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Habre W, Bergesio R, Johnson C, et al. Paediatric Anaesthesia 2000, 10:143-147.

Review: In attempt to evaluate the pharmacokinetics of ropivacaine in children, this study determined systemic venous concentrations of ropivacaine at different intervals following epidural administration. 10 healthy children undergoing elective surgery under general anesthesia were studied. After induction of general anesthesia, 1 ml/kg of 0.25% ropivacaine was administered into the caudal epidural space. Venous samples were drawn at 5, 10, 20, 30, 45, 60,120, 240, 360, and 720 minutes after injection of the local anesthetic and ropivacaine levels determined using high performance liquid chromatography. Peak plasma concentration and the time to achieve this concentration, elimination half-life, mean residence time, area under the plasma concentration-time curve and apparent volume of determination were determined.

Data from one child had to be excluded due to concomitant drug interference with the HPLC assay. Children included in the study had a mean age of 25 months. All the caudal blocks were reported as successful based on pain scores. The mean time to first analgesia requirement was 3.9 hours. The peak serum concentration of ropivacaine occurred between 0.3 and 2 hours and ranged from 623-1220 mg/l (median 799 mg/l) which is later than that reported in adults and later than the time to achieve peak concentrations following epidural administration of bupivacaine in children. The mean elimination half-life of plasma ropivacaine was 3.9 hours (longer than 2.6 hours as reported for adults) and the mean residence time was 5.9 hours. The mean apparent clearance was 7.6 ml/kg/min, similar to reported adult values. The mean apparent volume of distribution was 2.4 l/kg compared with 0.5 l/kg reported in adults. No electrocardiographic or hemodynamic changes were noted and there was no evidence of any neurological toxicity.

Comments: The purported benefits of ropivacaine are its favorable toxicity profile and that it causes a lesser degree of motor blockade. These properties would make ropivacaine particularly attractive for postoperative analgesia for children undergoing minor procedures such as hernia repairs on an ambulatory basis. Adult studies have confirmed these benefits. However, pediatric literature related to the use of this drug is insufficient. This study reports the clinical efficacy of ropivacaine in a small number of healthy children undergoing elective surgery. The investigators have addressed certain limitations of their study particularly related to the absence of toxicity. Most of the children were still anesthetized at the time peak plasma concentrations of ropivacaine were achieved and this may have masked any neurological symptoms that could have occurred. Further, the small sample size made it difficult to account for interindividual variability in ropivacaine kinetics across all age groups. Despite these limitations, the importance of this study is that it provides dosing guidelines for epidural ropivacaine use in the clinical setting. Furthermore, it provides preliminary data for further pharmacokinetic studies.

Reviewed by: Shobha Malviya, MD
University of Michigan Health System