Trauma Review: Drowning

Presented at Joint Trauma Conference on June 17, 2014. Mayo Clinic, Rochester MN.
Authors: Elizabeth Walter, Amy O'Neill and Masashi Okubo
Reviewed by: Kharmene Sunga and Daniel Cabrera.

Drowning

Drowning accounts for almost 4,000 deaths each year in the United States, while worldwide about 500,000 people die annually. The statistics for drowning are much more difficult to obtain but it may be several hundred fold greater than that of actual reported drownings.
Drowning is defined as “a process resulting in primary respiratory impairment from submersion or immersion in a liquid medium” (2010 American Heart Association Guidelines). We now try to avoid ambiguous or confusing terms such as “near-drowning,” “secondary drowning,” “wet drowning” (or aspiration of fluid into the lungs), or “dry drowning” (or asphyxia secondary to laryngospasm).

Epidemiology
In the United States, drowning is a common cause of accidental deaths. There are two peaks of incidence of submersion injury. The first occurs in children less than five years of age who are left mostly unattended or unsupervised in swimming pools and bathtubs. The second peak is seen in males between 15 and 25 years old and these tend to occur at rivers, lakes and beaches.
The following risk factors significantly contribute to drowning:

• Inability to swim or overestimation of swimming capabilities
• Risk-taking behavior -- alcohol and illicit drugs -- more than 50% of adult drowning deaths are believed to be alcohol related
• Inadequate adult supervision
• Concomitant trauma, seizures, cerebro-vascular accidents, myocardial infarctions and arrhythmia
• Hyperventilation (shallow water blackout) - swimmers commonly hyperventilate in order to prolong the duration of
• underwater swimming. However, by hyperventilating, the swimmer significantly lowers the partial pressure of carbondioxide
• (PaCO2), while the partial pressure of oxygen (PaO2) does not change appreciably. As the individual swims, the
• PaO2 will fall to 30-40 mm Hg before the CO2 reaches a normal level and the urge to breathe occurs. This can lead to
• cerebral hypoxia and loss of consciousness, which may result in drowning.
• • Hypothermia -- this can lead to arrythmias and rapid exhaustion.

Pathophysiology

The differences between salt water and fresh water drownings used to be emphasized. It was believed that the hypertonicity of salt water would cause plasma to be drawn into the pulmonary interstitium and alveoli leading to massive pulmonary edema and hypertonic serum. On the other hand, drowning in fresh water was thought to create the opposite effect: the aspirated hypotonic fluid in fresh water drownings would rapidly pass through the lungs and into the intravascular compartment leading to fluid overload and dilutional effects on serum electrolytes. However, these differences are rarely seen in patients who are alive on arrival at the hospital. Studies have suggested that aspiration of more than 11ml/kg of body weight must occur before blood volume changes occur and more than 22 ml/kg before electrolyte changes take place.
Today, the differences between salt water and fresh water drowning are downplayed, since it is unusual for drowning victims to aspirate more than 3 to 4 ml/kg. Rather, the temperature of the water and the possible contaminants contained therein appear to be more important.

Effect on organ systems

• Pulmonary: Both salt water and fresh water have the effect of washing out surfactant, which often produces noncardiogenic pulmonary edema, manifesting clinically as acute respiratory distress syndrome (ARDS). Pulmonary insufficiency can develop insidiously or rapidly. Signs and symptoms include shortness of breath, rales and wheezing. The chest radiograph, at presentation, can vary from normal to localized, perihilar or diffuse pulmonary edema.
• Neurologic: Hypoxia and ischemia cause neuronal damage that leads to cerebral edema and elevations in intracranial pressure. About 20% of drowning victims sustain neurologic damage and this continues to limit successful resuscitation of drowning victims.
• Cardiovascular: Arrhythmias, secondary to hypothermia, and hypoxia are often seen in drowning victims. Sinus bradycardia and atrial fibrillation are common, while ventricular fibrillation or asystole as the initial rhythm is relatively rare.
• Acid-base and Electrolytes: A metabolic and/or respiratory acidosis is often seen. Significant electrolyte imbalances do not occur in drowning survivors, except those exposed to unusual mediums, such as the Dead Sea, where the extremely concentrated sea water can lead to life-threatening changes in magnesium and calcium

Management

At the Scene:
Pulses may be very weak or difficult to palpate in the hypothermic patient in sinus bradycardia or atrial fibrillation. So, a careful search for pulses should be done for at least a minute before initiating chest compressions since these arrhythmias require no immediate treatment. The Heimlich maneuver or other postural drainage techniques are of no proven value and rescue breathing should not be delayed in order to perform these maneuvers. Attempts at rewarming all hypothermic patients (<33oC) should be initiated. This may be by passive (blankets) or active (radiant warmers, hot packs) procedures.
In the Emergency Department:
Most drowning victims are hospitalized because of the concern for clinical deterioration. However, a review of 75 pediatric patients found that all the patients who developed symptoms did so within seven hours of immersion. Based on that study and a similar study in adults, drowning victims, who are asymptomatic after eight hours of observation, can be discharged with a follow-up call or evaluation.
Core rewarming should be initiated in the hypothermic patient. Methods available include warmed intravenous fluids, heated oxygen via an endotracheal tube and warmed gastric, bladder, pericardial, pleural or peritoneal lavage. As a last resort, extracorporeal rewarming, using hemofiltration or cardiopulmonary bypass, can be tried. If cardiovascular stability cannot be achieved after rewarming, further attempts at resuscitation are futile.

The following factors, at presentation, have been associated with a poor prognosis in the drowning victim:

• Duration of submersion >10 minutes
• Time to effective basic life support >10 minutes
• Hypothermia (core temperature <33oC)
• Glasgow coma scale (GCS): comatose or GCS <5
• Age <3 years
• Persistent apnea and requirement of CPR in the emergency room
• Arterial blood pH at presentation <7.1
• Water temperature >10 degrees Celsius. Cold water is beneficial in that it tends to (a) decrease the metabolic demands of the body helping to prevent or delay the effects of hypoxia and (b) bring on the diving reflex, a primitive reflex often seen in children, that shunts blood to the vital organs.

Hospital management

Neurological
Although the major determinants of outcome are the duration of loss of consciousness and the state of the patient at the scene and in the emergency department, the goal of ICU management is directed towards the neurological system in an attempt to prevent secondary injuries because of ongoing ischemia, hypoxia, fluid and electrolyte imbalances, acidosis and seizure activity.
In 1978, Conn et al reported that the use of barbiturates and controlled hypothermia decreased mortality and neurologic morbidity in unconscious, drowning victims. However, subsequent studies failed to show any effects on outcome and may, in fact, leave more children in a persistent vegetative state. The use of hypothermia in the postresuscitation period has also been associated with increased incidence of sepsis, probably secondary to cold-induced immunosuppression.

• The treatment of hypoxic cerebral injury in drowning victims includes:
• Mild hyperventilation to maintain a PaCO2 around 30-35 mm Hg. Excessive hyperventilation should be avoided because it may induce vasoconstriction, decreasing cerebral flow and worsening cerebral ischemia.
• Aggressive control of seizure activity because cerebral oxygen consumption and blood flow are increased during a seizure. Phenytoin is the preferred anticonvulsant since it does not mask the neurologic examination.
• Elevation of the head of the bed if there is no suspicion of cervical spine injury.
• Pharmacologic paralysis should be avoided, unless required to treat respiratory failure, as neuromuscular blocking agents can mask neurologic signs.
• Maintenance of euglycemia -- both hypoglycemia and hyperglycemia may be harmful to the brain.
• Maintenance of euthermia -- the deleterious effects of hypothermia have been outlined above, while hyperthermia increases cerebral metabolic demands and lowers seizure threshold

Respiratory:
Severe pulmonary dysfunction often progresses to ARDS. There have been a few articles and case reports regarding the use of surfactant therapy for the drowning victim. The rationale was that there was depletion of the endogenous surfactant by the aspirated water causing reduced compliance, atelectasis and ARDS. However, recent clinical and animal studies have not demonstrated improved pulmonary function with surfactant therapy.
There is little evidence to support the use of corticosteroids or prophylactic antibiotics in drowning victims. Antibiotics should be used only in cases of obvious pulmonary infection or if the victim was submerged in grossly contaminated water.

Cardiovascular:
Cold water victims can have significant hypovolemia due to a brisk diuresis. This occurs because, during the early phase of vasoconstriction, blood moves to the core, causing central volume receptors to sense fluid overload, resulting in decreased antidiuretic hormone (ADH) production.

Outcomes

A review of the literature suggests that about 75% of drowning victims will survive. Of these, about 6% will be left with a residual neurological deficit. With improving respiratory salvage, the percentage of patients with residual neurological defect continues to increase, creating a pragmatic and moral issue as to when to cease or continue resuscitative efforts, especially in the emergency room. Because of inconclusive data on predictor variables of drowning victims, the ultimate decision to treat or not to treat the critical drowning victim with a poor prognosis rests with the physician in attendance.

References

1. Chandy, D, Weinhouse, GL. Drowning (submersion injuries). UpToDate. Nov 11, 2013
2. Golden, FC, Tipton, MJ, Scott, RC. Immersion, drowning and drowning. Br J Anaesth 1997; 79:214-25.
3. DeNicola, LK, Falk, JL, Swanson, ME, et al. Submersion injuries in children and adults. Crit Care Clin 1997; 13:477-502.
4. Papa L, Hoelle R, Idris A. Systematic review of definitions for drowning incidents. Resuscitation 2005; 65:255.
5. Salomez F, Vincent JL. Drowning: a review of epidemiology, pathophysiology, treatment and prevention. Resuscitation 2004; 63:261.