Drowning cases peak this time of year and represent a leading cause of mortality in children. For example, drowning represents the leading cause of death in boys ages 5-14 years old, and worldwide, there are 500,000 annual deaths from drowning.1 Hypoxic injury and subsequent respiratory failure represent the primary causes of morbidity and mortality. Although providers are typically taught to be aware of possible trauma (e.g. cervical spine fracture) when evaluating a drowning case, less than 0.5% of drownings are traumatic.2 The duration of immersion, volume of aspirated fluid, and water temperature dictate clinical outcomes.1 We review the presentation, pathophysiology, and management of drowning to raise awareness about this important public health issue.
What is drowning? What happens during a drowning event?
The CDC, AHA, and other multinational medical associations define drowning as “a process resulting in primary respiratory impairment from submersion or immersion in a liquid medium.”3 During a drowning event, small amounts of water cause laryngospasm, which leads to hypoxia and loss of consciousness, followed by respiratory failure and cardiac arrest. Simultaneously, pulmonary aspiration occurs, typically at small volumes that do not obstruct airways but cause chemical changes. While following ACLS algorithms, drowning resuscitation should therefore focus on reversing respiratory failure and hypothermia.
How do drowning victims present?
Although some patients will present with minimal symptoms, others may have amnesia to the event, or even hypothermia and cardiac arrest in severe cases.4 Witness accounts of the incident are important to obtain, but many drowning cases are unwitnessed and the patient may have little recollection.1
In cases involving a short episode of submersion or a small aspiration event, symptoms may be mild and include coughing, shortness of breath, and nausea or vomiting.1 However, longer submersion events put patients at risk for hypothermia, altered mental status, and cardiac arrest. Altered mental status may be secondary to hypothermia, hypoxia, or head injury. Drowning victims with a decreased Glasgow Coma Scale (GCS) on ED arrival are at increased risk for cardiac arrest and poor neurological outcomes.5 In drowning, cardiac arrest is typically secondary to hypoxia or acidosis, as most drownings do not involve enough water to alter the serum electrolyte composition.6
Undifferentiated patients presenting from an area with access to water should be evaluated for a possible drowning event. The airway should be assessed for patency and breathing adequacy, and lung sounds should be assessed for crackles. A GCS, rectal temperature, blood glucose level, and brief trauma survey should be included in the initial evaluation.
Prognostic Factors in Drowning
Predicting outcomes in drowning victims can be difficult. A grading system, called the Szpliman Drowning Classification, classifies victims into 6 grades, from normal pulmonary exam with coughing, to cardiac arrest.7
In addition to high Szpliman scores, other predictors of poor outcome include:8
- Prolonged submersion time
- Altered mental status
- Severe acidemia
- Elevated liver enzymes
Does the composition of inhaled water matter? Should abdominal thrusts be applied?
No and no. Both are common misconceptions. Volume, rather than composition, determines pulmonary derangement. Inhaled water causes loss of surfactant, alveolar collapse, noncardiogenic edema, intrapulmonary shunting, and VQ mismatch.9 Patients often require immediate positive pressure ventilation with high FiO2. Contrary to popular culture, abdominal thrusts are not indicated. These patients are at high risk of regurgitation and further aspiration.9
Why is the temperature of the patient more important than the temperature of the water?
Patients who suffer a submersion event may become hypothermic even in hot weather. There is a common misconception that cold water drowning is associated with better outcomes. However, in a retrospective case control study of 1,094 drowning victims, cold water did not have a protective effect against death, severe neurological sequelae, or persistent vegetative state. The duration of submersion was the most predictive of outcome.10
Patients with temperatures of 28-32°C require active rewarming. Strategies may include force air, radiant heat, and heat packs. In the unstable patient, the goal temperature is 34°C.2 Providers should also consider invasive warming techniques including:
- Warmed IV fluids
- Peritoneal lavage
- Bladder lavage
- Intrathoracic lavage
What is the role of ECMO in drowning victim resuscitation?
Although not all patients are a candidate, extracorporeal membrane oxygenation (ECMO) may be a temporizing measure to mitigate both the hypoxic and hypothermic complications of drowning. In previously healthy pediatric patients, it is hypothesized that extracorporeal life support (ECLS) may provide respiratory and circulatory support until pulmonary edema and inflammation improve. However, case reports represent the majority of data on outcomes in drowning victims managed with ECLS. A recent retrospective study of 247 patients who received ECLS following a drowning event suggests a 23.4% survival rate of patients placed on ECLS during cardiac arrest.11
What about Dry Drowning?
Confusing language used by news outlets and spread on social media has led to misguided fear of complications weeks after exposure to water. The terms “dry drowning”, “secondary drowning”, and “near drowning” are used to describe a variety of events. However, none of these are acceptable medical terminology.12
In one such case, a 4 year-old boy died one week after swimming in shallow water. His death was initially reported by news outlets as “dry drowning.” However, autopsy results showed that he died of myocarditis and not due to complications from swimming in shallow water. The effects of drowning present rapidly, and deterioration occurs within hours, not day to weeks later.13 Therefore, it is important to educate patients and families when presenting for evaluation after a possible drowning event or with concerns for “dry drowning.”
What are the key points to keep in mind during a drowning resuscitation?
Drowning can present with severe respiratory failure as well as hypothermia. Key resuscitation considerations include:
- Positive pressure ventilation
- Active rewarming to goal of at least 34°C
- Possibly ECLS