Near-drowning

Definition

Near-drowning is the term for survival after suffocation caused by submersion in water or other fluid. Some experts exclude from this definition cases of temporary survival that end in death within 24 hours, which they prefer to classify as drownings.

Description

Drowning is always fatal, but near-drowning may result in survival with no long-lasting effects; survival with permanent damage, usually to the brain; or death after a 24-hour survival period. Near drowning sets into motion a collection of reactions in the body that ultimately can damage the lungs and lead to an absence of oxygen in tissues, even when individuals have been removed from the water and begun breathing either on their own or with mechanical help.

Near-drowning happens very quickly. Within three minutes of submersion, most people are unconscious, and within five minutes the brain begins to suffer from lack of oxygen. Abnormal heart rhythms (cardiac dysrhythmias) often occur in near-drowning cases, and the heart may stop pumping (cardiac arrest). The blood may increase in acidity (acidosis) and, under some circumstances, near drowning can cause a substantial increase or decrease in the volume of circulating blood. If not rapidly reversed, these events cause permanent damage to the brain.

Demographics

About 1,500 children drown every year in the United States. Drowning is the second leading cause of injury-related deaths in children ages one month to 14 years of age in the United States as a whole, and the first leading cause of injury-related deaths in California, Arizona, and Florida. The rate of near drowning is much higher, as not all near drownings are reported. It is estimated that for every drowning, there are four additional hospitalizations and 14 additional emergency room visits due to near drowning.

Children under age four and between 15 and 19 years of age are at highest risk of drowning or near drowning. Most young children drown in swimming pools and bathtubs, while teens drown in natural bodies of water. Teen drownings are often associated with boating accidents, alcohol consumption, and illicit drug use. Boys are 12 times more likely to drown than girls, especially during adolescence , when risk-taking behavior is more pronounced in males. However, even in younger age groups, except in bathtub drownings, substantially more boys drown than girls.

Causes and symptoms

The circumstances leading to near-drownings and drownings are varied. Rarely do they involve nonswimmers accidentally entering deep water. In older children and adults, near-drownings are often secondary to an event such as or a head or spinal injury or (in adults) a heart attack that causes unconsciousness and prevents a diver from resurfacing.

Near-drownings can occur in shallow as well as deep water. Small children have drowned or almost drowned in bathtubs, toilets, industrial-size cleaning buckets, and washing machines. Bathtubs are especially dangerous for infants six months to one year of age, who can sit up straight in a bathtub but may lack the ability to pull themselves out of the water if they slip under the surface. One 2004 study found that 88 percent of children who drowned were under the supervision of another person, usually a family member. Seventy-seven percent of these children were under age ten. The most common occurrence was that the supervising adult knew the child was in or near the water but was distracted long enough for the child to drown.

A reduced concentration of oxygen in the blood (hypoxemia) is common to all near-drownings. When drowning begins, the larynx (a part of the air passage) closes involuntarily, preventing both air and water from entering the lungs. In 10 to 20 percent of cases, hypoxemia results because the larynx spasms and stays closed. This is called "dry drowning," and no water is breathed into the lungs. Hypoxemia also occurs in "wet drowning," when the larynx relaxes and water enters the lungs. Individuals who are close to drowning can also regurgitate their stomach contents and breathe these into the lungs.

The physiological mechanisms that produce hypoxemia in wet drowning are different for freshwater and saltwater, but only a small amount of either kind of water is needed to damage the lungs and interfere with lung's ability to remove oxygen from the air.

The signs and symptoms of near-drowning can differ from person to person depending in part on how long the individual has been submerged, the person's age, and the temperature of the water. Upon rescue, some victims are alert but agitated or disoriented, while others are comatose. Breathing and heartbeat may have stopped, or the victim may be gasping for breath. Bluish skin (cyanosis), coughing, vomiting , and frothy pink sputum (material expelled from the respiratory tract by coughing) are often observed. Rapid breathing (tachypnea) and a rapid heart rate (tachycardia) are common during the first few hours after rescue. The victim may experience hypothermia (drop in core body temperature).

When to call the doctor

Emergency medical aid should be sought with any near drowning incident. Even a child who appears to have recovered should be checked by a physician, since some internal reactions to near drowning can be delayed.

Diagnosis

Diagnosis relies on a physical examination of the victim, reports of observers, and a wide range of tests and other procedures. Blood is taken to measure oxygen levels and to determine electrolyte balances. Pulse oximetry, another way of assessing oxygen levels, involves attaching a device called a pulse oximeter to the patient's finger. An electrocardiograph is used to monitor heart activity. X rays can detect head and neck injuries and fluid in the lungs.

Treatment

Treatment begins with removing the victim from the water and performing cardiopulmonary resuscitation (CPR) as needed to restore heartbeat and provide oxygen until the individual is able to breath without assistance. When emergency medical help arrives, 100 percent oxygen is administered to the victim. If the victim's breathing has stopped or is otherwise impaired, a tube is inserted into the windpipe (trachea) to maintain the airway (endotracheal intubation). The victim is also checked for head, neck, and other injuries, and intravenously fluids may be started. Hypothermia from submersion in very cold water requires special handling to protect the heart.

On arriving at the emergency room, the individual continues receiving oxygen until blood tests show a return to normal. About one-third of near-drowning victims are intubated and initially need mechanical support to breathe. Treatment is administered as needed for cardiac arrest or cardiac dysrhythmias. Slow rewarming is undertaken when hypothermia is present. Individuals are observed for the development of acute respiratory distress syndrome (ARDS) or multi-organ failure, both of which can develop after near drowning. Lung problems can develop 12 or more hours after submersion.

Based on symptoms, individuals may be admitted to the hospital or discharged from the emergency department after four to six hours, if their blood oxygen level is normal and no signs or symptoms of near-drowning are present. Discharged individuals must understand that should complications arise, they must immediately seek additional medical care. Admission to a hospital for at least 24 hours for further observation and treatment is necessary for patients who do not appear to fully recover in the emergency department.

Prognosis

Recovery is directly related to the amount of time the body was without adequate oxygen (hypoxia). Brain damage is the major long-term concern in the treatment of near-drowning victims. Patients who arrive at an emergency department awake and alert usually survive with brain function intact, although they may initially have respiratory complications. Pneumonia is common following near drowning and often develops within the first 24 hours.

Death or permanent neurological damage is very likely when patients arrive at the emergency room comatose or without a heartbeat. Of these patients, 35 to 60 percent die in the emergency department, while almost all of those who survive have permanent disabilities. Early rescue of near-drowning victims (within five minutes of submersion) and prompt CPR (within less than ten minutes of submersion) seem to be the best guarantees of a complete recovery. However, in a phenomenon that is not well understood, extremely cold water (less than 41°F or 5°C) seems to protect individuals from some of the neurological damage that occurs with near drowning. Some hypothermic near-drowning victims have been revived after they appeared dead and have experienced few permanent disabilities.

Prevention

Drowning and near drowning are almost always preventable. Prevention depends on educating adults and children about water safety . Children cannot be left in or near water without adult supervision even for a short time. Unsupervised young children are at risk around swimming pools, bathtubs, toilets, buckets, and natural bodies of water. Pools and spas need to be enclosed with a fence at least 5 ft (1.5 m) high and have a self-closing and self-locking gate. Adults and teens should consider learning CPR. No one should swim alone or play along flooded streams or streets. Teens and adults should be educated to understand that alcohol and illicit drug use substantially increase the chances of a drowning accident. Boat owners need to participate in boat safety classes, and children should wear approved life preservers when boating, water skiing, or riding on a jet ski.

Parental concerns

Parents should be aware that physicians are required to consider the possibility of child abuse in every drowning or near drowning involving a child under the age of one year.

Resources

BOOKS

Kallas, Harry J. "Drowning and Near Drowning." In Nelson Textbook of Pediatrics, , 17th ed. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2004, pp 425–30.

Piantadosi, Claude A. "Physical, Chemical, and Aspiration Injuries of the Lung." In Cecil Textbook of Medicine , 21st ed. Edited by J. Claude Bennett and Fred Plum. Philadelphia: Saunders, 2000.

WEB SITES

Fiore, Michael, and Sabrina Heidemann. "Near Drowning." September 20, 2004. Available online at http://www.emedicine.com/ped/topic2570.htm (accessed January 14, 2005).

Plantz, Scott H., and Michael E. Zevitz. "Wilderness Near Drowning." December 14, 2004. Available online at http://www.emedicine.com/wild/topic34.htm (accessed January 14, 2005).

Shepherd, Suzanne, and James Martin. "Submersion Injury, Near Drowning." January 12, 2005. Available online at http://www.emedicine.com/emerg/topic744.htm (accessed January 14, 2005).

Tish Davidson, A.M.

Howard Baker