A 2-year-old presents with altered consciousness, coma score 8, and is found to have salicylate poisoning after ingesting aspirin tablets. Blood gas shows pH 7.55, pCO2 22 mmHg, HCO3 18 mEq/L. Urine pH is 5. Which intervention is MOST critical for enhancing salicylate elimination?
- A Activated charcoal repeated every 4 hours
- B IV sodium bicarbonate to alkalinize urine to pH 7.5–8 ✓
- C Forced acid diuresis with ammonium chloride
- D Vitamin C infusion to acidify urine
Explanation
Urinary alkalinization with intravenous sodium bicarbonate (targeting urine pH 7.5–8) dramatically enhances salicylate renal elimination by ion-trapping: salicylate (a weak acid, pKa ~3) becomes ionized in alkaline urine and cannot diffuse back across tubular membranes, promoting excretion. The paradoxical alkaline blood pH here reflects primary respiratory alkalosis (direct salicylate stimulation of respiratory center) with metabolic compensation. Acid diuresis (option C/D) would increase salicylate reabsorption and is contraindicated. Activated charcoal helps if given early but is not the most critical intervention for elimination.
Reference: Ghai Essential Pediatrics, 10th ed.
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