Initially, submersion or immersion results in aspiration of small amounts of fluid into the larynx, triggering breath holding or laryngospasm. In many cases, the laryngospasm resolves, and larger volumes of water or gastric contents are aspirated into the lungs, destroying surfactant and causing alveolitis and dysfunction of the alveolar-capillary gas exchange. The resulting hypoxemia leads to hypoxic brain injury that is exacerbated by ischemic injury after circulatory collapse.
Drowning deaths overall have decreased over the past decade; however, drowning is still a significant cause of morbidity and mortality. In 2010, drowning was the leading cause of injury death for children 1 to 4 years of age and the second leading cause of injury death for children 1 to 18 years of age. Boys are four times more likely than girls to drown. The most common location of drowning varies by age, with drowning in natural bodies of water becoming more frequent in older age groups.
Hypoxemia is the result of laryngospasm and aspiration during drowning. Victims may also develop respiratory distress secondary to pulmonary endothelial injury, increased capillary permeability, and destruction of surfactant. Clinical manifestations include tachypnea, tachycardia, increased work of breathing, and decreased breath sounds with or without crackles. The hypoxic-ischemic injury that may occur can lead to depressed myocardial function resulting in tachycardia, impaired perfusion, and potentially cardiovascular collapse. After resuscitation, acute respiratory distress syndrome is common. Altered mental status may be present and requires frequent monitoring of neurologic status. Following submersion in cold water, hypothermia may result in relative bradycardia and hypotension and place the child at risk for cardiac dysrhythmias.
After resuscitation, arterial blood gas measurement assists in assessing pulmonary gas exchange. A chemistry profile may reveal elevated liver enzymes if hypoxemia and ischemia were of long duration and provide baseline renal functions. Electrolytes are often obtained, although alterations of serum electrolytes are minimal, even in freshwater drowning.
Resuscitation of a drowning victim includes the basic ABCs (see Chapter 38). Victims of unwitnessed drowning require stabilization of the cervical spine because of the possibility of a fall or diving injury. Optimizing oxygenation and maintaining cerebral perfusion are two of the major foci of treatment. Rewarming the hypothermic patient requires careful attention to detail, including acid-base and cardiac status. Further treatment is based on the patient response to initial resuscitation. Some children begin breathing spontaneously and awaken before arrival at an emergency department. If the episode was significant, these children still require careful observation for pulmonary complications over the subsequent 6 to 12 hours. Children who have evidence of lung injury, cardiovascular compromise, or neurologic compromise should be monitored in an intensive care unit. Pulmonary dysfunction often results in hypoxemia. Oxygen supplementation should be implemented to maintain normal oxygen saturations. Mechanical ventilation may be needed in patients with significant pulmonary or neurologic dysfunction. Cardiovascular compromise is often the result of impaired contractility because of hypoxic-ischemic injury. The use of intracranial pressure monitoring devices and medical management with hypothermia and sedation is controversial and has not been shown to improve outcomes. Prophylactic antibiotics have not been shown to be beneficial and may increase the selection of resistant organisms.
The outcome of drowning is determined by the successof immediate resuscitation efforts and the severity of thehypoxic-ischemic injury to the brain. Patients who have regained consciousness on arrival to the hospital will likelysurvive with intact neurologic function. Unfavorable prognostic markers include the need for CPR for more than 25 minutes, continued CPR at the hospital, Glasgow Coma Scaleof 5 or less, fixed and dilated pupils, seizures, and coma formore than 72 hours.