The effects of pulsatile cardiopulmonary bypass on cerebral and renal blood flow in dogs

Objective: The purpose of this study was to determine the effects of pulsatility on cerebral blood flow, cerebral metabolism, and renal blood flow over a range of cardiopulmonary bypass temperature and flow conditions. Design/Setting: The investigation was prospective, randomized, and performed in a canine physiology laboratory at the Mayo Foundation. Participants and Interventions: Anesthetized dogs were studied during pulsatile (n = 9) or nonpulsatile (n = 10) cardiopulmonary bypass at two flow rates (2.4 and 1.2 L/min/m²) at each of three temperatures (37°, 32°, and 27°C). Pulsatility was achieved by use of a pediatric intraaortic balloon pump. Cerebral blood flow and metabolic rate were determined using the sagittal sinus outflow method. Renal blood flow was determined by s periarterial ultrasonic flow probe. Measurements and Main Results: In the pulsatile group, a pulse pressure of 29 mmHg had no effect on cerebral blood flow or metabolism at any temperature under either flow condition. Renal blood flow was also unaffected by pulsatility, but decreased with hypothermia and reduced pump flow. Pulsatility also did not attenuate the Systemic effects of normothermic hypoperfusion. Conclusions: Pulsatility has no significant effect on cerebral or renal perfusion over a broad range of cardiopulmonary bypass temperature and flow conditions. Cerebral blood flow and metabolism were functions of temperature but not pulsatility or flow rate. Renal blood flow was affected by both temperature and cardiopulmonary bypass flow rate but not by pulsatility. Finally, central nervous system perfusion may be preserved under low-flow cardiopulmonary bypass conditions by shunting of perfusion from splanchnic vascular beds.