What is the target organ of submersion injury in drowning?

Updated: Jun 19, 2019
  • Author: G Patricia Cantwell, MD, FCCM; Chief Editor: Joe Alcock, MD, MS  more...
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Answer

The target organ of submersion injury is the lung. Aspiration of as little as 1-3 mL/kg of fluid leads to significantly impaired gas exchange. Injury to other systems is largely secondary to hypoxia and ischemic acidosis. Additional CNS insult may result from concomitant head or spinal cord injury. The period of hypoxia/hypoxemia is initially limited to the duration of hypopnea or apnea and may resolve with initial rescue efforts. 

Patients with prolonged hypoxic episodes are prone to alveolar fluid aspiration resulting in vagally mediated pulmonary vasoconstriction, hypertension, and fluid-induced bronchospasm. Freshwater moves rapidly across the alveolar-capillary membrane into the microcirculation. Freshwater is considerably hypotonic relative to plasma and causes disruption of alveolar surfactant. Destruction of surfactant produces alveolar instability, atelectasis, and decreased compliance, with marked ventilation/perfusion (V/Q) mismatching. As much as 75% of blood flow may circulate through hypoventilated lungs.

Saltwater, which is hyperosmolar, increases the osmotic gradient and therefore draws fluid into the alveoli, diluting surfactant (surfactant washout). Protein-rich fluid then exudes rapidly into the alveoli and pulmonary interstitium. Compliance is reduced, the alveolar-capillary basement membrane is damaged directly, and shunting occurs. This results in rapid development of serious hypoxia.

The distinction between submersion fluid type is primarily academic and mostly connotes epidemiologic significance. Hypoxia serves as the primary insult and, with alveolar aspiration, culminates in surfactant disruption, alveolar collapse and derecruitment, intrapulmonary shunting, increased pulmonary vascular resistance, and ventilation-mismatch. These processes result in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS).


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