Chapter 136: Drowning

• Drowning is the second most common cause of nonintentional death in children and adolescents, with a bimodal distribution of peak incidence between the ages of 1 and 4 years and 11 and 14 years.

• Poor prognostic indicators include prolonged submersion asystole upon emergency department (ED) arrival and delay in effective cardiopulmonary resuscitation.

• Patients who have been asymptomatic and remain so, with a normal CXR and oxygenation, may be discharged after a 6-hour observation period.

Drowning is a major global health problem with significant mortality and morbidity in children.^1,2 It is the most preventable cause of unintentional injury in children. Children younger than 14 years of age comprise about 20% of all drowning victims. For every death secondary to drowning, there are five emergency department visits for submersion-related injuries.³

Drowning is the second leading cause of death from unintentional injuries in children aged from 1 to 14 years.⁴ It is the leading cause of death in children aged from 1 to 4 years, with home swimming pools being the most common site of occurrence.

• Males are more likely to drown than females in all age groups, with the highest rate in the 0–4-year-old age group.^8,9

• The fatality drowning rate of African-American children is three times that of Caucasian children.

• Low-income countries have the majority of drowning-related deaths (98.1%) as compared to middle- and high-income countries.⁵

• Poverty, education level of parents, number of children in the family, and ethnicity have also been associated with an increased risk of drowning.⁷

In the past, there have been a number of terms associated with drowning that caused much confusion.¹⁰ Therefore, in 2002, the World Congress on Drowning published the following consensus definition for drowning.¹¹

“Drowning is a process resulting from primary respiratory impairment from submersion/immersion in a liquid medium.”⁴ Drowning outcomes have been given the classification as either: death, morbidity, and no morbidity.

The terminologies that were previously used such as dry drowning, wet, active, silent, secondary and near drowning should no longer be utilized according to The International Liaison Committee on Resuscitation advisory statement recommendations.¹²

The most common locations where children drown are seas/oceans, lakes, streams, swimming pools, wells, cisterns, buckets, bathtubs, spas, and garden ponds.¹³

The drowning process is comprised of a continued series of events beginning from the point when the victim's airway lies below the water surface. This result in lack of oxygen and failure to eliminate carbon dioxide leading to hypoxemia, hypercarbia, and acidosis.¹⁴ The pathophysiology surrounding this event is complex and influenced by a number of factors (Table 136-1). Drowning medium, water temperature, associated trauma, and patient-specific factors are just a few of them. Despite the multitude of influencing variables, the primary insult is always hypoxia (Table 136-2).

The main organs that are affected are the pulmonary, neurologic, cardiac, and renal systems.

Pulmonary

After the patient is submerged, he or she aspirates a small amount of water causing reflex laryngospasm. Apnea leads to hypoxia and loss of consciousness. Once unconscious, most patients will aspirate a moderate amount of water. Approximately 10% of patients will maintain laryngospasm, causing what was previously described as “dry drowning.”¹⁵

Aspirated fresh water and salt water cause different path physiologic effects on the pulmonary system but ultimately lead to the same result. Aspirated fresh water causes surfactant to washout, thus altering the surface tension properties of the alveolus. The alveoli collapse, preventing ventilation and causing an intrapulmonary shunt. Some of the fluid diffuses into the cell walls of the alveoli, leading to cell rupture and edema. Most water, however, is absorbed into the plasma volume. The ultimate effects of fresh water aspiration are ventilation–perfusion (V/Q) mismatch from alveolar collapse and shunt (Fig. 136-1).^15,16

Salt water causes V/Q mismatch via a different mechanism. The aspirated hypertonic saltwater pulls fluid from the plasma into the alveolar spaces causing pulmonary edema. The fluid-filled alveoli thus are not ventilated, creating an intrapulmonary shunt (Fig. 136-1).¹⁴

Regardless of whether the event occurred in fresh water or sea water, the end result is pulmonary edema with a decrease in pulmonary compliance. This leads to an increased V/Q mismatch resulting from intrapulmonary shunting.

Neurologic

Most neurologic sequelae are because of hypoxia and ischemia. Decreased ventilation causes hypoxemia. Cardiopulmonary arrest leads to decreased cerebral blood flow. The combination of hypoxemia and decreased cerebral perfusion rapidly leads to ischemia. The neuronal cell destruction that occurs with ischemia subsequently causes cerebral edema and increased intracranial pressure (ICP). Despite a number of trials in previous decades, monitoring of ICP following drowning has not proven to influence management and thus is not recommended.^17–19 The presence of pupillary reactivity and motor activity on initial examination in ER may help to predict which patients survive. However, these findings have not been shown to assist in the differentiation of neurologically intact versus vegetative state survivors.²⁰ An EEG can be helpful in these patients.²¹ Predictors of poor outcome are burst suppression, generalized suppression, status epilepticus, and nonreactivity.^22,23 The data on the long-term neurological outcome in drowning patients is scarce.²⁴ MRI is better than CT scan in ascertaining the degree of brain swelling and edema.²² With cases of brain injury, tight glycemic control should be maintained, after CPR for 12–24 hours for children who remain comatose hypothermia has been recommended, but there is no strong scientific evidence for it.²⁴ Approximately 10% of drowning survivors will suffer severe neurologic sequelae.²⁴

Cardiovascular

Cardiac arrhythmias normally occur as a consequence of hypoxia, acidosis, and hypothermia. Decreased oxygen tension sensed by the carotid bodies leads to activation of the autonomic nervous system and frequently results in bradycardia and peripheral vasoconstriction. Sinus bradycardia and atrial fibrillation are the most commonly observed rhythms.²⁵ Catecholamine release that accompanies the stress response also contributes to increased systemic vascular resistance. The cardiovascular picture often resembles cardiogenic shock. Decrease in cardiac output is usually related to the degree of hypoxemia and can be reversible with treatment of the underlying cause.

The possibility of long QT syndrome should be kept in the differential when someone dies suddenly in water. It is difficult to confirm in the absence of family history, a previously abnormal ECG, and if an autopsy is not performed.^26,27

Electrolytes

Clinically, significant electrolyte derangements are uncommonly observed. Most patients who survive drowning aspirate less than 10 mL/kgwater. Dog studies have shown that more than 11 mL/kg water need to be aspirated for fluid shifts and more than 22 mL/kg for significant electrolyte imbalances.^1,6 Acidosis that is commonly seen is initially because of apnea-related hypercarbia causing respiratory acidosis, profound hypercalcemia, and hypermagnesemia.²⁸

Renal

Renal failure can occur because of hypothermia and shock-induced acute tubular necrosis. The cause is multifactorial including lactic acidosis, myoglobinuria because of muscle injury, hypoxemia, and hypo perfusion.²⁹

Hematologic

Disseminated intravascular coagulation (DIC) is uncommonly seen in the drowning victim and is a late finding when present.³⁰ Anemia can occasionally be seen in drowning victims. As the volume of aspirated water is rarely sufficient to cause hemodilution, any decrease in hemoglobin should be assumed to be because of blood loss.

Hypothermia

Hypothermia (core body temperature <35ºC) is often seen in drowning victims.³¹ It may contribute to bradycardia, ventricular fibrillation, acute respiratory distress syndrome (ARDS), and shock. Older literature has emphasized the importance of the “diving reflex.”³² This occurs in mammals when the face contacts cold water. The body responds with breath holding, vasoconstriction, bradycardia, and decreased cardiac output. The outcome is increased blood flow to cardiac and cerebral tissues. While there are a number of animals that exhibit this, it is not believed to play a significant role in humans. There is recent data to suggest that induced hypothermia may exert neuroprotective properties on victims of cardiac arrest.^19,33 While this is a promising avenue, further research needs to be performed in this area. Therapeutic hypothermia in the pediatric drowning victim cannot be universally recommended at this time.^34,35

Basic life support to drowning victims plays a key role in survival as the outcome from drowning largely depends on the restoration of oxygenation and ventilation.³⁷ Routine attempts at postural drainage or use of the Heimlich maneuver are not recommended. Suctioning is indicated in the event of vomiting which occurs in 66% of those receiving rescue breathing and 86% of those receiving chest compressions.^18,38 Coexistentcervical spine injury is rare in immersion injuries. Routine immobilization of the cervical spine is not recommended unless a potential high-impact mechanism exists, such as diving into shallow water, boating accident, fall from a height, or the presence of alcohol.^39,40

As these patients have profound vasoconstriction, pulses may be difficult to palpate so if there is any doubt, start the basic life support immediately with five initial rescue breaths. Cardiopulmonary resuscitation (CPR) is then continued with the ratio of 30 compressions and 2 breaths.^41,42

Emergency Department Management

For those in cardiac arrest, reevaluation of the effectiveness of CPR including intubation and ventilation and appropriate screening for cervical spine injuries are the management priorities. Early assessment for hypothermia should be performed with use of a low-reading rectal probe. The presence of severe hypothermia may dictate the duration of resuscitation and modify prognosis. Survival after prolonged submersion and cardiac arrest has been reported in cold water drowning.

Restoration of oxygenation in the victim who has a perfusing rhythm may require 100% oxygen and positive pressure treatment, such as continuous positive airway pressure (CPAP) or bi-level positive airway pressure (BiPAP). Intubation and ventilation with positive end-expiratorypressure (PEEP) are indicated for those with persistent hypoxia or ventilatory failure. Those with evidence of bronchospasm should be treated with β-agonists. Assessment of oxygenation and a baseline chest x-ray should be performed on all symptomatic patients. ARDS should be anticipated with significant fluid aspiration. There is no definitive evidence that empiric antibiotics or steroids have a positive effect on the incidence of ARDS or pneumonia.^43–45 Patients with altered mental status should be intubated for airway protection.

Obtain appropriate screening tests for alternate explanations of mental status changes including serum glucose, head CT scan, drug screening, and appropriate medication levels for patients with a history of seizures.⁴⁶ Serum electrolytes should be evaluated, but generally will not be affected without ingestion of a significant amount of water (>22 mL/kg).⁴⁴Survival has been reported after prolonged cardiac arrest in hypothermic patients. Consider transferring the patient to a facility capable of cardiopulmonary bypass for victims who are severely hypothermic (<28ºC).³⁶

Please refer to Fig. 136-2 for a summary of ED management of the drowning victim.

Predicting Outcome

• Much recent research has focused on outcomes of patients with drowning.

Most drowning victims either die or survive neurologically intact. Of those patients who arrive to the ED awake and alert, survival approaches 100%. Good prognostic indicators include short submersion time of less than 5–10 minutes and spontaneous pulse and respiration. For submersion for more than 25 minutes, the outcome is poor in almost 100 % of patients. Early life support, even by bystanders, at the scene of the accident has the highest impact on patient outcome. Continued need of CPR in the ED, time to initial resuscitation, age less than 3 years, level of consciousness, and acidosis are associated with poorer outcomes. If two or less poor prognostic factors are present, there is a 90% chance of full recovery, while if there are three or more poor prognostic factors are present, then there are only 5% chance of full recovery.^29,47

Table 136-2 shows a list of poor prognostic indicators.

Asymptomatic patients who have been adequately monitored for 6–8 hours can be discharged home. Hospitalization criteria are listed below:⁴¹

• Submersion for more than 1 minute

• Apnea or cyanosis at presentation

• Persistent oxygen requirement after observation period of 6–8 hours

• Persistent symptoms of aspiration like cough, tachypnea, chest pain, and fever

• Moderate to severe hypothermia

• Abnormal chest radiograph

• Acidosis on ABGs^18,48

Safety measures are key to reduce drowning-related morbidity and mortality.⁹ The use of four-sided fences around pools have been associated with a decrease in the incidence of drowning cases. Other measures such as water safety training, adult supervision near water, and the use of proper floating devices have also been shown to be effective.^18,35,49