[Thermal isolation of the heart by means of a plastic foam pad during surgical cooling of the heart: experimental study].

Abstract

Maintenance of myocardial cooling during aortic clamping is a problem encountered currently during heart surgery. A plastic foam isolation pad was studied. Eight animals (pigs weighing 50 kg) were placed on extracorporeal circulation, 4 of them constituting the control group (A). Two coronary injections of a cardioplegic solutions were administered, the first at the time of aortic clamping and the second 30 minutes later. The myocardium of the 4 animals in the treated group (B) was isolated with the foam pad, and this significantly prolonged the "cold" effect of the cardioplegic. Ten minutes after injection of the cardioplegic, temperature of the total myocardial mass with isolation was between 10.7 and 12 degrees C, as against 16 to 18 degrees C in the reference group (p less than 0.05). By the 20th minute, the isolated myocardium was at approximately 15 degrees C as against 22 degrees C in group A (p less than 0.01). Finally, by the 30th minute, temperature in group B was 17 degrees C as against 23 degrees C in group A (p less than 0.01). Reheating of the heart was significantly slowed by thermal isolation, though the limit of 15 degrees C was reached by the 20th minute. To ensure that myocardial temperature remains below this limit when the foam pad is employed, further injections of cardioplegic solutions are necessary every 20 minutes.