EPIDEMIOLOGY AND DEFINITIONS
Although substantial efforts have been taken by health care advocates and public health providers to develop appropriate prevention strategies, drowning remains a significant cause of morbidity and mortality in not only the United States, but also worldwide. The global statistics vary widely on the annual number of deaths from submersion injuries, but depending on sources cited, annual death rates range from 150,000 to 500,000 deaths per year.1,2,3–5 For each death that occurs, there are two to four other related water-related injuries that require hospitalization.6
In the United States, drowning is the second leading cause of death in children only surpassed by deaths from motor vehicle accidents.2 Of those who survive the drowning episode, one-third will suffer from significant morbidity due to irreversible anoxic brain injuries.7 The populations most at risk for submersion injuries are infants and toddlers aged 1 to 4 years. Children in this age bracket account for approximately 27% of all deaths due to submersion.1 Of those patients, males are more apt to suffer from drowning injuries when compared to their female counterparts.7
Most submersion injuries occur in freshwater, even in states with large areas of coastal access. The sites of drowning also vary with age. In the young infant population (<1 year), 55% of drownings occur in the bathtub.1 In older children, up to 50% occur in local swimming pools, followed by freshwater bodies of water (lakes, rivers, and streams).1,2,6,7 It is important to note in older children and adults that greater than 50% of submersion injuries are associated with the concurrent use of alcohol and drugs.1,6,7
For many years, the specific definitions of the types of submersion injuries have been blurred. In 2002, the First World Congress on Drowning met in Amsterdam to delineate definitions based on the mechanism of injury and subsequent physiologic sequelae.2 At the meeting, members defined drowning as the process of experiencing respiratory impairment from submersion or immersion. Patients who have had a mechanical obstruction due to a liquid medium regardless of outcome are said to have been involved in a drowning incident.
Since 2002, the definition of near drowning is slowly being phased out of use by medical professionals due to fact that it is imprecise and has a high level of interpretation by providers. However, it is worth defining due to fact that it is still common verbiage. Near drowning is defined as surviving, at least initially, after being submerged in a liquid medium. Since the decision in 2002 for a standard definition, further delineations have become increasingly irrelevant and for the sake of simplicity have not been included in the text.
As defined by the World Congress on Drowning in 20022:
Drowning is a process resulting in primary respiratory impairment from submersion/immersion in a liquid medium. Implicit in this definition is that a liquid/air interface is present at the entrance of the victim's airway, preventing the victim from breathing air. The victim may live or die after this process, but whatever the outcome, he or she has been involved in a drowning incident.
The process and subsequent continuum of drowning begins the moment the airway is obstructed by the noted liquid medium. Initially, victims are able to hold their breath briefly. This short period is immediately followed by laryngospasm due to the presence of liquid in the posterior oropharynx. This choking response represents the first anoxic insult that the patient experiences in the drowning process. If uncorrected, the patient will become even more hypoxic and hypercarbic due to the fact that gas exchange is inhibited. Depending on multiple physiologic factors and the mechanism of injury, 90% to 98% of cases, the laryngospasm will resolve resulting both swallowing and aspirating the liquid into the pulmonary tissues.2
In earlier literature, providers would describe those patients who had aspirated water, detritus, and vomitus to have suffered a “wet drowning.” Those who had limited abnormal findings on examination or autopsy were to have suffered from a “dry drowning” due to persistent laryngospasm. However, given the fact that the amount of water that can be found in drowning victim's pulmonary tissues can vary widely with no definable pattern, the differentiation between dry and wet drownings has also been discarded. The reason for this is due to the fact that most victims have a degree of fluid in the pulmonary tissues if the mechanism of death is associated with a submersion injury. It is important to note, however, that if the victim has no fluid in the lungs or respiratory tissues, the cause of death is not due to drowning. Fluid will not infiltrate the lungs or associated tissues without active respiratory effort.2,6
The initial hypoxemia that the victim suffers secondary to the apnea of submersion is then exacerbated by a variety of factors including surfactant washout, pulmonary hypertension, and intrapulmonary shunting. As fluid is aspirated, profound alterations in arterial oxygenation occur. Left uncorrected, alveolar collapse, atelectasis, or mechanical obstruction leads to acute lung injury and acute respiratory distress syndrome (ARDS) or noncardiogenic pulmonary edema.
The debate concerning whether respiratory collapse is exacerbated depending on the fluid in which the patient is submerged, salt versus fresh water, continues. Multiple studies have been completed examining the effects of hyper- and hypotonic fluids on blood volume and electrolyte abnormalities in this population, and it has been found that only a small population of less than 15% of individuals has documented physiologic electrolyte changes from the aspiration of the surrounding liquid medium.2 The end result, however, is the same. Whether it is due to mechanical obstruction, dilution of surfactant, loss of osmotic gradient, a ventilation and perfusion mismatch occurs, leading to profound hypoxemia.
Dysrhythmias and complete cardiovascular collapse can occur at the time of the initial hypoxic insult or several minutes after the noted laryngospasm has abated. If the victim is rescued prior to a prolonged period of submersion, the hypoxemia, acidosis, and subsequent electrolyte abnormalities will resolve with basic resuscitation. It is uncommon for drowning patients to suffer a primary ventricular fibrillation or ventricular tachycardic arrest giving the mechanism of injury. However, isolated events have been described anecdotally in lab models or in those patients who aspirate large volumes of fluid.
In the first several minutes of a drowning injury, cerebral ischemia occurs due to the cardiovascular compromise that occurs with submersion. The degree of injury to the brain and the remainder of the nervous system are dependent on the duration and severity of the initial hypoxic-ischemic injury. If the patient is extracted from the liquid medium and resuscitated appropriately, secondary ischemic injuries, including cerebral edema, can occur further exacerbating the initial insult. More than 10% of drowning survivors suffer permanent effects.1,6
Recovery of victims of drowning events vary widely based on duration of submersion injures, associated trauma, other medical conditions, and surrounding environmental factors. In young healthy patients, periods of submersion between 2 and 5 minutes are moderately well tolerated. However, submersions for greater than 25 minutes for all patients are associated with high morbidity and mortality rates.6,7 Many drowning patients present with associated hypothermia due to the immersion in the surrounding environment. Hypothermia as a whole can be indicative of prolonged duration in the water and is associated generally with a much poorer prognosis. In some cases, the cold temperature can limit end-organ perfusion and is associated with some anecdotal cases of prolonged submersion with little to no long-term deficits.6 Given the variability of factors, overall prognosis in victims of drowning incidents is difficult to predict.7
In patients who still have physiologic signs of spontaneous circulation at the time of rescue, the prognosis of recovery is variable. In those victims who are awake and oriented at the time of arrival in the emergency department, they typically survive without neurologic deficits if there is no respiratory compromise at the time of evaluation.1,6,7 Those patients who arrive with altered mental status, but responsive to pain (ie, a GCS of 6 or greater) also typically survive without neurologic sequelae greater than 90% of the time.6,7 However, those patients who arrived and were noted to be obtunded (with a GCS of 5 or less) tended to have poor outcomes.2,6,7 Between 10% and 23% of those patients were neurologically affected and of those impaired patients, 39% died soon after their arrival and 17% had irreversible and incapacitating brain injuries.2
Drowning emergencies can occur in a variety of environments. Proper initiation of prehospital care can heavily impact the overall morbidity and mortality in many cases. Bystander interventions, especially in children, are not uncommon. The role of the prehospital provider is to begin the initial resuscitation promptly to restore normal ventilation and circulation as quickly as possible. Concurrently, rescuers must not only begin basic cardiopulmonary resuscitative measures, but must also consider simultaneously the mechanism of injury and provide cervical spine precautions if applicable and prevent further heat loss if the patient is affected by the surrounding environment.
The initiation of the resuscitation will begin the assessment and establishment of an airway if indicated. If the patient is spontaneously breathing and there is no evidence of any traumatic injury, the patient should be placed in the left lateral decubitus position with supplemental oxygen. However, in most cases, the patient will be apneic and require clearing of the airway and subsequent positive pressure ventilation. As discussed previously, most patients will swallow large amounts of water during the drowning process, which can lead to significant gastric distention. Rescuers should be prepared for an abundance of vomiting and plan for immediate treatment to minimize further risk of an additional pneumonitis. In this early portion of the resuscitation, abdominal thrusts and the “Heimlich” maneuver are contraindicated. They have not shown to be beneficial and can precipitate further vomiting and are associated with additional complications.1,2,6 If the patient remains hypoxemic or continues to be obtunded, placement of a definitive airway (endotracheal intubation, Combitube, or King Airway) will prevent further aspiration and will continue to facilitate appropriate oxygenation and ventilation.
The resuscitation should continue with appropriate cardiac monitoring. As per advanced cardiac life support (ACLS) protocols, pulses should be routinely assessed, and if are not present, CPR should continue. Bystanders and prehospital providers have a variety of monitoring devices available. Automated external defibrillators are available at a variety of locations and have been used in many resuscitations successfully. Advanced Life Support EMS providers routinely use manual defibrillators and monitoring devices, thus demonstrating further benefits for activating a 9-1-1 response.
Once the patient arrives in an appropriate receiving facility, treatment is focused minimizing further hypoxia. If the patient remains obtunded, and a definitive airway has not been established, rapid sequence intubation is required. Patients who are able to protect their airway can be supported with supplemental oxygen or BiPAP. Positive pressure ventilation can aid in minimizing the respiratory effort of the patient until the respiratory status improves. FiO2 and PEEP should be titrated appropriately to maintain oxygen saturations of greater than 96%.
Additional sequelae following a drowning episode are common. Pulmonary edema and subsequent ARDS is a routine finding due to variety of factors including surfactant washout. These patients benefit from elevated PEEP or BiPAP levels to increase alveolar recruitment and ventilation. Diuretics have been used with some success, but it is important to assess the patient's fluid status prior to their routine administration. Lastly, the use of antibiotics is indicated when there is concern for immersion in grossly contaminated fluids. Their routine use is not indicated unless signs and symptoms occur. Other complications including traumatic injuries, hypothermia, and underlying comorbidities need to be addressed during each individual resuscitation. Overall outcomes are dependent on the quality and efficiency of the initial resuscitation and subsequent restoration of optimal oxygenation and ventilation.
When a water rescue team is activated for deployment, operations must be conducted in a safe and efficient manner. These specialty-trained teams undergo vigorous training and preparation to not only rescue victims, but also to conduct the deployments in a safe and efficient manner. Members adequately prepare for missions by not only perfecting skills as individual members by taking swiftwater rescue technician (SRT) courses and education on prehospital emergency care, but they will continuously train as a team to establish clear pathways and effective methods of recovery to minimize risk to the team and maximize the beneficial outcome.
During the course of rescue operations, standard operating procedures (SOPs) are typically defined prior to deployment to minimize adverse outcomes and mission failure. These protocols follow similar guidelines utilized in other rescue situations and are based on the Incident Command System (ICS). Once the mission is activated, staff must make rapid decisions during the course of the initial scene evaluation:
What is the nature of the call?
Is the activation for a rescue of living individual(s) or recovery of deceased victims?
What are the hazards?
Is there a need for additional resources beyond the scope of the first responders?
Once the initial scene assessment is completed, rescue operations can commence. Despite its simplicity, the standard Talk-Reach-Throw-Row-Go is still the standard in water rescue operations.8 Most scenarios requiring rescue personnel require the active intervention of providers, but all attempts should be made to minimize risk. There are clear examples when the standard operation procedures of water rescue cannot retrieve the victim without harming either the victim or placing the team at extreme risk. Helicopter utilization may be appropriate for patient extrication in these situations.
Once the patient is in a safe environment, trained personnel must complete rapid assessment for injuries and illnesses. In most cases, these patients are likely to have multiple complaints including traumatic injuries, hypothermia, and potentially, respiratory distress from inhalation of water. They will require aggressive management and transport to the nearest appropriate facility for evaluation and treatment.