Vasopressin for hypotension in severe amitriptyline poisoning

Background: Due to neurotransmitter reuptake inhibition, peripheral alpha receptor blocking effects, and sodium channel blockade, severe tricyclic antidepressant (TCA) poisoning may lead to intractable hypotension. We report a case of severe amitriptyline toxicity, with hypotension unresponsive to direct alpha receptor agonists after pH manipulation, but improved with intravenous (IV) vasopressin. Vasopressin use in the setting of TCA toxicity has not been previously reported. Case Report: A 56 year-old man was found unresponsive with convulsive activity near an empty bottle of amitriptyline. He was intubated and treated with sodium bicarbonate and midazolam in the field. He was resuscitated with IV fluid, additional sodium bicarbonate and a dopamine infusion but remained persistently hypotensive with a wide complex tachycardia. The vasopressor agent was changed to norepinephrine (NE) and bicarbonate therapy was continued, but limited by a serum pH of 7.64. Hypertonic saline was not used since his serum sodium remained above 145 mEq/L. A lidocaine infusion was initiated without improvement. Convulsions continued despite 46mg of lorazepam. Phenobarbital loading was limited by continued hypotension. At that time, a vasopressin infusion was initiated at 0.04 U/min. His blood pressure stabilized over the following hour and by 3 hours the NE infusion was decreased. A toxicology screen confirmed the presence of tricyclic antidepressant. After a complicated hospital course, the patient recovered with no neurologic sequelae. Conclusion: Vasopressin may be a beneficial agent in the treatment of recalcitrant hypotension associated with tricyclic antidepressant toxicity.
Barry JD *, Durkovich DW (+), Williams SR. * Department of Emergency Medicine, University of California, San Diego (UCSD), San Diego CA. (+) Department of Emergency Medicine, Naval Medical Center, [...]