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Ann Thorac Surg 2000;69:491-497
© 2000 The Society of Thoracic Surgeons

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Original Articles

Biologically variable pulsation improves jugular venous oxygen saturation during rewarming

^a Department of Anesthesia, University of Manitoba, Winnipeg, Manitoba, Canada
^b Department of Surgery, University of Manitoba, Winnipeg, Manitoba, Canada
^c Department of Community Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada

Address reprint requests to Dr Mutch, Department of Anesthesia, St. Boniface General Hospital, 409 Taché Ave, Winnipeg, MB, Canada R2H 2A6
e-mail: amutch{at}ms.umanitoba.ca

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 O₂ saturation (SjvO₂) below 50% during rewarming from hypothermia was compared for the two bypass techniques. A SjvO₂ 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 -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, SjvO₂ was measured at 5 minute intervals. The mean and cumulative area for SjvO₂ 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 O₂, and arterial partial pressure CO₂ 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 SjvO₂ 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 SjvO₂ during rewarming from hypothermic CPB. Both mean and cumulative area under the curve for SjvO₂ 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.

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