• R M Merivirta, K S Kuusniemi, S A Hurme, P J Neuvonen, P J Rautakorpi, K T Olkkola, and K A Leino.
• Department of Anaesthesiology, Intensive Care, Emergency Care and Pain Medicine of Turku University Hospital, Finland. riika.merivirta@tyks.fi
• Acta Anaesthesiol Scand. 2011 Feb 1;55(2):228-33.

BackgroundWe studied plasma bupivacaine concentrations in patients with a continuous subacromial bupivacaine infusion after an ambulatory arthroscopic shoulder surgery to evaluate whether it is feasible to discharge patients with an on-going infusion early on the operation day.MethodsSixteen ASA I-III patients undergoing elective arthroscopic shoulder surgery were randomized in 1:1 ratio to receive a continuous infusion of either 2.5 or 5.0 mg/ml bupivacaine subacromially for 48 h post-operatively. Before the commencement of the infusion, 20 ml of 5.0 mg/ml bupivacaine was injected subacromially in both groups. Plasma bupivacaine concentrations were defined as the primary endpoint and concentrations of its metabolites, side effects and pain scores as the secondary endpoints.ResultsThe mean total plasma bupivacaine concentration increased up to 48 h, the highest mean being 0.87 (SD 0.30) μg/ml during the 5.0 mg/ml treatment and 0.24 (0.10) μg/ml during the 2.5 mg/ml bupivacaine treatment. After 48 h, there was a significant difference between the groups in the plasma levels. The highest mean 4-hydroxy-bupivacaine and desbutylbupivacaine concentrations were 0.11 and 0.22 μg/ml, respectively. In the pain scores, no significant difference was found. No clear signs of toxicity were observed.ConclusionsThe concentrations of total bupivacaine and its metabolites remained below toxic levels. Excluding patients with renal or liver diseases, both 2.5 and 5.0 mg/ml bupivacaine as subacromial infusion 2 ml/h for 48 h following shoulder arthroscopy seem to be well tolerated, enabling patient discharge with an on-going infusion on the operation day. Because of similar side effects and pain scores in both groups, 2.5 mg/ml may be preferable.© 2010 The Authors. Journal compilation © 2010 The Acta Anaesthesiologica Scandinavica Foundation.

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