Estimated Maximal Safe Dosages of Tumescent Lidocaine

Abstract

Background: Tumescent lidocaine anesthesia consists of subcutaneous injection of relatively large volumes (up to 4 L or more) of dilute lidocaine (≤1 g/L) and epinephrine (≤1 mg/L). Although tumescent lidocaine anesthesia is used for an increasing variety of surgical procedures, the maximum safe dosage is unknown. Our primary aim in this study was to measure serum lidocaine concentrations after subcutaneous administration of tumescent lidocaine with and without liposuction. Our hypotheses were that even with large doses (i.e., >30 mg/kg), serum lidocaine concentrations would be below levels associated with mild toxicity and that the concentration-time profile would be lower after liposuction than without liposuction.

Methods: Volunteers participated in 1 to 2 infiltration studies without liposuction and then one study with tumescent liposuction totally by local anesthesia. Serum lidocaine concentrations were measured at 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, and 24 hours after each tumescent lidocaine infiltration. Area under the curve (AUC∞) of the serum lidocaine concentration-time profiles and peak serum lidocaine concentrations (Cmax) were determined with and without liposuction. For any given milligram per kilogram dosage, the probability that Cmax >6 μg/mL, the threshold for mild lidocaine toxicity was estimated using tolerance interval analysis.

Results: In 41 tumescent infiltration procedures among 14 volunteer subjects, tumescent lidocaine dosages ranged from 19.2 to 52 mg/kg. Measured serum lidocaine concentrations were all <6 μg/mL over the 24-hour study period. AUC∞s with liposuction were significantly less than those without liposuction (P = 0.001). The estimated risk of lidocaine toxicity without liposuction at a dose of 28 mg/kg and with liposuction at a dose of 45 mg/kg was ≤1 per 2000.

Conclusions: Preliminary estimates for maximum safe dosages of tumescent lidocaine are 28 mg/kg without liposuction and 45 mg/kg with liposuction. As a result of delayed systemic absorption, these dosages yield serum lidocaine concentrations below levels associated with mild toxicity and are a nonsignificant risk of harm to patients.

Conflict of interest statement

Conflict of Interest: See Disclosures at the end of the article.

Figures

Figure 1.

Serum lidocaine concentrations over time for each of the 14 subjects after subcutaneous infiltration of tumescent lidocaine anesthesia. Subject number and anatomic area of infiltration are presented on the top of each plot. The figure legend presents whether or not liposuction was done after tumescent infiltration indicated by “No Lipo” and “Lipo,” respectively, and the tumescent lidocaine dosage (mg/kg).

Figure 2.

Comparison of serum lidocaine concentrations at sequential times over 24 h following 45 mg/kg tumescent lidocaine, without liposuction (closed circles) and with liposuction (open circles). The AUC∞ of the mean concentrations (solid line) at each time point without liposuction (56.2 μg·h/mL) is 28% greater than the AUC∞ of the mean concentrations (dashed line) with liposuction (40.7 μg·h/mL).

Figure 3.

Scatter plot of tumescent lidocaine dosage versus peak serum lidocaine concentrations (Cmax) without liposuction. The solid line represents the line of regression with a coefficient of determination (R2) of 0.85.

Figure 4.

Scatter plot of tumescent lidocaine dosage versus peak serum lidocaine concentrations (Cmax) with liposuction. The solid line represents the line of regression with a coefficient of determination (R2) of 0.35.

Figure 5.

“Safety Label” applied to a bag tumescent lidocaine solution. The label overhangs the port for the IV tubing spike. A “Safety Label” is a visual reminder that the bag contains tumescent lidocaine for subcutaneous delivery and is not for IV delivery.