71 Drowning
Drowning is usually related to a leisure situation that turned into a dramatic, life-threatening event. Parents, friends, relatives, babysitters, or guardians may feel not only profound loss and grief but also either guilt for failure to fulfill protection responsibilities or intense anger at others who did not provide adequate supervision or medical care. Nevertheless, drowning is a neglected public health problem.1 Each year, drowning is responsible for an estimated 500,000 deaths around the world. The exact number is unknown because many deaths go unreported.2
Age, gender, alcohol use, socioeconomic status (as measured by income and/or education), and lack of supervision are key risk factors for drowning. Considering all ages, males die five times more often from drowning than females. An estimated 40% to 45% of deaths occur during swimming.3 Young children, teenagers, and older adults are at highest risk of drowning.4 In the age group of 5 to 14 years, drowning is the leading cause of death worldwide among males and the fifth leading cause of death for females.4 The patterns of drowning are highly dependent on geographic factors. In the United States, drowning is the third most common cause of unintentional injury death for all ages and ranks second for people aged 5 to 44 years.5 Considering all deaths by drowning in United States (3443 in 2007), 53% occurred in swimming pools.3
Drowning is the second leading cause of death for children aged 1 to 14 years and third cause of injury death for all ages in Brazil. With a population of 190 million inhabitants in 2007, a total of 7009 deaths by drowning in 2007 (3.7 per 100,000 inhabitants) were reported.6 Ironically, 90% of all drowning deaths occur within 10 m of safety.2 On Rio de Janeiro beaches, precipitant causes are discernable in 13% of all cases, with the most frequent being alcohol (37%), seizures (18%), trauma (including boating accidents; 16.3%), cardiopulmonary diseases (14.1%), snorkeling and SCUBA diving (3.7%), diving resulting in head or spinal cord injuries, and others (e.g., homicide, suicide, syncope, cramps, immersion syndrome (11.6%). It is important to recognize a precipitant cause to drowning, as this may guide specific approaches to rescue and resuscitation. In Brazil, freshwater drowning occurs more commonly in rivers and lakes, contributing to half of deaths by drowning.7
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.
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.)
Prevention
Despite the emphasis on immediate treatment, the definitive therapy for drowning is prevention (Table 71-1). Prevention remains the most powerful therapeutic intervention and can be effective in more than 85% of drownings.
TABLE 71-1 Preventive Measures
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 (keep horizontal if prolonged immersion or a history of immersion in cold water). The airways must be kept open at all times. The first procedure in on-land basic drowning life support (BDLS) should be placing the victim in a position parallel to the waterline,20 as horizontal as possible, lying supine, far enough away from the water to avoid incoming waves. If conscious, reposition the victim supine with head up. If breathing, place in recovery position (lateral decubitus position).20 In a 10-year study in Australia, vomiting occurred in more than 65% of victims who needed rescue breathing and in 86% of those who required both rescue breathing and chest compressions.21 Even in victims who required no interventions after water rescue, vomiting occurred in 50% once they reached shore. The presence of vomitus in the airway can result in further aspiration and impairment of oxygenation by airway obstruction; it can also discourage rescuers from attempting mouth-to-mouth resuscitation.21 The abdominal thrust (Heimlich) maneuver should never be used as a means of expelling water from the lungs; it is ineffective and carries significant risks. During resuscitation, attempts at active drainage by placing the victim head down increases the risk of vomiting more than fivefold and leads to a small but significant increase in mortality (19%) when compared with keeping the victim in a horizontal position.20 If vomiting occurs, turn the victim’s mouth to the side, and remove the vomitus with a finger sweep, a cloth, or use of suction.
One of the most difficult medical decisions a lifeguard or an emergency medical technician (EMT) must make is how to treat a drowning victim appropriately. A cardiopulmonary or an isolated respiratory arrest occurs in approximately 0.5% of all rescues. The questions that arise are should the rescuer administer oxygen, call an ambulance, transport the person to a hospital, or observe for a time at the site? Even emergency physicians may be in doubt as to the most appropriate immediate support measures; drowning victims vary in the severity of injury. Based on these needs, a classification system was developed in Rio de Janeiro (Brazil) in 1972 and updated in 199722 to assist lifeguards, ambulance personnel, and physicians with treatment priorities. It was based on analysis of 41,279 rescues, of which 2304 (5.5%) needed medical attention. The system was revalidated in 2001 by a 10-year study with 46,080 rescues.23 This classification (see Algorithm 71-1)22 encompasses all support from the site of the accident to the hospital, recommends treatment, and shows the likelihood of death based on the severity of injury. Severity is easily assessed by an on-scene rescuer, EMT or physician using only clinical variables.22
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