ICU · toxicology

Acute Organophosphate and Nerve Agent Poisoning

Also known as Organophosphate poisoning · OP poisoning · Nerve agent poisoning · Cholinergic crisis · Sarin poisoning · VX poisoning · Pesticide poisoning · Acetylcholinesterase inhibitor poisoning · SLUDGE syndrome · DUMBELS syndrome

Organophosphate (OP) and nerve agent poisoning — inhibition of acetylcholinesterase (AChE) → acetylcholine accumulation → overstimulation of muscarinic receptors (SLUDGE: salivation, lacrimation, urination, defecation, GI distress, emesis — PLUS miosis, bradycardia, bronchorrhoea, bronchospasm), nicotinic receptors (fasciculations, muscle weakness, paralysis, mydriasis, tachycardia), and CNS (confusion, seizures, coma). OPs: pesticides (chlorpyrifos, dichlorvos, malathion, parathion), nerve agents (sarin, soman, tabun, VX, novichok). Diagnosis: CLINICAL (history of exposure + cholinergic toxidrome) — confirm with RBC AChE activity (reduced) and plasma butyrylcholinesterase (reduced). Management: (1) DECONTAMINATION (remove clothing, wash skin with soap and water — STAFF PPE is critical to prevent secondary contamination), (2) ATROPINE (muscarinic antagonist — titrate to ENDPOINT: dried secretions, HR 80, SBP 80 — NOT to pupil size — escalating boluses — most regimens double after a failed bolus — to the endpoint; intubated survivors required a mean of 23.4 mg, range 1-75 mg), (3) PRALIDOXIME (2-PAM — reactivates AChE — WHO regimen 30 mg/kg bolus then 8 mg/kg/hr infusion, evidence contested — MUST be given BEFORE 'aging' of the enzyme-OP complex — dimethyl pesticide ageing t½ around 3 h, diethyl around 33 h, soman 4.2 min), (4) BENZODIAZEPINES (diazepam first-line for seizures; midazolam has FDA approval for seizures and is expected to replace diazepam in autoinjector form), (5) SUPPORTIVE: intubation (non-depolarising NMB — NOT succinylcholine — which is hydrolysed by plasma cholinesterase → prolonged paralysis), ventilation, treat arrhythmia. Complications: intermediate syndrome (24-96h post-exposure — proximal muscle weakness + cranial nerve palsies + respiratory failure — from prolonged AChE inhibition), OPIDPN is a later distal polyneuropathy, not reversed by atropine or oxime — do not confuse with IMS. Case fatality generally more than 15% (rural hospitals 15–30%).

Checked against its sources on 3 Sept 2026