The importance of electrodiagnostic studies in acute organophosphate poisoning

Six patients with acute organophosphate pesticide poisoning in whom electrodiagnostic studies influenced or supported specific decisions in management are described. One patient was admitted to hospital with a diagnosis of acute alcoholic intoxication. Electrodiagnostic studies revealed single stimulus induced repetitive responses and decrement-increment responses at 30 and 50 Hz repetitive nerve stimulation, findings that are indicative of a depolarization block due to inactivation of acetylcholinesterase at the motor end-plate. The patient was subsequently treated as a case of acute organophosphate poisoning. The administration of edrophonium (0.1 mg) to another patient with normal neuromuscular transmission studies unmasked the latent electrophysiological abnormalities. Three instances are described in which electrodiagnostic studies were useful in predicting whether pralidoxime administration was likely to be useful and for how long was pralidoxime therapy to be continued. Phrenic nerve conduction study in one patient with impending respiratory failure revealed an unstimulable phrenic nerve. The potential role of phrenic nerve conduction studies and neuromuscular transmission studies in influencing decisions like intubation and mechanical ventilation is discussed.