Management of Anticholinergic Toxicity
The management of anticholinergic toxicity requires prompt recognition and treatment with physostigmine as the specific antidote for severe cases, alongside supportive care measures to prevent morbidity and mortality. 1, 2
Clinical Presentation
Anticholinergic toxicity presents with a characteristic constellation of symptoms often remembered as "red as a beet, dry as a bone, hot as a hare, blind as a bat, mad as a hatter, full as a flask":
- Central nervous system effects: agitated delirium, hallucinations, seizures, coma 3
- Cardiovascular effects: tachycardia, mild hypertension 3
- Respiratory: tachypnea 3
- Skin: hot, dry, erythematous 3
- Eyes: mydriasis (dilated pupils) 3
- Gastrointestinal: hypoactive or absent bowel sounds 3
- Other: hyperthermia, urinary retention 3, 1
Management Algorithm
Initial Stabilization and Assessment
- Secure airway, breathing, and circulation 1
- Obtain vital signs with particular attention to temperature, heart rate, and blood pressure 3
- Perform focused neurological assessment to evaluate level of consciousness and presence of agitation 3
- Obtain ECG to assess for QRS prolongation or dysrhythmias 3
First-Line Interventions
- Discontinue the precipitating anticholinergic agent 3
- Provide supportive care including IV fluids for hydration 3
- Administer benzodiazepines for agitation and seizure control 3
- Consider activated charcoal if recent oral ingestion and airway is protected 1
Specific Antidotal Therapy
- Physostigmine is indicated for severe anticholinergic toxicity with significant central nervous system effects (agitated delirium, hallucinations) or life-threatening peripheral manifestations 2
- Adult dosing: 1-2 mg IV slowly over 5 minutes, may repeat after 10-30 minutes if needed 1, 4
- Pediatric dosing: 0.02 mg/kg IV (maximum 0.5 mg/dose) 1
- Monitor for response, which typically occurs within 15-20 minutes 4
Management of Specific Complications
- Hyperthermia: External cooling measures 3
- Urinary retention: Consider bladder catheterization 1
- Prolonged QRS or dysrhythmias: Sodium bicarbonate administration 3
- Severe agitation not responsive to benzodiazepines: Consider physostigmine 5
Special Considerations
- Patients receiving physostigmine have significantly lower rates of intubation (1.9%) compared to those receiving other treatments (8.4%) 5
- During physostigmine shortages, rivastigmine (oral or transdermal) may be considered as an alternative treatment 6
- Avoid succinylcholine in patients with anticholinergic crisis as it may cause prolonged paralysis 1
Monitoring and Follow-up
- Continuous cardiac monitoring for at least 6 hours after symptom resolution 1
- Serial neurological assessments to evaluate response to treatment 1
- Monitor for recurrence of symptoms as physostigmine has a relatively short duration of action (45-60 minutes) 2
Common Pitfalls and Caveats
- Physostigmine is contraindicated in patients with cardiovascular disease, asthma, gangrene, diabetes, or mechanical obstruction of the intestines or urinary tract 1
- Underdosing of physostigmine is common; larger doses than standard may be required in severe cases 1
- Anticholinergic toxicity can be caused by numerous medications including antihistamines, tricyclic antidepressants, phenothiazines, and atropine derivatives 2
- Central anticholinergic syndrome may be misdiagnosed as primary psychiatric disorder, leading to delayed appropriate treatment 7, 8