[Evolution of myocardial temperature following cardioplegia with and without complementary pericardial cooling....

Myocardial temperatures were measured after cardioplegia during cardiac surgery with and without pericardial cooling by a cold bath. Eight animals (50 kg pigs) were placed on cardiopulmonary bypass using a protocol reproducing clinical operating conditions as closely as possible: myocardial mass, median sternotomy, general hypothermia at 25 degrees. Two injections of cardioplegic solution were administered, one at aortic clamping and the other, 30 minutes later. Four animals (Group A) were used as reference. The four animals in Group B underwent pericardial irrigation with serum at 4 degrees C. Myocardial temperatures were measured at 9 anatomical sites every 10 minutes, (a total of 1008 measurements) and compared statistically. The results in the control group showed that myocardial warming after cardioplegia was intense and rapid at all sites. The sub-epi and sub-endocardial temperatures rose from 7 to 24 degrees in 30 minutes, and in the first 10 minutes, a rewarming of 8,5 degrees was observed. When pericardial cooling was used with cardioplegia, myocardial refrigeration was improved. The temperature remained below 15 degrees C (p less than 0,05 compared with Group A). Only a 3 degrees rise in temperature was observed at the 10th minute after cardioplegia (p less than 0,001). The rise temperature was of 2 degrees at the 20th minute, and 1 degree at the 30th minute. All temperatures remained below 15 degrees C (p less than 0,01). The authors emphasise the benefits of pericardial irrigation associated with cardioplegia for constant, durable and stable myocardial protection by cooling.