Near Drowning

Source:Tintanilli


Near-Drowning: Introduction

Submersion injuries that result in death in less than 24 h are termed drowning. Near-drowning is defined as survival longer than 24 h after a submersion event. As with other causes of accidental death, submersion injuries typically involve otherwise healthy, young individuals.

Epidemiology

Over the last decade more than 50,000 people have died from drowning in the U.S., and over 100,000 die each year worldwide. In the U.S., drowning is the fourth leading cause of accidental death overall, and is the second leading cause of death in those under 15 years of age. In addition, there are an estimated over 500,000 submersion events per year in the U.S. The vast majority of victims survive submersion events with outcomes ranging from minimal or transient injury to profound neurologic insult.

There are three peaks in near-drowning incidence: the first in toddlers and young children, a second in adolescents and young adults, and a third in the elderly. In addition to pools and bodies of water, infants and toddlers can drown in toilets, buckets, and bathtubs. The elderly also have an increased risk of bathtub drowning. Even in coastal areas most submersion events take place in warm, freshwater bodies of water (especially swimming pools).

Additional injuries or disorders that either precipitate or are associated with submersion events include: 1) spinal cord injuries that occur after diving into shallow water or boating mishaps, 2) hypothermia, 3) panicking, 4) syncope (e.g., due to hyperventilation prior to underwater diving), 5) seizures, and 6) other premorbid conditions (e.g., heart disease).1,2




Prevention

Submersion episodes among children less than 1 year of age are best prevented by parental vigilance during bathing. Child abuse should be considered when the victim is less than 6 months of age, or in toddlers with atypical presentations.3 In preschool children, adult supervision in conjunction with properly installed and maintained four-sided pool fences that completely isolate the pool could prevent 50 to 90 percent of preschool-aged drownings.4,5

Teen and young adult drowning may be reduced by the control of alcohol and illicit drug consumption that have been implicated in 40 percent of all adult drownings and 75 percent of boating-related adult drownings.6 The use of personal flotation devices decreases boating-related drowning. Practical experience suggests that the ability to swim is protective against teen and adult drowning, but there is little evidence to support the efficacy of swimming instructions for preventing drowning in infants and young toddlers.7

Drowning locations in the elderly closely parallel locations of infant and toddler drowning. Adequate pool fencing and bathtub handrails are important preventive means for the elderly population and in those patients with premorbid conditions.




Pathophysiology

After submersion, the degree of pulmonary, and in particular central nervous system (CNS) insult determines the ultimate outcome. It is thought that there could be transient protection from parasympathetic activation of the diving reflex (i.e., bradycardia, apnea, peripheral vasoconstriction, and central shunting of blood flow) during submersion. However, the diving reflex may not provide significant protection in humans as was once thought. The diving reflex is strongest in young infants <6 months old, but the effects decrease with age.8 In adults, vertical immersion (head out) and vertical submersion (head under) activates both the sympathetic and parasympathetic systems, blunting any effect of the diving reflex.9 Physiologic stress associated with submersion undoubtedly also activates the sympathetic nervous system. Cerebral protection in cold-water submersions most likely results from rapid CNS cooling before significant cardiac dysrhythmia.

"Dry-drowning," which accounts for 10 to 20 percent of submersion injuries, occurs when there is laryngospasm, followed by hypoxia leading to loss of consciousness. More commonly, "wet drowning" occurs in which there is aspiration of water into the lungs. The effect is dilution and washout of the pulmonary surfactant with resultant diminished gas transfer across the alveoli, atelectasis, and ventilation-perfusion mismatch. In fresh-water aspiration, there is transient hemodilution, and if large enough volumes are aspirated, significant hemolysis is possible. Factors such as aspiration of contaminated foreign material, particulate matter, bacteria, vomitus, or chemical irritants can affect eventual pulmonary recovery.

Prediction of eventual outcome in near-drowning is possible using factors such as submersion time and physiologic scoring systems.10,11 However, the utility of this prediction is debatable; the vast majority of patients who arrive at the hospital with fair cardiovascular and neurologic function survive with minimal disability, and those that arrive with unstable cardiovascular function and coma do poorly because of the hypoxic, ischemic CNS insult. Predictors are not accurate or useful for the 15 to 20 percent of near-drowning victims whose arrival condition is between these two extremes.12

Other end organs can also be affected from resultant hypoxemia and metabolic acidosis. Electrolyte abnormalities are seldom significant and usually transient unless there is significant renal injury from hypoxic injury, hemoglobinuria, or myoglobinuria.12,13 Hematologic values are usually normal unless there has been massive hemolysis. Rarely, disseminated intravascular coagulation can be a complicating factor in near-drowning.




Treatment

Prehospital Care

Resuscitation of a submersion victim as quickly as possible optimizes outcome. This emphasizes the need to train laypersons in cardiopulmonary resuscitation (CPR), particularly swimming pool owners. After careful removal of the victim from the water (with cervical spine control/protection if there is an unknown mechanism of injury or suspicion of spinal injury), CPR should be initiated as quickly as possible.

High-flow oxygen therapy by facemask should be administered if the patient is breathing, or by positive-pressure bag-valve-mask if the patient is not breathing. For those patients who do not recover spontaneous respiratory effort, endotracheal (ET) intubation with positive-pressure ventilation should be considered, particularly if the patient remains unconscious, because of the risk of aspirating emesis.

All patients with submersion associated with amnesia for the event, loss or depressed consciousness, an observed period of apnea, or those who require a period of artificial ventilation should be transported for evaluation to an ED, even if they are asymptomatic at the scene. The patients should be warmed and monitored, and intravenous access considered (Table 198-1).

Table 198-1 Prehospital Care of Submersion Victims





Rapid, cautious rescue

Spinal precautions

Cardiopulmonary resuscitation

Supplemental oxygen (all patients)

Transport (all patients)






Emergency Department

Upon arrival at the ED, the treating physician should assess and secure the airway, provide oxygen, and assist ventilation as necessary. Warmed isotonic intravenous fluids should be administered and warming adjuncts (e.g., blankets, overhead warmers, warming devices) should be used. Any associated injuries should be addressed.

Patients who present to the ED with a Glasgow Coma Scale (GCS) score of 13 should be administered oxygen as necessary to keep their oxygen saturation (SaO2) >95 percent (Table 198-2). They should be observed for 4 to 6 h, and if the pulmonary examination and room-air SaO2 remain normal, they can be safely discharged home. Laboratory examination and radiographs are unnecessary, and are not predictive of discharge.14 If, after 4 to 6 h, the patient still requires oxygen, has an abnormal pulmonary examination (rales, rhonchi, wheeze, retractions, etc.), or deteriorates in the ED, reassessment and admission or transfer to a monitored bed is needed.

Table 198-2 Hospital Care of Submersion Victims*






Presentation GCS 13
Presentation GCS <13*

Cervical spine
Clear
Clear

Ancillary tests
Only as indicated (routine studies such as CXR are not predictive of outcome)
ABG


CBC, electrolytes, glucose, PT/PTT, UA, CK, urine myoglobin, urine drug screen


CXR


ECG

Respiratory support
Oxygen to keep SaO2 >95%

Oxygen to keep SaO2 >95%



Intubation and positive-pressure ventilation as needed (PEEP, CPAP)

Monitor
Oxygen saturation
Oxygen saturation


Acid-base status


Temperature


Volume status (urine output, central venous pressure, etc.)





*Evaluate and treat any associated injuries or other conditions (e.g., hypovolemia, hypothermia, hypoglycemia, myocardial ischemia, seizures, etc.).

Including those patients presenting with GCS 13 who have abnormal examinations and/or abnormal oxygen saturations after observation for 4–6 h.

Abbreviations: CBC = complete blood count; CK = creatine kinase; CPAP = continuous positive airway pressure; CXR = chest radiograph; ECG = electrocardiogram; GCS = Glasgow Coma Score; PEEP = positive end-expiratory pressure; PT = prothrombin time; PTT = partial thromboplastin time; SaO2= oxygen saturations (via pulse oximetry); UA = urinalysis.


Patients who present to the ED with GCS <13 should be maintained on supplemental oxygen and ventilatory support as needed. If high-flow oxygen (FIO2 40 to 60 percent) cannot maintain an adequate PaO2 (>60 mm Hg in adults, >80 mm Hg in children), then the patient should be intubated and receive positive-pressure ventilation. Chest radiography and laboratory studies should be done to evaluate for pulmonary aspiration and other complications (see Table 198-2). Infrequently, childhood victims of freshwater near-drowning develop dilutional hyponatremia and seizures. In these cases, seizures are generally easily controlled with correction of the electrolyte abnormality, and residual seizure disorder is uncommon. Continuous cardiac monitoring, pulse oximetry, and frequent reassessments should be performed on all patients.

If the patient presents to the ED in cardiopulmonary arrest or asystole after a warm-water submersion event, serious thought should be given to discontinuing resuscitation efforts, as recovery without profound neurologic handicaps is rare.15

Hospital

Hospital management of near-drowning victims is largely supportive.16 All near-drowning victims who require emergency department resuscitation should be admitted to an intensive care unit (ICU) for continuous cardiopulmonary and frequent neurological monitoring. Most victims of significant submersion injury benefit from mechanical ventilation. Supranormal levels of positive end-expiratory pressure (PEEP) may be used to recruit fluid-filled lung units and aid oxygenation. Most victims demonstrate rapid improvement in oxygenation in the first 24 h. Victims presenting with significant aspiration pattern or severe cardiovascular collapse are predisposed to develop acute respiratory distress syndrome (ARDS). Care should be taken to avoid lung overdistension and ventilator-associated lung trauma. Bacterial pneumonia is rare and prophylactic antibiotics are not indicated.

For victims who have been resuscitated from cardiac arrest, the hemodynamic response to exogenously administered epinephrine is frequently short lived, and most will require a continuous infusion of dopamine or epinephrine in the ED or ICU. Invasive (pulmonary artery catheter) or noninvasive (echocardiogram) measures of ventricular function are often instructive. Hemodynamic recovery, when it occurs, can be expected within 48 h. Victims demonstrating no hemodynamic recovery after 48 h may slowly improve over the first week, but are more likely to have long-term neurologic damage.12

Results of "brain resuscitation" following significant warm-water near-drowning have been disappointing.12,16 The degree of cerebral edema is largely determined by the duration of the anoxic or ischemic insult at the time of submersion. Efforts to control cerebral edema including the administration of mannitol, loop diuretics, hypertonic saline, fluid restriction, and mechanical hyperventilation have not shown benefit.16 Controlled hypothermia, barbiturate "coma," and intracranial pressure monitoring have not been shown to improve outcome in pediatric near-drowning victims.12

Family members should be counseled about likely outcome. Using initial presentation, resuscitation, laboratory data, and serial examinations, experienced practitioners should be able to provide accurate predictions of outcomes in most cases.17




Prognosis and Disposition

Uncomplicated

As noted above, submersion victims who are asymptomatic or mildly symptomatic can be observed for 4 to 6 h. If they continue to have a normal pulmonary examination and normal room air oxygen saturation, they can be safely discharged home. The concern for "secondary drowning" (respiratory deterioration after initial stable presentation) is unwarranted, because if deterioration is going to occur, it will do so within the 4- to 6-h observation period.14,18,19 No data is available for long-term outcomes for these patients, but it is unlikely that there are any measurable adverse effects. Parents and patients should be advised to have close follow-up and to be evaluated for any respiratory complaints or fever.

Complicated

Since submersion time is frequently unknown or only estimated, the extent of required resuscitation is often the most objective measure of the degree of anoxic or ischemic insult. Details of initial presentation and resuscitation are frequently strong prognostic indicators.

If the submersion victim does not require cardiopulmonary resuscitation at the scene or in the ED, complete recovery within 48 h is expected. A small fraction of these patients with significant aspiration may develop severe, even life-threatening ARDS.

Victims requiring bystander CPR at the scene have a guarded prognosis. For scene-resuscitated pediatric victims, about 20 percent later die in hospital and about 5 percent are left with severe hypoxic-ischemic encephalopathy.20 Those victims who demonstrate continuous neurologic and cardiovascular improvement after hospital admission will generally make a complete recovery. Frequently, neurologic and cardiovascular examinations are normal within 24 h of the submersion event. Victims who later die in hospital usually demonstrate deteriorating cardiovascular status. Victims who are left with severe hypoxic-ischemic encephalopathy typically have persistent abnormal cranial nerve dysfunction and coma.

Victims undergoing ED CPR have a poor prognosis. These victims have usually sustained a significant anoxic or ischemic insult to the brain and other vital organs. Complete neurologic recovery is rare, although there are anecdotal reports of neurologic recovery following ED CPR of pediatric warm-water near-drowning, possibly due to the poor descriptions of the term "CPR." In our experience of over 500 pediatric warm-water submersion victims, 75 patients required ED CPR (defined as intravenous or endotracheal epinephrine or atropine with chest compressions and artificial ventilation). Of these cases, 84 percent died in the hospital, and 16 percent survived with severe hypoxic-ischemic encephalopathy. Asystole, whether noted at the scene or in the emergency department, is a near-universal sign of poor prognosis in warm-water pediatric submersion injuries.

For the emergency physician, the question of whom and how vigorously to resuscitate remains unclear.20 Though rare, complete or near-complete neurologic recovery after asystole has been reported following icy-water submersion episodes in children and adults. Consequently, victims of icy-water submersion, if removed from the water quickly, might reasonably undergo prolonged resuscitation maneuvers until CNS and cardiopulmonary viability are clear. Asystolic victims of warm-water submersion injuries with short submersion and transport times and CPR en route might reasonably undergo a vigorous resuscitation attempt.21 CPR should be abandoned if no response is noted. Conversely, because of the poor prognosis for intact neurologic survival, emergency department resuscitation attempts might reasonably be withheld from asystolic victims of warm-water submersion with longer submersion and transport times.