Pharmacokinetics of levobupivacaine 0.5% after superficial or combined (deep and superficial) cervical plexus block in patients undergoing minimally invasive parathyroidectomy

Study ObjectiveTo evaluate the pharmacokinetic profile of 0.35 mL/kg of 0.5% levobupivacaine during superficial and combined (deep and superficial) cervical plexus block (CPB) in patients undergoing minimally invasive parathyroidectomy.DesignProspective randomized study.SettingOperating theater of a university hospital.Patients12 ASA physical status II and III patients (11 women and 1 man), scheduled for minimally invasive parathyroidectomy.InterventionsSeven and 5 patients were randomly assigned to receive either superficial or combined CPB, respectively. The superficial CPB was performed with an injection of 0.35 mL/kg of 0.5% levobupivacaine subcutaneously along the posterior border of the sternocleidomastoid muscle and deeper on its medial surface. The combined CPB was initiated by the deep block at the C3 level vertebra by injecting 0.2 mL/kg of 0.5% levobupivacaine, followed by the superficial block with an injection of the remaining 0.15 mL/kg. After completion of the block, venous blood was sampled at the intervals of 5, 10, 15, 20, 30, 45, and 60 minutes.Measurements and Main ResultsVenous plasma concentrations were measured using gas chromatography-mass spectroscopy. Mean ± SD of maximal concentrations of levobupivacaine was 0.58 ± 0.41 mg/L in group superficial and 0.52 ± 0.28 mg/L in group combined (P = 0.71). The median (range) time required to reach the maximal concentrations was 30 minutes (20-30 min) in group superficial and 20 minutes (15-30 min) in group combined (P = 0.45). The areas under the drug concentration/time curve (AUC10-60) were also similar in both groups. No signs of central nervous system or cardiovascular toxicity or other untoward events were observed in any patient.ConclusionWith the given dose regimen, levobupivacaine plasma concentrations were within safe ranges.