Intravenous injection of rocuronium produces intense discomfort at the site of injection in conscious patients. We compared the efficacy of normal saline, and of lidocaine 10 mg, 20 mg, 30 mg, and 40 mg pretreatment at preventing pain caused by injecting rocuronium.

250 ASA physical status Iand II patients, aged 18 to 70 years, were randomized into 5 groups of 50 patients in a double blinded prospective study. After tourniquet application on the forearm, the control group received 2 ml of normal saline as a pretreatment. The other 4 groups received lidocaine 10 mg (Lido10 group), lidocaine 20 mg (Lido20 group), lidocaine 30 mg (Lido30 group), or lidocaine 40 mg (Lido40 group) as a pretreatment in a 2 ml solution. The tourniquet was released after 20 seconds and rocuronium was injected over 10 seconds. The patients were then observed and asked if they had pain in, and responses were assessed. Local signs (i.e. erythema, venous sequelae) on the arm where the rocuronium had been injected were recorded immediately after the injection and 12 h later, after recovery from anesthesia.

44 patients (88%) in the control group, 35 (70%) in the Lido10 group, 32 (64%) in the Lido20 group, 23 (46%) in the Lido30 group, and 16 (32%) in the Lido40 group reported pain. The medial pain score was 1.92 ± 1.04 in the control group, 1.12 ± 0.96 in the Lido10 group, 0.92 ± 0.85 in the Lido20 group, 0.52 ± 0.61 in the Lido30 group, and 0.34 ± 0.48 in the Lido40 group. Moderate to severe pain was observed in 33 patients (66%) in the control group, 16 (32%) in the Lido10 group, 12 (24%) in the Lido20 group, 3 (6%) in the Lido30 group, and none (0%) in the Lido40 group. No local signs were observed.

Pretreating with lidocaine at 10, 20, 30 or 40 mg reduced the incidence and severity of pain on injecting rocuronium, and the higher dose was more effective.