Which of the following is the primary mechanism of death in freshwater drowning?

Explanation

## Pathophysiology of Freshwater Drowning **Key Point:** In freshwater drowning, the primary mechanism of death is hypoosmolality and cerebral edema resulting from absorption of hypotonic fluid across the damaged alveolar-capillary membrane into the bloodstream. ### Mechanism 1. **Aspiration of hypotonic freshwater** → dilutes plasma osmolality 2. **Water moves into cells** (including brain cells) due to osmotic gradient 3. **Cerebral edema develops** → increased intracranial pressure 4. **Pulmonary edema** → impaired gas exchange 5. **Death occurs** from hypoxia, hypercarbia, and increased ICP ### Electrolyte Changes in Freshwater vs Saltwater | Parameter | Freshwater Drowning | Saltwater Drowning | |-----------|-------------------|-------------------| | **Plasma osmolality** | Decreases (hypoosmolal) | Increases (hyperosmolal) | | **Primary pathology** | Cerebral edema, pulmonary edema | Pulmonary edema, hemoconcentration | | **Serum Na⁺** | Decreases | Increases | | **RBC hemolysis** | Occurs (hypotonic environment) | Minimal | | **Fluid movement** | Into cells | Out of cells | **High-Yield:** Cerebral edema is the hallmark of freshwater drowning and explains why freshwater drowning victims may appear "drowned but not dead" initially, with delayed deterioration from brain swelling. **Clinical Pearl:** Hyperkalemia from hemolysis is a secondary phenomenon in freshwater drowning, not the primary cause of death. It becomes significant only in severe cases with massive hemolysis. [cite:Reddy Forensic Medicine Ch 8]