Cerebral oximetry during cardiac surgery: The association between cerebral oxygen saturation and perioperative patient variables

Objective: This "real-world" study was designed to assess the patterns of regional cerebral oxygen saturation (rSO₂) change during adult cardiac surgery. A secondary objective was to determine any relation between perioperative rSO₂ (baseline and during surgery) and patient characteristics or intraoperative variables. Design: Prospective, observational, multicenter, nonrandomized clinical study. Setting: Cardiac operating rooms at 3 academic medical centers. Participants: Ninety consecutive adult patients presenting for cardiac surgery with or without cardiopulmonary bypass. Interventions: Patients received standard care at each institution plus bilateral forehead recordings of cerebral oxygen saturation with the 7600 Regional Oximeter System (Nonin Medical, Plymouth, MN). Measurements and Main Results: The average baseline (before induction) rSO₂ was 63.9 ± 8.8% (range 41%-95%); preoperative hematocrit correlated with baseline rSO₂ (0.48% increase for each 1% increase in hematocrit, p = 0.008). The average nadir (lowest recorded rSO₂ for any given patient) was 54.9 ± 6.6% and was correlated with on-pump surgery, baseline rSO ₂, and height. Baseline rSO₂ was found to be an independent predictor of length of stay (hazard ratio 1.044, confidence interval 1.02-1.07, for each percentage of baseline rSO₂). Conclusions: In cardiac surgical patients, lower baseline rSO₂ value, on-pump surgery, and height were significant predictors of nadir rSO₂, whereas only baseline rSO₂ was a predictor of postoperative length of stay. These findings support previous research on the predictive value of baseline rSO₂ on length of stay and emphasize the need for further research regarding the clinical relevance of baseline rSO₂ and intraoperative changes.