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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 death in the US. It is the 2nd most common cause of death in children ages 1 to 14 yr. Rates are higher for the following:
Drowning is common in pools, hot tubs, natural water settings, and, among infants and toddlers, in toilets, bathtubs, buckets of water, and cleaning fluids. About 4 times as many people are hospitalized for nonfatal drowning as for fatal 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, particularly 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 heartbeat, 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, rarely 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.
Associated injuries:
Skeletal, soft-tissue, head, and internal injuries may occur. 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
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.
Diagnosis
Most people are found in or near water, making the diagnosis obvious clinically. Resuscitation may need to precede completion of the diagnostic assessment. Cervical spine injury is assumed, and the spine is immobilized in patients who have altered consciousness or whose mechanism of injury involves diving. Procedures to remove water from the lungs are generally not helpful. Secondary head injury and conditions that may have contributed to drowning (eg, hypoglycemia, stroke, MI) 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). 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.
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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 necessary, cardiac compression is started, followed by advanced cardiac life support (see Cardiac Arrest: Cardiopulmonary Resuscitation (CPR)). Oxygenation, endotracheal intubation, or both are done as soon as possible. Hypothermic patients are warmed as soon as possible (see Cold Injury: Treatment).
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 given 100% O2; the concentration is titrated lower based on ABG results. Positive end-expiratory pressure (see Respiratory Failure and Mechanical Ventilation: Ventilator settings) or intermittent positive pressure ventilation may be necessary to help expand or maintain patency of alveoli to maintain adequate oxygenation; pulmonary support may be necessary for hours or days. Nebulized β2-agonists may help reduce bronchospasm and wheezing. Patients with bacterial pneumonia are treated with antibiotics directed at organisms identified or suspected based on results of sputum analysis or blood cultures. Corticosteroids are not used.
Fluids or electrolytes are rarely required to correct significant electrolyte imbalances. Fluid restriction is rarely indicated, even if pulmonary or cerebral edema occurs. For prolonged brain hypoxia, treatment is similar to that for brain hypoxia after cardiac arrest (see Cardiac Arrest: Neurologic support). Concomitant disorders (eg, head or cervical injury, carbon monoxide poisoning) 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 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 must wear flotation devices when in or near water. They must be 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 and bathtubs. Swimming lessons are not recommended for children < 4 yr. Young children who have taken swim lessons or infant water safety classes still require supervision because these classes have not been proved to reduce drowning. 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.
Boaters are encouraged to wear flotation devices. Nonswimmers and small children are required to wear these devices.
People who are debilitated or elderly or have seizure disorders or other medical conditions that can alter consciousness require particular care when they are boating or swimming.
People with a personal and family history of unexplained drowning not attributable to alcohol, drug use, or a seizure disorder merit evaluation for long QT syndrome.
Community swimming areas should be supervised by trained lifeguards. 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.
Last full review/revision February 2009 by Norman L. Dean, MD
Content last modified February 2009
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