drowning

drowning is a topic covered in the Taber's Medical Dictionary.

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Submersion in and suffocation by a liquid.

INCIDENCE
In the U.S., drowning is the second most common cause of traumatic death in children and the third most common cause of death by trauma in any age group. In the U.S., approximately 3800 deaths and 5900 ER visits result from drowning each year. Near drowning occurs about 100 times as commonly as drowning.

CAUSES
The injuries suffered result from holding one's breath (“dry drowning”), the aspiration of water into the lungs (“wet drowning”), and/or hypothermia.

RISK FACTORS
A primary risk for drowning by children and adolescents is swimming or playing near water without adult supervision. Other important contributing factors to many drowning episodes include: lack of barriers around bodies of water, alcohol and drug use, inadequate use of flotation devices, and boating accidents. Seizure disorders increase the risk of drowning by about 15-fold relative to the population at large. Drowning is also unfortunately a common means of committing suicide.

SYMPTOMS AND SIGNS
Common symptoms of drowning result from oxygen deprivation, retention of carbon dioxide, or direct damage to the lungs by water. These include cough, dyspnea, coma, and seizures. Additional complications of prolonged immersion may include aspiration pneumonitis, noncardiogenic pulmonary edema, electrolyte disorders, hemolysis, disseminated intravascular coagulation, and arrhythmias.

PHYSIOLOGY
Drowning is a unique form of respiratory trauma. The drowning victim suffers damage to alveolar capillary membranes in the lungs, which leak fluids into the alveoli, dilute surfactant, and impair gas exchange. The inability to exchange gases results in asphyxia, inadequate oxygen supply to the brain, and within minutes, loss of consciousness.

DIAGNOSIS
The diagnosis is usually readily apparent, based on the patient’s presentation or the reports of witnesses or first responders. The diagnosis is supported by chest x-rays, which typically resemble pneumonia or, when capnography is immediately available, high levels of retained carbon dioxide.

PREVENTION
Water safety practices reduce the likelihood of drowning. These include: providing lifeguards, skilled rescuers, or adult supervision for young children in swimming areas; avoiding aggressive boating practices; avoiding the use of intoxicants; and wearing personal flotation devices.

TREATMENT
Resuscitative efforts for the drowning victim should begin in the water. Unlike victims of cardiac arrest, where chest compressions should be given first, in drowning the resuscitation of the patient begins with rescue breathing. As soon as a bag-valve-mask is available, breathing should be supported with this device. One hundred percent oxygen should be provided. Patients who cannot be easily ventilated or who cannot protect their airway, should be intubated and mechanically ventilated.

IMPACT ON HEALTH
The outlook for the patient who has submerged in liquid is closely linked to the duration of the submersion, the minute ventilation of the patient, and whether the patient arrives for treatment awake and alert, or unconscious. Most patients with a preserved minute ventilation (5-10 L/min) can be managed safely as outpatients and have a good prognosis. The patient who has drowned and arrives comatose at the hospital, has only a 15% chance of survival and a 7% chance of surviving without residualneurological deficits.

PATIENT CARE
Advanced respiratory support of the drowning patient relies on the use of low tidal volumes, e.g., 4 to 6 mL/kg body weight, and pressure support or positive end-expiratory pressure. Treatment in a hyperbaric chamber, the instillation of pulmonary surfactant, and the induction of hypothermia are techniques of interest that are being actively studied in an attempt to improve outcomes. Some survivors of drowning develop unusual fungal infections in the central nervous system, as a result of inhaling these organisms from water. Brain injury that results from asphyxia may require rehabilitative efforts by a multidisciplinary staff of nurses, physiatrists, neurologists, and occupational, speech, and physical therapists.

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