BackgroundEconomic evaluation has become an essential decision-making tool for health systems worldwide. This study was aimed at estimating the difference in the use of healthcare resources, days on sick leave, and costs between patients undergoing a standard-volume versus a low-volume ultrasound-guided interscalene brachial plexus block.MethodsThis is a post-hoc cost analysis of a double-blind, randomized, and controlled clinical trial. Forty-eight patients undergoing ultrasound-guided interscalene block received either 10 ml or 20 ml of levobupivacaine 0.25%. Analyses involved the public healthcare payer perspective (including visits to general practitioners, nursing staff, physiotherapy facilities, hospital admissions, outpatient diagnostic tests, etc.) and the limited societal perspective, including productivity losses (days on sick leave). Measurements were made at one-month and one-year follow-ups post-intervention. Differences in costs were estimated using two-part models adjusted by the costs incurred in the previous year.ResultsSubjects in the 10 ml group made greater use of general practitioner visits (mean difference [95% CI]: 3.35 [0.219 to 6.49]; p=0.036) and diagnostic tests (2.43 [0.601 to 4.26]; p=0.009), but less use of physical therapy (−12.9 [−21.7 to −4.06]; p=0.004). Mean (SD) cost differences from the public healthcare payer’s perspective were 1,461.34 $ (1,541.62) and 1,024.08$ (943.83) for the 10 ml and 20 ml groups, respectively (p=0.293). From the limited societal perspective, the differences were as follows: 7,036.53$ (8,077.58) and 8,666.56$ (9,841.10), respectively (p=0.937). While there were no differences in the above parameters at the one-month follow-up.ConclusionThe volume reduction proposed following interscalene block resulted in meaningful, albeit not statistically significant, clinical benefits and lower costs from a limited societal perspective for shoulder surgery. Thus, healthcare use and days on sick leave are variables to be taken into consideration when calculating the economic impact of surgical procedures.