Patient-initiated mandatory boluses for ambulatory continuous interscalene analgesia: An effective strategy for optimizing analgesia and minimizing side-effects

Abstract

Background: This prospective, randomized study tested the hypothesis that a reduced dose continuous interscalene regimen incorporating a low background infusion with mandatory boluses would provide similar shoulder surgery analgesia compared with a dose regimen incorporating a conventional higher background infusion.MethodsAfter rotator cuff surgery, patients received via an interscalene catheter, one of two elastomeric pumps, each having a 5 ml per 60 min bolus function and a 2 ml h-1 (n38) or 5 ml h-1 (n43) ropivacaine 2 mg ml-1 infusion. Boluses commenced from the onset of pain and continued for >48 h as required (pro re nata, PRN) up to every hour for a numerical rating pain score (NRPS, 010) >2. Group 2 ml h-1 received mandatory 6 hourly boluses irrespective of the NRPS. Rescue tramadol was available. Patients were questioned on postoperative days 1 and 2 for treatment effectiveness and side-effects.ResultsPostoperative pain was similar between the groups [Group 2 ml h-1 day 2 median (IQR) (95 confidence interval of the mean) worst movement pain4 (15) (2.84.7) vs 4 (25) (3.14.6), P0.99], as were night awakenings and tramadol consumption. Numerically rated numbness and weakness were similar between the groups; however, nine patients (21) in the 5 ml h-1 group vs one (3) in the 2 ml h-1 group required a temporary infusion cessation due to side-effects (predominantly hand numbness) (P0.02).ConclusionsContinuous interscalene ropivacaine 0.2 2 ml h-1 with mandatory 6 hourly (and PRN) boluses provides similar analgesia after rotator cuff repair but with reduced side-effects compared with 5 ml h-1 with PRN only boluses. © The Author [2010]. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved.