Factors contributing to episodes of bradycardia hypotension during shoulder arthroscopic surgery in the sitting position after interscalene block

BACKGROUND: Arthroscopic shoulder surgery has been performed in the sitting position under interscalene block (ISB). Bradycardia hypotension (BH) episodes have a reported incidence of 13-29% in this setting. We performed a retrospective study to investigate contributing factors to the occurrence of BH episodes. METHODS: According to BH episodes, we divided 63 patients into two groups: BH group (n = 13) and non-BH group (n = 50). Anesthetic records and block data sheets were reviewed for demographic data, intraoperative medications, sites of ISB, use of epinephrine in local anesthetics, degree of sensory blockade, and percent change of heart rate or systolic blood pressure (SBP). Statistical analysis was done using Chi square test and Student's t-test. RESULTS: There were no significant differences in the use of epinephrine in local anesthetics between the two groups. The location of ISB site was different between the two groups in that there were relatively more right-sided ISBs in the BH group than in the non-BH group (P = 0.048). The degree of sensory blockade was lower, but not significantly, in the C8 and T1 dermatomes of the BH group than in the non-BH group (P = 0.060 and 0.077, respectively). There was a relatively higher incidence of fentanyl supplementation in the BH group than in the non-BH group (P = 0.000). CONCLUSIONS: These results suggest that right ISB and perioperative supplementation of fentanyl due to incomplete block are possible contributing factors to the occurrence of BH episodes in the sitting position during shoulder surgery using ISB.