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SUBMERSION INJURIES: DROWNING AND NEAR-DROWNING
Andrea R. Gravatt, M.D.
Objectives:
• Oceans with lovely beaches, waterfalls and deep swimming holes, romantic hot tubs, and swimming pools all favorite places for relaxation not usually thought of as death scenes.
Drowning is a major health problem in the world and accounts for significant morbidity and mortality. In the United States, it is estimated that between 5 to 6 persons per 100,000 die as a result of drowning and these figures may be inaccurate due to under-reporting. The Center for Disease Control reported 3,482 drowning deaths in the United States during the year 2000. That statistic did not include boating related accidents, which in the year 2002 for example, accounted for 701 additional deaths.
Ranking fourth in all causes of child death, drowning is second only to motor vehicle accidents as a cause of unintentional injury death in the United States. Variations in the number of warm weather months, and characteristics of terrain account for the difference in the number of child drowning deaths from state to state and country to country. A study of King County, Washington reported a submersion incidence rate of 5.5 with a mortality rate of 2.6 per 100,000 children. In Hawaii, on the other hand, submersion incidence was reported as high as 14 per 100,000 with a mortality rate of 3.1. Cuba, a country surrounded by water, reported the lowest overall drowning rate of any country at 2.9 per 100,000.
The economic cost of near drowning is one of the highest for any injury group. The financial cost to society is significant, as many drowning victims require prolonged hospitalizations and chronic care. One series reported that for every three deaths one brain-damaged child results from near drowning.
DEFINITIONS Many terms are used in the drowning literature. Drowning is defined as water submersion resulting in asphyxia and death within 24 hours. The term submersion injury has been introduced to replace the confusing term near drowning. The equivalent terms imply that survival occurred past 24 hours, after which the child may die or survive in a normal or impaired neurological state.
The terms wet drowning and dry drowning describe lung pathology with respect to aspiration of water.
Wet drowning refers to pulmonary edema developing after the victim aspirates water.
Dry drowning refers to the occurrence of laryngospasm, protecting the victim from aspirating water, thereby preventing pulmonary edema. The incidence of dry drowning occurs 10 to 15 percent of the time. The occurrence of pulmonary edema in this setting is presumably secondary to high negative intrathoracic pressures from attempts to inspire on a closed glottis.
Immersion syndrome is sudden death as a result of vagally induced ventricular fibrillation or cardiac arrest from cold-water contact and immediate onset of asphyxia, before preliminary cooling has occurred.
Immersion hypothermia occurs as the core temperature gradually falls through surface cooling. Delirium occurs at 34°C and unconsciousness at 30°C with subsequent drowning. Nevertheless, this may be compatible with complete recovery. Acute submersion hypothermia is defined as the rapid development of hypothermia during freshwater drowning due to core cooling from both aspiration and absorption of cold water.
Cold-Shock Response is the most common cause of drowning in cold water. This response affects both respiratory and cardiac systems. Upon immersion in cold water uncontrollable gasping occurs and lasts approximately one minute. Lack of understanding of this phenomenon may result in the gasping of water unless the head is kept above water level. The sudden cooling of the skin results in the increase peripheral vascular resistance of superficial blood vessels. The heart rate and cardiac output increases. The outpouring of catecholamines places one at risk for fatal arrthymias. Local cooling decreases nerve conduction. Muscle control becomes uncoordinated and inefficient, making any reasonable attempt to self-rescue almost impossible. Hyperventilation results in hypocapnia and metabolic alkalosis. The subsequent decrease in cerebral blood flow results in disorientation and eventually unconsciousness.
EPIDEMIOLOGYAge
A bimodal curve of age distribution characterizes drowning in children with preschool children and adolescents accounting for the peaks. In the adult population, another peak occurs in the elderly.
Young children are most vulnerable to drowning. This is due to their lack of awareness of danger, poor swimming techniques, and the size of their heads in relation to body size making them susceptible to falling into containers. Children under 1 year of age drown most frequently in bathtubs, toilets, and buckets. Children ages 1 to 4 drown most commonly in pools.
Teen drowning is due to risk taking behaviors and lack of supervision, compounded by drug and alcohol intake. The drowning scene in this age group is most commonly natural bodies of water such as lakes, natural pools, and rivers. Incidents often occur far from sites of medical intervention and may be in places where rescue is challenging. Boating related drowning deaths in one study involving adolescents are reported as 18% of drowning in this age group. One study demonstrated detectable blood alcohol in boating related teen fatalities to be 25%. Gender
Males in 2000 accounted for 79% of all US drowning. This is largely due to risk taking behaviors characteristic of the adolescent male group. Beyond the toddler age group, boys have a three times greater risked of drowning. Females in all age groups have a more constant and lower rate of drowning than boys. Ethnicity
In the 10 to 14 years old age group, drowning rates are highest among African Americans and the lowest in Whites. In the 15 to 19 age group drowning rates were number were highest among Native Americans. Swimming Ability
Although swimming programs for very young children have proliferated, there are no studies showing that they prevent drowning. Such programs may offer a false sense of security. For this reason, the American Academy of Pediatrics does not endorse swimming instruction for infants and toddlers.
Good swimmers are not immune to drowning. Even competitive swimmers and divers can drown as a result of hyperventilation prior to competition. Deliberate hypocapnia delays onset of the drive to breathe from rising carbon dioxide, which allows the development of hypoxia that results in unconsciousness and underwater breathing. Pre-Existing Disease
Underlying seizure disorder is implicated in bathtub submersions in children less than 5 years of age. Both children with therapeutic and sub therapeutic anticonvulsant drug levels are at risk for drowning. Child Abuse
Abuse or neglect accounted for 19% of bathtub submersion victims less than 5 years of age. Alcohol And Drug Use
As in adult drowning, alcohol is an important contributing factor in the adolescent age group.
Pathophysiology
While there are differences in the mechanisms of drowning between fresh and salt water, the common pathway for organ system failure and degree of morbidity or mortality is hypoxemia.
The sequence of events is typically an initial period of both panic and struggle with breath holding. Volumes of water are inhaled or swallowed. Once asphyxia occurs, the victim becomes unconscious and water passively enters the airways as airway reflexes become absent. Cardiopulmonary arrest follows. Different events may surround submersion following unconsciousness where struggling is not a hallmark. This is often the case in trauma-associated drowning.
Fluid in the lungs resulting in vagally mediated reflexes cause pulmonary vasoconstriction and pulmonary hypertension. Non-ventilated alveoli are perfused, and a right to left intrapulmonary shunt develops. As hypoxia ensues, irreversible brain damage may occur in as little as six minutes. Metabolic acidosis develops with subsequent organ system failure.
Electrolyte Abnormalities
In both salt and fresh water drowning, electrolytes are usually normal. In fresh water drowning hyperkalemia may occur as a result of red blood cell lysis. A unique situation occurs with drowning in the Dead Sea where there is an unusually large solute load. The mortality rate in one study on Dead Sea drowning was 50%. These specific deaths resulted from pulmonary complications as well as the arrhythmias induced by severe imbalances of sodium, calcium, and magnesium. Fresh Water Drowning
Aspiration of fresh water, a hypotonic solution, causes the disruption of surfactant (washout). This alters surface tension in the lungs, resulting in alveolar collapse and instability. Microatelectasis results in ventilation/perfusion (V/Q) mismatch. The capillary and alveolar membrane damage results in fluid leak and subsequent pulmonary edema. As little as 1 to 3 cc/kg of aspirated water have been associated with significant falls in PaO2. Fresh water aspirated into the lungs is rapidly taken up into the circulation; however, the volumes are seldom large enough to cause significant changes in electrolyte concentration and increases in central venous pressure (CVP) are transitory. Salt Water Drowning
Saltwater is hypertonic: 3 to 4 times greater osmolality than blood. This hypertonicity (approximately 3.5% sodium chloride) is irritating to the terminal bronchioles and produces an osmotic gradient resulting in intra alveolar fluid accumulation. The result is pulmonary edema and V/Q mismatch and shunt. Pulmonary edema is compounded by injured the alveolar-capillary membrane which is directly injured by the hypertonic saline.
Cohen, et al reported in an adult that fluid from the alveoli had a minimal protein concentration. The rapid clearance of edema fluid suggested minimal injury to the alveolar epithelial barrier thereby preserving its function of fluid reabsorbtion.
Hypermagnesemia has also been associated with salt-water aspiration and may contribute to hypotension, neuromuscular blockade, respiratory depression, and cardiac abnormalities.
Predictors Of Outcome
The poor neurological outcome of up to one fourth of near drowning victims has brought forth the question about the justification for prolonged and vigorous resuscitation in hospital settings. Investigators have sought features that predict which child victims of submersion injuries will have a normal outcome. Hospital assessment criteria have been developed to predict the outcomes of injured children. Others have indicated that these tools may miss potential survivors.
Biggart et al reported that the presence of apnea and pulselessness, in non-hypothermic victims at a medical facility is associated with high mortality and neurological morbidity. They advocated that the definitive assessment by the Glasgow Coma Score (GCS) be performed 6 to 12 hours after ICU admission in for hypothermic patients. Prolonged resuscitation and aggressive treatment of normothermic individuals who present with to the medical facility with absent vital signs only increases the number of survivors in a vegetative state. In their series, the only intact survivors with GCS of 3 at the time of admission were patients who were hypothermic.
Orlowski used five criteria: age, immersion time, resuscitation time, coma, and pH to predict a less than 5% chance of normal recovery. He found that in children less than 3 years of age, maximum submersion time over 5 minutes and resuscitative attempts not begun for 10 minutes after rescue, coma on admission to the hospital, and pH less than 7.10 was associated with a mortality rate of 89% if three or more factors matched those criteria. Dean and Kaufman reported a series of children with GCS of 6 or greater who survived intact. If the GCS was <5, there was 80% mortality or neurological sequelae.
Jacobson's classification reviewed prognostic factors and concluded that all patients exhibiting spontaneous respirations immediately following CPR survived with minimal or no residual impairment. Those that remained apneic after CPR had irreversible neurological complications.
Cerebral blood flow (determined by stable xenon CT) and blood glucose levels within 48 hours of admission were predictive of eventual death. Significantly higher blood glucose concentrations were found in those children who died (mean of 511 mg %) or had severe neurological sequelae (mean of 465 mg%) was found compared to those children who recovered (mean of 238 mg%). Cerebral blood flow was significantly lower in the patients who died when compared to intact and vegetative survivor. The uses of both measurements were able to prognosticate outcome to 79%.
Conn reported a method of classification recommending neurological assessment in the Emergency Dept within 1 to 2 hours after successful CPR. This classification system was clinically applicable to all types of drowning. Survival and outcome decreases with each class.
Survivors are classified as:
An awake, alert and fully conscious. GCS 15
B blunted, obtunded but arousable, with spontaneous respirations, purposeful movements. GCS 10-13
C comatose
C1. Decorticate flexion response to pain; Cheyne Stokes respirations. GCS 5 C2. Decerebrate extension response to pain; central hyperventilation. GCS 4 C3. Flaccid response to pain; apnea or cluster breathing. GCS 3 C4. Flaccid, apneic, no detectable circulation (deceased?). GCS <3
Christiansen, et al used published criteria to evaluate 274 near drowning patients. As high as 6.3% of the patients predicted to have poor outcome on admission actually survived intact. They concluded that individual outcomes can-not be reliably predicted in the Emergency Department, and aggressive resuscitation should continue for 48 hours. Withdrawing therapy from survivors who show no clinical improvement after such time was suggested.
SURVIVAL AFTER PROLONGED SUBMERSION
Tramatic recoveries after prolonged hypothermia have been well documented.
A 5 -year -old boy fell into a frozen lake and was submerged for 40 minutes. Upon arrival to the hospital his temperature was 24°C. He survived neurologically intact.
A 3-year old girl was admitted after near drowning with a core temperature of 18.4C. After rewarming on cardiopulmonary bypass and extracorporeal membrane oxygenation. (ECMO) She survived and was found to be without neurological deficits 20 months later.
A 7-year old boy fell into a culvert and was found 15 minutes later. His temperature was 27C. After an initial period of gross and fine motor deficits and psychometric delays, he ultimately was found to be above average in school performance.
Such cases drive heroic attempts in saving lives. Two theories have been proposed to account for these outcomes: hypothermia and the diving reflex.
Hypothermia has a protective benefit if it is coincident with the submersion event, whereas the use of hypothermia to reduce hypoxic swelling has not been found to improve neurologic outcome. Some speculate that the protective effect of cold water is enhanced by the absorption of the cold water into the circulation of a small child. There is subsequent cooling of the brain, together with decreasing metabolic demands and oxygen requirements. The relative greater surface area in children compared to adults may also help to contribute to the rapid cooling. Others postulate that enough water cannot possibly be absorbed to account for this difference.
The diving reflex consists of apnea, bradycardia, and vasoconstriction in all vascular beds except the heart and brain, triggered by facial immersion in cold water or by fear. This reflex, most noted in water animals such as seals, can be induced in some humans. In children, this reflex may be pronounced, and is offered as a contributing factor for some successful outcomes. Others discount its role. CLINICAL PRESENTATION
Children who have drowned present with a spectrum of findings that ranges from a totally normal, asymptomatic appearance to overt cardiac arrest. Pulmonary findings include a normal exam, cyanosis, wheezing, rales, or profound respiratory distress. Neurological findings may include an alert and oriented child or one who is combative, stuporous or comatose.
The presence of traumatic injuries, particularly head and neck trauma should be determined. Findings or circumstances consistent with child abuse, seizures or cardiac arrthymias should be ascertained.
MANAGEMENT On Scene
Although studies of the quality of outcome when a bystander initiates immediate CPR show inconsistent results, it is still recommended that early CPR be initiated.
Initial management focuses on assessment of the pulmonary, cardiovascular system (CPR) and the central nervous system (GCS). Consensus supports immediate CPR and removal of airway foreign bodies, administration of supplemental oxygen (100%). Continual positive airway pressure (CPAP) of 10 to 12 cm H2O or PEEP of at least 5 cm of H2O should be provided if available.
In cases of hypothermia, the patient should be warmed immediately. Others state that rewarming of deep hypothermia in the field is inappropriate. Heat loss through convection (remove from wind), conduction (place body on barrier surface) and evaporation (remove wet clothing) should be minimized. A low temperature may be overlooked if a low reading clinical thermometer inserted at least 10cm is not used. Hypotension may be a presenting feature after saltwater drowning. Persons who drown in salt water, unlike those drowning in freshwater, may be hypovolemic and require fluid administration.
Surrounding water pressure produces 32-66% increase in cardiac output when in an upright immersion position. Victims removed from the water suddenly loose the resistance to circulation and venous pooling combined with this lack of systemic resistance results in circulatory collapse. Keeping the patient prone and horizontal as the person is lifted from the water may prevent this hypotensive phenomenon.
Cervical spine injury may be present a precipitating factor in drowning. Attention to head and neck trauma with appropriate immobilization is essential. Furthermore, additional fractures or internal injuries should be looked for.
Mouth to mouth ventilation should be performed with the head in a neutral position. (jaw thrust) If foreign bodies are suspected, the Heimlich maneuver should be implemented. Reviews have suggested that the Heimlich maneuver be performed, while others state no evidence supports performance of the Heimlich maneuver to simply remove water from the airways. Once out of the water, chest compressions may begin if pulselessness is present. Defibrillation is ineffective if the myocardium is cold. In RoutePatient should be kept warm to at least 37°C, but hyperthermia from overzealous warming should be avoided. Patient shivering, although a good prognostic sign, will increase tissue oxygen demands. Adequate circulation and substrate intake (warm glucose drinks) is important. Pulmonary support with supplemental oxygen and PEEP should be provided. Blood pressure should be stabilized with restricted fluid administration (half maintenance rate) once the person is normotensive. Choosing a medical facility that has the ability to provide extracorporeal membrane oxygenation (ECMO) is ideal.
AT A MEDICAL FACILITY
Pulmonary Status
Reassessments of pulmonary, cardiovascular, and metabolic status are necessary as pulmonary deterioration may be delayed. Baseline chest radiograph regardless of clinical appearance should be obtained. (25) Oxygen (100%) should be administered to all drowning victims. Nasal CPAP has been successfully used in patients who are breathing spontaneously. Ventilation support should be provided for more severely impaired patients. Caution should be exercised in weaning individuals from respiratory support as 48 to 72 hours are required for surfactant to be resynthesized.
Pulmonary infections following near drowning are often difficult to diagnose. Aspirated lake, pond, or canal water is much more likely to be contaminated than swimming pool or hot tub water. Infections from Pseudomonas and Vibrio species are more likely from salt-water aspirations. Leptospirosis may be a cause of pneumonia as a result of water aspirated containing rat urine. Nevertheless, prophylactic antibiotics are not widely recommended. At one time, steroids were advocated in the treatment of drowning. Now, they are no longer recommended due to the associated with side effects which may complicate the clinical picture.
Central Nervous System
Sequencing of the effects of neurological insult has been speculated although studies are few. Hypoxemia and hypoperfusion result in cerebral anoxia and tissue acidosis that produces neuronal damage. The resultant loss of cell membrane integrity results in extra-cellular fluid leak and cerebral edema. This may produce elevated intracranial pressure (ICP) and possible herniation. ICP monitors have been advocated by some and found to not be helpful by others. Diuretics and mannitol have been recommended if clinically indicated, but no studies have documented that osmotic diuretics in improve the neurological outcome of drowning victims.
Fluid management should focus on preventing hyperglycemia. Glucose should be maintained in the 150 mg/dl range. In cases where CNS damage is evident, fluid restriction may be necessary. The development of inappropriate secretion of antidiuretic hormone with retention of free water is not uncommon. Seizures should be controlled.
Neutropenia and immune suppression are undesired complications of prolonged hypothermia, despite the protective effect of hypothermia for cerebral function during submersion. Infected material from the lungs colonized with aspergillus may be embolized to the brain resulting in abcess formation.
Cardiac
Acidosis, hypoxia, and hypothermia lead to the development of cardiac arrhythmias. Since cardiac disease is not the primary cause of these arrhythmias, they respond to correction of metabolic acidosis. Hypothermic ventricular fibrillation (VF) occurs spontaneously, presumably triggered by an ectopic beat or asynchrony in the repolarization process. Rarely does VF occur above 25°C. Blood pressure should be initially stabilized using crystalloid fluid boluses. Once normotension has been reached, fluid restriction (one- half maintenance rate) and diuretic therapy may be implemented to improve gas exchange. Hematologic
Acidosis, hypoperfusion, sepsis, and hemolysis with the release of tissue thromboplastin, and activation of the Hageman factor, may result in coagulation disorders. The treatments of the coagulopathies includes fresh frozen plasma, platelets and heparin drip, although the latter is controversial. Hemoglobin should be maintained above10 g/100ml.
Renal
Hemolysis and myoglobulinuria secondary to muscle trauma, hypoperfusion, acidosis, and hypoxia have all been implicated in the etiology of renal failure in drowning victims. Correction of renal perfusion with the use of mannitol has been recommended. Peritoneal dialysis should be considered for drowning victims in renal failure.
PREVENTION
Passive strategies appear to be the most successful in preventing drowning injuries. Perhaps the largest impact of passive strategies has been with swimming pools. Pools with fences, which have been shown to reduced the incidence of drowning by approximately 50%. Unfortunately, passive strategies tend to have little effect on the adolescents. Primary strategies that require thought and judgment have also usually not been effective in adolescents. Supervision
Inadequate supervision has an impact on the incidence of drowning. The quality and proximity of supervision are both significant factors. . The case fatality rate for victims supervised by adults was 30%, by lifeguards 42%, and by peers 71%. Young children should never be left alone, even momentarily, where there is standing water. Lifeguards
No studies document the effectiveness of lifeguards, however, the general feeling is that many more would have drowned without their assistance. CPR training and competency is not mandated for lifeguards in all localities. Upgrading lifeguard effectiveness has been recommended. Swimming Techniques
Smith reviewed studies of the impact of swimming lessons in the prevention of drowning. In fact, swimming ability may lead to overconfidence and swimming in hazardous situations. Although swimming lessons are recommended for ages 5 and up, educational efforts to explain high-risk situations and avoidance activities may be more beneficial. Personal Floatation Devices
Coast Guard statistics in 2000 indicated that over 85% of boating related drowning could have been prevented by personal floatation devices. Alcohol And Drugs
Legal and societal acceptance of alcohol combined with recreational activities when compared to driving is lax. In fact, advertisements widely promote its appeal. Any drinking or use of other recreational drugs in an aquatic environment is risky and should be discouraged.
The American Academy of Pediatrics has issued recommendations for various age groups.
Infants and children:
• Careful supervision • Emptying all water containers such as buckets and kiddy pools • Not allowing swimming lessons to provide a false sense of security • Four -sided fences around swimming pools • CPR instruction and 911 phone access • Floatation devices
Children 5 to 12 years:
• Swimming instruction • Buddy swimming with supervision • Personal floatation devices • Knowing the depth of the water • Recognizing drowning risks such as skating on thin ice Adolescents:
• Avoidance of alcohol and drug use • CPR instruction • Prohibiting alcohol during boat operation SUMMARY
Prevention has been a hallmark in the treatment/management of most medical diseases. In wilderness medicine, preparation and prevention is of paramount importance. Drowning prevention reflects this same phi-losophy. Prevention programs saves hundreds of lives, thousands of health care dollars and keeps times at the beaches, waterfalls, and in hot tubs or pools as safe and a source of of wonderful memories.
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