26. Drowning

2002 WHO definition: “Drowning is the process of experiencing respiratory impairment from submersion/immersion in liquid”

Fatal drowning: If the victim dies at any time as a result of drowning.

Nonfatal drowning: If the victim is rescued at any time, the process of drowning is interrupted.

Any submersion or immersion incident without evidence of respiratory impairment should be considered a water rescue and not a drowning.

Terms such as “near drowning,” “dry or wet drowning,” “secondary drowning,” “active and passive drowning,” and “delayed onset of respiratory distress” are ambiguous and should be avoided.

Epidemiology

0.7% of all deaths worldwide (> 500,000 deaths each year) are due to unintentional drowning.

This number likely underestimates the real figures.

Leading cause of death worldwide among boys 5 to 14 years of age.

Second leading cause of injury-related death in the United States

In many developing countries, the incidence of drowning is 10 to 20 times higher than in the United States.

Estimated that > 85% of cases of drowning can be prevented by supervision, swimming instruction, technology, regulation, and public education

Risk Factors

Male, age < 14 years, alcohol use, low income, poor education, rural residency, aquatic exposure, risky behavior, and lack of supervision

For people with epilepsy, the risk is 15 to 19 times as high

For every person who dies from drowning, four persons receive care in the emergency department for nonfatal drowning

Key Pathophysiology

Drowning sequence

Begins when the victim’s airway lies below the surface of a liquid (usually water), at which time the victim voluntarily holds his or her breath

Breath holding is usually followed by an involuntary period of laryngospasm secondary to the presence of liquid in the oropharynx or larynx.

During the period of breath holding and laryngospasm, the victim is unable to participate in gas exchange.

The victim then becomes hypercarbic, hypoxemic, and acidotic.

This quickly leads to loss of consciousness and apnea.

Laryngospasm abates, and the victim actively breathes liquid, with the amount inhaled varying considerably from victim to victim.

The sequence of cardiac rhythm deterioration is usually tachycardia followed by bradycardia, pulseless electrical activity, and, finally, asystole.

Changes occur in the lungs, body fluids, blood-gas tensions, acid-base balance, and electrolyte concentrations, which are dependent on the composition and volume of the liquid aspirated and duration of submersion.

Water in the alveoli causes surfactant dysfunction and washout.

Aspiration of salt water and aspiration of fresh water cause similar degrees of injury, although with differences in osmotic gradients.

The osmotic gradient disrupts the integrity of alveolar–capillary membrane, which increases its permeability, and exacerbates fluid, plasma, and electrolyte shifts.

The clinical picture of the damage caused to the alveolar–capillary membrane is massive, often bloodstained, pulmonary edema, decreased lung compliance, increased V/Q mismatch, atelectasis, and bronchospasm.