eMedicine - Plant Poisoning, Hemlock : Article by Daniel E Brooks, MD
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Plant Poisoning, HemlockSynonyms, Key Words, and Related Terms: poison hemlock (Conium maculatum), water hemlock (Cicuta maculata) |
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| eMedicine Journal > Emergency Medicine > Toxicology > Plant Poisoning, Hemlock |
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AUTHOR INFORMATION | Section 1 of 10    |
Authored by Daniel E Brooks, MD, Fellow, Department of Medical Toxicology, Good Samaritan Regional Medical Center
Daniel E Brooks, MD, is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, and Society for Academic Emergency Medicine
Edited by David A Peak, MD, Instructor, Staff Physician, Department of Emergency Services, Massachusetts General Hospital, Harvard Medical School; John T VanDeVoort, PharmD, DABAT, Manager, Clinical Assistant Professor, Pharmacy Department, Regions Hospital; Michael Hodgman, MD, Assistant Clinical Professor of Medicine, Department of Emergency Medicine, Bassett Healthcare; John Halamka, MD, Chief Information Officer, CareGroup Healthcare System, Assistant Professor of Medicine, Department of Emergency Medicine, Beth Israel Deaconess Medical Center; Assistant Professor of Medicine, Harvard Medical School; and Raymond J Roberge, MD, MPH, FAAEM, FACMT, Research Director, Department of Emergency Medicine, Ohio Valley Medical Center; Clinical Associate Professor, Department of Emergency Medicine, University of Pittsburgh
| Author's Email: | Daniel E Brooks, MD |  |
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| Editor's Email: | David A Peak, MD |
eMedicine Journal, May 11 2001, Volume 2, Number 5
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INTRODUCTION | Section 2 of 10  |
Background: Toxic plant exposure is the fourth most common cause of nationwide poisoning, accounting for more than 100,000 annual reports to poison control centers. Pediatric patients comprise more than 80% of plant related exposures. Only 5-20% of plant exposures require medical management; only a few plants, poison hemlock and water hemlock included, are associated with life-threatening toxicity.
Hemlock poisoning may refer to poisoning by either poison hemlock (Conium maculatum) or water hemlock (Cicuta maculata). Historically, poison hemlock was reportedly used to execute Socrates and the Old Testament describes rhabdomyolysis in Israelites who consumed quail fed on hemlock.
Although related, poison hemlock and water hemlock toxicity have different pathophysiology and clinical presentations. The root contains the greatest concentration of toxin in both species, although all plant parts are toxic. Poison hemlock causes "crooked calf disease," a congenital abnormality, among cattle formed via fetal exposure. No antidote is available for either toxin.
Poison hemlock, an exotic species introduced to the US, is a ubiquitous plant with fernlike properties that may reach a height of 2 meters. Poison hemlock grows in diverse settings, including wooded areas, ditches, and waysides throughout the US, and may be mistaken for edible plants such as wild carrot; it also may be confused with water hemlock (C maculata).
Water hemlock is found in moist habitats, such as drainage ditches, marshes, and near bodies of fresh water. Water hemlock has compound leaves, small white or green flowers, and tuberous, large, hollow roots. Water Hemlock may reach a height of 6-8 feet.
Pathophysiology: Poison hemlock contains several alkaloid toxins that are structurally similar to nicotine. Initially, nicotinic activation from poison hemlock may lead to early CNS stimulation, headache, and ataxia. Nicotinelike effects at autonomic ganglia may cause tachycardia, salivation, mydriasis, and diaphoresis. In severe cases the acetylcholine receptors are overstimulated and finally fatigued, producing cholinergic blockade. The clinical effects therefore change from a stimulation phase to a depressant phase characterized by bradycardia, ascending motor paralysis, CNS depression, and respiratory paralysis.
Water hemlock contains cicutoxin, a potent toxin that acts as a noncompetitive gamma-aminobutyric acid (GABA) receptor antagonist. A single bite of the root, which contains the highest concentration of cicutoxin, has been reported to kill an adult. Ingestion of water hemlock produces GI symptoms (eg, salivation, nausea, emesis) within 15 minutes, rapidly followed by CNS effects (eg, excitation, convulsions, seizures, coma). Using a rat model, Uwai et al have shown cicutoxin derivates to bind and block GABA-chloride channels.
Frequency:
- In the US: In 1999, 113,864 plant exposures were reported to the American Association of Poison Control Centers Toxic Exposure Surveillance System. No human deaths from hemlock ingestion were reported to US Poison Control Centers between 1997 and 1999. Incidence was low for US livestock.
- Internationally: Livestock exposures in New Zealand, South America, Europe, and southern Canada have been reported.
Mortality/Morbidity: Poison hemlock poisoning is potentially lethal with large ingestions; water hemlock fatalities have occurred following a few bites of the root.
- Poison hemlock's human median lethal dose (LD50) is not known. Mortality from poison hemlock ingestion is usually secondary to respiratory paralysis.
- Water hemlock had a 30% mortality rate in one series of 86 patients. Mortality from water hemlock is usually secondary to refractory status epilepticus.
Age: Younger patients with accidental ingestions are at an increased risk because of smaller body mass.
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CLINICAL | Section 3 of 10 |
History: In cases of plant toxicity, history may be obscure and ingested plants may not be available for identification.
Physical:
- Poison hemlock: Signs of poison hemlock toxicity can be divided into an early stimulation phase and, in severe poisonings, a later depressant phase.
- Emesis
- Salivation
- Mydriasis
- Tachycardia, then bradycardia
- Initial fasciculations, then flaccid paralysis
- Hypoventilation, respiratory arrest
- Water hemlock: Signs of water hemlock toxicity begin with GI symptoms, which are rapidly followed by CNS overstimulation.
- Emesis
- Mydriasis
- Agitation
- Delirium
- Convulsions
- Seizures
- Coma
Causes:
- Hemlock plants may be intentionally ingested. However, most ingestions are accidental.
- Poison hemlock may be mistaken for wild carrots.
- Water hemlock may be mistaken for wild parsnips or artichokes.
- Potential exposure from consuming meat of exposed wildlife (eg, fowl, sheep, pork, beef, goat) exists.
- Birds ingesting hemlock during migratory flight may cause coturnism (human poisoning after eating quail).
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DIFFERENTIALS | Section 4 of 10 |
Encephalitis
Hypoglycemia
Schizophrenia
Toxicity, Cyclic Antidepressants
Toxicity, Hallucinogen
Toxicity, Methamphetamine
Toxicity, Mushroom - Gyromitra Toxin
Toxicity, Mushroom - Hallucinogens
Toxicity, Mushrooms
Toxicity, Phencyclidine
Other Problems to be Considered:
Botulism
Nicotine (wild tobacco)
Golden chain (Laburnum anagyroides)
Strychnine
Cholinergic poisoning
Psychosis
Encephalopathy
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WORKUP | Section 5 of 10 |
Imaging Studies:
- Perform chest radiographs if aspiration is suspected.
Other Tests:
- Chemical screening test for alkaloids in plant material provides confirmation of toxicity due to poison or water hemlock. However, a plant specimen is required and these tests are not routinely available.
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TREATMENT | Section 6 of 10 |
Prehospital Care: Secure airway, assist ventilation, and obtain IV access as needed.
Emergency Department Care: Rapidly assess and correct any life-threatening conditions. Since no antidote exists for either toxin, aggressive decontamination and supportive care are mainstays of treatment.
- Secure airway.
- Decontaminate GI tract.
- If no contraindications exist, gastric lavage may be of limited benefit if performed within the first hour or so following ingestion.
- Administer activated charcoal. Ipecac should not be used.
- Initially treat seizures with benzodiazepines or barbiturates and subsequently, if required, treat with phenytoin.
- Provide prophylaxis with water hemlock ingestion.
- Benzodiazepines and barbiturates can help control agitation.
- Aggressively administer IV fluids.
- Replete volume if signs of hypovolemia or hypotension are present.
- Correct electrolyte abnormalities.
- Administer fluids with sodium bicarbonate alkali for urinary alkalinization and diuresis if evidence of rhabdomyolysis and myoglobinuria exists. If using sodium bicarbonate, it is important to mix it in 5% dextrose in water (D5W), or D5W with half normal saline to limit amount of sodium that the patient is receiving.
- Potassium levels should be monitored and corrected as needed.
- Administer antiemetics. Many antiemetics may lower the seizure threshold and should be used cautiously.
- Provide ventilatory support, if necessary, with water hemlock.
Consultations: A regional poison center or a medical toxicologist can assist with patient treatment and plant identification.
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MEDICATION | Section 7 of 10 <img src="/images/top4.gif" align="middle" width=31 height |