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.

Trial registration: ClinicalTrials.gov NCT01024868.