I.V. and perineural dexamethasone are equivalent in increasing the analgesic duration of a single-shot interscalene block with ropivacaine for shoulder surgery: a prospective, randomized, placebo-controlled study

Interscalene brachial plexus block (ISB) provides excellent, but time-limited analgesia. Dexamethasone added to local anaesthetics prolongs the duration of a single-shot ISB. However, systemic glucocorticoids also improve postoperative analgesia. The hypothesis was tested that perineural and i.v. dexamethasone would have an equivalent effect on prolonging analgesic duration of an ISB. We performed a prospective, double blind, randomized, placebo-controlled study. Patients presenting for arthroscopic shoulder surgery with an ISB were randomized into three groups: ropivacaine 0.5 (R); ropivacaine 0.5 and dexamethasone 10 mg (RD); and ropivacaine 0.5 with i.v. dexamethasone 10 mg (RDiv). The primary outcome was the duration of analgesia, defined as the time between performance of the block and the first analgesic request. Standard hypothesis tests (t-test, MannWhitney U-test) were used to compare treatment groups. The primary outcome was analysed by KaplanMeier survival analysis with a log-rank test and Coxs proportional hazards regression. One hundred and fifty patients were included after obtaining ethical committee approval and patient informed consent. The median time of a sensory block was equivalent for perineural and i.v. dexamethasone: 1405 min (IQR 10151710) and 1275 min (IQR 10952035) for RD and RDiv, respectively. There was a significant difference between the ropivacaine group: 757 min (IQR 635910) and the dexamethasone groups (P0.0001). I.V. dexamethasone is equivalent to perineural dexamethasone in prolonging the analgesic duration of a single-shot ISB with ropivacaine. As dexamethasone is not licensed for perineural use, clinicians should consider i.v. administration of dexamethasone to achieve an increased duration of ISB.