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

ABSTRACT

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 (Cmax) of ropivacaine. RESULTS: Data were analysed from N = 18 patients. The median dose of ropivacaine was 2.7 mg kg(-1) (range 1.9-4.2 mg kg(-1)). Median total ropivacaine concentrations were 1.0, 1.6 and 1.7 µg ml(-1) at 10, 30 and 60 min, respectively. Six patients (33%) had Cmax values above 2.2 µg ml(-1) and the highest concentration measured was 5.1 µg ml(-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.