Toxicology in the ICU — CritCare.in

General Approach to Poisoning

ABCDE resuscitation first — stabilise before diagnosis. Key principles:

Airway: Intubate early if GCS ≤8, impending respiratory failure, or risk of aspiration
Identify the toxin: History, toxidrome, serum/urine levels, call Poison Control (India: 1800-11-6117)
Decontamination: Activated charcoal 1g/kg PO within 1h of ingestion if airway protected and no contraindication
Enhanced elimination: Multiple-dose activated charcoal, urinary alkalinisation, dialysis (see dialysable toxins)
Specific antidote if available (see table below)

Extremely common in India (pesticide ingestion). Inhibits acetylcholinesterase → acetylcholine accumulation → muscarinic + nicotinic + CNS effects.

Salivation, Lacrimation, Urination, Defaecation, GI cramps, Emesis — plus bronchospasm, bradycardia, miosis.

Atropine: 2–4mg IV bolus every 5–10 min until secretions dry. No ceiling — may need 20–100mg total. Target: dry secretions, HR >80, clear chest. Do NOT target pupil size.
Pralidoxime (2-PAM): 1–2g IV over 15–30 min, then 0.5g/hr infusion. Give within 24–48h of exposure (before ageing). Efficacy contested but give early if available.
Intubation: Early RSI if respiratory failure; avoid succinylcholine (prolonged paralysis due to pseudocholinesterase inhibition — use rocuronium)
Benzodiazepines for seizures; no phenytoin
Intermediate syndrome: day 2–4 weakness (neck flexors, proximal limb, cranial nerves) — watch for late respiratory failure

Toxic dose: >150 mg/kg or >7.5g in adults. NAPQI (toxic metabolite) depletes glutathione → hepatocellular necrosis.

Plot serum paracetamol level vs time after ingestion. Treat if level above "possible hepatotoxicity" line (150 mcg/ml at 4h).

IV NAC: 150 mg/kg in 200ml D5W over 1h → 50 mg/kg over 4h → 100 mg/kg over 16h
Start within 8h for maximum benefit; still give up to 24h (or beyond if encephalopathy)
Oral NAC: 140 mg/kg loading, then 70 mg/kg q4h × 17 doses (if IV unavailable)

Refer for transplant if: pH < 7.30 after resuscitation; OR all of: PT >100s + creatinine >300 + Grade III–IV encephalopathy.

Toxin	Antidote	Dose
Paracetamol	N-Acetylcysteine	150mg/kg/h then 50 then 100 (IV)
Organophosphate	Atropine + Pralidoxime	Atropine: 2–4mg q5-10min until dry; 2-PAM 1–2g then infusion
Opioid	Naloxone	0.4–2mg IV/IM/IN q2–3min; infusion for long-acting opioids
Benzodiazepine	Flumazenil	0.2mg IV over 15s, repeat to max 1mg; caution in benzo-dependent/seizure risk
Beta-blocker OD	Glucagon + High-dose insulin	Glucagon 5–10mg IV; Insulin 1 U/kg/hr + D50W (HIET therapy)
Digoxin	Digoxin-specific antibody fragments (Fab)	Based on ingested dose or serum level — refer package insert
Methanol / Ethylene glycol	Fomepizole or Ethanol + Dialysis	Fomepizole 15mg/kg IV loading; haemodialysis for severe toxicity
Cyanide	Hydroxocobalamin	5g IV over 15 min (or sodium thiosulphate 12.5g IV)
Iron overdose	Deferoxamine	15mg/kg/hr IV (max 80mg/kg/day)
CO poisoning	100% O2 / HBO	100% O2 by non-rebreather mask × 4–6h; consider HBO if severe