Pulsatile perfusion improves regional myocardial blood flow during and after hypothermic cardiopulmonary bypass in a neonatal piglet model.

Abstract

Pediatric myocardial related morbidity and mortality after cardiopulmonary bypass (CPB) are well documented, but the effects of pulsatile perfusion (PP) versus nonpulsatile perfusion (NPP) on myocardial blood flow during and after hypothermic CPB are unclear. After investigating the effects of PP versus NPP on myocardial flow during and after hypothermic CPB, we quantified PP and NPP pressure and flow waveforms in terms of the energy equivalent pressure (EEP) for direct comparison. Ten piglets underwent PP (n = 5) or NPP (n = 5). After initiation of CPB, all animals underwent 15 minutes of core cooling (25 degrees C), 60 minutes of hypothermic CPB with aortic cross-clamping, 10 minutes of cold reperfusion, and 30 minutes of rewarming. During CPB, the mean arterial pressure (MAP) and pump flow rates were 40 mm Hg and 150 ml/kg per min, respectively. Regional flows were measured with radiolabeled microspheres. During normothermic CPB, left ventricular flow was higher in the PP than the NPP group (202+/-25 vs. 122+/-20 ml/l 00 g per min). During hypothermic CPB, no significant intragroup differences were observed. After 60 minutes of ischemia and after rewarming (276+/-48 vs. 140+/-12 ml/100 g per min; p < 0.05) and after CPB (271+/-10 vs. 130+/-14 ml/100 g per min; p < 0.05), left ventricular flow was higher in the PP group. Right ventricular flow resembled left ventricular flow. The pressure increase (from MAP to EEP) was 10+/-2% with PP and 1% with NPP (p < 0.0001). The increase in extracorporeal circuit pressure (ECCP) (from ECCP to EEP) was 33+/-10% with PP and 3% with NPP (p < 0.0001). Pulsatile flow generates significantly higher energy, enhancing myocardial flow during and after hypothermic CPB and after 60 minutes of ischemia in this model.