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Drowning is respiratory impairment resulting from submersion in a liquid medium. It can be nonfatal (previously called near drowning) or fatal. Drowning results in hypoxia, which can damage multiple organs, including the lungs and brain. Treatment is supportive, including reversal of respiratory and cardiac arrest, hypoxia, hypoventilation, and hypothermia.
Drowning is one of the leading causes of accidental deaths worldwide, particularly in children and adolescents < 19 yr. From 2005 to 2009 in the US, children 1 to 4 yr had the highest drowning death rates, and drowning was the 2nd most common cause of death (after congenital anomalies). Drowning was the 2nd most common cause of death by injury in children ages 5 to 9 yr and the third leading cause for children < 1 yr and ages 10 to 19 yr. Other groups at higher risk of drowning death include
Drowning is common in pools, hot tubs, natural water settings, and, among infants and toddlers, in toilets, bathtubs, and buckets of water or cleaning fluids. About 4 times as many people are hospitalized for nonfatal drowning as die as a result of drowning.
Pathophysiology
Hypoxia
Hypoxia is the major insult in drowning, affecting the brain, heart, and other tissues; respiratory arrest followed by cardiac arrest may occur. Brain hypoxia may cause cerebral edema and, occasionally, permanent neurologic sequelae. Generalized tissue hypoxia may cause metabolic acidosis. Immediate hypoxia results from aspiration of fluid or gastric contents, acute reflex laryngospasm, or both. Lung injury due to aspiration or hypoxia itself may cause delayed hypoxia. Aspiration, especially with particulate matter or chemicals, may cause chemical pneumonitis or secondary bacterial pneumonia and may impair alveolar secretion of surfactant, resulting in patchy atelectasis. Extensive atelectasis may make the affected areas of the lungs stiff, noncompliant, and poorly ventilated, potentially causing respiratory failure (see Respiratory Failure and Mechanical Ventilation: Acute Hypoxemic Respiratory Failure (AHRF, ARDS)) with hypercapnia and respiratory acidosis. Perfusion of poorly ventilated areas of the lungs (V/Q mismatch) worsens hypoxia. Alveolar hypoxia may cause noncardiogenic pulmonary edema.
Hypothermia
Exposure to cold water induces systemic hypothermia (see Cold Injury: Hypothermia), which can be a significant problem. However, hypothermia can be protective by stimulating the mammalian diving reflex, slowing the heart rate, and constricting the peripheral arteries, shunting oxygenated blood away from the extremities and the gut to the heart and brain. Also, hypothermia decreases the O2 needs of tissues, possibly prolonging survival and delaying the onset of hypoxic tissue damage. The diving reflex and overall clinically protective effects of cold water are usually greatest in young children.
Fluid aspiration
Laryngospasm often limits the volume of fluid aspirated; however, large volumes of water are occasionally aspirated, on rare occasions enough to change electrolyte concentrations and blood volume. Seawater may increase Na and Cl slightly. In contrast, large quantities of fresh water can decrease electrolyte concentration significantly, increase blood volume, and cause hemolysis. Aspiration can lead to pneumonia, sometimes with anaerobic pathogens.
Associated injuries
Skeletal, soft-tissue, head, and internal injuries may occur, particularly among surfers, water skiers, boaters, flood victims, and occupants of submerged vehicles. People who dive into shallow water may sustain cervical and other spine injuries (which may be the cause of drowning).
Rarely, drowning occurs when people develop carbon monoxide poisoning when they are swimming near an exhaust port of a boat. Only a few breaths may cause unconsciousness.
Symptoms and Signs
During drowning, panic and air hunger occur. Children who are unable to swim may become submerged in < 1 min, more rapidly than adults. After rescue, anxiety, vomiting, wheezing, and altered consciousness are common. Patients may have respiratory failure with tachypnea, retractions, or cyanosis. Sometimes respiratory symptoms are delayed until several hours after submersion. Patients may have symptoms due to injuries or exacerbations of underlying disorders.
Diagnosis
Most people are found in or near water, making the diagnosis obvious clinically. Resuscitation, if indicated, should precede completion of the diagnostic assessment. Cervical spine injury is considered, and the spine is immobilized in patients who have altered consciousness or whose mechanism of injury involves diving or trauma. Secondary head injury and conditions that may have contributed to drowning (eg, hypoglycemia, MI, stroke, intoxication, arrhythmia) are considered.
All patients undergo assessment of oxygenation by oximetry or, if results are abnormal or if there are respiratory symptoms or signs, ABG and chest x-ray. Because respiratory symptoms may be delayed, even asymptomatic patients are transported to the hospital and observed for several hours.
In patients with symptoms or a history of prolonged submersion, core body temperature is measured, ECG and serum electrolytes are obtained, and continuous oximetry and cardiac monitoring are done. Patients with possible cervical spine injury undergo cervical spine imaging (see Spinal Trauma: Diagnosis).
Patients with altered consciousness undergo head CT. Any other suspected predisposing or secondary conditions are evaluated with appropriate testing (eg, fingerstick glucose for hypoglycemia, ECG for MI, cardiac monitoring for arrhythmia, evaluation for intoxication). Patients who drown without apparent risk factors are evaluated for long QT syndrome. In patients with pulmonary infiltrates, bacterial pneumonia is differentiated from chemical pneumonitis using blood cultures and sputum Gram stain and culture. If indicated (eg, bacterial pneumonia is suspected but the pathogen cannot be otherwise identified), bronchial washings are obtained for testing, including culture, Anaerobic pathogens should be considered.
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Prognosis
Factors that increase the chance of surviving submersion without permanent injury include the following:
Survival may be possible in cold water submersion that lasts > 1 h, especially among children; thus, even patients with prolonged submersion are vigorously resuscitated.
Treatment
Treatment aims to correct cardiac arrest, hypoxia, hypoventilation, hypothermia, and other physiologic insults.
Resuscitation
In apneic patients, rescue breathing is started immediately—in the water, if necessary. If spinal immobilization is necessary, it is done in a neutral position, and rescue breathing is done using a jaw thrust without head tilt or chin lift. Emergency medical services are called. If the patient does not respond to rescue breathing, cardiac compression is started, followed by advanced cardiac life support (see Cardiac Arrest: Cardiopulmonary Resuscitation (CPR) in Adults). Although the 2010 American Heart Association Guidelines for CPR recommend chest compressions as the first step in resuscitation of patients in cardiac arrest, drowning is an exception to this recommendation.. Attempts to remove water from the lungs are avoided because they delay ventilation and increase the risk of vomiting. Oxygenation, endotracheal intubation, or both should proceed as soon as possible. Hypothermic patients are warmed as soon as possible (see Cold Injury: Treatment). Immediate measures may include removing clothing, drying, and insulation.
Hospital care
All hypoxic or moderately symptomatic patients are hospitalized. In the hospital, supportive treatment continues, aimed primarily at achieving acceptable arterial O2 and CO2 levels. Mechanical ventilation may be necessary. Patients are initially given 100% O2; the concentration is titrated lower based on ABG results. Positive end-expiratory pressure (see Respiratory Failure and Mechanical Ventilation: Ventilator settings) ventilation is usually necessary to help expand or maintain patency of alveoli to maintain adequate oxygenation. Pulmonary support may be necessary for hours or days. If adequate oxygenation is impossible despite maximizing ventilator settings, extracorporeal membrane oxygenation may be considered. Nebulized β2-agonists may help reduce bronchospasm and wheezing. Patients with bacterial pneumonia are treated with antibiotics targeting organisms identified or suspected based on results of sputum testing and/or blood cultures. Corticosteroids are not used. Core body temperature is monitored, and hypothermia is treated.
Fluids or electrolytes are rarely required to correct significant electrolyte imbalances. Fluid restriction is rarely indicated, even if pulmonary or cerebral edema occurs. Concomitant injuries and disorders (eg, head or cervical injury, carbon monoxide poisoning) may also require treatment.
Discharge
Patients with mild symptoms and normal oxygenation can be observed in the emergency department for several hours. If symptoms resolve and oxygenation remains normal, they can be discharged with instructions to return if symptoms recur.
Prevention
Use of alcohol or drugs, a major risk factor, should be avoided before and during swimming and boating and when supervising children around water.
Swimmers should use common sense and be aware of weather and water conditions. Swimmers should be accompanied by an experienced swimmer or swim only in guarded areas. Swimming should stop if the swimmer looks or feels very cold, because hypothermia may impair judgment. Ocean swimmers should learn to escape rip currents by swimming parallel to the beach rather than toward the beach. Swimmers should avoid swimming near a boat exhaust port, which can cause carbon monoxide poisoning.
Children should wear Coast Guard approved flotation devices when in or around water. Air-filled swimming aids and foam toys (water wings, noodles, etc.) are not designed to keep swimmers from drowning and should not be used as a substitute for US Coast Guard approved equipment. Children must be constantly supervised by an adult when around water, including beaches, pools, and ponds. Infants and toddlers should also be supervised, ideally within arm's length, when near toilets, bathtubs, or any collection of water. Studies in the US and China have shown that formal swimming lessons reduce the risk of fatal drowning among children ages 1 to 4; however, even children who have been taught how to swim require constant supervision when in or around water. Adults should remove water from containers such as pails and buckets immediately after use. Swimming pools should be surrounded with a locked fence ≥ 1.5 m in height.
Before embarking, boaters should wear Coast Guard approved life jackets and should check weather and water conditions. . Nonswimmers and small children in a boat should wear Coast Guard approved life jackets at all times. Because consuming any quantity of alcohol increases the risk of drowning, operators and passengers on recreational boats should generally avoid consuming alcohol.
People who are debilitated or elderly or have seizure disorders or other medical conditions that can alter consciousness require constant supervision when they are boating or swimming and when in bathtubs.
People with a personal or family history of unexplained drowning not attributable to alcohol use, drug use, or a seizure disorder merit evaluation for long QT syndrome.
Public swimming areas should be supervised by lifeguards trained in water safety and resuscitation as well as rescue techniques. Life preservers, life jackets, and shepherd's crook should be available close to poolside. Emergency airway equipment, automated external defibrillators (AEDs), and immediate telephone access to emergency medical services should be available. Comprehensive community prevention programs should target high-risk groups, teach children to swim as early as possible, and teach CPR to as many adolescents and adults as possible. Owners of private pools should also have immediate telephone access to emergency medical services and know about resuscitation after drowning.
Key Points
Last full review/revision April 2013 by Norman L. Dean, MD
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