Prolonged rewarming after hypothermic cardiopulmonary bypass does not attenuate reduction of jugular bulb oxygen saturation

Abstract

Objective: This study investigates the effects of rapid versus graded rewarming on decreases in jugular bulb oxygen saturation (SjO2) during cardiopulmonary bypass (CPB) in a prospective nonrandomized and nonblinded design.

Setting and participants: At the Department of Anesthesiology (University Hospital Eppendorf, Germany), 28 patients (ASA III) undergoing coronary artery bypass graft were investigated.

Intervention: CPB was managed according to alpha-stat conditions during moderate hypothermia (27 degrees C). In group 1 (n = 17), rewarming was performed by increasing the perfusate temperature to 36 degrees C within 7 minutes, in group 2 (n = 11) within 15 minutes.

Measurements and main results: SjO2 was measured by a fiberoptic catheter placed in the right jugular bulb. Data were recorded before and 40 minutes after the start of rewarming every 5 minutes. During rewarming of CPB, SjO2 was decreased to 43 +/- 7% in group 1 and to 44 +/- 4% in group 2. In groups 1 and 2, the maximum reduction of SjO2 occurred 17 minutes and 30 minutes after start of rewarming, respectively. The delayed reduction of SjO2 in group 2 correlated strongly with the prolonged increase in jugular bulb temperature.

Conclusion: The current data show that slow rewarming does not attenuate reductions of SjO2. This suggests that the reduction of SjO2 during rewarming of CPB is not a function of the rewarming speed but is strongly correlated with the increase in jugular bulb temperature, with a maximum effect just before reaching normothermia of the brain.