Serum concentrations of lignocaine before, during and after fiberoptic bronchoscopy

Background Lignocaine is commonly used for local anesthesia during fiberopt ic bronchoscopy (FOB). Several studies have reported the peak serum concent ration of lignocaine in relation to time, but most of them did not specify the administered dose of lignocaine gel and its possible correlation with p eak serum concentration. Objective: The aim of our study was to record the plasma concentrations of lignocaine before, during and after FOE and to eva luate whether the doses for nasal and tracheobronchial anesthesia have any correlation with the peak serum concentrations of the drug. Methods: Twelve patients with no comorbid conditions undergoing FOE were studied. Lignocai ne was administered as a 2% solution using a larynx syringe, 2% gel (mean d ose 182.5 +/- 15 mg) and finally 2% solution th rough the bronchoscope (mea n dose 339 +/- 12 mg). Total dose was 622 +/- 20 mg. Venous blood samples w ere taken before the beginning of local anesthesia and then at 5, 10, 20, 6 0, 90 and 120 min thereafter. Results: Our results showed that peak plasma concentrations of lignocaine were observed in 8 patients 20 min after the b eginning of local anesthesia, in 3 patients 30 min afterwards and in 1 pati ent 60 min afterwards (2.15 +/- 0.4 mu g/ml, 1.9 +/- 0.3 mu g/ml, 1.81 mu g /ml, respectively). None of our patients exceeded the-critical level of tox icity (5 mu g/ml). Both the total and tracheobronchial doses of lignocaine were significantly correlated with peak serum concentration (r = 0.63, p = 0.05 and r = 0.64, p = 0.02, respectively). No correlation was found betwee n the dose for nasal anesthesia and peak serum concentration, No adverse re actions were observed. Conclusions: In conclusion our data show that althou gh the amount of lignocaine used in this study exceeded the recommended hig hest dose (400 mg) in all patients, no toxic levels were observed. Peak pla sma concentrations were found within 20-30 min from the beginning of local anesthesia. The dose for the anesthesia of nasal mucosa represented a signi ficant percentage of the total dose, but did not correlate with the peak se rum concentration of the drug. Copyright (C) 2000 S. Karger AG, Basel.