Anticholinergic Syndrome Symptoms
Anticholinergic syndrome presents with a characteristic constellation of symptoms captured by the classic mnemonic "Red as a beet, dry as a bone, hot as a hare, blind as a bat, mad as a hatter, full as a flask," with the pathognomonic features being dry mucous membranes and hot, dry, erythematous skin. 1
Central Nervous System Manifestations
The central anticholinergic effects produce a spectrum of neuropsychiatric symptoms:
- Agitated delirium with visual hallucinations ("mad as a hatter") is the hallmark central manifestation 1, 2
- Altered mental status ranging from confusion and disorientation to stupor and coma in severe cases 2, 3
- Anxiety, hyperactivity, and seizures may occur in more severe poisoning 4
- Thought impairment, disturbance of recent memory, and amnesia are common cognitive effects 5, 6
- Dysarthria and ataxia can develop as part of the central syndrome 5
Peripheral Anticholinergic Signs
The peripheral manifestations are equally distinctive:
- Dry mucous membranes (oral cavity) - this is pathognomonic when combined with hot, dry skin 1, 2
- Hot, dry, erythematous (flushed) skin ("red as a beet, dry as a bone") - another pathognomonic feature 1, 2
- Mydriasis (dilated pupils) causing blurred vision ("blind as a bat") 2, 3
- Hyperthermia ("hot as a hare") with mild temperature elevation, though severe cases can progress to dangerous hyperpyrexia 1, 2
- Tachycardia is consistently present 1, 2, 4
- Hypoactive or absent bowel sounds with decreased gastrointestinal motility ("full as a flask") 1, 2
- Urinary retention due to decreased bladder motility 4, 3
- Decreased secretions in salivary and sweat glands, as well as pharynx, bronchi, and nasal passages 4
Cardiovascular and Autonomic Features
- Tachycardia with hypertension or blood pressure fluctuations (≥20 mm Hg diastolic or ≥25 mm Hg systolic change within 24 hours) 2, 7
- Vasodilation contributing to the flushed appearance 4
Severe Manifestations
In extreme poisoning, life-threatening complications include:
- Coma and medullary paralysis potentially leading to death 4
- Respiratory failure and cardiovascular collapse in the most severe cases 3
- Severe hyperpyrexia that can be life-threatening 6
Critical Diagnostic Distinction
The key distinguishing features that differentiate anticholinergic syndrome from other toxidromes are the combination of dry mucous membranes, hot dry erythematous skin, mydriasis, agitated delirium with visual hallucinations, and hypoactive bowel sounds. 1, 2 This constellation, particularly the pathognomonic dry mucous membranes and hot dry skin, allows rapid clinical recognition even before confirmatory treatment with physostigmine.