A 6-year-old boy is brought to the mortuary after being recovered from a swimming pool. Autopsy findings include pulmonary edema, frothy fluid in the airways, and water in the stomach. Which of the following is the most common mechanism of death in this case of drowning?

Explanation

## Mechanism of Death in Drowning **Key Point:** Hypoxemia secondary to aspiration of water, pulmonary edema, and impaired gas exchange is the most common mechanism of death in drowning, accounting for >80% of cases. ### Pathophysiology of Drowning Death 1. **Water aspiration** → disrupts surfactant and alveolar lining 2. **Pulmonary edema** → fluid accumulation in alveoli (frothy fluid in airways is pathognomonic) 3. **Ventilation-perfusion mismatch** → severe hypoxemia 4. **Hypoxic cardiac arrest** → terminal event ### Comparison of Mechanisms in Drowning | Mechanism | Frequency | Notes | |-----------|-----------|-------| | **Hypoxemia (aspiration + pulmonary edema)** | **80–90%** | **Most common; explains frothy fluid at autopsy** | | Laryngospasm | 10–15% | "Dry drowning" — water does not enter lungs; rare | | Vagal inhibition (cold water) | <5% | Occurs in immersion in very cold water; cardiac syncope | | Hyponatremia/cerebral edema | Rare | Only in freshwater drowning with massive aspiration | **High-Yield:** The classic autopsy triad of drowning is: - Pulmonary edema with frothy fluid - Water in stomach and airways - Absence of other significant injuries **Clinical Pearl:** In saltwater drowning, hypernatremia and pulmonary edema are more pronounced due to osmotic fluid shift into alveoli. In freshwater drowning, hyponatremia can occur but is not the primary cause of death. ### Why Laryngospasm Is NOT the Most Common Cause **Warning:** "Dry drowning" (laryngospasm preventing water entry) occurs in only 10–15% of cases. Most drowning victims DO aspirate water, making hypoxemia the dominant mechanism.