Drowning
Katherine V. Biagas
Linda Aponte-Patel
KEY POINTS
Drowning injury is a leading cause of accident-related childhood death and disability.
Two age groups are primarily affected (infant/toddler and adolescent).
Epidemiology is related to developmental risks and behaviors at these ages.
Therapy at the scene focuses on initial restoration of respiration and circulation.
Rapid transportation to a hospital is essential for those who remain “lifeless” with consideration of appropriate transfer to a specialty center for definitive care (cerebral resuscitation).
Drowning events are distinct from more usual forms of cardiac arrest in that drowning is an asphyxia event with subsequent cessation of cardiac function.
Rescue breathing and chest compressions, rather than chest compressions alone, are indicated for those who remain “lifeless.”
Cerebral resuscitation is primary. Evidence extrapolated from clinical events and laboratory experiments supports the consideration of mild hypothermia as a cerebral resuscitation method.
Temperature monitoring to maintain body cooling in the emergency department and pediatric intensive care unit is indicated.
Rewarming should be reserved for those with persistent nonperfusing rhythms.
Treatment of injury to the lungs and cardiovascular system contributes to the potential for brain resuscitation.
A “protective lung strategy” should be adopted as long as it does not contribute to increased intracranial pressure.
Prognosis is difficult to determine in the early phases of care.
A picture of likely outcome develops over time with repeated neurological examinations and adjunctive studies such as magnetic resonance imaging (MRI) scans.
The pediatric intensivist can be an important advocate for responsible community action focusing on drowning prevention.In 2005, the World Health Organization (WHO) defined drowning as “… the process of experiencing respiratory impairment from submersion/immersion in liquid” (1). The WHO estimates that nearly 400,000 persons die from drowning annually. In many countries, drowning is the second or third most frequent cause of childhood death (2). In the United States, drowning events account for ˜1000 deaths and more than 3000 emergency department (ED) visits annually for children less than 19 years of age (3). In some states, drowning is the leading cause of death for children under the age of five (4). Despite recent efforts to prevent such events and advances in medical care, outcomes for many drowning injuries remain quite poor.
The previous terminology describing drowning events was confusing and much of it is no longer used. Terms such as “wet drowning,” “dry drowning,” “near-drowning,” and “drowning injury” did not offer clinically important distinctions and have been abandoned in favor of using the definition mentioned above and the general term “drowning” for all (1). Similarly, the terms used for the outcomes from drowning have been simplified to death, morbidity, and no morbidity.
EPIDEMIOLOGY
Sociodemographic considerations have significant effects on the epidemiology of drowning events (Table 31.1). The majority of drowning events occur in freshwater with a large proportion of these occurring in natural bodies of water—rivers, creeks, lakes, and ponds. Drowning also occurs frequently in domestic sites—home pools, spas, or bathtubs—and recreational community pools, water parks, schools, etc. As few as 4% of events occur in salt water, although this incidence is higher in coastal communities (5). The three groups of children at particular risk for drowning include the very young, male adolescents, and African-American children. Drowning events that involve infants and toddlers commonly occur in sources of water in the home (5,6). Infants 6-11 months of age drown in bathtubs and these 
are not prevented by the use of bathtub seats (5,7). Older infants and toddlers drown as the result of a fall into a shallow body of water (i.e., a wading pool) as well as in bathtubs (5,7). Outcomes in these children are usually poor. Infants and toddlers are the group least likely to have a witnessed drowning event, which is associated with longer drowning time. In this age group, males and females drown with equal frequency; in all other age groups the prevalence of drowning is higher in males (5,7).
are not prevented by the use of bathtub seats (5,7). Older infants and toddlers drown as the result of a fall into a shallow body of water (i.e., a wading pool) as well as in bathtubs (5,7). Outcomes in these children are usually poor. Infants and toddlers are the group least likely to have a witnessed drowning event, which is associated with longer drowning time. In this age group, males and females drown with equal frequency; in all other age groups the prevalence of drowning is higher in males (5,7).Boys 15-19 years of age have the second highest drowning rate. Events in this age group are generally related to recreational water activities. These male adolescents have the highest rate of drowning while swimming, boating, or driving a car even when compared with adults who over a lifetime engage in such activities to a greater extent (7). African-American children have higher drowning rates and the highest drowning mortality rates are seen in 15 to 19-year-old African-American males as compared with Caucasian and Hispanic counterparts (8).
Certain medical conditions may predispose children to drowning. Drowning risk is elevated in children with epilepsy and certain neurologic conditions with the most events occurring in bathtubs and pools. Epilepsy, excluding other
neurologic disabilities, results in a 10-fold increased risk of drowning (9). In one report, 7% of pediatric drowning victims had a prior history of seizure (7). Hyperventilation with swimming exertion may predispose a child with epilepsy to have a seizure, precipitating the drowning event. The risk of drowning is also greater in children with autism (10) or mental retardation.
neurologic disabilities, results in a 10-fold increased risk of drowning (9). In one report, 7% of pediatric drowning victims had a prior history of seizure (7). Hyperventilation with swimming exertion may predispose a child with epilepsy to have a seizure, precipitating the drowning event. The risk of drowning is also greater in children with autism (10) or mental retardation.
TABLE 31.1 EPIDEMIOLOGIC, SOCIODEMOGRAPHIC, AND PREVENTION CONSIDERATIONS IN DROWNING ACCIDENTS | ||||||||||||||||||||||||||||||||||||
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Patients with long QT syndrome (LQTS) or other cardiac “channelopathies” are also at increased risk of drowning (11,12). In these patients, ventricular tachyarrhythmias may be exacerbated by swimming. In one report, 91% of patients presenting for cardiac evaluation who also had a personal or family history of swimming-related syncope had mutations in the LQTS1 gene (11). Similar results have been found with other genes associated with LQTS (13). Swimming is an arrhythmogenic trigger with activation of the “diving reflex,” which alters autonomic stability (14). The “diving reflex” is elicited in mammals by contact of the face with cold water and consists of breath-holding, bradycardia, and intense peripheral vasoconstriction. Swimming also involves physical exertion, which may be a syncopal trigger in some. Screening of relatives is recommended for anyone suspected of having a swimming-related arrhythmia syndrome. Counseling regarding safe water-related activities and β-blockade therapy are recommended for affected individuals.
The use of alcohol or other intoxicating substances is associated with drowning in adolescents and adults. Thirty to seventy percent of boating and swimming fatalities in these age groups have measurable blood alcohol levels (15). Moreover, the intoxicated victim may vomit and aspirate gastric contents. Other medical conditions that less frequently predispose to drowning include depression, coronary artery disease, cardiomyopathy, hypoglycemia, and hypothermia.
Drowning injuries in older children and adolescents may be associated with cervical spine injury. The incidence of such injury is low, estimated at 0.5%-5.0% of drowning events (4). The mechanism of injury is diving or falling into a body of water with a blow that hyperextends the cervical spine. A history of diving is usually elicited. When evaluating victims of unwitnessed events, the possibility of associated cervical spine injury should be considered. Immobilization of the cervical spine at the scene is important. As with other injuries of the spine, the diagnosis is a clinical one and is based on suspicion about the mechanism of injury and the patient’s neurologic condition. Radiographs of the cervical spine may be normal despite debilitating cord injury and MRI is usually necessary to confirm the clinical suspicion.
PATHOPHYSIOLOGY
The initial sequence of events in drowning was studied in the 1930s in animals and consists of the following: an initial struggle sometimes with a surprise inhalation, suspension of movement and exhalation of a little air frequently followed by swallowing, violent struggle, convulsions with spasmodic respiratory efforts through an open mouth, loss of reflexes, and death. This sequence has been confirmed in many cases by bystanders who witness this progression. During the initial seconds of drowning, small amounts of aspirated fluid often cause laryngospasm. Victims who are resuscitated at this phase will have little water aspiration, but ventilation by rescue breathing may be difficult because of glottic closure. If the victim loses muscle tone while submerged, larger quantities of fluid may be aspirated. In addition, a victim may swallow a large amount of fluid, vomit, and aspirate gastric contents.
The development of hypothermia is common with drowning and the presence of hypothermia should not be interpreted as a cold water drowning (discussed later). Hypothermia during drowning is usually secondary to rapid radiant heat losses in tepid water. As core temperature drops below 32°-35°C, unconsciousness and muscular weakness develop and the risk of aspiration is increased. Atrial fibrillation occurs with core temperatures in the low 30°C and ventricular fibrillation or asystole with severe hypothermia at a core temperature less than 28°C.
Cardiorespiratory Arrest
Drowning is an asphyxial cardiac arrest (ACA), which is distinct from more usual forms of primary cardiac arrest (CA) such as ventricular fibrillation. This distinction has implication for brain resuscitation therapies (discussed below). In ACA, victims have cessation of gas exchange first with resultant hypoxic deterioration and eventual CA. For the ACA victim, hypoxemia precedes ischemia and may augment injury.
Respiratory and Cardiovascular Dysfunction
In drowning victims with brief episodes of hypoxia, hypoxemia is limited to the duration of hypopnea or apnea and resolves with rescue or initial resuscitation efforts. However, in patients with longer hypoxic episodes and alveolar aspiration, these processes are more aggressive with surfactant washout, resultant lung collapse, alveolar derecruitment, intrapulmonary shunting, raised pulmonary vascular resistance, and ventilation-perfusion mismatching. In combination, these processes create the clinical syndromes of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Aspiration of gastric contents may add caustic injury to airways and alveoli, worsening ALI. Lastly, neurogenic pulmonary edema may contribute to deficits in gas exchange and lung function.
The hallmark of cardiovascular dysfunction associated with drowning is decreased myocardial contractility with hypoxemia. Ventricular end-diastolic pressures are raised, as are atrial pressures, with resultant congestion of central and pulmonary veins. Poor myocardial contractility, in combination with raised systemic vascular resistance, results in lower cardiac output. Cessation of cardiac function occurs as body temperature or oxygenation decreases as previously discussed.
Brain Injury
The important sequela of ACA is hypoxic-ischemic brain injury. Metabolically active areas, such as subcortical tissues, and regions with so-called “watershed” perfusion are the most vulnerable. Global brain involvement is seen in the most severe cases. The combination of hypoxemia and low-flow states results in a host of pathologic processes including energy failure, lipid peroxidation, production of free radicals, inflammatory responses, and release of excitotoxic neurotransmitters. There is disruption of neuronal and glial functions. Neuronal losses occur in selectively vulnerable zones with “delayed neuronal drop out.” ACA may differ importantly from CA in the development of microinfarctions in addition to selective neuronal injury (16). The reader is referred to the thorough review of brain injury and resuscitation after ACA by Topjian et al. (17) for a more complete discussion of research on the unique mechanisms of ACA and putative therapeutic targets.
Drowning in Ice-Cold Water
The terms “cold water” or “ice water” drowning are worth retaining when used correctly. Brain function may be preserved in “ice-cold water drowning” with good and even normal neurologic outcomes observed despite extensive submersion times. Numerous reports have documented dramatic cases of intact neurological functioning in children who drowned in ice-cold water (6,18,19). The term “cold water drowning” is a misnomer in that the drowning must occur in ice-cold water and, with very rare exceptions, is a phenomenon restricted to cold weather climates (18). Patients who have drowned in more temperate water but who have become hypothermic should be considered to have hypothermia from prolonged submersion. Such secondary hypothermia is often a poor prognostic sign associated with prolonged submersion before rescue.
Young children are particularly susceptible to rapid cooling of the brain in ice-cold water because of little subcutaneous fat and large head-to-body ratio. Moreover, brain preservation may be augmented by activation of the “diving reflex,” which slows metabolism and may preserve some perfusion to the heart and brain. Additionally, neurologic preservation can be seen when the lower body is submersed in ice water and the head remains above water allowing the victim to continue to breathe. The result is rapid brain cooling in the face of residual perfusion and provision of brain substrates.
It should be noted that ice-cold water drowning is associated with a rather high incidence of arrhythmias. Shattock and Tipton (20) studied this phenomenon by investigating the parasympathetic and sympathetic responses in healthy volunteers to ice water immersion of the face. Simultaneous activation of the diving response and the breath-holding response was noted inducing responses of bradycardia and tachycardia, respectively. They refer to this phenomenon as “autonomic conflict” and point to it as a cause of arrhythmias (20).
MANAGEMENT
Prehospital Management
The clinical management of drowning begins at the scene and continues during transport, at the ED, and when necessary into the pediatric intensive care unit (PICU) followed by a rehabilitation center. Table 31.2 outlines the three most active areas of 
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