Pharmacokinetics of ropivacaine during extradural anesthesia for total hipreplacement

Study Objective: To determine concentratinos of ropivacine during epidural anesthesia with ropivacine 10 mg/mL in patients undergoing elective total h ip replacement. Design: Phase III prospective study. Setting: Orthopedic surgical unit of the University Hospital in Kiel, Germa ny. Patients: 11 ASA physical status I, II, and III patients undergoing electiv e total hip replacement after premedication with a benzodiazepine. Interven tions: Peripheral venous plasma samplles were collected prior to and 10, 15 , 20, 30, 45, 60, 90, and 120 minutes following the epidural dose. Measurements and Main Results: After solid phase extraction, plasma concent rations of ropivacaine were measured by high-perfromance liquid chromatogra phy (HPLC). Free unbound concentrations were determined after ultracentrifu gation. In 9 of 11 patients excellent epidural anestesia was achieved with an initial dose of 114 +/- 13 mg (120 to 150 mg) of roppivacaaine correspon ding to a dose of 1.9 +/- 0.4 mg/kg body weight. We suspected inadvertant i ntrasvasccular catheter malposition in one case. Peak plasma concentrations occured after 20 minutes (10 to 30) with a mean of 1.38 +/- 0.42 mu g/mL ( range 0.95 to 2.26 mu g/mL). Maximum unbound free plasma concentrations of roppivaacaine were 0.05 +/- 0.03 mu g/mL (range 0.02 to 0.13 mu g/mL). Conclusion: Ropivacaicne 10 mg/mL proved to be suitable for epidural anesth esia for total hip replacement. The plasma concentrations after 120 to 200 mg of its epidural applicatino were not associated with signs of local anes thetic toxicity in patients pretreated with benzodiazepines, even in one ca se of suspected inadvertent intravascular application. (C) 2000 by Elsevier Science Inc.