The Sedative Effect of High Dose Lidocaine

Abstract

To the Editor: In their case report Gaughen and Durieux (1) report hypotension, and a BIS value of zero in a 75-yr-old woman who received an unintended infusion of 800 mg of lidocaine over 8 min while also anesthetized with sevoflurane. Following recovery, weakness persisted for more than an hour. We would like to support their findings with our experience. A few years ago one of us (PS) together with eight other anesthesiologists took part as volunteers in a clinical study of the effects of IV lidocaine on pain perception (unpublished data). We received 1 mg/kg IV lidocaine as a bolus, followed by an infusion of 5 mg/kg over 2 hr. Even though the blood lidocaine concentrations were less than that associated with toxicity (5 μg/mL) (2), all subjects reported deep sedation, and muscle weakness. Some had speech disturbances and diplopia but none reported tinnitus or metallic taste. The presence of sedation as an early sign of lidocaine toxicity is not well documented in the anesthetic literature even though it has been described elsewhere (3). We suggest monitoring for sedation during lidocaine (and possible other local anesthetics) administration as an early sign of a high blood concentration. Using BIS in these cases might provide an objective measurement of the level of sedation. Peter Szmuk, MD Department of Anesthesiology University of Texas Medical School Dallas, TX Children’s Medical Center at Dallas Dallas, TX Outcome Research Institute Louisville, KY [email protected] Alan Farrow-Gillespie, MD Paul Sheeran, MD Department of Anesthesiology University of Texas Medical School Dallas, TX Children’s Medical Center at Dallas Dallas, TX Tiberiu Ezri, MD Department of Anesthesia The Edith Wolfson Medical Center, Holon Affiliated to Sackler Medical School Tel Aviv University, Israel Outcome Research Institute Louisville, KY