RESUMO
OBJECTIVE: Endovenous laser therapy (EVLT) requires tumescent lidocaine anesthesia. Although it is well known that the absorption of local anesthetic varies according to the injection site, little evidence exists establishing the maximum recommended safe dose for extravascular injections such as those used for EVLT. The aim of this study was to evaluate plasma concentration of lidocaine over time after administration of tumescent lidocaine during EVLT procedures in healthy volunteers. METHODS: Between January 2011 and February 2013, 10 healthy patients scheduled for an EVLT procedure performed in a hospital setting were recruited to participate in an observational study. For each subject, a total of 10 venous samples were obtained for analysis after surgical injection of the tumescent lidocaine solution (0.1% concentration). Samples were collected at baseline (before the surgical procedure start) and then every 30 minutes for the first 2 hours after the initial lidocaine injection. Thereafter, venous samples were obtained every 2 hours, with the last sample drawn 12 hours after the surgeon's initial lidocaine injection. All specimens were drawn from a dedicated intravenous catheter, immediately placed in a heparinized blood collection tube, and centrifuged for 10 minutes at 3000 rpm. Plasma was then removed with a pipette and stored at -70 °C until analyzed. Total and free plasma lidocaine concentrations were determined by immunoassay. Plasma lidocaine concentrations were normalized by peak concentration for statistical comparisons. RESULTS: Laboratory data were available for nine of the 10 volunteers. The mean total lidocaine dose administered was 6.38 (± 2.2) mg/kg (range, 3.57-10.7 mg/kg). The total lidocaine blood levels ranged from 0.48 (± 0.28) to 1.3 (± 0.49) mcg/mL. The free lidocaine blood levels ranged from nondetectable to 0.76 (± 0.43) mcg/mL. The average total time of injection for the group was 32.8 (± 10.0) minutes (range, 21-49 minutes). Among all dose ranges, both total and free lidocaine peak blood level ratios occurred at times 60 to 120 minutes (P < .05). No value considered in the statistical analysis exceeded 5 mcg/mL at any time. CONCLUSIONS: Tumescent lidocaine without epinephrine for EVLT procedures produces a peak serum concentration at 60 to 120 minutes. The peak plasma concentration as observed with the standard institutional dosing of tumescent lidocaine appeared below the threshold for human toxicity.
