What is the treatment for a patient experiencing an anticholinergic crisis?

Treatment of Anticholinergic Crisis

Administer atropine 2-4 mg IV immediately for adults (0.05-0.1 mg/kg IV for pediatrics), repeated every 5-10 minutes until secretions are controlled and cholinergic symptoms resolve. 1, 2

Critical Distinction: Anticholinergic vs. Cholinergic Crisis

This question requires immediate clarification—anticholinergic crisis and cholinergic crisis are opposite toxidromes requiring opposite treatments:

Cholinergic Crisis (Excessive Acetylcholine)

• Caused by: Organophosphate poisoning, nerve agents, or anticholinesterase medications 1
• Clinical features: Bradycardia, hypotension, bronchorrhea, bronchospasm, excessive secretions, GI hypermotility, urinary incontinence, muscle fasciculations, weakness, flaccid paralysis, seizures 1
• Treatment: Atropine (anticholinergic agent) 1

Anticholinergic Crisis (Acetylcholine Blockade)

• Caused by: Antihistamines (diphenhydramine), tricyclic antidepressants, antispasmodics, antipsychotics 2
• Clinical features: Agitated delirium, hallucinations, tachycardia, hyperthermia, mydriasis, hot/dry/flushed skin, urinary retention, absent bowel sounds 2
• Treatment: Physostigmine (cholinesterase inhibitor) 2

Management Algorithm for Anticholinergic Toxicity

Immediate Stabilization

• Secure airway, breathing, and circulation with particular attention to airway protection in obtunded patients 2
• Obtain vital signs focusing on temperature (hyperthermia), heart rate (tachycardia), and blood pressure (mild hypertension) 2
• Perform ECG to assess for QRS prolongation or dysrhythmias that may indicate tricyclic antidepressant co-ingestion 2
• Discontinue all anticholinergic medications immediately 2

First-Line Supportive Care

• Administer IV fluids for hydration and circulatory support 2
• Give benzodiazepines (diazepam or midazolam) for agitation and seizure control as first-line sedation 2
• Consider activated charcoal (1 g/kg) if oral ingestion occurred within 1 hour and airway is protected 2
• Apply external cooling measures for hyperthermia (avoid antipyretics as they are ineffective) 2

Antidotal Therapy: Physostigmine

Indications for physostigmine: 2

• Severe anticholinergic delirium with significant CNS effects (hallucinations, severe agitation, obtundation)
• Life-threatening peripheral manifestations
• Agitation refractory to benzodiazepines
• Impending need for intubation due to delirium

Dosing: 2

• Adults: 1-2 mg IV slowly over 5 minutes; may repeat after 10-30 minutes if needed
• Pediatrics: 0.02 mg/kg IV (maximum 0.5 mg per dose)

Key advantage: Patients receiving physostigmine have significantly lower intubation rates compared to benzodiazepines alone 2

Absolute contraindications: 2

• Cardiovascular disease
• Asthma
• Mechanical obstruction of intestines or urinary tract
• QRS prolongation >100 ms (suggests tricyclic antidepressant toxicity)

Alternative When Physostigmine Unavailable

Due to national shortages of physostigmine, oral rivastigmine has emerged as an alternative: 3, 4

• Oral rivastigmine: 3-6 mg via nasogastric tube, may repeat hourly until symptom resolution 3, 4
• Transdermal rivastigmine: 9.5 mg/24-hour patch (less effective due to slow onset; oral route preferred) 3
• Evidence: In a 50-patient case series, oral rivastigmine required less additional parenteral sedation (32%) compared to transdermal formulation (73%) 3

Management of Specific Complications

• Urinary retention: Bladder catheterization 2
• Prolonged QRS or dysrhythmias: Sodium bicarbonate 1-2 mEq/kg IV bolus 2
• Severe agitation despite benzodiazepines: Physostigmine (if not contraindicated) 2

Monitoring Requirements

• Continuous cardiac monitoring for minimum 6 hours after symptom resolution 2
• Serial neurological assessments every 1-2 hours to evaluate treatment response 2
• Temperature monitoring given risk of severe hyperthermia 2

Critical Pitfalls to Avoid

• Underdosing physostigmine: Severe cases may require larger and more frequent doses than standard protocols suggest 2
• Using succinylcholine: Absolutely avoid in anticholinergic crisis as it may cause prolonged paralysis 2
• Confusing toxidromes: Administering atropine for anticholinergic toxicity (or physostigmine for cholinergic crisis) will worsen the patient's condition catastrophically 1, 2
• Missing tricyclic antidepressant co-ingestion: Always obtain ECG; QRS >100 ms contraindicates physostigmine and requires sodium bicarbonate 2

Special Populations

Elderly patients: 5

• More susceptible to anticholinergic toxicity due to baseline decreased acetylcholine physiology
• Common culprits include diphenhydramine, cyclobenzaprine, and oxybutynin
• Lower threshold for physostigmine administration given higher risk of falls and delirium complications

Pediatric patients: 1

• May be more susceptible due to higher minute ventilation
• Greater risk of dehydration requiring aggressive fluid resuscitation
• Use weight-based dosing for all medications