Biologically variable pulsation improves jugular venous oxygen saturation during rewarming

Abstract Background . Conventional pulsatile (CP) roller pump cardiopulmonary bypass (CPB) was compared to computer controlled biologically variable pulsatile (BVP) bypass designed to return beat-to-beat variability in rate and pressure with superimposed respiratory rhythms. Jugular venous O 2 saturation (SjvO 2 ) below 50% during rewarming from hypothermia was compared for the two bypass techniques. A SjvO 2 less than 50% during rewarming is correlated with cognitive dysfunction in humans. Methods . Pigs were placed on CPB for 3 hours using a membrane oxygenator with α-stat acid base management and arterial filtration. After apulsatile normothermic CPB was initiated, animals were randomized to CP (n = 8) or BVP (roller pump speed adjusted by an average of 2.9 voltage output modulations/second; n=8), then cooled to a nasopharyngeal temperature of 28°C. During rewarming to stable normothermia, SjvO 2 was measured at 5 minute intervals. The mean and cumulative area for SjvO 2 less than 50% was determined. Results . No between group difference in temperature existed during hypothermic CPB or during rewarming. Mean arterial pressure, arterial partial pressure O 2 , and arterial partial pressure CO 2 did not differ between groups. The hemoglobin concentration was within 0.4 g/dL between groups at all time periods. The range of systolic pressure was greater with BVP (41 ± 18 mm Hg) than with CP (12 ± 4 mm Hg). A greater mean and cumulative area under the curve for SjvO 2 less than 50% was seen with CP (82 ± 96 versus 3.6% ± 7.3% · min, p = 0.004; and 983 ± 1158 versus 42% ± 87% · min; p = 0.004, Wilcoxon 2-sample test). Conclusions . Computer-controlled BVP resulted in significantly greater SjvO 2 during rewarming from hypothermic CPB. Both mean and cumulative area under the curve for SjvO 2 less than 50% exceeded a ratio of 20 to 1 for CP versus BVP. Cerebral oxygenation is better preserved during rewarming from moderate hypothermia with bypass that returns biological variability to the flow pattern.