Experimental determination of the safe minimum perfusion flow rate for low-flow hypothermic cardiopulmonary bypass

This study investigated the safe minimum perfusion flow rate for low-flow h ypothermic cardiopulmonary bypass in a canine model. The adequacy of cerebr al oxygenation was determined from the adenosine concentration, the oxygen saturation of cerebral venous blood and brain oxyhemoglobin level. In exper iment 1, nine beagles were cooled on bypass to a nasopharyngeal temperature of 18 degrees C and the perfusion flow rate was reduced in a stepwise fash ion every 30 min from 100 to 50, 30, 20 and 10 ml/kg per min. In experiment 2, six beagles were cooled on bypass as in experiment 1, and flow was main tained at 30 ml/kg per min for 120 min. At a perfusion flow rate of 30 ml/k g per min, adequate cerebral oxygenation was maintained for 120 min, In con trast, perfusion flow rates of 20 and 10 ml/kg per min were associated with cerebral ischemia, (C) 1999 The International Society for Cardiovascular S urgery. Published by Elsevier Science Ltd. All rights reserved.