Drowning may result in an acute asphyxial cardiac arrest, which emanates from hypoxemia that precedes the development of ischemia. This scenario results from initial cessation of gas exchange followed by worsening hypoxia and eventual cardiac arrest. Myocardial dysfunction may result from ventricular dysrhythmias, pulseless electrical activity, and asystole due to hypoxemia, hypothermia, acidosis, or less commonly, electrolyte abnormalities. Pulmonary hypertension may result from the release of pulmonary inflammatory mediators, increasing right ventricular afterload and thus decreasing pulmonary perfusion and left ventricular preload. However, although cardiovascular effects may be severe, they are usually transient, unlike severe CNS injury.
Pneumonia is a rare consequence of submersion injury and is more common with submersion in stagnant warm and fresh water. Uncommon pathogens, including Aeromonas, Burkholderia, and Pseudallescheria, cause a disproportionate percentage of cases of pneumonia. Pneumonia is uncommon early in the course of treatment of submersion injuries, so the use of prophylactic antimicrobial therapy has not proven to be of any benefit.
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.
Primary CNS injury is initially associated with tissue hypoxia and ischemia. If the period of hypoxia and ischemia is brief or if the person is a very young child who rapidly develops core hypothermia, primary injury may be limited, and the patient may recover with minimal neurologic sequelae, even after more prolonged immersion. In contrast, drowning that is associated with prolonged hypoxia or ischemia is likely to lead to both significant primary injury and secondary injury, especially in older patients who cannot rapidly achieve core hypothermia.
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Cite this: Richard H. Sinert. Fast Five Quiz: Drowning - Medscape - Jun 25, 2020.