH 8.2 at 25 degrees C), (2) the washout of acid metabolites with each administration, and (3) hypothermia per se. To investigate the relative effects of each of these three factors on intramyocardial pH, dogs on cardiopulmonary bypass received crystalloid cardioplegic solution either at 10 degrees C (n = 9) or at 37 degrees C (n = 8) every 30 min during 2 hr of aortic cross-clamping. Myocardial temperature, intramyocardial pH, and CO2 tension (Pmco2) were measured continuously. Needle biopsy specimens were taken every 30 min for biochemical and ultrastructural analysis. Before aortic cross-clamping, intramyocardial pH was 7.07 +/- 0.06 in both groups (+/- SEM). Upon each administration of cardioplegic solution, hearts in the 10 degrees C group cooled to 10 degrees to 15 degrees C and intramyocardial pH increased on the average by 0.31 +/- 0.03 units (p less than .001). In the 37 degrees C group intramyocardial pH was unaffected by cardioplegic solution. At the end of the cross-clamping period, intramyocardial pH had declined to 6.49 +/- 0.13 in the 10 degrees C group and to 5.60 +/- 0.08 in the 37 degrees C group, the fall in pH being significantly greater in the 37 degrees C group than in the 10 degrees C group (p less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001639:Bicarbonates; D001831:Body Temperature; D002021:Buffers; D002245:Carbon Dioxide / Q000378:metabolism; D004285:Dogs; D005260:Female; D006324:Heart Arrest, Induced / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007036:Hypothermia, Induced; D008297:Male; D009206:Myocardium / Q000378:metabolism / Q000648:ultrastructure; D012996:Solutions; D013696:Temperature
chemical_list: D001639:Bicarbonates; D002021:Buffers; D012996:Solutions; D002245:Carbon Dioxide; D000255:Adenosine Triphosphate