A New Definition

Sound epidemiologic data on drowning are lacking. Data collection for such purposes has been hampered by the absence of a uniform and internationally accepted definition. A lack of consensus is present with respect to definitions and terminology used by different water safety and health organizations, experts in the field, papers in the scientific medical literature, and laypersons.⁸ Within the framework of the first World Congress on Drowning (WCOD), a definition was developed to provide a common basis for future epidemiologic studies in all parts of the world. The following definition was adopted in June 2002: “Drowning is the process of experiencing respiratory impairment from submersion or immersion in liquid.”

The drowning process is a continuum beginning when the patient’s airway is below the surface of the liquid, usually water, which—if this process continues—may or may not lead to death. A patient can be rescued at any time during the process and be given appropriate resuscitative measures, in which case the process is interrupted. Furthermore, any submersion or immersion incident without evidence of liquid aspiration should be considered a water rescue (i.e., events where no respiratory impairment is evident, whether with or without other injury or hypothermia). The term near-drowning was abandoned. Confusing terms like dry drowning and secondary drowning (delayed onset of respiratory distress) are now eliminated.⁹

Pathophysiology

Despite pathophysiologic differences between drowning in fresh or salt water in experimental models, from a clinical and therapeutic view, there are no important differences in humans. The most significant pathophysiologic alteration in drowning relates to hypoxia.¹⁰ When there is no way to keep the airways out of water, breath holding is the first automatic response when there is no hypoxia and consciousness is still preserved. Water in the mouth is spit out or swallowed actively. When the first involuntary aspiration of water occurs, it produces coughing or rarely laryngospasm (less than 2%), leading to hypoxia. If laryngospasm occurs, hypoxia will lead to its rapid termination. More water is gradually aspirated into the lungs, leading to further hypoxia, loss of consciousness, irreversible apnea, and then asystole.

The respiratory disturbances depend less on the composition of the water and more on the amount of water aspirated. The aspiration of either fresh or salt water produces surfactant destruction, alveolitis, and a noncardiogenic pulmonary edema resulting in increased intrapulmonary shunt and hypoxia.¹¹ In animal research, the aspiration of 2.2 mL of water per kilogram of body weight decreases the arterial oxygen pressure (PaO₂) to approximately 60 mm Hg within 3 minutes.¹² In humans, it seems that as little as 1 to 3 mL/kg of water aspiration produces profound alterations in pulmonary gas exchange and decreases pulmonary compliance by 10% to 40%.¹¹ Humans rarely aspirate sufficient amounts of water to provoke significant electrolyte disturbances, and victims need no initial electrolyte correction.¹³

Ventricular fibrillation in humans, when it occurs, is related to hypoxia and acidosis, not to hemolysis and hyperkalemia. Hypoxia produces a well-established sequence of cardiac deterioration, with tachycardia, then bradycardia, then a pulseless phase of ineffective cardiac contractions (PEA phase) followed by complete loss of cardiac rhythm and electrical activity (asystole). Decreased cardiac output, arterial hypotension, increased pulmonary arterial pressure, and pulmonary vascular resistance are the results of hypoxia.¹¹ Intense peripheral vasoconstriction can also be caused by hypoxia, catecholamine release, and hypothermia.

A drowning victim can be rescued at any time during the process and may not require any intervention at all or may receive appropriate resuscitative measures, in which case the drowning process is interrupted. The victim may recover from the initial resuscitation efforts with or without subsequent therapy aimed at eliminating hypoxia, hypercarbia, and acidosis. In drowning, apnea is one of the first events, and if the victim is not ventilated soon enough, circulatory arrest will ensue and, in the absence of effective resuscitative efforts, death will result. It should be noted that the heart and brain are the two organs at greatest risk for permanent damage from relatively brief periods of hypoxia. The development of posthypoxic encephalopathy with or without cerebral edema is the most common cause of death and morbidity in hospitalized drowning victims.

Chain of Survival, Prevention to Hospital

In 2007, the United States Lifesaving Association reported 74,463 rescues on the shores of U.S. beaches, with estimates of 683 cases of rescues for each reported death (www.usla.org/Statistics/public.asp). On Rio de Janeiro beaches, approximately 290 rescues for each reported death (0.34%) occurred, and there was one death for each 10 victims admitted for medical care in the Drowning Resuscitation Center (DRC). In the past 31 years of work, the Rescue Service of Rio de Janeiro made approximately 166,000 rescues by lifeguards on the beaches, and 8500 victims needed medical attention in the DRC.¹⁴ For drowning, rescue is an essential component to keep the patient alive, and the initial evaluation is made in a hostile environment (water). Therefore, it is essential for physicians to be aware of the drowning chain of survival,¹⁵ from prehospital care to hospital admission (Figure 71-1).¹⁵

Figure 71-1 Drowning chain of survival.

(Adapted from Szpilman D, Morizot-Leite L, Vries W, et al. First aid courses for the aquatic environment. In: Bierens J, ed. Handbook on Drowning: Prevention, Rescue, and Treatment. Berlin: Springer-Verlag, 2006:342-7.)

Recognition of the Incident

Initiation of help to a drowning victim must be preceded by a recognition that someone is drowning. Contrary to popular opinion, the victim (especially males) does not wave or call for help.¹⁶ The victim is typically in an upright posture, with arms extended laterally, thrashing and slapping the water. Individuals close by may not recognize that the victim is struggling and may assume that the victim is playing and splashing in the water. The victim may submerge and resurface several times during this phase. Children can struggle for only 10 to 20 seconds before final submersion, and adults may be able to struggle for up to 60 seconds.¹⁶ Because breathing instinctively takes precedence, the drowning victim is usually unable to cry for help.

In-Water Basic Life Support and Rescue

For nonlifeguards, an attempt to help without becoming a second victim is the priority. If possible, potential rescuers can use techniques like “throw before you go and reach (with long objects) before you assist” or can advise the victim on how to get out of this situation (e.g., choosing a better way to escape, swim, float, reassuring the victim that assistance is coming). The decision when to do basic water life support (BWLS)¹⁵ is based on the victim’s consciousness level. If conscious, rescue to land without any further medical care is the protocol.¹⁷ The panicked and struggling victim can be dangerous to a would-be rescuer. A victim attempting to cling to life and breathe can drown a potential rescuer. For this reason, it is always best to approach a struggling victim with an intermediary object. Lifeguards use rescue or torpedo buoys for this purpose that also can double as a thorax and face flotation device to keep the head out of the water and the airways free.¹⁶

For an unconscious victim, the most important step is the immediate institution of resuscitative measures. Hypoxia caused by submersion results first in cessation of breathing, leading to cardiac arrest within a variable but short time interval if not corrected. In-water resuscitation (ventilation only) provides the victim a 3.15 times better chance of survival without sequelae. Rescuers should check ventilation and, whenever possible and if indicated, attempt to provide mouth-to-mouth resuscitation while still in the water. Unfortunately, external cardiac compressions cannot be performed effectively in the water, so assessment for pulse and compression must be delayed until the victim is out of the water.¹⁷ Very few studies have examined how often in-water cervical spine injury (CSI) occurs. In one study concerning sand beaches, 46,060 water rescues were retrospectively evaluated; this study found that the incidence of CSI in this setting was very low (0.009%).¹⁸ In another retrospective survey of more than 2400 drownings, only 11 (<0.5%) had CSI, and all of these had a history of obvious trauma from diving, falling from height, or a motor vehicle accident.¹⁹ Other water locations may have different rates of CSI depending on a wide variety of elements. Furthermore, any time spent on immobilizing the cervical spine in unconscious victims with no signs of trauma could lead to cardiopulmonary deterioration and even death.

Considering the low incidence of CSI and the high risk of wasted time in ventilation when needed, routine cervical spine immobilization of water rescues without reference to whether a traumatic injury was sustained is not recommended.^18,19 Rescuers who suspect a spinal cord injury should float the victim supine in a horizontal position, allowing the airways to be out of the water, and check to see if there is spontaneous breathing. If the victim is not breathing, protocols should be started for in-water resuscitation (mouth-to-mouth) while maintaining the head in a neutral position as much as possible. The rescuer should then use a jaw thrust without head tilt or chin lift to open the airway, without risking him- or herself or the victim. If there is spontaneous breathing, the rescuer’s hands should be used to stabilize the victim’s neck in a neutral position. If possible, a back-support device should be applied before moving the individual from the water. The victim should be rescued to a dry place, maintaining the neck in a neutral position as much as possible. The head, neck, chest, and body should be kept in alignment if the victim must be moved or turned.¹⁰

On-Land Basic Drowning Life Support

Removal of the victim from the water should be performed according to their level of consciousness, but preferably a vertical position should be adopted to avoid vomiting and further complications to the airways.²⁰ If the victim is exhausted, confused, or unconscious, transport should be in as near a horizontal position as possible but with the head still maintained above body level²⁰