Jugular bulb oxygen saturation and middle cerebral blood flow velocity during cardiopulmonary bypass

This study investigates changes of jugular bulb oxygen saturation (SjO2) measured by fiberoptic jugular bulb oximetry and changes of intracranial hemodynamics using transcranial Doppler sonography (TCD) during cardiopulmonary bypass (CPB) for coronary artery bypass graft (CABG) in 17 ASA III patients. Anesthesia was maintained with fentanyl, midazolam, and continuous infusion of etomidate. Hypothermic CPB (27 degrees C) was managed according to alpha-stat conditions. SjO2 (%) was measured by a fiberoptic catheter (Opticath F 5.5; Abbott Critical Care Systems) placed in the right jugular bulb via the right internal jugular vein. Mean blood flow velocity (Vmean, cm/s) was measured in the middle cerebral artery using a bidirectional 2-MHz TCD system (Transpect, Medasonics). Data were recorded continuously from the beginning to the end of the CPB. During cooling and hypothermia (27 degrees C); SjO2 and Vmean did not change compared with values at the start of CPB. However, with the beginning of rewarming, Vmean was increased 65% compared with stable hypothermia (27 degrees C). This increase in Vmean was associated with a 25% decrease in SjO2. Maximum desaturation occurred at a 36 degrees C jugular bulb temperature. During cooling and stable hypothermia, global oxygen balance and intracerebral perfusion seemed to be maintained. However, a major alteration in the balance of the cerebral oxygen supply and demand may occur in response to rewarming despite increases in Vmean. Findings suggest inadequate increases in CBF to meet cerebral metabolic demand. Further investigations need to validate these findings with biochemical techniques and neuropsychological tests.