PURPOSE: Hypotension in the sitting position may reduce cerebral perfusion and oxygenation. We prospectively determined the incidence of cerebral oximetry (rSO2) desaturation in seated patients undergoing ambulatory shoulder arthroscopy. METHODS: A cohort of 99 patients received regional anesthesia and intravenous sedation, and their blood pressure was recorded every five minutes. Hypotension was defined as the occurrence of any of the following: > 30% decline in mean arterial pressure (MAP), systolic blood pressure < 90 mmHg, or MAP <66 mmHg. Cerebral desaturation was defined as a > 20% decrease in rSO2 from baseline. The association of rSO2 desaturation with potential risk factors was examined by the generalized estimating equation to account for within patient correlation and multiple observations per patient. We fitted desaturation with three models: 1) unadjusted (i.e., hypotension as sole regressor); 2) time-trend adjusted; and 3) baseline-factors adjusted model. RESULTS: Hypotension occurred in 76% of observations (mean duration 4,261 sec), but cerebral desaturation was seen in only 0.77% of observations (mean duration 426 sec). Ninety-nine percent of patients experienced hypotension, but cerebral desaturation occurred in only 10%. By unadjusted modelling, hypotension was associated with cerebral desaturation (odds ratio = 3.21; P = 0.02). Once time-trend adjusted, cerebral desaturation was associated with time from baseline but not with hypotension (P = 0.14). When adjusted for baseline factors, the analysis demonstrated a non-significant association with hypotension (P = 0.34) but a significant association with the presence of risk factors for cerebrovascular disease (P = 0.01). CONCLUSIONS: Despite frequent hypotension in the sitting position, rSO2 desaturation was uncommon during shoulder arthroscopy performed in the sitting position with regional anesthesia.
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