Comparison of analgesia induced by continuous epidural infusion of plain 1% lidocaine and 1% lidocaine prepared by dilution of 2% lidocaine with the same volume of saline.

Author(s): Kanai A, Koiso S, Hoka S

Affiliation(s): Department of Anesthesiology, Kitasato University School of Medicine, Sagamihara, Japan. kanaiakifumi@aol.com

Publication date & source: 2007-11, J Clin Anesth., 19(7):534-8.

Publication type: Comparative Study; Randomized Controlled Trial

STUDY OBJECTIVE: To compare the extent of sensory block induced by continuous epidural infusion of plain 1% lidocaine and 2% lidocaine diluted with saline to 1% lidocaine. DESIGN: Prospective, randomized, blinded study. SETTING: University hospital. PATIENTS: 40 ASA physical status I inpatients scheduled for lower extremity orthopedic surgery. INTERVENTIONS: After surgery with lumbar epidural anesthesia with 0.75% ropivacaine, patients were randomized to two postoperative epidural infusion groups to receive plain 1% lidocaine (plain group) or 2% lidocaine diluted with the same volume of normal saline (dilution group). Continuous epidural infusion was started at a rate of 6 mL/h. MEASUREMENTS AND MAIN RESULTS: Regression of sensory block was significantly prolonged in the plain group, resulting in a significant difference in the spread of sensory block between the two agents from 4 to 6 h postoperatively. There also was a significant difference from the two groups in the level of motor block (modified Bromage scale) between 3 and 5 h postoperatively. CONCLUSIONS: Two percent lidocaine diluted with the same volume of saline is a less potent than the plain 1% lidocaine. The effect of saline as a diluent on epidurally administrated local anesthetics may be of clinical importance.