PULSATILE VERSUS NONPULSATILE CARDIOPULMONARY BYPASS - NO DIFFERENCE IN BRAIN BLOOD-FLOW OR METABOLISM AT 27-DEGREES-C

Background: It is unclear whether nonpulsatile perfusion adversely affects the brain. This study compared cerebral blood now (CBF) and cerebral metabolic rate for oxygen (CMR(O2)) between pulsatile and nonpulsatile cardiopulmonary bypass (CPB) in rabbits at 27 degrees C. Methods: In experiment A, 24 anesthetized New Zealand white rabbits underwent pulsatile CPB at 27 degrees C, using or-stat acid-base management. Animals were randomized to three groups based upon the duration of the period of systolic ejection (100, 120, 140 ms) and were perfused for 20 min at each of three pulse rates (150, 200, 250 pulse/min), generating nine arterial pressure waveforms. Arterial pressure waveform, arterial and cerebral venous oxygen content, CBF (radiolabeled microspheres), and CMR(O2), (Fick) were measured at the end of each 2O-min period. In experiment B, 16 anesthetized rabbits were randomized to pulsatile (120-ms ejection period, 250 pulse/min) or nonpulsatile CPB at 27 degrees C. After 1 h, arterial pressure waveform, arterial and cerebral venous oxygen content, CBF and CMR(O2), were measured. Results: In experiment A, CBF and CMR(O2), were independent of ejection period and pulse rate. Thus, all nine waveforms were physiologically equivalent. In experiment B, CBF did not differ between pulsatile and nonpulsatile bypass, 30+/-4 versus 32+/-5 ml.100 g(-1).min(-1), respectively. CMR(O2) did not differ between pulsatile and nonpulsatile bypass, 1.7+/-0.2 versus 1.6+/-0.2 ml.100 g(-1).min(-1), respectively. Conclusions: During CPB in rabbits at 27 degrees C, neither CBF nor CMR(O2), is affected by now character.