Ethanol use is the major risk factor in submersion accidents. Thirty percent to 70% of drownings are associated with alcohol consumption [5,6,7]. Alcohol use seems to be an issue in drowned men in particular [8]. Alcoholic beverages reduce the ability to deal with emergency situations by depressing coordination, increasing response time, and decreasing awareness of stimuli. Furthermore, alcohol consumption by a potential rescuer or by the adult responsible for supervising a child in the water can destroy that person’s ability to function effectively, often resulting in a double tragedy [7]. In addition, alcohol is
frequently a factor in drownings that result from automobile accidents [9].

Children die in water because adults do not supervise them well enough. The backyard pool and family bathtub are common sites of pediatric drowning [10,11,12,13,14]. Lack of appropriate precautions and supervision play a major role in most of these cases. Studies have shown lower rates of drowning in areas where swimming pools are required by law to be surrounded by a fence [15,16]. The fence must completely isolate the pool from unsupervised access by children to be effective. Appropriate sign posting in hazardous areas, effective educational programs on the dangers of water recreation, and the presence of lifeguards also minimize risk and improve survival [10,17,18].

Inattentive guardians also contribute to bathtub-related drownings. In one study, all bathtub-related submersions in children younger than 5 years occurred while the child was bathing unattended or with another young child [19]. The use of infant bath seats, while providing some sense of security to parents, may actually predispose to submersion accidents as the child may slip and become trapped by the seat, making it impossible to escape the water [20]. The practice of leaving infants to bathe in the custody of a toddler is inappropriate and should be discouraged [11,12]. Immersion in large industrial buckets used for home cleaning may also make up a substantial percentage of drownings of infants and toddlers [21].

Unfortunately, submersion injuries in children are sometimes inflicted intentionally. One study indicated that 29% of all nonfatal pediatric drownings in bathtubs were purposely caused to inflict harm on the child. Another 38% of all nonfatal pediatric drownings revealed evidence of severe neglect [22]. In general, these children are younger than average for submersion injuries, and many have signs of previous abuse on close examination.

Drowning is 15 to 19 times more common in people with epilepsy than in the general population [23]. In one study, a history of seizure disorder was found in 17 of the 293 cases of drowning that were reviewed [9]. This contrasts with the prevalence of seizures of 6 per 1,000 in the general population. Poor adherence to anticonvulsant regimens often plays a role. Many drownings of epileptic children occur in the bathtub [24]. Seizures that include a tonic component may be the most dangerous to victims. Tonic seizures include a forced exhalation component that increases body density and causes the victim to sink. When the tonic component relaxes, the negative intrathoracic pressure leads to an inhalation that will then be composed of water [25]. The intensity of supervision needed by epileptics in a water environment is frequently underestimated.

Of the 710 boating fatalities in the United States in 2006, 70% were due to drowning [2]. Both alcohol intake and failure to use personal flotation devices contributed to these deaths [9,26]. A blood alcohol level of 0.10 g per 100 mL is estimated to increase the risk of death associated with boating by a factor of 10 [6].

Water-related activities produce approximately 140,000 injuries annually. Diving, surfing, and water skiing account for 77% of the 700 spinal cord injuries produced annually by aquatic sports. Diving and sliding headfirst produce the most serious injuries as a result of striking the bottom or side of a shallow body of water [10]. Patients who experience these injuries are at subsequent risk of drowning. In addition, injuries associated with the use of personal watercraft contribute to drowning incidence [27].

Centrally acting drugs not only can cloud the sensorium, causing disorientation and inducing sleep, but also impair coordination and reduce the ability to swim. Existing data implicate both legal, therapeutic medications and illegal drugs [9,28].

Two mechanisms produce the major pathologic changes responsible for morbidity in drowning: anoxia and hypothermia.

The effects of aspiration of various water solutions on lung injury have been studied in animals [39,40]. Sterile water was found to be the most disruptive of pulmonary function. Normal and hypertonic saline solutions also cause significant increases in (PA-a)O₂ gradient and shunt fraction, with a decrease in the PaO₂ to FIO₂ ratio. Decreases in arterial oxygen saturation and dynamic compliance as well as increases in minute ventilation, mean pulmonary artery pressure, and shunt fraction are seen in sheep after bilateral aspiration of either fresh- or seawater [40].

On a microscopic level, freshwater and saline solutions may cause their adverse pulmonary effects by different mechanisms. Atelectasis due to increased surface tension, bronchoconstriction, and noncardiogenic pulmonary edema all play a role in the development of hypoxemia at different times after freshwater aspiration [40,41]. Freshwater acts in part by inactivating surfactant in the alveoli and in part by damaging type-II pneumocytes, thereby preventing the production of surfactant for up to 24 hours [42,43]. The combination of these effects may damage the alveolar capillaries and interstitium and lead to the acute respiratory distress syndrome (ARDS). Hypertonic seawater may draw additional fluid from the plasma into the alveoli, thereby causing pulmonary edema despite a decreased intravascular volume [39]. The fluid-filled alveoli are then unavailable for efficient gas transfer, and a ventilation–perfusion mismatch occurs. This fluid may also damage the type-II pneumocytes by hypoxic and osmotic effects [41]. Aspiration of gastric contents and particles in the water complicates both fresh- and saltwater drowning. In clinical practice, the difference in the situation caused by freshwater and saltwater aspirations is small. In both cases, pulmonary edema causes decreased respiratory system compliance and hypoxemia. Unless specific therapies are developed that target the different mechanisms, there is probably little advantage in emphasizing the described differences.

Several other mechanisms of lung injury may occur with nonfatal drowning. Bacterial pneumonia, barotrauma, mechanical damage from cardiopulmonary resuscitation (CPR), chemical pneumonitis, centrally mediated apnea, and oxygen toxicity can cause respiratory deterioration in the postresuscitation period [41]. These must be considered along with ARDS in cases of respiratory distress occurring 1 to 48 hours after the event.

The pathologic effects that most affect prognosis in drowning are related to the central nervous system (CNS). Cerebral injury is produced as a result of anoxia due to gas exchange impairment and subsequent cardiopulmonary arrest.

Anoxic damage begins 4 to 10 minutes after cessation of cerebral blood flow in most situations [44]. The actual time course and clinical significance of anoxia in a specific drowning victim is notoriously uncertain in cases of drowning because of the emotional condition of the witnesses and because the impact of hypothermia is difficult to judge [45].