Biologically variable pulsation improves jugular venous oxygen saturation during rewarming

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 pressur e with superimposed respiratory rhythms. Jugular venous O-2 saturation (Sjv O(2)) below 50% during rewarming from hypothermia was compared for the two bypass techniques. A SjvO(2) less than 50% during rewarming is correlated w ith cognitive dysfunction in humaas. Methods. Pigs were placed on CPB for 3 hours using a membrane oxygenator wi th a-stat acid base management and arterial filtration. After apulsatile no rmothermic 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 degrees C. During rewarming to stable normothermia, SjvO(2) was measured at 5 minut e intervals. The mean and cumulative area for SjvO(2) less than 50% was det ermined. Results. No between group difference in temperature existed during hypother mic CPB or during rewarming. Mean arterial pressure, arterial partial press ure O-2 and arterial partial pressure CO2 did not differ between groups. Th e hemoglobin concentration was within 0.4 g/dL between groups at all time p eriods. The range of systolic pressure was greater with BVP (41 +/- 18 mm H g) 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 = 0.00 4, Wilcoxon 2-sample test). Conclusions. Computer-controlled BVP resulted in significantly greater SjvO (2) during rewarming from hypothermic CPB. Both mean and cumulative area un der 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 re rewarming fr om moderate hypothermia with bypass that returns biological variability to the flow pattern. (C) 2000 by The Society of Thoracic Surgeons.