Chapter 215: Drowning

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.

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 between these two extremes.⁹

End organs can also be affected by hypoxemia and metabolic acidosis. Aspiration of substances such as contaminated foreign material, particulate matter, bacteria, vomitus, or chemical irritants can affect eventual pulmonary recovery. Electrolyte abnormalities are seldom significant and are usually transient unless there is significant hypoxia, central nervous system depression, renal injury from hemoglobinuria, or myoglobinuria.^8,9 Hematologic values are usually normal unless there has been massive hemolysis. Disseminated intravascular coagulation can be a complicating factor in drowning outcome but usually occurs following severe hypoxic insult.

PREHOSPITAL CARE

Rapid resuscitation of a drowning victim (quickly restoring ventilation and oxygenation) optimizes outcome. After safe removal of the victim from the water, CPR should be initiated as quickly as possible. Trauma as a cause of drowning is uncommon, and most injured drowning patients have a history of trauma or signs of injury on examination.¹⁰ Cervical spine injury is rare (0.5%) in drowning unless there is a history of diving, falling from a significant height, or motorized vehicle crash.¹¹ Use cervical spine precautions if the history warrants it.

Administer high-flow oxygen by facemask if the patient is breathing or by positive-pressure bag-valve mask ventilation if the patient is not breathing. For patients who do not recover spontaneous respiratory effort, endotracheal intubation and positive-pressure ventilation are necessary.

All patients with drowning amnesia for the event, loss of or depressed consciousness, or an observed period of apnea, as well as those who require a period of artificial ventilation, should be transported to an ED for evaluation, even if they are asymptomatic at the scene. The patient should be warmed and monitored, and IV access should be established (Figure 215-1).

ED MANAGEMENT

Upon the patient's arrival at the ED, assess and secure the airway, provide oxygen, determine core temperature, and assist ventilation as necessary. If the patient is hypothermic, administer warmed isotonic IV fluids and apply warming adjuncts (e.g., blankets, overhead warmers, warming devices). Address any associated injuries. Because cervical injury is rare without a history of diving or associated trauma, routine cervical immobilization and CT of the brain are not necessary.¹¹

Patients who present to the ED with a Glasgow Coma Scale score of >13 and an oxygen saturation of ≥95% are at low risk for complications (Figure 215-1) and should be observed for 4 to 6 hours. If the pulmonary examination does not reveal rales, rhonchi, wheezing, or retractions and arterial oxygen saturation on room air remains ≥95%, the patient can be safely discharged home. Laboratory studies and radiographs are unnecessary and are not predictive of discharge.¹² The patient should be told to return if fever, mental status changes, or pulmonary symptoms occur. If, after 4 to 6 hours, the patient develops an oxygen requirement, the findings on pulmonary examination are abnormal (rales, rhonchi, wheeze, retractions, etc.), or the patient's condition deteriorates, reassessment and admission or transfer to a monitored bed are needed.

Patients who present to the ED with a Glasgow Coma Scale score of <13 should be maintained on supplemental oxygen and ventilatory support as needed. If high-flow oxygen (fraction of inspired oxygen of 40% to 60%) cannot maintain an adequate partial pressure of arterial oxygen (>60 mm Hg in adults, >80 mm Hg in children), then intubate the patient and provide positive-pressure ventilation. Chest radiography and laboratory studies should be done to evaluate for pulmonary aspiration and other complications (Figure 215-1). Although aspiration is common, prophylactic antibiotics have not been shown to improve outcome and may be associated with resistant infections.¹³ Continuous cardiac monitoring, pulse oximetry, temperature monitoring, and frequent reassessments should be performed for all patients. Hypothermia is a concern in patients who have been submerged in cold water (see chapter 209, Hypothermia).

If the patient is normothermic upon arrival in the ED and in cardiopulmonary arrest or asystole, serious thought should be given to discontinuing resuscitation efforts because recovery without profound neurologic complications is rare.^14,15

CONTINUED MANAGEMENT

Hospital management of drowning victims is largely supportive.¹⁶ All drowning victims who require ED resuscitation should be admitted to an intensive care unit for continuous cardiopulmonary and frequent neurologic monitoring. Most victims of significant submersion injury benefit from mechanical ventilation. Supernormal levels of positive end-expiratory pressure may be used to recruit fluid-filled lung units and aid oxygenation. Most patients demonstrate rapid improvement in oxygenation in the first 24 hours. Patients presenting with a significant aspiration pattern or cardiovascular collapse are predisposed to develop acute respiratory distress syndrome. Although prophylactic antibiotics lack supporting evidence, delayed pulmonary infection, particularly among patients requiring mechanical ventilation, is a risk, and unusual organisms, including Aeromonas species, should be considered if treatment is initiated. Care should be taken to avoid lung overdistention and ventilator-associated barotrauma.

For patients who have been resuscitated from cardiac arrest, the hemodynamic response to exogenously administered epinephrine is frequently short-lived, and most require a continuous infusion of dopamine or epinephrine in the ED or intensive care unit. Invasive (pulmonary artery catheter) or noninvasive (echocardiogram) measurement of ventricular function is often instructive. Hemodynamic recovery, when it occurs, can be expected within 48 hours. Patients demonstrating no hemodynamic recovery after 48 hours may slowly improve over the first week but are more likely to have long-term neurologic damage.¹⁷

Results of "brain resuscitation" after significant warm water drowning have been disappointing.^9,16 The degree of cerebral edema is largely determined by the duration of the anoxic or ischemic insult at the time of submersion. Efforts to control cerebral edema, including the use of mannitol, loop diuretics, hypertonic saline, fluid restriction, and mechanical hyperventilation, have not shown benefit.¹⁶ Controlled hypothermia, barbiturate "coma," and intracranial pressure monitoring do not improve outcome in pediatric drowning victims.⁹ Although rare, complete or near-complete neurologic recovery after asystole has been reported in both children and adults after icy water submersion episodes.

Family members should be counseled about likely outcome. Based on initial presentation, resuscitation, laboratory data, and serial examinations, experienced practitioners should be able to provide accurate predictions of outcomes in most cases.¹⁷ There are no standardized terms for describing drowning incidents.¹ This chapter uses the terms asymptomatic and symptomatic drowning.

ASYMPTOMATIC DROWNING

Drowning victims who are asymptomatic or mildly symptomatic can be observed for 4 to 6 hours. If the findings of pulmonary examination and oxygen saturation on room air remain normal, patients can be discharged home. If deterioration is going to occur, it will do so within the 4- to 6-hour observation period.^12,18,19 No data are available regarding long-term outcomes, but it is unlikely that there are any measurable adverse effects. Patients and/or parents should be advised to seek medical care for any respiratory complaints or fever.

SYMPTOMATIC DROWNING

Because submersion duration is frequently unknown or only estimated, the extent of required resuscitation is often the most objective measure of the degree of anoxic or ischemic insult (Table 215-2). Details of initial presentation and resuscitation are frequently strong prognostic indicators.

For patients who require hospital admission, if the submersion victim does not require cardiopulmonary resuscitation at the scene or in the ED, complete recovery within 48 hours is expected. A small fraction of patients with significant aspiration may develop severe, even life-threatening acute respiratory distress syndrome.

Victims requiring bystander CPR at the scene have a guarded prognosis. Of scene-resuscitated pediatric victims, about 20% later die in the hospital, and about 5% are left with severe hypoxic-ischemic encephalopathy.^15,20 Those victims who demonstrate continuous neurologic and cardiovascular improvement after hospital admission generally make a good recovery. Frequently, neurologic and cardiovascular examinations are normal within 24 hours of the drowning event. Victims who later die in the hospital usually demonstrate deteriorating cardiovascular and neurologic status.

Victims undergoing CPR in the ED have a poor prognosis. Prolonged (>30 minutes) CPR in drowning victims indicates significant anoxic or ischemic insult to the heart, brain, and other vital organs. Complete neurologic recovery is rare, with only anecdotal reports of neurologic recovery after ED CPR of pediatric drowning victims. Asystole, whether noted at the scene or in the ED, is a near-universal sign of poor prognosis in both adult and pediatric drowning injury.^16,21

For the emergency physician, the answers to the questions of whom and how vigorously to resuscitate remain challenging.^16,20 Complete or near-complete neurologic recovery after asystole has been reported in both children and adults after drowning in icy water, although such occurrences are rare and documented mostly in case reports or small series. A large series of 1377 open-water drowning victims found no intact survivors among the group submerged for more than 15 minutes, whether in warm or cold water, and there were no survivors of submersion greater than 60 minutes.²² There was also no difference in survival for children compared with adults in several studies, which contradicts the common belief that pediatric patients do better than adults.^7,21 For asystolic victims of drowning with short submersion durations (i.e., a few minutes) and short transport times who receive CPR en route, a vigorous resuscitation attempt is reasonable.²³ CPR should be abandoned if no response is noted. Conversely, because of the poor prognosis for intact neurologic survival, ED resuscitation attempts can reasonably be withheld from asystolic victims of drowning with longer submersion and transport times.^15,20

Submersion episodes in children <1 year of age are best prevented by parental vigilance during bathing. Child abuse or neglect, particularly bathtub drownings in young children, and those with atypical presentations, should be considered.²⁴ Bath seats may give parents a false sense of reassurance. Parents should never leave infants in bath seats unattended.²⁵ Bathtub drownings are rare outside of the toddler age range, so abuse or seizures should be suspected.²⁶ Among preschool children, adult supervision in conjunction with properly installed and maintained four-sided pool fences that completely isolate the pool could prevent 50% to 90% of drownings.^27,28

Teen and young adult drownings may be reduced by avoiding alcohol and illicit drug use, which has been implicated in 40% of all adult drownings and 75% of boating-related adult drownings.²⁹ The use of personal flotation devices decreases boating-related drowning deaths.³⁰ Practical experience suggests that the ability to swim protects against teen and adult drowning, but evidence only supports the efficacy of swimming lessons for decreasing drowning death in young children.³¹ Efforts to decrease risk-taking behavior in the high-risk adolescent and young adult age groups need to be developed.

Swimmers with seizure disorders must be constantly monitored by an experienced professional or competent bystander while they are in the water.

In the elderly, drowning locations closely parallel those of infant and toddler drowning. Adequate pool fencing and bathtub handrails are important preventive measures for the elderly population and patients with premorbid conditions.

Acknowledgment: The authors gratefully acknowledge that portions of this chapter are based on previous work by Bruce E. Haynes, Alan L. Causey, and Mark A. Nichter (dec.)