Organophosphate (OP) Poisoning: Pediatric Management

Why Children Are More Vulnerable

• Smaller body mass means a given dose produces higher mg/kg exposure
• Lower baseline cholinesterase activity - less enzyme reserve means inhibition reaches toxic threshold faster
• Higher surface area-to-body-mass ratio increases transdermal absorption
• Developing nervous systems are more sensitive to neurotoxic effects, including the neurodevelopmental effects of chronic low-level exposure

Pathophysiology (Brief Recap)

• Muscarinic sites (exocrine glands, smooth muscle, heart)
• Nicotinic sites (skeletal muscle neuromuscular junction, autonomic ganglia)
• CNS sites

Clinical Presentation

• Muscle fasciculations, cramps, weakness
• Progression to paralysis and areflexia (can mask seizure activity)
• Respiratory muscle paralysis - the most common cause of death

• Anxiety, restlessness, seizures, coma

Four Recognized Clinical Syndromes

1. Acute cholinergic crisis - immediate onset, classic SLUDGE/nicotinic/CNS findings
2. Intermediate syndrome - 1-5 days post-exposure, seen in up to 40% after ingestion; neck flexor and proximal limb paralysis, cranial nerve involvement, respiratory failure (no cholinergic excess); resolves within ~7 days
3. Chronic toxicity - symmetrical sensorimotor axonopathy (mostly agricultural workers)
4. OP-induced delayed neuropathy - cognitive dysfunction, peripheral neuropathy, extrapyramidal signs - Tintinalli's Emergency Medicine, p. 1343

Management

Step 1: Decontamination

• Remove clothing (can reduce ongoing absorption by up to 80%)
• Wash skin and hair thoroughly with soap and water
• Eye irrigation for ocular exposure
• Healthcare staff must use PPE (gloves, gown) to avoid secondary contamination

Step 2: Airway & Respiratory Support

• This is the priority - death is from respiratory failure
• Early endotracheal intubation for respiratory muscle weakness, excessive secretions, or declining consciousness
• Succinylcholine should be avoided (or used cautiously) - OP inhibits pseudocholinesterase, prolonging neuromuscular blockade; use rocuronium instead if paralysis needed
• Suction bronchorrhea aggressively

Step 3: Atropine (Anti-muscarinic Antidote)

• Tachycardia and mydriasis are not endpoints to stop atropine - only secretion drying is
• Expect very large total doses (200-500 mg in adults; children proportionally large) - do not be alarmed
• Atropine does not reverse nicotinic effects (muscle paralysis, fasciculations)
• • Rosen's Emergency Medicine, p. 1492

Step 4: Pralidoxime / 2-PAM (Oxime - AChE Reactivator)

• Give as early as possible - before aging occurs
• If fat-soluble OPs are involved, patient may require prolonged infusion for weeks while awaiting new AChE synthesis
• Discontinue trial by withdrawing pralidoxime; if symptoms recur, continue therapy
• • Rosen's Emergency Medicine, p. 1492-1493; Tintinalli's Emergency Medicine, p. 1344

Step 5: Benzodiazepines for Seizures

• Seizures are treated with benzodiazepines (diazepam, lorazepam, or midazolam)
• Phenytoin is NOT recommended for OP-induced seizures (no evidence of benefit)
• Standard pediatric weight-based dosing applies

Step 6: GI Decontamination

• Activated charcoal (1 g/kg, max 50 g) may be considered for recent oral ingestion (<1 hour) if airway is protected
• Gastric lavage rarely indicated and poses aspiration risk
• DO NOT induce vomiting

Cholinesterase Levels (Lab)

• Plasma butyrylcholinesterase - more available but less specific; easier to run
• RBC acetylcholinesterase - more accurate marker of synaptic inhibition
• Important: Do NOT wait for results before starting treatment. Treatment is clinical. Baseline variability and lack of standardized normal ranges limit these assays.

Disposition

Special Pediatric Notes

• Carbamates (e.g., carbaryl) differ from OPs: they do NOT cause aging and spontaneously dissociate from AChE. Pralidoxime is generally not recommended for carbamate poisoning
• Diazinon and chlorpyrifos were removed from household use in the US in 2000 due to neurotoxicity on developing brains, but remain in use globally
• Consider child abuse or intentional poisoning if exposure history is inconsistent
• Always contact Poison Control (1-800-222-1222) early - they assist with specific product ingredient identification and management guidance

Quick Reference Summary Card

OP Poisoning in Peds:
1. Decontaminate (remove clothes, wash skin) + PPE for staff
2. Airway first - early intubation; avoid succinylcholine
3. ATROPINE: 0.05 mg/kg IV → double q5-10min → titrate to DRY secretions
4. PRALIDOXIME: 25-50 mg/kg IV over 30 min → infusion 10-20 mg/kg/h
5. BENZOS for seizures
6. PICU admission for moderate-severe cases

Sources: Tintinalli's Emergency Medicine, pp. 1342-1344; Rosen's Emergency Medicine, pp. 1492-1494