Validity of fiber optic cerebral vein oximetry during extracorporeal circulation

This study investigates the accuracy of continuous jugular bulb venous oximetry during different conditions of hypothermic cardiopulmonary bypass (CPB) (27 degrees C) for coronary artery bypass graft. 38 ASA III patients were studied following Ethical Care Committee approval and informed consent. Patients were anaesthetized with fentanyl, midazolam, continuous infusion of etomidate and pancuronium. Ventilation was performed with oxygen in air. CPB was managed according to alpha-stat conditions under moderate hypothermia (27 degrees C). SjO2 (%) and jugular bulb temperature (degree C) were measured by a fiberoptic thermodilution catheter (Opticath F 5.5, Abbott Critical Care Systems) placed in the jugular bulb via the internal jugular vein. Appropriate catheter position was x-ray controlled prior to the measurements. The fiberoptic data were compared to co-oximetric data of blood samples after induction of anaesthesia, 2 min following start of CPB, during cooling, stable hypothermia and rewarming of CPB. Assessing of agreement (Bland/Altman and Bartko). Jugular venous oximetry correlated closely with the co-oximeter determinations after induction of anaesthesia. However, following start of CPB accuracy was decreased. During cooling, stable hypothermia and rewarming oximetric data correlated well with co-oximetry, however, over-estimating the SjO2 by 1.4 to 2%. The present data show that continuous jugular bulb venous oximetry is accurate and reliable for continuous SjO2 monitoring during hypothermic CPB for cardiac surgery. Induction of CPB and hemodilution affect accuracy slightly, but changes are well detected. Before clinical intervention SjO2 should be confirmed by laboratory co-oximetry.