What is drowning?

Causes and Symptoms

Drowning is one of the leading causes of accidental death. The victim dies by suffocation from submersion in a liquid medium. Although suffocation most commonly results from the aspiration of fresh or salt water into the lungs, about 10 percent to 20 percent of victims experience a laryngospasm with subsequent glottic closure, followed by asphyxiation. Near-drowning is defined as recovery after submersion. Victims are typically children or adolescents. Males more often engage in risk-taking behavior and have a significantly greater incidence of drowning and near-drowning than do females.

Victims of near-drowning, if rescued and resuscitated quickly enough, may fully recover. In many instances, however, near-drowning victims are left with mild to severe neurologic effects. Even if the victim has been submerged in water for some time, vigorous attempts at resuscitation are indicated because of documented recovery following such incidents.

Boating and swimming accidents account for the largest number of drownings in the adult population, and many are alcohol-related. Factors that influence the extent of damage in near-drowning include the length of time submerged, the temperature of the water, and the victim’s resistance to asphyxia and anoxia (oxygen deprivation). Recovery may be more successful if the victim drowns in cold water, because the induced hypothermia lowers the body’s metabolic demands and, therefore, oxygen needs. Extremely cold water may decrease the victim’s core body temperature so rapidly that death from hypothermia may actually occur before drowning.

Generally, there is an inverse relation between the victim’s age and the victim’s resistance to asphyxia and anoxia. The younger the victim, the greater the resistance. The resistance is especially strong in very young victims, usually under two or three years of age, because of the diving reflex triggered in young children when the face is immersed in very cold water. Blood is shunted to the vital organs, especially the brain and heart. Hypothermia offers some protection to the hypoxic brain by reducing the cerebral metabolic rate. Although the victim suffers severe bradycardia, the remaining oxygen supply is concentrated in the heart and brain. The diving reflex is generally not a factor in adult drownings.

Approximately 10 percent of drowning victims develop laryngospasm concurrently with the first gulp of water and thus do not aspirate (swallow) fluid. Even in the majority of victims who do aspirate, the amount of fluid aspirated is small. In the past, salt water and freshwater drowning were differentiated. These differences are of little clinical significance in humans, primarily because so little fluid is aspirated. In both cases, drowning quickly diminishes perfusion to the alveoli, interfering with ventilation and soon leading to hypoxemia, ineffective circulation, cardiac arrest, brain injury, and brain death.

When water is aspirated into the lungs, the composition of the water is a key factor in the pathophysiology of the near-drowning event. Aspiration of freshwater causes surfactant to wash out of the lungs. Surfactant reduces surface tension within the alveoli, increases lung compliance and alveolar radius, and decreases the work of breathing. Loss of surfactant from freshwater aspiration destabilizes the alveoli and leads to increased airway resistance. Conversely, salt water—a hypertonic fluid—creates an osmotic gradient that draws protein-rich fluid from the vascular space into the alveoli. The consequences of both types of aspiration include impaired alveolar ventilation and resultant intrapulmonary shunting, which further compound the hypoxic state.

When submersion is brief, the near-drowning victim may spontaneously regain consciousness or may recover quickly following rescue. Even when victims have not aspirated fluid, they should be hospitalized for observation because respiratory symptoms may not develop for twelve to twenty-four hours. Victims who have been submerged for longer periods may show varying degrees of recovery following resuscitation. Manifestations may include acute respiratory failure, pulmonary edema, shock acidosis, electrolyte imbalance, stupor, coma, and cardiac arrest. Damage causes cerebral edema (brain swelling) and may lead to increased intracranial pressure. Care for the patient who has suffered brain damage involves careful and frequent assessment of the patient’s neurologic status, including vital signs, pupil reaction, and reflexes.

Treatment and Therapy

Immediate care should focus on a safe rescue of the victim. Once rescuers gain access to the victim, priorities include safe removal from the water, while maintaining spine stabilization with a board or flotation device, and initiating airway clearance and ventilatory support measures. If hypothermia is a concern, then gentle handling of the victim is essential to prevent ventricular fibrillation. Abdominal thrusts should only be delivered if airway obstruction is suspected. Once the victim is safely removed from the water, airway and cardiopulmonary support interventions begin. Emergency care involves cardiopulmonary resuscitation (CPR), intubation, and mechanical ventilation with 100 percent oxygen.

In the clinical setting, stomach decompression using a tube down the nose or mouth is indicated to prevent the aspiration of gastric contents and to improve breathing.

Patients who experience near-drowning require complex care to support their body systems. The full spectrum of critical care
technology may be needed to manage the physiological problems and effects associated with near-drowning, including lung infection, acute respiratory distress syndrome, and central nervous system impairment. Metabolic acidosis results from severe hypoxia. Arterial blood gases must be monitored frequently, and sodium bicarbonate is usually administered to correct the acidosis. Coma may be induced with barbiturates and a state of hypothermia maintained for several days following the near-drowning. These interventions reduce the metabolic and oxygen demands of the brain. Diuretics are prescribed to treat pulmonary and cerebral edema. Fluid therapy must be monitored carefully to prevent fluid overload and to promote adequate renal function.

Perspective and Prospects

Drowning is the third leading cause of preventable death worldwide, according to the World Health Organization. The Centers for Disease Control and Prevention states that drowning is the leading cause of preventable death in children ages one to four. Drowning prevention recommendations warn parents to be certain that everyone caring for a child understands the need for constant supervision around water and other liquids.

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