Brain tissue pH, oxygen tension, and carbon dioxide tension in profoundly hypothermic cardiopulmonary bypass. Pulsatile assistance for circulatory arrest, low-flow perfusion, and moderate-flow perfusion.

Abstract

The brain tissue pH, oxygen tension, and carbon dioxide tension were experimentally examined during profoundly hypothermic cardiopulmonary bypass with core cooling and core rewarming. Sixty-minute circulatory arrests (n = 28, group I), 120-minute low-flow perfusions (25 ml/kg/min; n = 16, group II), and 120-minute moderate-flow perfusions (50 ml/kg/min; n = 16, group III) were accomplished with and without pulsatile flow. In group I, progressive brain tissue acidosis and hypercapnia were recovered with pulsatile assistance. In group II, brain tissue acidosis and hypercapnia were recovered completely with pulsatile assistance but incompletely without it. In group III mild acidosis was eliminated with pulsatile assistance where the pH was significantly higher than in groups I and II, and brain tissue carbon dioxide pressure was significantly lower than in groups I and II with and without pulsatile assistance. Brain tissue hypoxia was severe in group I, slight in group II, but not found in group III. We concluded that a perfusion flow rate will decide the safe period, and a pulsatile assistance will promote brain protection at any flow rate in profoundly hypothermic cardiopulmonary bypass.