In a review by Papa (2005 Resuscitation) over 20 different definitions for drowning were found. In 2002 scientists attending the first World Congress on Drowning sought to develop a universal definition for drowning episodes. They used the “Utstein Style” which had been earlier coined by a group who met at Utstein Abbey in Norway to develop similar standards on resuscitation. In 2003, the International Liaison Committee on Resuscitation published their results (Idris, et al. Resuscitation 2003) with the following key definition: “Drowning is a process resulting in primary respiratory impairment from submersion/immersion in liquid medium.”
Importantly, this definition no longer implies that drowning is synonymous with death. Drowning outcomes are now classified as death (immediately or after initial resuscitation), morbidity, and no morbidity. The group also developed a “core” data set that included valid information to be used in all future research (see table). Of note, although “submersion time” is considered a major factor associated with outcome, it is classified as “supplemental” Utstein data because it is often unknown or inaccurate.
What is the sequence of events that leads to a drowning death?
A victim’s mouth and nose becomes immersed in a liquid which blocks gas exchange. They hold their breath but eventually involuntarily gasp. Liquid rushes into their mouths and irritates the back of their throat causing laryngeal spasm leading to hypercarbia, hypoxia and acidosis. They also may swallow large amounts of water.
In most cases the laryngeal muscles will eventually relax but now they literally “breath” the liquid medium in which they are immersed along with possible aspirate from their stomach. This leads to further hypoxia by destruction of surfactant and massive pulmonary shunting. If they are not promptly resuscitated they will soon die of hypoxia or secondary cardiac arrhythmias from diffuse acidosis. If they do survive their functional outcome is usually related to the degree of brain hypoxia, but they can also suffer from secondary lung injury, renal failure or disseminated intravascular coagulation.
Where do people drown?
This is quite age dependent. In infants most drowning deaths occur in bathtubs, often due to neglect or poor parenting skills. Buckets and toilets can also be hazards as children are top heavy and once immerged may not be able to extricate themselves. Toddlers mostly drown in swimming pools which disturbingly about half the time belong to their own family. These deaths often occur after a seemingly minimal supervisory lapse. Adolescents are more likely to drown in rivers, lakes and canals while engaged in risky behavior and using alcohol or drugs.
Recommended treatment
Treatment is aimed at correcting hypoxia and acidosis. Rescue breathing should begin as soon as possible, even during the water rescue if feasible, with standard CPR beginning immediately after extrication. Although there should always be a suspicion of trauma, a reassuring paper by Watson (J Trauma 2001) found that cervical spine injuries were rare in drowning episodes unless the patient had obvious physical findings or there was a suggested mechanism such as fall/dive or motor vehicle crash. This becomes important in that proper immobilization may potentially delay definitive and lifesaving airway management.
The vast majority of patients who do well will respond to routine pre hospital interventions prior to ER arrival.
Once in the ER, asymptomatic patients with normal physical exams, normal oxygen saturations and no suspicion of child abuse may be discharged after an observation period of 6-8 hours. Patients with any pulmonary findings should be placed on oxygen, and undergo an X-ray, arterial blood gas and routine admission labs (at a minimal CBC, electrolytes and glucose.) They will need to be admitted to monitor for secondary pulmonary insult. These patients may benefit from a beta-agonist treatment and may require intravenous fluids to maintain an adequate blood pressure especially if they are hypothermic.
In awake, moderately-ill patients, continuous positive airway pressure (CPAP) is appropriate if their PaO2 is less than 80 (child) or 60 (adult). Comatose patients or those in severe distress require intubation with positive end expiratory pressure support. Extracorporeal membrane oxygenation may ultimately be beneficial in the small group of patients that appear to be neurologically intact with severe respiratory distress that doesn’t improve with mechanical ventilation. There is no role for prophylactic antibiotics.
Hypothermic patients need to be rewarmed until their core body temperature reaches 30 degrees or there serum potassium is greater than 10. Extracorporeal blood rewarming should be strongly considered in coding hypothermic patients found in cold water less than 10 degrees Celsius. Finally, any precipitating factors such as seizure, trauma, mental status change, or arrhythmia need to be addressed.
Although inducing hypothermia in comatose adults surviving a ventricular fibrillation arrest has produced encouraging neurological results it is unclear how to extrapolate this data to drowning victims. A new NEJM study (Hutchinson 2008) suggests that induced hypothermia did not help children with traumatic brain injuries.
Current prevention strategies
The vast majority of drowning deaths are preventable. A 4-5 foot, self-locking, non-climbable fence which fully surrounds the pool decreases drowning risk by 50-80%. Parent education about supervised bathing/swimming and proper storing of large buckets is also important. As most deaths occur close to safety, teaching children water safety rules and how to swim is encouraged with the obvious caveat that a small child’s ability to swim is no substitute for active adult supervision.
In older populations prevention is geared towards encouraging all pool and boat owners to learn CPR and enforcement of laws which prohibit excessive alcohol use by motor vehicle operators.
Fatal unintentional drownings in the United States
-Numbered 3,582 in 2005
-More than 25% are less than 14 years of age
-2nd leading cause of death in age group 1-14
Highest risk of drowning
-Ages 1 to 4 and 15 to 24
-Black males greater than white males (ages 10 to 19)
-Fatalities across all ages are 1.3 times greater in blacks and 1.8 times greater in American Indians and Alaskan natives compared to whites Miscellaneous facts
-Up to 50% of pool owners do not know CPR
-Proper fencing can reduce pool drowning deaths by 50-80%
-Most deaths occur within 10 yards of safety
-10% of surviving patients will have devastating neurological outcome
FACT- Although vomiting is common during drowning resuscitation, there is no proven role for the Heimlich maneuver.
Myth- Significant electrolyte disorders result after a drowning.
FACT- Unless the drowning occurred in the Dead Sea it is extremely unlikely that there will be an important electrolyte disorder. Most drowning victims aspirate less than 200 ml which is not enough to disrupt electrolytes.
Myth- Determining cause of death is straight forward in submersion cases.
FACT- In cases where a submersed body is simply found, confidently identifying a cause of death can be difficult. It has even been proposed that so called “dry drownings” which have been historically viewed as drownings secondary to severe laryngeal spasm without significant water aspiration may represent death from another cause.
Hypothermia
The Good-
-Hypothermia decreases cellular metabolism and may limit secondary reperfusion injuries after resuscitation
-There are cases of functioning survivors after prolonged submersion in icy cold water including a toddler who was submerged for 66 minutes.
-Theories of how neuroprotective hypothermia may occur before irreversible hypoxia include
(1) The diving reflex which induces bradycardia, apnea and peripheral vasoconstriction and (2) A combination of external skin exposure, icy water aspiration and ingestion enabling a rapid core temperature drop
-Water has thermal conductivity of 25-30 times that of air
-Children are at greater risk due to their larger surface area
-Hypothermia leads to muscle fatigue and poor judgment decreasing the ability to self rescue.
-Immersion into cold water causes catecholamine release, tachycardia and hyperventilation. This can trigger an arrhythmia and lead to sudden death (immersion syndrome.)
-Most hypothermic drowning patients are cold from prolonged submersion and are simply dead.
{mospagebreak Title=Utstein Style for Drowning}
(core data)
Victim Information
>Victim identifier
>Gender
>Age
>Date and time of day of incident
Precipitating event (known/unknown)
Scene Information
>Witnessed (submersion is observed): yes/no
>Body of water: bathtub, swimming pool, ocean, lake, river, or other
>Unconscious when removed from water: yes/no
>Resuscitation before EMS arrived: yes/no
>EMS called: yes/no
>Initial vital signs (spontaneous breathing, palpable pulse)
>Time of first EMS resuscitation attempt
>Neurological Status: awake, blunted, comatose, or other neurological assessment
Emergency department evaluation and treatment
>Vital signs: temperature, HR, respiratory rate, blood pressure
Oxygen hemoglobin saturation
Arterial blood gas analysis, if unconscious or SaO2<95% on room air
>Initial neurological status (GCS, AVPU, or ABC)
>Airway & ventilation requirements
Hospital Course
>Airway & ventilation requirements
Disposition
>Alive or dead; if dead, report date, place, and time of death
>Date of hospital discharge
>Neurological outcome at hospital discharge
Adapted from Idris, et al. Resuscitation (59) 2003