Introduction
Not only is the identification of toxic plants from their gross appearance a commonly tested topic in Emergency Medicine Board Exams, but it is also a necessary skill for doctors operating in institutions where an established Toxicology division does not exist or where the opinion of a specialist in the field is not immediately available.
Various mnemonics and visual aids serve to highlight a few classes of common toxic plants that are prominent for both their inclusion in the academic assessment as well as their prevalence in the community. This series will sequentially present a series of visual aids and mnemonics that highlight key features in the identification of well-known toxic plant species, designed to aid clinicians from various regions of the globe as well as hone the skills of aspiring toxicologists.
Picture the Scene
A 28-year-old male is brought to your Emergency Department (ED) via ambulance due to a reportedly altered mental status. His wife, who accompanied the paramedics, states that she found him lying unconscious in the grass near a basket he was using to collect berries during an outdoor picnic in the fields. He was arousable at the scene but has had a fluctuating level of consciousness up to arrival to the hospital.
Upon initial examination, the patient is observed to be irritable with irregular, shallow breathing. Vital signs revealed a Blood Pressure of 127/75 mmHg, Heart Rate of 140, Respiratory rate of 24, Temperature of 37.9 C, and spO2 96% on room air. His pupils were found to be equally reactive to light but were significantly dilated, and his mucus membranes were notably dry.
The patient’s wife, believing the cause for her husband’s condition to be ingestion of the berries from the field, approaches you and shows you pictures of the plants she had photographed near where her husband was found. (see below images)
Why we care about toxic plant identification
The intoxicated patient, while frequently encountered in the ED, poses a uniquely challenging puzzle for the average ED Physician. Beyond the routine resuscitative and supportive care, the doctor who receives a patient that has consumed an unknown substance is tasked with the burden of deducing what kind of substance was taken and the expected sequelae for the same.
Among the numerous causes of intoxication, ingested plant species are a particularly ambiguous class of toxic substances to identify because the vast majority of intoxicated patients consume them unknowingly with only vague descriptions for what they ate. Often, however, these plants are brought with the patient or are present on their person at the time of arrival.
Whereas a vast majority of cases that present to the Emergency Department may not exhibit similar tell-tale signs and symptoms, the patient in the case described above displayed clinical manifestations typical to an anticholinergic syndrome. Furthermore, the photographs provided by the patient’s wife confirmed the cause of his symptoms as toxic ingestion of berries from the plant species Atropa Belladonna.
Plants with anticholinergic toxicity
The two most important plant species that contribute to this class of toxicity are the Datura stramonium (Jimson weed, angel’s trumpet), and the Atropa Belladonna (Deadly nightshade). The seeds of D. Stramonium and the berry-like fruits and leaves of A. Belladonna contain scopolamine, hyoscyamine and atropine. Ingestion of these parts of the plant results in suppression of Acetylcholine in the body, manifesting as an antimuscarinic syndrome that is characterized by dry skin, altered mental status, flushing, decreased gastrointestinal motility, increased body temperature, tachycardia, pupillary dilation (mydriasis) and urinary retention.
The above constellation of symptoms is usually simplified by using the following phrases:
‘Mad as a Hatter’ – Delirium/Altered Mental Status
‘Hot as a Hare’ – Hyperthermia
‘Red as a Beet’ – Flushing
‘Bloated as a Toad’ – Decreased gut motility/Constipation
‘Blind as a Bat’ – Mydriatic pupils
‘Dry as a Bone’ – Dry skin/decreased sweat production
Management involves benzodiazepines for agitation, adequate hydration, and supportive care. Physostigmine is reserved for cases refractory to Benzodiazepines.
Plant Identification
A useful method of visual identification of the plant species outline above is as follows:
Black in green, Black on green Don’t trust their high, they inhibit Acetylcholine!
Mnemonic break-down
Reference
- Lim, C.S., Aks, S.E. (2017), ‘Chapter 158 – Plants, Mushrooms and Herbal Medications’, Rosen’s emergency medicine 9th edition, Pg. 1957 – 1973