Pathophysiology
Clinical meaning
Drowning is defined as the process of experiencing respiratory impairment from submersion or immersion in liquid. The pathophysiology centers on two primary organ injuries: pulmonary damage and hypoxic-ischemic brain injury. Pulmonary pathophysiology: When water is aspirated (even as little as 1-3 mL/kg), it disrupts the surfactant layer lining the alveoli. Surfactant normally reduces alveolar surface tension, preventing alveolar collapse at end-expiration. Loss of surfactant leads to alveolar collapse (atelectasis), decreased lung compliance, ventilation-perfusion (V/Q) mismatch, and intrapulmonary shunting โ all producing profound hypoxemia. BOTH freshwater and saltwater aspiration produce similar clinical outcomes (the historical distinction between freshwater causing dilutional hyponatremia and saltwater causing hemoconcentration is clinically insignificant at the volumes typically aspirated). Aspirated water also triggers an intense inflammatory response in the alveolar epithelium, with neutrophil infiltration and capillary leak leading to non-cardiogenic pulmonary edema (ARDS). This can develop within hours of the submersion event and may progress over 24-72 hours โ hence the need for observation even in initially asymptomatic patients who aspirated water. Neurological pathophysiology: The brain is the organ most vulnerable to hypoxic injury. After 4-6 minutes...