• M G E Fenten, S M K Bakker, D J Touw, B J F van den Bemt, G J Scheffer, P J C Heesterbeek, and R Stienstra.
• Department of Anesthesiology, Sint Maartenskliniek, Nijmegen, The Netherlands.
• Acta Anaesthesiol Scand. 2017 Mar 1; 61 (3): 338-345.

BackgroundAlthough considered safe, no pharmacokinetic data of high dose, high volume local infiltration analgesia (LIA) with ropivacaine without the use of a surgical drain or intra-articular catheter have been described. The purpose of this study is to describe the maximum total and unbound ropivacaine concentrations (Cmax , Cu max ) and corresponding maximum times (Tmax , Tu max ) of a single-shot ropivacaine (200 ml 0.2%) and 0.75 mg epinephrine (1000 μg/ml) when used for LIA in patients for total knee arthroplasty.MethodsIn this prospective cohort study, 20 patients were treated with LIA of the knee for primary total knee arthroplasty. Plasma samples were taken at 20, 40, 60, 90, 120, 240, 360 min and at 24 h after tourniquet release, in which total and unbound ropivacaine concentrations were determined.ResultsResults are given as median [IQR]. Highest ropivacaine concentration (Cmax ) was 1.06 μg/ml [0.34]; highest unbound ropivacaine concentration (Cu max ) was 0.09 μg/ml [0.05]. The corresponding time to reach the maximum concentration for total ropivacaine was 312 min [120] after tourniquet release, and for the unbound fraction 265 [110] min after tourniquet release.ConclusionAlthough great inter-individual variability was found between the maximum ropivacaine concentrations, both maximum total and unbound serum concentrations of ropivacaine remained well below the assumed systemic toxic thresholds of 4.3 and 0.56 μg/ml.© 2017 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

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