To the Editor:-In their recent article concerning transient radicular irritation, Pollock et al. incorrectly represented our earlier work. They wrote that our study of the neurotoxic potential of commercially available local anesthetics used for spinal anesthesia in sciatic nerves "showed that 5% hyperbaric lidocaine, 0.5% tetracaine, and 0.75% bupivacaine caused nonreversible ablation of the stimulated compound action potential." Although it is true that 5% lidocaine and 0.5% tetracaine abolished the compound action potential, 0.75% bupivacaine did not.
This is important, because the reports of cauda equina syndrome after continuous spinal anesthesia implicate lidocaine and tetracaine, but not bupivacaine. [3,4]In addition, lidocaine, but not bupivacaine, produces the so-called transient radicular irritation syndrome. [1,5-9]In our study, 0.75% bupivacaine, the highest concentration of bupivacaine used clinically, did not cause nerve injury. It is our opinion that bupivacaine is probably the safest local anesthetic for intrathecal use because it is the only local anesthetic that, to our knowledge, has not caused neural injury in patients, and it shows the least toxicity from intrathecal infusions in rats [10,11]or exposure to isolated nerves in vitro. In addition, intrathecal infusions of clinical concentrations of bupivacaine are nontoxic in dogs. [12,13]
Donald H. Lambert, Ph.D., M.D., Chief, Anesthesiology, Associate Chief, Surgical Services, Brockton-West Roxbury VAMC, West Roxbury, Massachusetts, Associate Professor of Anaesthesia, Harvard Medical School, Boston, Massachusetts.
Laura A. Lambert, M.D., Resident in Surgery, Department of Surgery, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire.
Gary R. Strichartz, Ph.D., Vice Chairman for Research, Director, Anesthesia Research Laboratories, Brigham and Women's Hospital, Boston, Massachusetts, Professor of Anaesthesia (Pharmacology), Harvard Medical School, Boston, Massachusetts.
(Accepted for publication August 19, 1996.)