Drowning

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 (previously called dry drowning), or both. Lung injury due to aspiration or hypoxia itself may cause delayed hypoxia (previously called secondary drowning). 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 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.

Exposure to cold water induces systemic 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 oxygen 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.

Laryngospasm often limits the volume of fluid aspirated. Distinction between freshwater and seawater drowning was once considered important due to the potential electrolyte shifts, hemolysis, and fluid compartment shifting that possibly could occur. However, studies have shown that in most patients, too little liquid is aspirated to have these effects. Aspiration can lead to pneumonia, sometimes with anaerobic or fungal pathogens, and pulmonary edema.

Dangerous underwater breath-holding behaviors are practiced mostly by healthy young men (often good swimmers) trying to prolong their capacity to remain submerged. There are 3 described types of DUBB:

• Intentional hyperventilation—blowing off carbon dioxide before submerged swimming, thereby delaying central hypercarbic ventilatory responses

• Hypoxic training—extending capacity for underwater distance swimming or breath-holding

• Static apnea—breath-holding for as long as possible while submerged and motionless, including as a game

In DUBBs, while submerged, hypoxia occurs first, followed by loss of consciousness (hypoxic blackout, breath-hold blackout) and then drowning.

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).

1. 1. Centers for Disease Control and Prevention. Injury Prevention & Control : Leading causes of death and injury, United States, 2020. Accessed October 27, 2022.

2. 2. Centers for Disease Control and Prevention. Morbidity and Mortality Weekly Report: Racial/Ethnic disparities in fatal unintentional drowning among persons aged ≤ 29 years – United States 1999-2010. MMWR 63:421-426, 2014.

3. 3. Day G, Holck P, Strayer H, et al:  Disproportionately higher unintentional injury mortality among Alaska Native people, 2006-2015.  Int J Circumpolar Health 77(1):1422671, 2018. doi: 10.1080/22423982.2017.1422671

4. 4. Felton H, Myers J, Liu G, et al:  Unintentional, non-fatal drowning of children: US trends and racial/ethnic disparities. BMJ Open 5(12):e008444, 2015. doi: 10.1136/bmjopen-2015-008444

5. 5. Sillanpää M, Shinnar S: SUDEP and other causes of mortality in childhood-onset epilepsy. Epilepsy Behav 28(2):249-255, 2013. doi: 10.1016/j.yebeh.2013.04.016

6. 6. Centers for Disease Control and Prevention. Drowning Prevention: Drowning facts. Adapted from Centers for Disease Control and Prevention, National Center for Injury Prevention and Control. Web-based Injury Statistics Query and Reporting System (WISQARS). Accessed August 10, 2022.

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 compressions are started, followed by advanced cardiac life support. Although the 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation (CPR) recommend chest compressions as the first step in resuscitation of patients in cardiac arrest, drowning is an exception to this recommendation and rescue breathing is started first (1). 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. Immediate treatment measures may include removing clothing, drying, and insulation. Prolonged resuscitation efforts should be considered especially in young patients involved in cold water drownings.

All hypoxic or moderately symptomatic patients are hospitalized. In the hospital, supportive treatment continues, aimed primarily at achieving acceptable arterial oxygen and carbon dioxide levels. Mechanical ventilation may be necessary. Patients are initially given 100% oxygen; the concentration is titrated lower based on arterial blood gas (ABG) results. Positive end-expiratory pressure ventilation is sometimes 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 beta-2 agonists may help reduce bronchospasm and wheezing. Surfactant administration may be helpful in critically ill patients with significant lung compliance issues after drowning, although no large clinical trials have addressed this.

Core body temperature is monitored, and hypothermia is treated. Fluids or electrolytes are rarely required to correct significant volume or electrolyte imbalances. Fluid restriction is rarely indicated unless pulmonary or cerebral edema occurs. Concomitant injuries and disorders (eg, head or cervical injury, seizure, arrhythmia) may also require treatment. Patients who have persistent altered mental status despite correction of respiratory compromise should be evaluated for other injuries (eg, occult seizures, intracranial injury). Patients with pneumonia, confirmed by results of sputum testing and/or blood cultures, are treated with antibiotics that target identified or suspected organisms. Corticosteroids are not used.

Patients with mild symptoms, clear lungs, and normal mentation and oxygenation should be observed in the emergency department for at least 8 hours (2, 3). If symptoms resolve and the examination and oxygenation remain normal, patients can be discharged with instructions to return if symptoms recur.

1. 1. Panchal AR, Bartos JA, Cabanas JG, et al: Adult Basic and Advanced Life Support Writing Group. Part 3: Adult Basic and Advanced Life Support: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 142(16_suppl_2):S366-S468, 2020. doi: 10.1161/CIR.0000000000000916

2. 2. Brennan C, Hong T, Wang VJ: Predictors of safe discharge for pediatric drowning patients in the emergency department. Am J Emerg Med 2018, 36(9):1619-1623. doi: 10.1016/j.ajem.2018.01.050

3. 3. Shenoi RP, Allahabadi S, Rubalcava DM, et al: The pediatric submersion score predicts children at low risk for injury following submersions. Acad Emerg Med 24(12):1491-1500, 2017. doi: 10.1111/acem.13278

Use of alcohol or drugs is a major risk factor and 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 directly toward the beach. Swimmers should be discouraged from dangerous underwater breath-holding behaviors (DUBBs). If they practice them, they should be supervised and should know their dangers. Swimmers should avoid swimming near a boat exhaust port, which can cause carbon monoxide poisoning.

Public swimming areas should be supervised by lifeguards trained in water safety and resuscitation as well as rescue techniques. Life preservers, life jackets, and a 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 cardiopulmonary resuscitation (CPR) to as many adolescents and adults as possible. Owners of private pools should comply with local laws regarding pool safety, have immediate telephone access to emergency medical services, and know about resuscitation after drowning.

Children should wear flotation devices that have been approved by the US Coast Guard or other equivalent authority 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 approved safety 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 life jackets approved by the US Coast Guard or other equivalent authority and they should check weather and water conditions. Nonswimmers and small children in a boat should wear appropriately 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 older 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 arrhythmogenic cardiac disorders.