Chapter 215: Drowning

INTRODUCTION AND EPIDEMIOLOGY

Drowning is submersion in a liquid medium resulting in respiratory difficulty or arrest.¹ As with other causes of accidental death, drowning injury typically involves otherwise healthy, young individuals, but can involve individuals of any age or background.

Worldwide, drowning accounts for >500,000 deaths annually and is the leading cause of injury death among children <15 years of age. In the United States, there are >500,000 drowning events each year and 1100 deaths, which makes drowning the second leading cause of unintentional death of individuals from birth to age 19 years old.^2,3 However, the rate of drowning deaths has decreased over the past 40 years. In 1970, there were nearly 8000 deaths due to drowning in the United States,⁴ and education with public awareness has been the major contributor to the decreased incidence. The vast majority of victims survive submersion events, with effects ranging from minimal or transient injury to profound neurologic insult.

Drowning incidence peaks in three age groups: The highest is in children <5 years old, the second peak is in those aged 15 to 24 years, and the third peak is in the elderly. Toddlers drown primarily after falling into swimming pools or open water, but they also drown in bathtubs and buckets in the home. Physicians also need to evaluate for intentional drowning (child abuse) or factitious disorder by proxy (formerly Munchausen's by proxy). In teenagers and adults, suicide, homicide, and domestic violence can be causes of drowning. The elderly also have an increased risk of bathtub drowning, often related to comorbid medical conditions or medications. Even in coastal areas, most drownings take place in warm, freshwater bodies of water (especially swimming pools).

Additional injuries or disorders that either precipitate or are associated with drowning events are shown in Table 215-1.

PATHOPHYSIOLOGY

After submersion, the degree of hypoxic insult to the central nervous system determines the ultimate outcome. It was previously thought that parasympathetic activation of the diving reflex (i.e., bradycardia, apnea, peripheral vasoconstriction, and central shunting of blood flow) provided transient protection during submersion. The diving reflex is strongest in infants <6 months of age, but the effects decrease with age.⁵ In adults, vertical immersion (head out) and vertical submersion (head under) activate both the sympathetic and parasympathetic systems, which blunts any effect of the diving reflex.⁶ Furthermore, physiologic stress associated with submersion also activates the sympathetic nervous system. Thus, the diving reflex is not protective. Cerebral protection in cold water submersions most likely results from rapid central nervous system cooling before significant hypoxic damage occurs.

Physiologic scoring systems^7,8 to predict drowning outcome have been devised but are not clinically helpful. The vast majority of patients who arrive at the hospital with sTable cardiovascular signs and awake, alert neurologic function survive with minimal disability, whereas those who arrive with unsTable cardiovascular function and coma do poorly because of the hypoxic-ischemic insult. Predictors are not accurate for the 15% to 20% of drowning victims whose condition on arrival is ...