Plasma lidocaine concentrations following insertion of 2% lidocaine gel into the uterine cavity after uterine balloon thermal ablation

Background. Uterine balloon thermal ablation is used to treat menorrhagia. We thought that intrauterine application of 2% lidocaine gel could reduce postoperative pain after this procedure. Before using this technique we wished to establish how much lidocaine is absorbed systemically from the uterine cavity after thermal ablation. Methods. Ten ASA I-II patients (age 38-50 yr) underwent uterine balloon thermal ablation under general anaesthesia. They each had 11 ml of 2% lidocaine gel (Instillagel ) inserted into the uterine cavity at the end of the procedure. Blood samples were taken at 5, 15, 30 and 60 min after insertion and lidocaine concentrations were measured using high-performance liquid chromatography. Results. Mean (range) plasma lidocaine concentrations at 5, 15, 30 and 60 min were 40.3 (0-221.9), 66.3 (0-271.9), 64.9 (0-208) and 75 (0-212) ng ml^-1, respectively. Conclusion. There was minimal.systemic absorption of lidocaine from the uterus following uterine balloon thermal ablation. Measured concentrations were well below the toxic plasma concentration for lidocaine (8-10 μg ml^-1).