A 32-year-old farmer from Punjab presents to the emergency department 45 minutes after accidental exposure to an organophosphate pesticide (malathion) while spraying crops. He is diaphoretic, tremulous, and complains of blurred vision and chest tightness. Vital signs: HR 52/min, BP 110/70 mmHg, RR 24/min. Examination reveals pinpoint pupils, bronchospasm with audible crackles, and visible fasciculations in the limbs. Serum cholinesterase activity is 25% of normal. What is the immediate next step in management?

Explanation

## Immediate Management of Organophosphate Poisoning **Key Point:** Atropine is the cornerstone of acute organophosphate poisoning management and must be given immediately to counteract muscarinic toxicity (bronchospasm, bradycardia, miosis, salivation). ### Pathophysiology Organophosphates irreversibly inhibit acetylcholinesterase, causing accumulation of acetylcholine at muscarinic and nicotinic receptors. The clinical picture reflects both: - **Muscarinic effects** (miosis, bronchospasm, bradycardia, salivation, lacrimation, urination, defecation, GI motility, emesis — mnemonic: **SLUDGE**) - **Nicotinic effects** (fasciculations, paralysis, tachycardia in severe cases) ### Why Atropine First? | Feature | Atropine | Pralidoxime (2-PAM) | |---------|----------|--------------------| | **Onset** | Immediate (IV) | 15–30 min | | **Target** | Muscarinic receptors (blocks ACh) | Reactivates AChE (nicotinic + muscarinic) | | **Efficacy window** | Any time | **Best within 24–48 hrs** (before "aging") | | **Life-saving in acute phase** | Yes — reverses bronchospasm, bradycardia | Adjunct only | | **Dose escalation** | Yes, titrate to drying of secretions | Fixed dose | **Clinical Pearl:** The patient has **severe muscarinic toxicity** (pinpoint pupils, bronchospasm, bradycardia, fasciculations). Atropine must be given immediately to prevent respiratory failure. Pralidoxime is added after atropine is initiated, not instead of it. ### Atropine Titration Protocol 1. Initial dose: 2–5 mg IV bolus 2. Repeat every 5–10 minutes until: - Pupils dilate - Bronchospasm resolves - Heart rate increases (target >60/min) - Dry mouth achieved (sign of atropinization) 3. Then switch to continuous infusion (0.5–1 mg/hr) or repeat boluses as needed **High-Yield:** Atropine does NOT reverse nicotinic effects (fasciculations, paralysis) — that is the role of pralidoxime. However, atropine is given FIRST because muscarinic toxicity is immediately life-threatening. ### Adjunctive Measures - **Pralidoxime (2-PAM):** 1 g IV over 15–30 min, then 0.5 g/hr infusion. Reactivates AChE at nicotinic sites and some muscarinic sites. Most effective if given early (within 24–48 hrs before "aging"). - **Benzodiazepines:** Reserved for seizures or agitation, not first-line. - **Decontamination:** Remove clothes, wash skin; gastric lavage/charcoal if ingested (but not if already vomiting). [cite:Harrison 21e Ch 473]