Pharmacokinetics of high-dose diluted lidocaine in local anesthesia for facelift procedures

Abstract

The maximal recommended local anesthetic dose of lidocaine is 7 mg/kg; higher doses are used in tumescent liposuction. The objective of this study was to characterize the pharmacokinetics of high-dose diluted lidocaine administered together with epinephrine for local anesthesia in facelift procedures. This was a prospective study of six female patients undergoing elective facelift surgery. The local anesthetic solution consisted of 0.33% lidocaine, 0.07% sodium bicarbonate, and 1:600,000 epinephrine in normal saline. Plasma lidocaine levels were determined in the course of 24 hours and were subjected to pharmacokinetic analysis. Patients' age was 58.5 +/- 8 years and weight 68.5 +/- 18.7 kg. Mean lidocaine dose was 21.6 +/- 3.6 mg/kg (range, 17.5-26.3 mg/kg) infiltrated subcutaneously over 20 minutes or less. No lidocaine-related adverse effects were recorded. Major bleeding was not observed. Postoperative analgesia was required only at 11.8 +/- 4.6 hours after surgery. Pharmacokinetic analysis was peak concentration 1.41 +/- 0.4 microg/mL, time to reach peak concentration 9.3 +/- 1.6 hours, terminal half-life 6.2 +/- 1.5 hours, area under the curve from time zero to last data point 1379.8 +/- 470 microg/min/mL, and area under the curve from time zero to infinity 1530.6 +/- 471.6 microg/min/mL. Plasma lidocaine concentrations formed almost a plateau between 2 and 12 hours (ie, at approximately 1.2 microg/mL) after infiltration. It is concluded that local anesthesia with diluted lidocaine at a dose 3.1 times higher than the currently recommended dose (7 mg/kg) administered with epinephrine yielded a peak plasma lidocaine level that was 72% below the level considered safe (5 microg/mL).