Near-Drowning - Environmental Emergencies

NEAR-DROWNING

Near-drowning is survival for at least 24 hours after submersion. The most common consequence is hypoxemia. Drowning is one of the leading causes of unintentional death in children younger than 14 years of age. An estimated 7000 drownings and 90,000 near-drownings occur yearly in the United States. There are ap-proximately 1000 deaths by drowning of children every year. Children younger than 4 years of age account for 40% of drown-ings (Suominen et al., 2002).

Factors associated with drowning and near-drowning include alcohol ingestion, inability to swim, diving injuries, hypothermia, and exhaustion. Efforts to save the victim should not be aban-doned prematurely. Successful resuscitation with full neurologic recovery has occurred in near-drowning victims after prolonged submersion in cold water. This is possible because of a decrease in metabolic demands or the diving reflex.

After resuscitation, hypoxia and acidosis, the primary problems of a victim who has nearly drowned, require immediate inter-vention in the ED. Resultant pathophysiologic changes and pul-monary injury depend on the type of fluid (fresh or salt water) and the volume aspirated. Fresh water aspiration results in a loss of surfactant, hence an inability to expand the lungs. Salt water aspiration leads to pulmonary edema from the osmotic effects of the salt within the lung. After a person survives submersion, acute respiratory distress syndrome resulting in hypoxia, hypercarbia, and respiratory or metabolic acidosis can occur.

Management

Therapeutic goals include maintaining cerebral perfusion and adequate oxygenation to prevent further damage to vital organs. Immediate cardiopulmonary resuscitation is the factor with the greatest influence on survival. The treatment goal, prevention of hypoxia, is accomplished by ensuring an adequate airway and res-piration, thus improving ventilation (which helps to correct res-piratory acidosis) and oxygenation. Arterial blood gas analyses are performed to evaluate oxygen, carbon dioxide, and bicarbonate levels and pH. These parameters determine the type of ventilatory support needed. Use of endotracheal intubation with positive-pressure ventilation (with PEEP) improves oxygenation, prevents aspiration, and corrects intrapulmonary shunting and ventilation– perfusion abnormalities (caused by aspiration of water). If the pa-tient is breathing spontaneously, supplemental oxygen may be administered by mask. However, an endotracheal tube is neces-sary if the patient does not breathe spontaneously.

Because of submersion, the patient is usually hypothermic. A rectal probe is used to determine the degree of hypothermia. Prescribed rewarming procedures (eg, extracorporeal warming, warmed peritoneal dialysis, inhalation of warm aerosolized oxy-gen, torso warming) are started during resuscitation. The choice is determined by the severity and duration of hypothermia and available resources. Intravascular volume expansion and inotropic agents are used to manage hypotension and impaired tissue per-fusion. ECG monitoring is initiated, because dysrhythmias fre-quently occur. An indwelling urinary catheter is inserted to measure urine output. Hypothermia and accompanying metabolic acidosis may compromise renal function. Nasogastric intubation is used to decompress the stomach and to prevent the patient from aspi-rating gastric contents.

In case the patient appears deceptively healthy, close moni-toring continues with serial vital signs, serial arterial blood gas values, ECG monitoring, intracranial pressure assessments, serum electrolyte levels, intake and output, and serial chest x-rays. After a near-drowning, the patient is at risk for complications, such as hypoxic or ischemic cerebral injury, acute respiratory distress syndrome, pulmonary damage secondary to aspiration, and life-threatening cardiac arrest.