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 treatmenorrhagia. 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 muchlidocaine is absorbed systemically from the uterine cavity afterthermal ablation. Methods. Ten ASA I–II patients (age 38–50 yr) underwentuterine balloon thermal ablation under general anaesthesia.They each had 11 ml of 2% lidocaine gel (Instillagel^TM) insertedinto the uterine cavity at the end of the procedure. Blood sampleswere taken at 5, 15, 30 and 60 min after insertion and lidocaineconcentrations 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 lidocainefrom the uterus following uterine balloon thermal ablation.Measured concentrations were well below the toxic plasma concentrationfor lidocaine (8–10 µg ml^–1). Br J Anaesth 2002; 89: 846–8