Pharmacokinetics of 400 mg ropivacaine after periarticular local infiltration analgesia for total knee arthroplasty

Background and Aims: Although 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) and corresponding times to maximum concentration (Tmax) of a single shot ropivacaine (200ml 0.2%) and 0.75 mg epinephrine (1000μg mL-1) when used for LIA. Methods: In this prospective cohort study twenty 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 minutes and at 24 hours after tourniquet release, in which total and unbound ropivacaine concentrations were determined. Results: Results are given as mean (SD); median (range). Maximum total ropivacaine concentration was 1.06 (0.36); 1.00 (0.61 - 2.26) μg mL-1, corresponding Tmax was 311 (227); 240 (40-1440) minutes after tourniquet release (Figure 1). The highest measured unbound ropivacaine concentration was 0.13 μg mL-1. Conclusions: Maximumtotal and unbound serum concentrations of ropivacaine remained well below the assumed toxic thresholds of 4.3 and 0.56 μg mL-1, respectively, for systemic toxicity. (Figure Presented)