Emergency & Toxicology

Cholinergic toxidrome and organophosphate poisoning

Clinical Overview and When to Suspect Cholinergic Toxicity

— Organophosphates (OPs): agricultural insecticides (malathion, parathion, chlorpyrifos), nerve agents (sarin, VX, novichok). Form irreversible phosphorylated AChE bond after "aging."

— Carbamates: insecticides (carbaryl, aldicarb), medications (pyridostigmine, neostigmine, physostigmine, donepezil, rivastigmine). Reversible inhibition, generally shorter course.

— Direct muscarinic agonists: pilocarpine, bethanechol, muscarine-containing mushrooms (Inocybe, Clitocybe).

— Nerve agent terrorism scenarios on Step 3 emphasize mass-casualty triage and decontamination.

— Farmworker, pesticide applicator, or rural pediatric ingestion presenting with diaphoresis, vomiting, miosis, and bronchorrhea

— Garlic/solvent odor on clothing

— Cluster of patients from same field, building, or public space (consider nerve agent or mass pesticide exposure)

— Suicidal ingestion in regions with agricultural access (leading cause of self-poisoning death globally)

— Unexplained bradycardia + bronchospasm + altered mental status

Board pearl: The classic "wet" presentation (SLUDGE/DUMBELS) is muscarinic; if your patient is tachycardic, weak, fasciculating, and hypertensive, do not exclude OP poisoning — that is the nicotinic phenotype, and it predicts respiratory failure from diaphragmatic paralysis.

Step 3 management: First action at the door is provider PPE and external decontamination (remove clothes, copious water irrigation) — secondary contamination of ED staff is a tested patient-safety theme.

Cholinergic toxidrome results from excess acetylcholine at muscarinic, nicotinic, and CNS receptors due to acetylcholinesterase (AChE) inhibition or direct receptor agonism.

Major exposure categories the ED must recognize:

When to suspect:

Pathophysiology shortcut: AChE inhibition → ACh accumulates → muscarinic (parasympathetic end organs, sweat glands), nicotinic (NMJ, autonomic ganglia, adrenal medulla), and CNS effects coexist. Nicotinic effects can paradoxically cause tachycardia, hypertension, mydriasis — so vital signs may not look "purely cholinergic."

Presentation Patterns and Key History

— Inhalation/nerve agent: seconds to minutes

— Liquid OP dermal/ingestion: 30 min–12 hr

— Highly lipophilic OPs (fenthion, chlorfenthion): delayed onset up to 24 hr and prolonged course (days–weeks) due to fat redistribution

— Carbamates: rapid onset, resolves in <24–48 hr; do not cross BBB well, so CNS effects are milder

— Diarrhea, Urination, Miosis, Bronchorrhea/Bronchospasm/Bradycardia, Emesis, Lacrimation, Salivation/Sweating

— Salivation, Lacrimation, Urination, Defecation, GI cramping, Emesis; Killer Bs = Bronchorrhea, Bronchospasm, Bradycardia (the actual cause of death)

— Mydriasis, Tachycardia, Weakness, Thrashing fasciculations, Fasciculations/paralysis, hypertension, hyperglycemia

— Occupation (farming, landscaping, pest control, lab/military)

— Container or product name, concentration, solvent (hydrocarbon solvents add aspiration risk)

— Time since exposure, route, co-ingestants (alcohol common in suicidal ingestions)

— Pre-event symptoms (chronic low-dose OP exposure → headache, fatigue, peripheral neuropathy)

— Mushroom ingestion timing — early-onset (<2 hr) GI symptoms with muscarinic features = Inocybe/Clitocybe; late-onset (>6 hr) GI symptoms suggest Amanita (hepatotoxic, NOT cholinergic)

Key distinction: Patients who appear "dry, tachycardic, and seizing" are not having a cholinergic crisis — that is anticholinergic toxidrome. The diaphoretic, drooling, bronchorrheic patient with miosis is cholinergic. Sweating is muscarinic via sympathetic cholinergic fibers and is preserved in both — but the wet airway is the giveaway.

Board pearl: Death in OP poisoning is from respiratory failure — combined bronchorrhea, bronchospasm, central apnea, and diaphragmatic nicotinic paralysis.

Symptom onset depends on agent and route:

Muscarinic mnemonic — DUMBELS:

Alternate mnemonic — SLUDGE + Killer Bs:

Nicotinic mnemonic — "days of the week" MTWThF:

CNS effects: anxiety, restlessness, confusion, seizures (especially pediatric), coma, central apnea

History to obtain rapidly:

Physical Exam Findings and Hemodynamic Assessment

— HR: bradycardia (muscarinic, ~50%) or tachycardia (nicotinic/sympathetic, ~25%)

— BP: hypotension or hypertension

— RR: tachypnea early → hypoventilation/apnea late

— SpO₂: falls due to bronchorrhea and bronchospasm before frank apnea

— Temp: usually normal; hyperthermia suggests seizure activity or co-ingestant

— Miosis is the most consistent finding (>90%); pinpoint pupils unresponsive to light

— Profuse lacrimation, rhinorrhea, salivation pooling in oropharynx

— Wheezing + diffuse rhonchi + copious frothy secretions — sounds like CHF or aspiration

— Accessory muscle use; later, paradoxical breathing as diaphragm fails

— Bradyarrhythmias, AV block; QT prolongation is common — risk of torsades

— Fasciculations (visible muscle twitching, often starting in eyelids, tongue, pectorals) are pathognomonic in the right clinical setting

— Generalized weakness, flaccid paralysis, seizures, coma

— Deep tendon reflexes initially brisk → absent

Step 3 management: Place the patient in left lateral decubitus with suction to manage airway secretions while preparing for intubation. Avoid succinylcholine if possible for RSI — it is metabolized by plasma cholinesterase, which is inhibited, producing prolonged paralysis (sometimes hours). Use rocuronium instead; if succinylcholine is the only option, anticipate extended neuromuscular blockade and have ventilator support ready.

Board pearl: Miosis + bronchorrhea + fasciculations is a near-pathognomonic triad — give atropine empirically while confirmatory labs are pending.

General appearance: diaphoretic, drooling, soiled clothing, garlic or petroleum/solvent odor, often agitated then obtunded.

Vital signs are mixed — do not anchor on bradycardia alone:

HEENT:

Pulmonary:

Cardiac:

Abdomen: hyperactive bowel sounds, involuntary defecation, urinary incontinence

Neuro:

Skin: profuse sweating; check for liquid pesticide residue (decontaminate before deeper exam).

Diagnostic Workup — Initial Labs, Imaging, ECG

— Fingerstick glucose (rule out hypoglycemia as cause of altered mental status; OPs can also cause hyperglycemia from nicotinic catecholamine release)

— ECG:

— Pulse oximetry and continuous capnography — early respiratory monitoring

— CXR: pulmonary edema (non-cardiogenic from bronchorrhea), aspiration pneumonitis, hydrocarbon pneumonitis if solvent vehicle aspirated

— CBC, CMP (look for anion-gap metabolic acidosis from seizures/hypoperfusion; hyperglycemia; hypokalemia from β-agonist therapy later)

— Lipase (OPs can cause acute pancreatitis)

— Lactate

— Troponin if ECG changes or chest pain

— VBG/ABG — monitor for hypercapnia heralding respiratory failure

— CK (rhabdomyolysis from fasciculations/seizures)

— Pregnancy test in reproductive-age women

— Acetaminophen and salicylate levels in intentional ingestions

— Plasma (pseudo)cholinesterase (butyrylcholinesterase) — falls earliest, easy to measure, used to confirm and trend exposure

— Erythrocyte (true) acetylcholinesterase — more specific marker of neuronal toxicity; correlates better with severity but takes longer to result

— Both are typically sent but not required before treatment

CCS pearl: Order in this sequence — fingerstick glucose, ECG, pulse ox/capnography, CXR portable, CBC/CMP/lipase/CK/lactate/VBG, RBC AChE and plasma cholinesterase, urine tox, acetaminophen/salicylate. Then immediately move to atropine and pralidoxime — do not delay therapy for results.

Board pearl: A normal cholinesterase level does not rule out poisoning — individual baseline variation is wide, and severity correlates better with RBC AChE.

Cholinergic poisoning is a clinical diagnosis — treatment must not wait for lab confirmation.

Bedside studies to order immediately:

Sinus bradycardia, 1st/2nd/3rd-degree AV block

QTc prolongation in up to 2/3 of patients — predicts mortality

Torsades de pointes, polymorphic VT

ST changes from myocardial ischemia (catecholamine surge or hypoxia)

Core labs:

Toxicology-specific:

Diagnostic Workup — Advanced and Confirmatory Studies

— Reflects synaptic/neuronal enzyme more accurately than plasma cholinesterase

— Activity <20% of normal = severe poisoning; 20–50% = moderate; 50–90% = mild

— Recovery requires new RBC synthesis (~1% per day) — takes weeks to months after irreversible OP binding

— Synthesized by liver, recovers in days–weeks

— More sensitive but less specific (also low in liver disease, malnutrition, pregnancy, genetic variants)

— Useful for serial trending during recovery and to time pralidoxime discontinuation

— Adult test dose 1 mg IV (children 0.01 mg/kg)

— Absence of expected anticholinergic response (tachycardia, mydriasis, dry mouth) supports significant cholinergic toxicity

— Identifies specific OP/carbamate; rarely changes acute management but important for forensic, occupational, and public health investigations (CDC, poison control)

— Mandatory in suspected nerve agent / mass-casualty / criminal poisoning

— Head CT if persistent altered mental status, focal deficit, or seizure to exclude alternative etiology

— Abdominal imaging if peritoneal signs (rare OP-induced pancreatitis or ileus)

— Indicated for nonconvulsive status epilepticus in patients with persistent unexplained coma after initial stabilization

— Nerve conduction studies / EMG at 1–4 days for intermediate syndrome (proximal weakness, cranial nerve and respiratory muscle paralysis): repetitive nerve stimulation shows decrement

— At 1–3 weeks for OP-induced delayed neuropathy (OPIDN): distal sensorimotor axonopathy from neuropathy target esterase (NTE) inhibition

Key distinction: Plasma cholinesterase falls and recovers faster — useful in carbamate poisoning. RBC AChE falls and recovers slowly — better reflects OP severity and need for ongoing pralidoxime.

Board pearl: If you see proximal/respiratory weakness re-emerging 24–96 hours after apparent recovery, think intermediate syndrome — pralidoxime does not reliably prevent it; supportive ventilation is the cure.

RBC acetylcholinesterase activity:

Plasma butyrylcholinesterase:

Atropine challenge test (clinical, not lab):

GC-MS or LC-MS confirmation:

Imaging beyond CXR:

EEG:

Late testing — intermediate syndrome and OPIDN:

Risk Stratification and First-Line Management Logic

— Airway/Breathing — bronchorrhea kills before paralysis does

— Circulation — IV access, fluids for hypotension

— Decontamination — remove clothing, copious water (and soap) irrigation; staff in nitrile gloves, gowns, eye protection

— Antidotes — atropine and pralidoxime (oxime) early

— Mild: muscarinic symptoms only, normal mental status, no respiratory compromise. RBC AChE 20–50%

— Moderate: muscarinic + nicotinic symptoms, mild respiratory distress, mild AMS

— Severe: coma, seizures, frank respiratory failure, hemodynamic instability, fasciculations/paralysis. RBC AChE <20%. ICU admission mandatory.

— Skin: remove all clothing (double-bag as hazmat), copious soap and water for ≥15 min; pay attention to hair, axillae, groin

— Eyes: continuous saline irrigation if ocular exposure

— GI: activated charcoal 1 g/kg within 1 hour of oral ingestion if airway protected; gastric lavage is not routinely recommended (low benefit, aspiration risk)

— Avoid hot water (vasodilation increases absorption) and bleach (some OPs become more toxic)

— Bronchorrhea unresponsive to atropine

— SpO₂ <90% on supplemental O₂

— Rising PaCO₂ or declining mental status

— Seizures

— Target clear lungs (no rales/wheezes), SBP >90, HR >80 — these are the endpoints

— Pupils dilate slowly and inconsistently; do not chase miosis

CCS pearl: Move the simulated patient to ICU before writing antidote orders if severe — Step 3 CCS rewards correct location of care. Order continuous cardiac monitoring, pulse oximetry, capnography, foley, and frequent neuro checks.

Step 3 management: Atropine first, oxime second. Atropine reverses the life-threatening muscarinic effects (the airway); pralidoxime reverses nicotinic effects and prevents aging but is adjunctive and slower-acting.

Three simultaneous priorities — "ABC-DA":

Severity grading:

Decontamination details:

Airway management triggers:

Atropine titration goal — NOT pupil size:

Pharmacotherapy — Atropine and Pralidoxime

— Adult initial dose: 1–3 mg IV bolus (military/severe: 2–5 mg). Pediatric: 0.05 mg/kg IV (min 0.1 mg).

— Double the dose every 3–5 minutes until bronchial secretions dry and bronchospasm resolves

— Cumulative doses can reach hundreds of milligrams over 24 hours in severe poisoning — do not underdose

— Once stabilized, start continuous infusion at 10–20% of total loading dose per hour; titrate to clear lungs

— Endpoints: clear chest auscultation, HR >80, SBP >90, no diaphoresis. Pupils and bowel sounds are unreliable endpoints

— Atropine toxicity: hyperthermia, ileus, urinary retention, delirium, agitation — pause infusion, do not reverse

— Reverses nicotinic effects (weakness, fasciculations, respiratory paralysis) that atropine does not address

— Adult: 30 mg/kg (max 2 g) IV over 30 min, then 8–10 mg/kg/hr continuous infusion (or 1–2 g IV q6–8h)

— Pediatric: 25–50 mg/kg load, then 10–20 mg/kg/hr

— Must be given before aging occurs — aging time varies (sarin: 5 hr; soman: 2–6 min; parathion: 24+ hr). Soman is essentially untreatable by oxime unless pretreated.

— Continue at least 24 hr after atropine requirement falls and clinical improvement — fat-soluble OPs may require days

— Side effects: hypertension, tachycardia (slow infusion), dizziness, transient neuromuscular blockade if pushed too fast

— Diazepam 5–10 mg IV or lorazepam 2–4 mg IV; midazolam IM if no IV access

— Also reduces CNS-mediated mortality and protects against nerve-agent–induced brain injury

— DuoDote/Mark I autoinjectors (atropine 2.1 mg + pralidoxime 600 mg) ± CANA (diazepam 10 mg) for field/mass-casualty use

Board pearl: A patient needing >5 mg atropine has significant poisoning — start the pralidoxime drip and admit to ICU. Stopping atropine too early causes rebound bronchorrhea and arrest.

Key distinction: Atropine treats muscarinic (and CNS) effects; pralidoxime treats nicotinic effects. You need both for OP poisoning. Carbamates: atropine essential, pralidoxime usually unnecessary (controversial; give if severe or unclear agent).

Atropine — competitive muscarinic antagonist:

Pralidoxime (2-PAM) — oxime that reactivates AChE before aging:

Benzodiazepines for seizures and agitation:

Adjunctive and Advanced Pharmacology, Ventilator Strategy

— RSI agent choice: rocuronium 1.2 mg/kg preferred. Avoid succinylcholine (prolonged paralysis from cholinesterase inhibition — up to several hours)

— Sugammadex can reverse rocuronium if needed urgently

— Avoid ketamine alone if hypertensive crisis is severe; otherwise acceptable as induction

— Lung-protective ventilation (Vt 6 mL/kg IBW); expect high secretion load — frequent suctioning, consider closed inline suction

— PEEP titrated for non-cardiogenic pulmonary edema

— Hypotension: IV crystalloid bolus, then norepinephrine if persistent

— Bradycardia unresponsive to atropine: epinephrine infusion; transcutaneous pacing as bridge

— Torsades from QT prolongation: magnesium sulfate 2 g IV, correct K⁺, overdrive pacing if recurrent; avoid QT-prolonging antiemetics (ondansetron caution)

— First line: benzodiazepines (diazepam, lorazepam, midazolam)

— Second line: levetiracetam preferred; phenobarbital alternative

— Phenytoin is generally ineffective for OP/nerve agent seizures (GABAergic mechanism predominates)

— Magnesium sulfate (4 g IV) may reduce atropine requirement and mortality in some trials

— Sodium bicarbonate for severe acidosis

— Clonidine, fresh frozen plasma (source of butyrylcholinesterase) — limited evidence, not standard

— Hemodialysis/hemoperfusion: not effective for most OPs (high protein binding, large Vd); exception: dimethoate may benefit from hemoperfusion

— Succinylcholine (prolonged paralysis)

— Morphine (respiratory depression)

— Theophylline (lowers seizure threshold)

— Furosemide before atropine for pulmonary "edema" — the secretions are bronchial, not cardiogenic; atropine is the diuretic here

CCS pearl: Order closed-system endotracheal suction explicitly — the volume of secretions is enormous and open suctioning exposes staff to contaminated aerosols.

Step 3 management: Pair every escalation of atropine with re-assessment of lung exam, HR, BP, and secretions q3–5 min — document the trend in the CCS chart.

Airway and ventilation:

Hemodynamics:

Antiseizure pharmacology:

Investigational / adjunctive:

Drugs to avoid:

Special Populations — Elderly and Renal/Hepatic Impairment

— Higher baseline anticholinergic burden (Beers criteria meds) — may mask early muscarinic symptoms or amplify atropine-induced delirium

— Reduced cardiac reserve — bradycardia and QT prolongation poorly tolerated; lower threshold for pacing

— Polypharmacy interactions: β-blockers blunt nicotinic tachycardia; diuretics worsen hypokalemia and QT risk

— Atropine cautions: acute angle-closure glaucoma, BPH urinary retention, pre-existing dementia (worsened delirium). Risk-benefit still favors atropine in life-threatening cholinergic crisis — do not withhold

— Falls risk during recovery; physical therapy consult before discharge

— Baseline cholinesterase activity already reduced — smaller OP exposure produces larger effect

— Cholinergic crisis vs myasthenic crisis in MG patients: edrophonium test rarely used; clinical context (recent dose escalation, GI illness causing pyridostigmine accumulation) guides

— Pralidoxime is renally cleared — reduce dose and extend infusion interval in CrCl <50; consider 50% dose reduction or every 12–24 h dosing

— Atropine has minimal renal adjustment but accumulates with hepatic dysfunction

— Avoid nephrotoxic adjuncts; monitor urine output, AKI from rhabdomyolysis common

— Plasma butyrylcholinesterase produced by liver — baseline lower, less reliable marker

— Atropine hepatically metabolized — titrate carefully, watch for prolonged anticholinergic delirium

— Coagulopathy and hypoalbuminemia alter drug binding

— Atypical pseudocholinesterase (dibucaine-resistant variant, ~1:3200) — produces prolonged succinylcholine apnea even without OP exposure; another reason to default to rocuronium

Board pearl: A dementia patient on donepezil who develops bradycardia, syncope, diarrhea, and weight loss may have iatrogenic cholinergic excess — check for recent dose escalation or new CYP2D6 inhibitor (paroxetine, fluoxetine).

Step 3 management: In CKD patients, don't skip pralidoxime — adjust dose, monitor for hypertension and neuromuscular dysfunction, and trend RBC AChE.

Elderly patients:

Patients on cholinesterase inhibitors (dementia therapy — donepezil, rivastigmine, galantamine; or myasthenia gravis — pyridostigmine):

Renal impairment:

Hepatic impairment:

Genetic variants:

Special Populations — Pregnancy and Pediatrics

— OPs cross the placenta; fetal AChE inhibition documented

— Maternal stabilization takes priority — hypoxia is the greatest fetal risk

— Atropine is pregnancy category C but indicated — life-threatening cholinergic crisis outweighs theoretical fetal tachycardia risk

— Pralidoxime is also indicated; animal data reassuring, no human teratogenicity signal — give standard doses

— Continuous fetal monitoring after 23–24 weeks gestation; involve OB early

— Decontamination as for non-pregnant patients; left lateral tilt for IVC offloading

— Postpartum: counsel on breastfeeding — limited data, generally safe once acute toxicity resolves and antidotes cleared

— Higher risk: greater surface area-to-mass ratio (dermal absorption), hand-to-mouth behavior, lower baseline cholinesterase

— Presentation often CNS-predominant: seizures, lethargy, coma; classic muscarinic signs may be subtle

— Hypersalivation may be misread as teething or viral illness — high index of suspicion in rural/agricultural communities

— Atropine pediatric dose: 0.05 mg/kg IV (min 0.1 mg), double q3–5 min until secretions clear; no maximum total dose

— Pralidoxime: 25–50 mg/kg load, then 10–20 mg/kg/hr infusion

— Pediatric DuoDote/atropine autoinjectors available for mass-casualty triage; weight-based selection

— Decontamination: warm (not hot) water, attention to skin folds and diaper area; prevent hypothermia

— Farmworker children, take-home pesticide residue on parent's clothing

— Cognitive, behavioral, and ADHD-like effects associated with prenatal/childhood OP exposure

— Mandatory reporting to child protective services if exposure reflects neglect or unsafe housing

— Inocybe/Clitocybe (muscarinic) — rapid GI + SLUDGE within 30 min–2 hr; atropine effective; rarely fatal

— Distinguish from Amanita (delayed GI >6 hr, hepatic failure, no SLUDGE)

Board pearl: In a child with unexplained seizure, miosis, and hypersalivation, ask about parental occupation and home pesticide storage — diagnosis is missed when farm exposure is not volunteered.

Step 3 management: Engage Poison Control (1-800-222-1222) early — it is the standard of care, documented in CCS, and supports legal/forensic chain of custody.

Pregnancy:

Pediatrics:

Chronic low-dose pediatric exposure:

Mushroom ingestion pediatrics:

Complications and Adverse Outcomes

— Respiratory failure — primary cause of death; combined bronchorrhea, bronchospasm, central apnea, diaphragmatic paralysis

— Aspiration pneumonitis — vomiting + altered mental status; worse with hydrocarbon solvent vehicles

— Cardiovascular: bradyarrhythmias, AV block, QT prolongation, torsades, polymorphic VT, MI from hypoxia/catecholamine surge

— Seizures and status epilepticus — especially nerve agents and pediatric patients

— Acute pancreatitis — OPs directly toxic to pancreatic acinar cells; check lipase

— Hyperglycemia/DKA-like state from nicotinic catecholamine release; usually transient

— Rhabdomyolysis from fasciculations, seizures, prolonged immobility → AKI

— Onset 1–4 days after exposure, after apparent recovery from cholinergic crisis

— Proximal limb weakness, neck flexor weakness, cranial nerve palsies, recurrent respiratory failure

— Mechanism: persistent nicotinic receptor dysfunction at NMJ

— Pralidoxime does not prevent it; treatment is supportive ventilation × 5–18 days

— Occurs in ~20–50% of severe OP poisonings

— OP-induced delayed neuropathy from inhibition of neuropathy target esterase (NTE)

— Distal, symmetric, painful sensorimotor axonopathy; foot drop, wrist drop; pyramidal signs late

— Recovery incomplete; physical therapy, gait training

— Classically with triorthocresyl phosphate, chlorpyrifos, dichlorvos

— Chronic OP-induced neuropsychiatric disorder (COPIND): memory deficits, depression, anxiety, parkinsonism

— Increased risk of Parkinson disease with chronic pesticide exposure

— Persistent low RBC AChE for months after irreversible binding

— Atropine toxicity — hyperthermia, ileus, urinary retention, agitated delirium

— Pralidoxime-related hypertension if infused too quickly

— Prolonged succinylcholine paralysis if used for intubation

Board pearl: A patient who looked recovered on hospital day 2 and then re-decompensates with proximal weakness and rising CO₂ has intermediate syndrome — re-intubate and ventilate; do not assume relapse of original toxicity.

Key distinction: Intermediate syndrome = proximal motor weakness, days 1–4. OPIDN = distal sensorimotor, weeks 1–3. Different mechanisms, different prognoses.

Acute phase (0–24 hr):

Subacute phase (24–96 hr) — Intermediate Syndrome:

Delayed phase (1–3 weeks) — OPIDN:

Long-term:

Iatrogenic:

When to Escalate — ICU, Consultation, Inpatient Triage

— Any respiratory symptoms requiring more than minimal O₂

— Need for atropine infusion or repeat boluses beyond initial dose

— Altered mental status, seizure, or coma

— Hemodynamic instability, dysrhythmia, or QTc >500 ms

— Severe poisoning (RBC AChE <30% if available) regardless of initial appearance

— Intentional ingestion (psychiatric and medical comorbidities)

— Nerve agent or mass-casualty exposure

— Pediatric or pregnant patients with confirmed exposure

— Mild muscarinic symptoms resolved with single atropine dose

— Stable vitals × 6–12 hours

— Asymptomatic carbamate exposure with normal labs — typically observe 6–8 hours

— Asymptomatic dermal/inhalation exposure with appropriate decontamination

— Carbamate ingestion with full resolution at 8 hours, no medication required, and safe disposition (not intentional, intact social support)

— Medical toxicology / Poison Control (1-800-222-1222) — for every case; consult drives dosing and provides public-health surveillance

— Pulmonary/critical care for ventilator management

— Cardiology if persistent arrhythmia or QT prolongation

— Psychiatry for all intentional ingestions before discharge

— Occupational medicine / public health for workplace exposures — OSHA reporting trigger

— Pediatrics + CPS if pediatric exposure suggests neglect

— OB for pregnant patients

— Tertiary center with ECMO if refractory respiratory failure

— Hyperbaric not indicated

— Mass casualty: activate hospital incident command, hazmat decon zone, regional poison center, CDC if nerve agent suspected

CCS pearl: Document "Poison Control contacted" with case number — Step 3 examiners reward this and it is a real-world legal protection.

Step 3 management: In intentional ingestion cases, psychiatric evaluation and safety planning are required before discharge — patient cannot leave AMA from the ED if active suicidal ideation persists; involve psychiatry and pursue involuntary hold if criteria met.

ICU admission criteria (low threshold):

Floor/observation admission:

Discharge after ED observation acceptable for:

Consultations:

Transfer considerations:

Key Differentials — Same-Category (Cholinergic and Toxidrome Mimics)

— Identical muscarinic + nicotinic presentation but reversible, shorter duration (<24–48 hr)

— Pralidoxime not strictly required for pure carbamate poisoning (some toxicologists give it; some withhold for carbaryl due to theoretical worsening)

— Atropine is mainstay; mortality lower than OPs

— More rapid onset (seconds–minutes inhalation), more potent, mass-casualty pattern

— Soman ages within minutes — pralidoxime must be given within minutes to be useful; consider pretreatment with pyridostigmine in military setting

— Mark I/DuoDote autoinjectors stockpiled for first responders

— Therapeutic AChE inhibitors: pyridostigmine (myasthenia gravis), neostigmine, edrophonium, donepezil/rivastigmine/galantamine (dementia), physostigmine (anticholinergic reversal)

— Cholinergic crisis in MG patient: overdosed pyridostigmine, especially during GI illness — distinguishable from myasthenic crisis by muscarinic features and fasciculations

— Inocybe and Clitocybe species — high muscarine content, pure muscarinic toxidrome

— Onset <2 hr; atropine reverses; rarely fatal

— Distinct from Amanita muscaria (despite name, contains ibotenic acid/muscimol → anticholinergic-like GABAergic syndrome, not cholinergic)

— E-liquid ingestion (children), tobacco overuse, varenicline overdose

— Early phase mimics nicotinic excess (vomiting, tachycardia, hypertension, seizures); late phase = depression and paralysis

— Lacks prominent muscarinic features unless severe

— Latrotoxin causes massive ACh release at NMJ — diaphoresis, hypertension, abdominal rigidity, fasciculations; usually no miosis or bronchorrhea

Key distinction: All of these reverse with atropine for muscarinic component, but only OPs and nerve agents require pralidoxime for nicotinic reversal and prevention of aging.

Board pearl: A myasthenic patient with weakness + fasciculations + diarrhea = cholinergic crisis (too much pyridostigmine). Weakness + dry mouth + improvement with edrophonium = myasthenic crisis (too little). Holding pyridostigmine and supportive care distinguishes them.

Carbamate insecticide poisoning:

Nerve agent exposure (sarin, VX, soman, tabun, novichok):

Medication-induced cholinergic excess:

Muscarinic mushroom poisoning:

Nicotine toxicity:

Black widow envenomation:

Key Differentials — Other-Category Causes

— Hot, dry skin, mydriasis, urinary retention, ileus, delirium, tachycardia

— Diphenhydramine, TCAs, atropine overdose, jimsonweed

— Treated with physostigmine (which itself can cause cholinergic excess if overdosed — comes full circle)

— Cocaine, methamphetamine, MDMA, bath salts

— Tachycardia, hypertension, mydriasis, diaphoresis, agitation, hyperthermia

— Distinguished by absence of bronchorrhea, salivation, miosis, fasciculations

— Miosis + respiratory depression overlaps with cholinergic crisis

— No bronchorrhea, no diaphoresis, no fasciculations, decreased bowel sounds — opposite GI picture

— Naloxone trial diagnostic

— Frothy sputum and rales overlap with bronchorrhea

— Look for cardiac history, elevated BNP, cardiogenic CXR pattern; miosis and fasciculations absent

— Wheezing prominent; lack the SLUDGE features

— Status epilepticus with autonomic features, serotonin syndrome (hyperreflexia, clonus, hyperthermia, mydriasis — distinct), neuroleptic malignant syndrome (rigidity, hyperthermia)

— Diaphoresis and hypotension overlap; lack of pinpoint pupils and bronchorrhea distinguishes

— Decreased ACh release → descending paralysis, dry mouth, mydriasis, no SLUDGE

— Same final pathway (respiratory failure) but opposite autonomic signature

Key distinction: The wet vs dry axis is the fastest bedside differentiator. Wet (sweating, drooling, bronchorrhea, miosis) → cholinergic. Dry (dry skin/mucosa, mydriasis, urinary retention) → anticholinergic.

Board pearl: Miosis is shared by opioid and cholinergic toxidromes — the wet airway with fasciculations is what makes it cholinergic. Trial naloxone if uncertain; absence of response and persistent secretions points to OP.

Anticholinergic toxidrome (the "opposite"):

Sympathomimetic toxidrome:

Opioid toxidrome:

Sedative-hypnotic toxidrome: CNS depression, normal-to-small pupils, normal vitals; no autonomic storm

Acute pulmonary edema / CHF exacerbation:

Status asthmaticus or anaphylaxis:

Cholinergic-like seizure mimics:

Sepsis with shock and altered mental status:

Botulism (the inverse of cholinergic excess):

Strychnine poisoning: muscle spasms with preserved consciousness; no SLUDGE.

Secondary Prevention, Discharge Planning, Long-Term Management

— Off atropine ≥24 hr without rebound symptoms

— Stable respiratory status, normal mental status

— RBC AChE trending upward (helpful but not required)

— Cleared by psychiatry for intentional ingestions

— Safe disposition (housing, exposure source removed)

— Usually none specific to the poisoning if recovered

— Inhaled bronchodilators if persistent reactive airways

— Treat residual neuropathic pain (gabapentin) if OPIDN emerging

— Avoid restarting therapeutic cholinesterase inhibitors (donepezil, pyridostigmine) until ≥1–2 weeks symptom-free and cholinesterase recovering — coordinate with prescriber

— Engineering controls: closed pesticide application systems, ventilation, scheduled re-entry intervals after spraying

— PPE: chemical-resistant gloves, respirators, coveralls, eye protection

— Administrative: training, OSHA Worker Protection Standard compliance, MSDS access

— Biomonitoring: baseline and periodic plasma cholinesterase for applicators; remove from exposure if >30% decrease from baseline

— Hygiene: shower before going home, separate laundering of work clothes (prevents "take-home" pediatric exposure)

— Locked storage, original labeled containers, out of pediatric reach

— Integrated pest management to reduce overall use

— Public health referral if community-wide exposure

— Psychiatric follow-up arranged before discharge; means restriction (removal of remaining pesticide from home is a proven mortality-reducing intervention)

— Document suicide safety plan; engage family if patient consents

— Report to public health, FBI, CDC; preserve clothing and biologic samples as evidence

— Stockpile review for emergency preparedness

Step 3 management: Means restriction for suicidal ingestion (locking up or removing remaining pesticide) is one of the highest-yield prevention interventions on Step 3 — comparable to firearm restriction counseling.

Board pearl: A worker with >30% drop in plasma cholinesterase from their baseline must be removed from OP exposure even if asymptomatic — OSHA-style preventive medicine question.

Hospital discharge criteria:

Discharge medications and prescriptions:

Occupational exposure — secondary prevention:

Home pesticide safety counseling:

Intentional ingestion / suicide attempt:

Mass-casualty / terrorism context:

Follow-Up, Monitoring, Rehabilitation, Counseling

— Primary care or toxicology clinic within 1 week — symptom check, medication reconciliation, mental health screen

— Repeat cholinesterase (plasma + RBC) at 2 weeks and 6 weeks — confirms recovery trajectory; plasma normalizes in days–weeks, RBC AChE in 1–3 months

— Neurology referral at 2–4 weeks if any sensory or motor symptoms (screen for OPIDN, intermediate syndrome sequelae)

— Psychiatry follow-up within 1 week for intentional ingestion patients; ensure outpatient appointment booked before discharge, not just referral made

— Symptom diary: weakness, paresthesias, GI symptoms, mood, sleep, cognition

— Spirometry if persistent reactive airway symptoms

— Nerve conduction studies if distal sensorimotor symptoms develop

— Liver and kidney function periodically if recovery slow

— Physical therapy for proximal weakness (intermediate syndrome survivors) and gait training (OPIDN)

— Occupational therapy for return to work — especially relevant for agricultural workers

— Pulmonary rehab if ventilator-dependent recovery

— Cognitive rehabilitation for chronic neuropsychiatric symptoms

— Avoid re-exposure during recovery — AChE is depleted, even subclinical exposure can recrash

— Alcohol potentiates CNS depression; avoid during recovery

— Mood, anxiety, PTSD screening at each visit

— Sleep disturbance and chronic fatigue common; reassure about typical timeline (weeks–months)

— Do not return until plasma cholinesterase >80% baseline and asymptomatic

— Workplace evaluation by occupational medicine before re-entry

— Document medical surveillance per OSHA

— Defer until cognitive and motor recovery complete; formal driving evaluation if any residual deficit

— Developmental and neurocognitive assessment at 6 and 12 months; chronic OP exposure linked to attention and IQ deficits

Board pearl: RBC acetylcholinesterase recovers at ~1% per day after irreversible OP binding — full recovery takes roughly 3 months. Use this to counsel patients and time return to occupational exposure.

Step 3 management: For intentional ingestion patients, confirmed outpatient psychiatry appointment must exist before discharge — a referral alone is inadequate documentation on Step 3.

Post-discharge follow-up schedule:

Monitoring parameters:

Rehabilitation:

Counseling content:

Return to work guidance (occupational cases):

Driving and machinery:

Pediatric long-term follow-up:

Ethical, Legal, and Patient Safety Considerations

— Suspected occupational pesticide exposure: OSHA reportable; state pesticide regulatory agencies

— Pediatric exposure suggesting neglect or unsafe environment: child protective services notification — physicians are mandated reporters in every US state

— Suspected nerve agent / chemical terrorism: notify FBI and local public health/CDC; clothing and biologic samples preserved as evidence (chain of custody documented)

— Cluster of cases (≥2 from same source): state and local public health department

— Intentional poisoning by another person (homicide attempt): law enforcement; preserve evidence

— Altered patient cannot consent to lifesaving antidote therapy — emergency doctrine applies; document inability to consent and clinical urgency

— Pregnant patient with intentional ingestion may refuse care — generally autonomy honored if decisional capacity intact, but involve OB and ethics if fetus is viable; document capacity assessment carefully

— Jehovah's Witness or other religious objection rarely affects antidote use specifically, but transfusion refusal for associated bleeding/coagulopathy must be honored if capacitated

— Suicidal ingestion patients require capacity assessment — active suicidality + recent attempt typically equals lack of capacity to refuse psychiatric evaluation

— Use state-specific involuntary hold (5150/equivalent) when criteria met; documentation crucial for legal defensibility

— Medication reconciliation at discharge — list all AChE inhibitors (donepezil, pyridostigmine), explicit instructions on when to resume

— Communicate clearly to outpatient prescribers — fax/EMR message documented

— Means restriction counseling and pesticide removal from home documented as part of safety planning — this is a USPSTF-supported intervention for suicide prevention

— Failure to decontaminate exposes ED staff — secondary contamination has caused real-world outbreaks

— Hospital incident command and hazmat protocols should be drilled

— Occupational exposures are compensable; physician documentation supports claims and triggers workplace inspection

— Avoid discouraging legitimate workers' comp filing

Step 3 management: A patient with intentional OP ingestion who is now medically stable but still expressing suicidal ideation cannot be discharged on AMA — assess capacity, document deficit, place psychiatric hold, and arrange transfer to psychiatric facility. This is a tested transition-of-care patient-safety scenario.

Board pearl: Means restriction (removing pesticides from the home) is a Level A intervention for suicide prevention in agricultural communities — counsel and document for every case.

Mandatory reporting:

Informed consent edge cases:

Capacity and involuntary holds:

Transition-of-care safety:

Staff safety / patient safety overlap:

Workers' compensation and disability:

High-Yield Associations and Rapid-Fire Clinical Facts

— DUMBELS = muscarinic: Diarrhea, Urination, Miosis, Bronchorrhea/Bronchospasm/Bradycardia, Emesis, Lacrimation, Salivation/Sweating

— MTWThF = nicotinic: Mydriasis, Tachycardia, Weakness, Twitching (fasciculations), Fasciculations/Paralysis (Th = "thrashing")

— Killer Bs: Bronchorrhea, Bronchospasm, Bradycardia — cause of death

— Soman: 2–6 minutes (essentially untreatable by oxime post-exposure)

— Sarin: ~5 hours

— VX: ~48 hours

— Most OP insecticides: 24–48 hours

Board pearl: If asked "which intervention reduces mortality most in agricultural OP suicide attempts in the population?" — answer is means restriction (regulating/locking pesticides), not better antidotes.

Step 3 management: Continuous atropine infusion at 10–20% of total loading dose per hour is the maintenance standard.

Mnemonics:

The most lethal feature: bronchorrhea + bronchospasm + central apnea → respiratory failure. Atropine, not furosemide, is the diuretic.

Atropine endpoint: clear lungs, HR >80, SBP >90. NOT pupils.

Pralidoxime works on nicotinic effects (weakness, fasciculations, paralysis). Atropine does not reverse these.

Aging time pearls:

Avoid succinylcholine in OP poisoning — prolonged paralysis from inhibited plasma cholinesterase.

Avoid morphine, theophylline, phenothiazines, loop diuretics in early management — worsen respiratory depression, seizures, or hypotension.

Pediatric OP exposure: more CNS-predominant (seizures > SLUDGE).

Carbamates = reversible, no aging, pralidoxime usually unnecessary; donepezil and pyridostigmine are therapeutic carbamates.

Black widow envenomation mimics nicotinic excess (massive ACh release).

Mushrooms causing muscarinic excess: Inocybe, Clitocybe. Amanita muscaria is misleadingly named — actually causes anticholinergic-GABAergic syndrome.

Sarin attack on Tokyo subway (1995), Khan Shaykhun Syria (2017), Salisbury novichok (2018) — classic exam-cited mass-casualty events.

Intermediate syndrome: proximal weakness 24–96 hr after recovery; ventilator support is the answer.

OPIDN: distal sensorimotor neuropathy 1–3 weeks out; classic with chlorpyrifos, triorthocresyl phosphate ("ginger jake paralysis").

Plasma cholinesterase recovers in days–weeks; RBC AChE recovers ~1%/day, full ~3 months.

Magnesium sulfate adjunct: may reduce atropine requirement and mortality.

Poison Control: 1-800-222-1222 — call every case.

Board Question Stem Patterns

A 42-year-old male crop duster develops nausea, vomiting, diaphoresis, blurred vision, and shortness of breath 1 hour after spraying. Exam: pinpoint pupils, drooling, diffuse wheezes, HR 52, RR 28. Best initial step? → Decontaminate (remove clothing, wash skin) and give atropine; then pralidoxime. Distractor: physostigmine (would worsen).

A 3-year-old from a rural home becomes lethargic with seizures and copious oral secretions. Father uses pesticides for work. → OP poisoning; atropine + pralidoxime + benzodiazepines for seizures. Mandatory reporting if exposure reflects unsafe storage.

Patient with OP poisoning needs intubation. Which neuromuscular blocker? → Rocuronium. Succinylcholine causes prolonged paralysis.

After 8 mg atropine, the patient's HR is 110 and pupils remain 2 mm. What's the next step? → Continue atropine if lungs not yet clear; pupils are not the endpoint.

On hospital day 3, the patient develops new proximal weakness and rising PaCO₂. → Reintubate and provide supportive ventilation. Not "more pralidoxime" — pralidoxime does not prevent or reverse it.

MG patient on pyridostigmine develops weakness, diarrhea, fasciculations. → Cholinergic crisis from pyridostigmine excess. Hold pyridostigmine, supportive care.

Pesticide applicator's plasma cholinesterase falls 40% from baseline; he feels well. → Remove from exposure until recovery >80% baseline.

Forager with diaphoresis, salivation, miosis 1 hour after mushroom meal. → Inocybe/Clitocybe (muscarine); treat with atropine.

Stable after antidotes but still suicidal. → Psychiatric hold; do not discharge.

Three workers from same farm present together. → Notify public health and OSHA; investigate site.

Pregnant patient with OP poisoning. → Atropine and pralidoxime indicated; maternal stabilization first; fetal monitoring.

Board pearl: The wrong answer that traps students is "furosemide for pulmonary edema" — bronchorrhea is treated with atropine, not diuresis.

Step 3 management: When in doubt on a stem, the first two correct steps are nearly always (1) decontaminate + protect staff and (2) atropine before pralidoxime.

Stem 1 — Classic farmworker:

Stem 2 — Pediatric ingestion:

Stem 3 — RSI choice:

Stem 4 — Endpoint of atropine:

Stem 5 — Intermediate syndrome:

Stem 6 — Myasthenic vs cholinergic crisis:

Stem 7 — Occupational surveillance:

Stem 8 — Mushroom ingestion:

Stem 9 — Disposition for intentional ingestion:

Stem 10 — Public health:

Stem 11 — Pregnancy:

One-Line Recap

Cholinergic toxidrome from organophosphate poisoning is a life-threatening muscarinic + nicotinic + CNS crisis killed by bronchorrhea and respiratory failure, diagnosed clinically, and treated with immediate decontamination, escalating atropine titrated to dry lungs, pralidoxime to reverse nicotinic effects before aging, and benzodiazepines for seizures — while anticipating intermediate syndrome and delayed neuropathy in survivors.

High-yield rapid recaps:

Board pearl: Atropine first (saves the airway); pralidoxime second (saves the diaphragm); benzodiazepines third (save the brain) — A-P-B in that order is the Step 3 algorithm.

Step 3 management: Never forget that decontamination and staff PPE precede every other intervention — secondary contamination of ED personnel is the most-tested patient-safety point of this topic.

Recognize: Wet patient — miosis, drooling, bronchorrhea, fasciculations, diaphoresis, often in a farmworker, child of one, or mass-exposure setting. Mixed vitals (brady- or tachycardia) reflect competing muscarinic and nicotinic effects.

Act: Provider PPE → decontaminate (remove clothing, irrigate skin/eyes) → secure airway (rocuronium, not succinylcholine) → atropine 1–3 mg IV doubling q3–5 min until lungs clear, HR >80, SBP >90, then continuous infusion → pralidoxime 30 mg/kg load, then 8–10 mg/kg/hr within minutes-to-hours before aging → benzodiazepines for seizures → ICU admission and Poison Control (1-800-222-1222).

Anticipate: Intermediate syndrome at 24–96 hours (proximal weakness, respiratory failure — supportive ventilation), OPIDN at 1–3 weeks (distal sensorimotor neuropathy), prolonged paralysis if succinylcholine used, QT prolongation/torsades (give magnesium), and rebound bronchorrhea if atropine stopped prematurely.

Prevent and follow: Means restriction for intentional ingestion (locked pesticide storage saves lives), psychiatric clearance before discharge, occupational removal from exposure until cholinesterase >80% of baseline, mandatory reporting (CPS for unsafe pediatric exposure, OSHA/public health for occupational and cluster cases), and outpatient follow-up at 1 week with serial cholinesterase trending over 1–3 months.