Beta-adrenergic blockers and vasovagal episodes during shoulder surgery in the sitting position under interscalene block.

UNLABELLED: Shoulder surgery is often performed with patients in the sitting position under interscalene block anesthesia. Vasovagal episodes, characterized by a sudden decrease in heart rate and/or blood pressure, have a reported incidence of 17%-24% in this setting. We performed a retrospective study to determine whether there was an association between the use of beta-adrenergic blockers and the incidence of these episodes. Of the 150 patients identified, 20 (13.3%) had a vasovagal event. Similar proportions of patients had received a beta-adrenergic blocker in the group who had a vasovagal event compared with those who did not (20% vs 18%; P = 0.95). No other differences could be identified. We conclude that vasovagal episodes occur frequently in this setting with no identifiable risk factors. Beta-adrenergic blockers were not associated retrospectively with either an increased or decreased incidence of these episodes. The most likely mechanism involves the Bezold-Jarisch reflex.

IMPLICATIONS: In this retrospective study of 150 patients who underwent shoulder surgery in the sitting position under interscalene block, we found a 13% incidence of vasovagal episodes. Unlike a previous study, this was not affected by the use of beta-blockers. A randomized, prospective study is necessary to clarify this issue.