Drowning patients can present with mild, moderate, or severe symptoms.21
The primary source of morbidity and mortality is anoxic brain injury, and the immediate treatment priority after rescue is providing oxygen to the brain.22,23
If the person survives the initial incident, then further morbidity and deterioration are determined by the amount of anoxic brain injury. Drowning is a brain problem with lung complications.
The drowning process begins when the mouth and nose fall below the water, or are immersed from the action of waves, sea spray, swiftwater, or other such means. During the initial struggle, there is breath holding. Very little, if any, water enters the lungs during the struggle, and the amount that does enter is typically less than 30 mL
The published medical literature and anecdotal experience show that time to unconsciousness and pulselessness in drowning patients is varied based on the person’s age, comorbidities, underlying physical conditioning, and physiologic state.24,25
In operating room studies of normal, healthy, adults, the time to unsafe apnea, with resultant loss of consciousness, is 1 minute, as compared to 8 minutes if they receive high flow oxygenation prior to induction of paralysis. From the same studies, an obese (127 kg) adult would only have 162 seconds of safe apnea after prolonged preoxygenation and a 10-kg child only 200 seconds.24,25
This time is expected to be significantly shortened in a drowning person who obviously did not receive preoxygenation. Thus, many drowning persons will lose consciousness within seconds or 1 to 2 minutes.
Before losing consciousness, there may or may not be additional aspiration of water. This was previously attributed to laryngospasm, which is much more rare than previously described and in reality occurs in only 3% to 5% of drowning patients.21
In the first few minutes after losing consciousness, the person will still have protective airway reflexes. As water enters the mouth, oropharynx, and upper airways, it may be spat out or reflexively swallowed, which prevents water from entering the lungs. Autopsy studies of known drowning patients show that only 1 to 2 mL
/kg body weight actually enters the lungs.26
It is thought that some of the water may also be absorbed across the alveolar membrane. Conversely, these same patients may have no water or several liters of water in the stomach.26
Drowning is not necessarily a problem of the lungs filling with water.27
While the person is underwater, the blood becomes progressively more hypoxemic and acidemic. The brain is the most sensitive organ to hypoxemia and may begin to suffer irreversible damage within minutes.21,26
Drowning is a brain problem with lung complications. Reversing the cerebral hypoxia is the primary goal of emergent treatment.
The small volumes of water that enter the lungs can still complicate efforts at initial oxygenation and ventilation. Regardless of salinity, the water damages pneumocytes resulting in atelectasis and impaired gas exchange at the alveolar level.21,26
The aspirated water also mixes with the pulmonary surfactant, causing atelectasis and creating potentially large volumes of non-cardiogenic pulmonary edema (foam). Pediatric patients, the elderly, and persons with medical comorbidities are the most sensitive to decompensation from an initially minor drowning incident. In the absence of an anoxic brain injury, the amount of water aspirated determines the severity of initial injury. For patients who survive the initial incident without cerebral hypoxia, long-term pulmonary morbidity has not been described in the literature, and the lungs tend to heal themselves over the next 24 to 48 hours.21,26,28
Table 16.1 Classification of Drowning Patients
Cough, no foam at mouth/nose
Thorough history—Release home with education
Small amount foam in mouth or nose, +Rales
Large amount foam, normal BP (radial pulse present)
Large amount foam, low BP (radial pulse absent)
ETT/NRB O2, IV Fluids—Hospital
ETT/NRB O2, IV Fluids—Hospital
ETT/NRB O2, IV Fluids, AED—Hospital Do not resuscitate if down >1 h
From Szpilman D. Near-drowning and drowning classification: a proposal to stratify mortality based on the analysis of 1,831 cases. Chest. 1997;112(3):660-665.
The largest case series to date on drowning patients describes the rescue and treatment of nearly 42,000 patients rescued by ocean lifeguards in Brazil.29
In the model proposed by this case series, drowning patients may present with mild, moderate, or severe symptoms (Table 16.1
The Minimally Symptomatic Grade: Grade 0 to 1
These patients may have been underwater for only a brief time, or have had their face intermittently immersed from waves, whitewater, sea spray, etc. Their symptoms are limited to a mild cough and no foam present at the mouth or nose. There is typically no aspirated water in the lower airways and they are able to clear the upper airways by coughing alone. Based on the largest case series to date, mortality is 0%.
The Moderately Symptomatic Grade: Grade 2 to 3
These patients will present with small or large amounts of foam from the mouth or nose. They may be conscious and coughing or, due to decreased oxygen delivery to the brain, their mental status may range from confused to combative to unconscious. Whether the patient is an adult struggling in whitewater or a child sinking silently to the bottom of a pond, they are releasing large amounts of epinephrine and endogenous catecholamines to keep the hypoxic heart beating. Upon rescue, they will likely be completely exhausted and seemingly unresponsive despite being conscious. Grade 2 and 3 drowning patients will often have reversible degrees of cerebral hypoxia and respond well to oxygenation and interruption of the drowning process. Mortality in this group is 0.5% to 5%.
These patients have previously been mislabeled as “dry,” “secondary,” “delayed,” “near,” or “parking lot” drownings. There is no accepted medical definition of these terms and all major accrediting bodies actively discourage their use. Because the
term “drowning” is often used to mean death, we often are at a loss for a way to describe the patients who are initially symptomatic and later survive. These cases are frequently described in the media as children or adolescents who “drown on dry land” or “drown in their sleep,” which can be frightening to medical professionals and the lay public. In reality, these patients show symptoms as soon as they come out of the water. There are no published case reports of a completely asymptomatic patient later developing symptoms. With a mortality of 0.5% to 5%, all symptomatic patients require evaluation in an ED
and are monitored for the development of symptoms over the next 4 to 8 hours. Disposition is discussed in detail below.
The Severely Symptomatic Patient: Grade 4 to 6
Progressive hypoxemia eventually leads to hypotension followed by respiratory and then cardiac arrest. There is often a large amount of foam in the mouth and nose, cold, clammy, cyanotic skin, and rapid heart rate. Grade 4 to 6 patients are unconscious and in need of immediate resuscitation to interrupt the drowning process. Mortality in this group ranges from 20% to 93%.