Potentially toxic concentrations in blood of total ropivacaine after bilateral transversus abdominis plane blocks; a pharmacokinetic study

Context Elevated blood levels of lidocaine and ropivacaine have been described after transversus abdominis plane (TAP) block. Objective To investigate the pharmacokinetic profile of ropivacaine after bilateral TAP blocks. Design Prospective observational pharmacokinetic study. Setting University teaching hospital in Copenhagen, Denmark. Patients Twenty-one adult patients presenting for abdominopelvic surgery with bilateral TAP blocks were enrolled. Procedures Ultrasound-guided TAP blocks with bilateral injections of 20 ml ropivacaine 0.5% w/v (total dose 200 mg). Blood was sampled at 0, 10, 30 and 60 min after TAP blocks. Measures Total and free peak blood concentrations (C-max) of ropivacaine. Results Data were analysed from N = 18 patients. The median dose of ropivacaine was 2.7mgkg(-1) (range: 1.9-4.2mgkg(-1)). Median total ropivacaine concentrations were 1.0, 1.6 and 1.7mgml(-1) at 10, 30 and 60 min, respectively. Six patients (33%) had C-max values above 2.2 mu gml(-1) and the highest concentration measured was 5.1 mu gml(-1). One patient had a 33% drop in mean arterial blood pressure. Conclusion TAP blocks with bilateral injections of 20 ml ropivacaine 0.5% w/v gave rise to potentially toxic peak blood concentrations of total ropivacaine in one-third of the patients. Eur J Anaesthesiol 2012; 29: 235-238 Published online 26 March 2012