Adjuvant dexamethasone with bupivacaine prolongs the duration of interscalene block: a prospective randomized trial.

PURPOSE

To identify the effects of adding two different doses of dexamethasone on the duration and quality of interscalene block in patients undergoing shoulder surgery in ambulatory surgery settings.

METHODS

The study design was reviewed and approved by the University at Buffalo Institutional Review Board for Human Subjects. After obtaining informed consent, a total of 90 patients undergoing shoulder surgery using interscalene block with 0.5% bupivacaine (40 mL) were assigned randomly to one of three groups: control patients, "Group C," who received no additive; low dose, "Group L," who received additional dexamethasone 4 mg; and high dose, "Group H," who received dexamethasone 8 mg in addition to 0.5% bupivacaine. Postoperative analgesia was assessed using the numeric rating scores of pain and the postoperative consumption of acetaminophen 325 mg + hydrocodone 7.5 mg tablets. Analysis was by intention to treat. Statistical significance was tested using a two-way analysis of variance and a nonparametric analysis of variance for consumption of analgesics.

RESULTS

Four patients were excluded from the study due to either a failed block or inadequate follow-up. The duration of analgesia was significantly prolonged in both Group L (21.6 ± 2.4 h) and Group H (25.2 ± 1.9 h) compared with Group C (13.3 ± 1.0 h) (p < 0.05). Similarly, the duration of motor block was longer in both Group L (36.7 ± 4.1 h), and Group H (39.2 ± 3.9 h) compared to Group C (24.6 ± 3.3 h) (p < 0.05). Postoperative analgesic consumption for the first 48 h was significantly lower in Group L (6.5 [4-8] tabs) and in Group H (5.5 [4-7] tabs) vs. 9.5 [8-12] tabs in Group C (p < 0.01). There were no adverse events related to dexamethasone during the 4-week follow-up period.

CONCLUSION

The addition of dexamethasone to bupivacaine significantly prolonged the duration of the motor block and improved the quality of analgesia following interscalene block. There was no difference in the duration of analgesia and motor block between low-dose and high-dose dexamethasone.