Motor Nerve Conduction Velocity Is Useful for Patients with Tetrodotoxin

To the Editor: Japanese sometimes eat puffer fish, the livers and ovaries of which contain tetrodotoxin (TTX). We present a typical case of severe puffer fish poisoning with apnea in which the serum level of TTX and the motor nerve conduction velocity of the right median nerve (MCV) could be recorded Table 1.Table 1: Serum Level of TTX, MCV, and Percent Vital Capacity After TTX IngestionA 64-yr-old man, a nonprofessional puffer fish cook, ate a puffer fish at home. One hour later, he noticed difficulty of breathing and was brought into the hospital. He had generalized flaccid paralysis, hypotension, and apnea on arrival at the hospital. Then, he was mechanically ventilated with circulatory support for 5 days. The patient did not respond to any stimuli; however, he demonstrated normal patterns on electroencephalogram from the first hospital day. Patients with puffer fish poisoning experience difficulty of breathing because TTX blocks the voltage-dependent sodium channels on the surface of nerve cells [1]. This patient could not breathe when the serum level of TTX was high. At that time, MCV could not be detected (first hospital day). When MCV appeared, serum TTX could not be detected. The patient did not move on the bed but revealed weak ventilation. Recovery of MCV was coincident with recovery of vital capacity. We suggest that recording MCV is useful to estimate the severity of respiratory problems due to TTX poisoning. Mitsuaki Yamazaki, MD, PhD Department of Intensive Care Unit Nobuko Shibuya, MD, PhD Department of Anesthesiology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Toyama 930-01, Japan