Cerebral desaturation events in the beach chair position: correlation of noninvasive blood pressure and estimated temporal mean arterial pressure.

BACKGROUND

Cerebral oximetry (rSO2) has emerged as an important tool for monitoring of cerebral perfusion during surgery. High rates of cerebral desaturation events (CDEs) have been reported during surgery in the beach chair position. However, correlations have not been made with blood pressure measured at the cerebral level. The purpose of this study was to examine the correlations between brachial noninvasive blood pressure (NIBP) and estimated temporal mean arterial pressure (eTMAP) during CDEs in the beach chair position.

METHODS

Fifty-seven patients underwent elective shoulder surgery in the beach chair position. Values for eTMAP, NIBP, and rSO2 were recorded supine (0°) after induction and when a CDE occurred in the 70° beach chair position. Twenty-six patients experienced 45 CDEs, defined as a 20% drop in rSO2 from baseline.

RESULTS

Median reduction in NIBP, eTMAP, and rSO2 from baseline to the CDE were 48.2%, 75.5%, and 33.3%, respectively. At baseline, there was a significant weak negative correlation between rSO2 and NIBP (rs = -0.300; P = .045) and no significant association between rSO2 and eTMAP (rs = -0.202; P = .183). During CDEs, there were no significant correlations between rSO2 and NIBP (rs = -0.240; P = .112) or between rSO2 and eTMAP (rs = -0.190; P = .212). No significant correlation between the decrease in rSO2 and NIBP (rs = 0.064; P = .675) or between rSO2 and eTMAP (rs = 0.121; P = .430) from baseline to CDE was found.

CONCLUSION

NIBP and eTMAP are unreliable methods for identifying a CDE in the beach chair position. Cerebral oximetry provides additional information to the values obtained from NIBP and eTMAP, and all should be considered independently and collectively.