NORMOTHERM CONTINUOUS BLOOD CARDIOPLEGIA FOR 4 HOURS IN AN IN-VIVO PIG MODEL

Warm, continuous blood cardioplegia should theoretically maintain card iac arrest for hours without ischaemic or hypothermic injury. In the a bsence of in vivo studies of myocardial metabolism and ultrastructural and/or functional preservation during and after more than 2 hours of cardiac arrest and after weaning from bypass, we devised a porcine mod el with a closed extracorporeal circuit for the heart alone. Normother mic blood cardioplegia was administered antegrade and recirculated for 2 or 4 hours, each in seven pigs. After aortic decramping all were su ccessfully weaned from bypass and reperfused for 1 hour. Thereafter we found no significant intergroup difference in haemodynamic characteri stics (average fall in mean arterial pressure 31.7 +/- 3.2% and 26.9 /- 2.6%) or blood analyses. After 5 and 60 minutes of cardiac arrest t here was minimal lactate production (5.7 +/- 10.7 and 0.5 +/- 10.5 nmo l/l, respectively), whereas in the remainder of the arrest period ther e was lactate uptake, indicating aerobic heart metabolism. Our setup a voids systemic hyperkalaemia, gives good cardiac protection with no de terioration between 2 and 4 hours and is well suited for studies on th e quiescent, blood-perfused oxygenated heart.