COMPUTER-CONTROLLED CARDIOPULMONARY BYPASS INCREASES JUGULAR VENOUS OXYGEN-SATURATION DURING REWARMING

Background. Conventional roller pump apulsatile cardiopulmonary bypass (CPB) was compared with computer-controlled pulsatile bypass, which w as designed to recreate biological variability (return of beat-to-beat variability in rate and pressure with superimposed respiratory rhythm s). The degree of jugular venous oxygen saturation (SjvO(2)) less than 50% during rewarming from hypothermic CPB was compared for the two by pass techniques. An SjvO(2) less than 50% during rewarming from hypoth ermic CFB is correlated with cognitive dysfunction in humans. Methods. Pigs were placed on CPB for 3 hours using a membrane oxygenator with alpha-stat acid-base management and arterial filtration. After baselin e measurements and normothermic CPB, the animals were randomized to ap ulsatile CPB (n = 12) or computer-controlled pulsatile CPB (roller pum p speed adjusted by an average of 2.9 voltage output modulations/s; n = 12). The animals were then cooled to a nasopharyngeal temperature of 28 degrees C. During rewarming to stable normothermic temperatures, S jvO(2) was measured at 5-minute intervals. The mean and cumulative are as for an SjvO(2) less than 50% were determined for all animals. Resul ts. No between-group differences in temperature were noted during hypo thermic CPB or during rewarming. The rate of rewarming was not differe nt between groups. Mean arterial pressure, partial pressure of oxygen in arterial blood, and partial pressure of carbon dioxide in arterial blood also did not differ between groups. The hemoglobin concentration was within 0.4 g/dL between groups at all time periods. Mean pulse pr essure was 10.0 +/- 4.8 mm Hg in the apulsatile CPB group and 20.7 +/- 5.2 mm Hg in the pulsatile CPB group (p = 0.0002; unpaired t test). M arkedly greater mean and cumulative areas under the curve for SjvO(2) less than 50% were seen with apulsatile CPB (164 +/- 209 versus 1.9 +/ - 3.6% . min, p = 0.021; and 1,796 +/- 2,263 versus 23 +/- 45% . min, p = 0.020, respectively). Conclusions. Computer-controlled pulsatile C PB was associated with significantly greater SjvO(2) during rewarming from hypothermic CPB. Both the mean and cumulative areas under the cur ve for SjvO(2) less than 50% exceeded a ratio of 75:1 for apulsatile v ersus computer-controlled pulsatile CPB. These experiments suggest tha t cerebral oxygenation was better preserved during rewarming from mode rate hypothermia with computer-controlled pulsatile CPB, which returne d biologic variability to the now pattern. (C) 1998 by The Society of Thoracic Surgeons.