Drowning

Etiology

Accidental or deliberate exposure to submersion in water or other liquid substances that inhibit the body's ability to oxygenate tissues and organs.[4][5][6]

Risk factors for drowning include:

• Head trauma
• Seizure
• Cardiac arrhythmia
• Hypoglycemia
• Hypothermia
• Alcohol and drug use
• Suicide
• Panic attack
• Myocardial infarction
• Depression
• Poor judgment
• Scuba diving
• Natural disaster

In infants, the cause is often accidental and may occur in the bathtub or even the bathing pail. Most infant deaths occur within 5 minutes of a lapse in supervision. Older children tend to drown in the swimming pool. Often the gate or the fence to the pool is open and the child just jumps in. Adults tend to drown in lakes, rivers, and the sea. In many adult cases of drowning, there may be an associated injury, like diving in shallow waters and hitting a rock.

Epidemiology

Worldwide, drowning accounts for an estimated 360, 000 deaths annually. This represents 7% of all injury-related fatalities and is the leading cause of death among young males. It is estimated that 4, 000 fatalities occur each year in the United States. Furthermore, it is estimated that for every fatal drowning, four non-fatal drowning victims seek medical care. Fifty percent of those patients require hospital admission and interventions. There are three age-related peaks of victims which include small children (younger than 5), adolescents, and the elderly. Patients may drown in bathtubs, pools, large bodies of water or even rain-filled buckets in the yard. Risk factors for drowning include children and teenagers, residents of southern states, occurring during summer months, concomitant drug or alcohol use, and associated medical problems including dysrhythmias or epilepsy.

Pathophysiology

When a person suffers from submersion or immersion in a liquid medium, vital tissues may become hypoxic and acidotic which may result in cardiac dysrhythmias (progressing from tachycardia, bradycardia, pulseless electrical activity, and asystole). Aspirated fluid can lead to surfactant washout and dysfunction, increased permeability of the alveolar-capillary membrane, decreased lung compliance, and ventilation/perfusion ratio mismatching. This can result from minor to no respiratory complaints to fulminant non-cardiogenic pulmonary edema, with a clinical picture similar to adult or acute respiratory distress syndrome (ARDS). The highest morbidity and mortality are related to cerebral hypoxia, and management is aimed at reversing hypoxia as quickly as possible. Interestingly, hypothermic exposure with the incident may be tissue-protective, although may result in an increased occurrence of cardiac dysrhythmias.[7][8][9]

Determination of the toxicity of the water that the victim was immersed in (eg saltwater versus freshwater) is of little importance in non-fatal drowning. Volume or serum (electrolyte) changes only occur when a significant volume of fluid is aspirated. It is more important to note if the fluid was obviously contaminated (sewage), as those patients are highly prone to pulmonary infection and prophylactic antibiotics may be warranted at presentation. Additionally, current recommendations state that routine use of cervical spine immobilization and imaging is not warranted unless the history or exam suggests that the patient suffered from a traumatic injury.

At least 20% of individuals develop tight laryngospasm that lasts even after cardiac arrest. These victims seldom aspirate any fluid and are said to have dry drowning.

The two major sequelae of drowning are to the CNS and cardiac system. Within 2 minutes most victims lose consciousness and within 4-6 minutes will develop irreversible brain injury. Global CNS hypoperfusion induces releases of excitotoxic neurotransmitters, free radicals, and lipid peroxidation. Cerebral edema followed by autonomic instability often results followed by ST-segment changes, indicating stress-related myocardial damage. The hypoxemia also induces ventricular arrhythmias and severe pulmonary hypertension.

History and Physical

The history should determine the circumstances surrounding the drowning; one needs to know if the individual died accidentally or if it was a homicide or suicide. Intentional deaths in newborns are not uncommon and the risk factors include:

• Maternal depression
• Unwed mother
• Young mother
• Financial crises
• Inability to cope with a newborn

Someone who is drowning or nearly drowning usually has a history of struggling to breathe after an extended period of water submersion. The skin may appear blue or pale from lack of oxygen in the blood. The patient may be in respiratory distress with apnea or shallow breathing, have an altered level of consciousness, be coughing, fatigued, or have other neurological findings.

Evaluation

Labs and/or imaging studies are not always warranted in well-appearing, normoxic, asymptomatic patients. If obtained, the workup should be directed towards the patient’s history and exam (eg for continued hypoxia a chest x-ray and blood gas may be warranted or for altered mental status a head CT, blood glucose, blood gas, toxicology analysis, ethanol level, and a metabolic panel may be needed). The most common laboratory abnormality noted in these patients is metabolic acidosis secondary to a lactic acidosis. Electrolyte abnormalities are uncommon in non-fatal drowning patients despite the type of fluid in which the patient was immersed.

A chest x-ray is not required in all drowning victims. Moreover, the initial chest x-ray has little correlation with the patient’s clinical course or outcome. However, one should be obtained with continued hypoxia or worsening respiratory symptoms. Patients may develop a non-cardiogenic pulmonary edema/ARDS-type presentation and should be treated accordingly.  Routine use of glucocorticoids, diuretics, and empiric antibiotics is not currently recommended. Antibiotics should be withheld until the patient begins to develop infectious signs and/or symptoms. In significantly unstable patients, providers may consider using extracorporeal membrane oxygenation (ECMO) as salvage treatment for refractory hypoxia or hypothermia. Therapeutic hypothermia has also been discussed as being a beneficial treatment adjuvant.

Treatment / Management

The greatest morbidity and mortality associated with non-fatal drowning is due to tissue hypoxia, specifically cerebral hypoxia, and thus, the greatest priority in the resuscitation process is to address and correct hypoxia quickly. Current recommendations state that rescue breaths should begin as soon as possible, and the breaths should be given with the patient's their chin and airway extended when safe to do so. One recommendation is to start resuscitation with five rescue breaths instead of the usual two and to perform the rescue breaths before performing chest compressions. The Heimlich maneuver is no longer recommended and should be avoided. Hypothermic patients should have their pulse assessed for 30 seconds, as their pulse may be weak, and starting CPR on a heart that has an organized rhythm may trigger life-threatening dysrhythmia. When examining, manipulating, and moving hypothermic patients, it is important to be gentle to prevent inciting a dysrhythmia. Passive and active rewarming methods should be employed to warm the patient’s core temperature.[10][11][12](B3)

Initial management of the patient includes delivering oxygen via nasal cannula, non-rebreather, non-invasive positive pressure ventilation, or endotracheal tube. Oxygen should be titrated to maintain oxygen saturation between 92% - 96% and to avoid over oxygenation.  Nebulized albuterol may be given for bronchospasm. Cardiac support should be employed. Advanced cardiac life support (ACLS) protocol should be followed if needed. Infusion of crystalloids, and at times vasopressors, may be needed for refractory hypotension.

Differential Diagnosis

• Arrhythmia

• Child sexual abuse

• Factitious disorder imposed on another(Munchausen by proxy)

• Gang initiation

• Homicide

• Hazing

• Physical child abuse

• Spinal cord injuries

• Suicide

• Fibrillation in emergency medicine

Prognosis

Only patients who are alert or mildly confused at the initial presentation have a good prognosis. Victims who are comatosed usually fair poorly. Those who are comatosed and resuscitated with CPR often develop severe brain injury and hypoxic encephalopathy. At least 10-30% of children with brain damage require long term rehabilitation. Hypothermia can protect the brain in some children. Other risks of drowning include aspiration, ARDs, and death.