Jugular venous bulb oxyhemoglobin saturation during cardiac surgery : accuracy and reliability using a continuous monitor

Previous studies have demonstrated the feasibility of continuously monitoring jugular venous oxygen saturation (SjO2) with a fiberoptic catheter during hypothermic cardiopulmonary bypass (CPB). In the present study, with patients maintained at either moderate (28 degrees C) or mild (32-34 degrees C) hypothermia during CPB, SjO2 values obtained from a fiberoptic catheter were compared to intermittent samples analyzed by a co-oximeter. Twenty patients scheduled for elective coronary artery or valvular surgery had a 5.5 Fr Opticath catheter inserted into the left internal jugular bulb after induction of general anesthesia. The catheter was calibrated in vitro and in vivo according to the manufacturer's specifications. Catheter and co-oximetry SjO2 values obtained at four time points--1) pre-CPB, 2) target CPB temperature, 3) mid-rewarming, and 4) post-CPB--were compared using linear regression, Bland-Altman analysis, and Shrout-Fleiss interclass correlation coefficient analysis. These statistical methods revealed poor correlation between the catheter and co-oximetry SjO2 values: r = 0.44 by linear regression and 0.32 by interclass correlation coefficient analysis, and was unacceptably discrepant by Bland-Altman analysis. Oxyhemoglobin saturation values obtained continuously from a jugular venous bulb fiberoptic catheter during CPB may not accurately reflect true oxyhemoglobin saturation, and caution is warranted when interpreting SjO2 values obtained from a fiberoptic catheter during CPB.