Water Hemlock

Water hemlock comprises a group of herbaceous plants that are often confused with the edible water parsnip, as well as with wild parsnip, wild carrot, and wild celery. It is easily found across the wetlands and wet meadows of North America, and is distinguished from the poison hemlock by its purple streaks and gradients.

All parts of the water hemlock contain cicutoxin, a polyacetylene alcohol that noncompetitively antagonizes GABA, and thus leads to uninhibited depolarizations of neurons.

Presentation:

In the early phase, patients who have ingested cicutoxins present with nausea, vomiting, diarrhea, abdominal pain, and tachycardia.

In the next phase (faster with higher doses), patients present with mydriasis, confusion, diaphoresis, cardiac dysrhythmias (e.g. heart block or ventricular fibrillation), convulsions (which, in turn, lead to hyperthermia, rhabdomyolysis, and renal failure), and coma.

The typical cause of death in cicutoxin ingestion is respiratory failure.

Management:

Decontamination with activated charcoal or gastrointestinal lavage is possible if the ingestion occurred within 1-2 hours.

Otherwise, treatment comprises primarily of seizure control with GABAergic medications (benzodiazepines or barbiturates), and intubation and mechanical ventilation in the event of respiratory compromise. Other symptoms (such as dehydration, acidosis, hyperthermia, arrhythmia, acute tubular necrosis, etc.) can be addressed in the usual manner.