The Effects of Rewarming Speed on Cerebral Circulation and Oxygen Metabolism during the Rewarming Period of Cardiopulmonary Bypass / 日本心臓血管外科学会雑誌

ABSTRACT

We investigated the effects of rewarming speed on cerebral circulation and oxygen metabolism during cardiopulmonary bypass (CPB). Twenty-four adult patients who had undergone open heart surgery with moderately hypothermic CPB were divided into two groups. In the slow rewarming group (group S), the rates of increase of blood temperature were under 0.1°C/min. In the rapid rewarming group (group R), they were more than 0.1°C/min. Mean blood flow velocity in the middle cerebral artery (mean MCAv) was measured by transcranial Doppler ultrasonography, and the index of cerebral oxygen consumption was evaluated by Doppler-estimated cerebral metabolic rate for oxygen (D-CMRO₂). The change of oxyhemoglobin level in the brain (Oxy Hb) was monitored by near-infrared spectroscopy. In group S, mean MCAv and D-CMRO₂ changed in a parallel manner following the changes of the rectal temperature throughout the periods, and mean MCAv was always higher than D-CMRO₂. In group R, however, the rate of increase of D-CMRO₂ was more rapid than that in group S from the beginning of rewarming, and D-CMRO₂ exceeded the level of mean MCAv just before termination of CPB. In addition, Oxy Hb in group R showed more rapid changes than that of group S. In conclusion, rapid rewarming during CPB may cause the disruption of cerebral flow-metabolism coupling.