Background
We examined the effects of different anesthetics on cerebral oxygenation and systemic hemodynamics in patients undergoing surgery in beach chair position (BCP). Jugular venous bulb oxygen saturation (SjvO2) and regional cerebral tissue oxygen saturation (SctO2) were determined while patients were placed from the supine to BCP. Whether SctO2 and SjvO2 are interchangeable in assessing the cerebral oxygenation was also examined.
Methods
Forty patients undergoing shoulder surgery in BCP were randomly assigned to receive sevoflurane-nitrous oxide (S/N) or propofol-remifentanil (P/R) anesthesia. Four patients taking angiotensin II receptor antagonists were excluded post hoc. Mean arterial pressure and heart rate, as well as SjvO2 and SctO2, were measured before (postinduction baseline in supine position) and after BCP.
Results
Mean arterial pressure decreased by BCP in both groups. It was, however, significantly higher in S/N (n = 19) than in P/R group (n = 17) at 7 to 8 min after the positioning. SjvO2 also significantly decreased after BCP in both groups, the magnitude of which was lower in S/N than in P/R group (11 ± 10% vs. 23 ± 9%, P = 0.0006). The incidences of SjvO2 <50% and mean arterial pressure less than 50 mmHg were lower in S/N group, but SctO2and the incidence of cerebral desaturation (more than 20% decrease from baseline) did not significantly differ between the groups. SctO2 and SjvO2 were only weakly correlated (β = 0.218, r2 = 0.133). Bland-Altman analysis showed a mean difference of -7.2% with 95% limit of agreement between -38.2% and 23.8%.
Conclusions
The margin of safety against impaired cerebral oxygenation is greater and SjvO2 is more preserved with S/N than with P/R anesthesia. SctO2 may not be reliable in detecting a low SjvO2 during the surgery in BCP.
Oral clonidine premedication reduces induction dose and prolongs awakening time from propofol-nitrous oxide anesthesia
