1337 115 Drowning JAMIE L BELL, AJIT A SARNAIK, AND ASHOK P SARNAIK • For drowning victims in cardiac arrest, it is important that cardiopulmonary resuscitation be performed in the traditional airway[.]
115 Drowning JAMIE L BELL, AJIT A SARNAIK, AND ASHOK P SARNAIK PEARLS • For drowning victims in cardiac arrest, it is important that cardiopulmonary resuscitation be performed in the traditional airway-breathing-circulation rather than circulation-airwaybreathing sequence • Drowning is a process causing respiratory insufficiency from submersion or immersion in a liquid medium, which may or may not result in the victim’s death • The outcome of drowning victims depends largely on the success of resuscitative measures at the scene of injury and the duration of submersion • Intensive care management of multisystem organ dysfunction following drowning is similar to that of other disease entities It centers around early hemodynamic support, open-lung strategies for acute respiratory distress syndrome, and cerebral resuscitation strategies to prevent secondary brain injury Of all of the clinical entities encountered in a pediatric intensive care unit (PICU), drowning is among the most tragic Within minutes, previously healthy children with hopeful futures die or may be left severely incapacitated with no chance of meaningful cognition The parents, once full of dreams for their children, are suddenly beset with tremendous grief and guilt because, in most instances, the accident could have been prevented by simple measures “… 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.”3 Immersion is defined as having face and airway covered in water Submersion is defined as the entire body, including the airway, being under water The definition implies that a drowning victim develops an air-liquid interface that prevents the victim from breathing air A recommendation was made to abandon all other terms such as near drowning and secondary drowning Outcome is described according to death or survival, and survivors can be further categorized according to neurologic function.4 Papa and colleagues performed a systematic review of definitions for drowning accidents in 2005, identifying at least 43 publications in which various definitions of drowning were used (Table 115.1).5 They concluded that there is a need to use a single, uniform definition of drowning and supported the one recommended by the Utstein Focus World Congress on Drowning The Second International Utstein-Style Consensus on drowning, which convened in Potsdam, Germany, in 2013, recommended updates on data that should be used in reporting of resuscitation events in drowning.3 Definitions The definition of drowning events continues to be a source of confusion While there has been some improvement in the use of appropriate terms, review of literature shows that terms such as near drowning and suffocation by submersion in water remain in use The use of terms other than drowning makes it difficult to analyze and compare studies and outcomes Similar issues involving terminology and definitions existed in the resuscitation literature These problems were addressed in 1990 by a group of investigators who met at the Utstein Abbey in Stavanger, Norway, by coming up with a standardized format for reporting of research involving out-of-hospital cardiac arrest.1 In June 2002, the World Congress on Drowning was convened to develop a more standard definition of drowning using the Utstein style for uniform reporting of data and to make recommendations regarding preventive measures and care The Congress was initiated by the Maatschappij tot Redding van Drenkelingen (Dutch Organization to Rescue People from Drowning), an organization established in Amsterdam in 1767 to promote drowning awareness in the Netherlands.2 The final recommendation of the Congress was to define drowning as Epidemiology Childhood drowning deaths have decreased from 2.68 per 100,000 in 1985 to 1.11 per 100,000 in 2017 in the United States, perhaps because of greater emphasis on water safety.6,7 1337 1338 S E C T I O N X I I Pediatric Critical Care: Environmental Injury and Trauma TABLE Summary of Categories and Terms Used to Describe Drowning 115.1 Terms Explanation Specific Categories Primary vs secondary Secondary drowning is delayed death from drowning due to complications or death occurring in minutes to days after initial recovery Wet vs dry/with aspiration versus without aspiration Dry drowning or without aspiration is defined as laryngeal spasm with no or little aspiration of water or from respiratory obstruction and asphyxia from a liquid medium Wet drowning or with aspiration indicates that aspiration of fluids has occurred Warm vs cold water Cold-water drowning is defined as drowning in an outside body of water during the autumn, winter, and early spring months with a patient core temperature of #32°C on arrival to the emergency department Some use water temperature ,20°C Saltwater vs freshwater Describes kind of water in which incident occurred Active vs passive (or silent) Active refers to a witnessed drowning event in which the victim makes some motion In passive, the victim is found motionless Intentional vs nonintentional Describes cause Fatal vs nonfatal Describes outcome With and without hospitalization Describes whether the victim was admitted to hospital Specific Circumstances Iceberg phenomenon Iceberg phenomenon is described as people who have been submerged but have subsequently not died from drowning Immersion frigida Immersion frigida is defined as death from cooling in water Immersion syndrome/immediate disappearance syndrome Occurs when syncope is provoked by sudden contact with water at least ,5°C presumably from bradycardia, tachycardia, or arrhythmia Save Rescue of victim from water by someone who perceived individual to be a potential victim of submersion injury From Papa L, Hoelle R, Idris A Systematic review of definitions for drowning incidents Resuscitation 2005;65:255-264 Australia has reported a similar decline in deaths due to drowning in recent years The greatest decline (46%) occurred in infants under the age of year, followed by persons aged to 19 years (30%).7 Despite these encouraging data, drowning remains a major cause of death from unintentional injury in young children worldwide According to the World Health Organization (WHO), there are an estimated 372,000 drowning deaths per year, accounting for the third leading cause of worldwide unintentional injury death.8 In the United States, drowning is the leading cause of death in children ages to 14 years.9 Further stratifying this age group, in 2013, drowning was also reported as the number one cause of death from unintentional injuries (393 of 1316) in children aged to years Of these, 52.2% occurred in a swimming pool.10 Drowning is the second most common cause of death from unintentional injuries in children aged to years (15.5%) and, in children aged 10 to 14 years (12%), second to motor vehicle accidents While the majority of drowning deaths in children aged to years occurred in a swimming pool, drowning deaths in older children aged 10 to 14 years occurred in natural bodies of water Sociodemographic factors also impact drowning rates in children.6 There are disparities in participation in swimming among different racial, religious, and ethnic groups Among children in the United States, African Americans have the highest population-based drowning mortality rate, followed by Native American/Alaskan Native, white, Asian/ Pacific Islander, and Hispanic groups Drowning is also an important cause of morbidity in children In 2017, almost 9000 children younger than 20 years were treated in an emergency department for drowning, and 25% were admitted to a hospital or transferred for further care.6 In 2011, Shields and colleagues reported on drowning events in portable aboveground pools.11 Data were obtained from the US Consumer Product Safety Commission There were 209 fatal and 35 nonfatal drowning cases in children younger than 12 years Of the victims, 94% were less than years of age, and 56% were boys Portable aboveground pools pose a special risk because they are small, inexpensive, installed by the consumer, and not generate the same feeling of risks associated with in-ground pools In some instances, water depth was as low as inches (wading pools) In addition, it is uncommon to provide barriers for portable aboveground pools Ladders cannot be moved to block access, and wading pools not come with safety covers Children younger than year most often drown in bathtubs, buckets, or toilets While child abuse should be suspected in these situations, as many as 35% of children between the ages of 10 to 18 months were shown to be able to climb into a bathtub.12,13 Drowning in a bathtub should therefore not be considered as prima facie evidence of child abuse Others at risk for bathtub drowning are those with seizure disorders.14 Drowning is highest during the summer months and on weekends Most children who drown were last seen inside the home, in the care of one or both parents, but left unsupervised for less than minutes.15 Other important risk factors in drowning deaths include failure to wear a life jacket and alcohol use In 2006, the US Coast Guard reviewed reports of boating incidents Of the 500 people who drowned, out of 10 were not wearing life jackets.16 Alcohol CHAPTER 115 Drowning use is involved in up to half of adolescent and adult deaths associated with water recreation.17 Ethanol and other neurotropic agents can diminish manual dexterity, impair judgment, and increase risk-taking behavior Recent alcohol consumption by supervising adults may also contribute to drowning accidents involving children.18 Expert swimmers have also been known to drown during underwater swimming The practice of hyperventilation to prolong the duration of underwater swimming is particularly hazardous in this regard because significant hypoxemia may result in loss of consciousness before hypercarbia stimulates respiration.19 Although an uncommon cause of drowning, arrhythmia from long QT syndrome (LQTS) should be suspected and investigated after syncope, seizure, or cardiac arrest during or after swimming.20 The key to prevention includes careful supervision of children and education of the public regarding drowning prevention and the hazards of drowning Children playing near or in water should always be supervised by a responsible adult who is not distracted by any other activity Alcohol should be avoided before or during swimming, boating, and while supervising children A four-sided, self-closing, self-latching fence at least feet high that completely separates the house and play area of the yard should be installed around household pools Those who are in or around natural bodies of water should wear US Coast Guard–approved life jackets irrespective of distance to be travelled, size of boat, or swimming ability Pathophysiologic Considerations The sequence of events after submersion has been described by Karpovich in animal studies.21 The drowning process has been described by the World Congress on Drowning as a continuum that begins when the victim’s airway lies below the surface of the liquid (Fig 115.1).4 After an initial period of voluntary breath holding, reflex laryngospasm is initiated by the penetration of liquid in the oropharynx or larynx Hypoxia, hypercarbia, and acidosis ensue and, when sufficiently severe, result in lessening of laryngospasm, and breathing of liquid into the lungs The amount of liquid aspirated varies considerably among the victims Once the liquid reaches the alveoli, a pernicious sequence develops A 1339 characterized by marked disruption in pulmonary architecture and pathophysiologic alterations These include surfactant washout, atelectasis, pulmonary edema, pulmonary hypertension, and continuing intrapulmonary shunting The victim may be rescued at any time during the drowning process thus aborting or minimizing lung injury Although the term dry drowning had previously been used in the pathology literature to describe autopsy cases without evidence of water in the airways and alveoli, this terminology has been abandoned by the Utstein-style definition of drowning The single most important and prognostically significant consequence of drowning is decreased oxygen (O2) delivery to the tissues A number of clinical variables determine the magnitude of hypoxia and the subject’s ability to withstand it Thus, the pathophysiology of drowning is closely integrated with the genesis of hypoxemia and its effects on various organ functions A working knowledge of these pathophysiologic principles and multiorgan involvement is extremely helpful in directing therapeutic strategies for optimum survival Type of Aspirated Fluid There are several reports in the literature regarding physiologic differences in electrolytes and blood volume after seawater and freshwater drowning Aspiration of more than 11 mL of fluid per kg of body weight is required for blood volume to be altered, and aspiration of more than 22 mL/kg is necessary before significant electrolyte changes occur.22,23 Drowning victims are often hypovolemic regardless of the type of aspiration because of increased capillary permeability resulting from asphyxia and the loss of protein-rich fluid into the alveoli In a canine model of drowning, aspiration of cold fresh water led to a 16% increase in body weight, compared with 6% for saltwater aspiration.24 Reported outcomes in freshwater drowning are worse than in saltwater drowning In a meta-analysis of seven studies with 2163 drowning victims, saltwater drowning compared to freshwater drowning was associated with a favorable outcome, with a relative risk of 1.16 (95% confidence interval, 1.08–1.24).25 Also, hypoxia, as assessed by partial pressure of arterial O2/fraction of inspired O2 (Pao2/Fio2) ratios, was worse in a matched cohort of freshwater B • Fig 115.1 Near-drowning with and without aspiration Radiographs show a patient with severe pulmonary edema (A) and another without significant fluid aspiration (B) (From Ciullo JV, ed Clin Sports Med Philadelphia: WB Saunders; 1986.) 1340 S E C T I O N X I I Pediatric Critical Care: Environmental Injury and Trauma versus saltwater adult drowning victims upon ICU admission.26 This is consistent with the known effect of the aspirated fluid on pulmonary surfactant, which is destroyed by fresh water but only diluted by salt water Pulmonary Effects Functional residual capacity (FRC) is the only source of gas exchange at the pulmonary capillary level in the submerged state Increased metabolic demands from struggling, breath holding, a depletion of FRC from breathing efforts, and aspiration of fluid into the lungs all result in seriously compromised O2 uptake and carbon dioxide (CO2) elimination, with consequent hypoxia and hypercarbia Between 10% and 15% of drowning victims have severe laryngospasm after submersion, resulting in fatal asphyxiation without aspiration of significant water into their lungs (see Fig 115.1) There is often a combined respiratory and metabolic acidosis caused by hypercapnia and anaerobic metabolism Patients without significant fluid aspiration recover from asphyxia rapidly if they are successfully resuscitated before cardiac arrest or irreversible brain damage occurs Aspiration of fluid, however, results in persistently abnormal gas exchange Aspiration of as little as to mL per kg body weight results in profound impairment of gas exchange.23,27 Soon after the aspiration of fluid, there is an elevation of partial pressure of arterial carbon dioxide (Paco2) and a fall in Pao2 as a result of airway obstruction, hypoventilation, and impaired gas exchange between alveoli and pulmonary capillary blood With adequate resuscitation, normocapnia or even hypocapnia is usually achieved while hypoxemia persists, indicating a significant ventilation/perfusion mismatch and diffusion defect leading to intrapulmonary shunting and venous admixture.28 The surfactant system of the lung is affected differently in freshwater versus seawater aspiration.29 Freshwater aspiration results in marked disruption of the surfactant system of the lung, leading to alveolar instability and atelectasis Sea water, because of its hypertonicity, draws water into the alveoli Although surfactant may be diluted by the presence of sea water in the alveoli, its surface tension properties are not significantly altered Zhu and colleagues examined serum levels of pulmonary surfactantassociated protein (SP-A) and lung weights in 53 victims of fatal drowning.30 They showed significantly heavier lungs in those who drowned in sea water versus fresh water, suggesting an osmolar effect Although they found no difference in serum SP-A, intraalveolar aggregates of pulmonary surfactant-associated protein were noted more frequently in those who drowned in fresh water This is likely related to the disruption of surfactant noted in freshwater drowning Karch demonstrated marked changes in the pulmonary vasculature in rabbits within 30 minutes of aspiration of both fresh water and salt water.31 Mitochondrial swelling and disruption of pulmonary vascular endothelial cells were consistently observed in these experiments Clinically, pulmonary abnormalities are encountered in both freshwater and seawater aspiration These are consistent with pronounced injury to alveoli and pulmonary capillaries resulting in increased membrane permeability, exudation of proteinaceous material in alveoli, pulmonary edema, decreased lung compliance, and increased airway resistance The extent of these abnormalities may not be manifested fully for several hours after the submersion episode and may be progressive in nature Acute respiratory distress syndrome (ARDS) is the hallmark of delayed pulmonary insufficiency resulting from aspiration in drowning This is characterized by progression of ventilation/perfusion mismatch, alveolar-capillary block, increased capillary permeability, and pulmonary edema Reduced FRC and diffusion barrier resulting from accumulation of fluid and inflammatory cells in the alveoli and interstitium further accentuate hypoxemia Aspiration of stomach contents and other debris such as sand, mud, and algae may also impair gas exchange Bacterial pneumonia resulting from aspiration of contaminated water may further contribute to pulmonary insufficiency Factors that contribute to drowning-associated pneumonia include aspiration of vomitus or aspiration of contaminated material from water that may contain sewage Water temperature plays a role, with warmer temperatures predisposing to a higher number of organisms The chemical composition of the water—such as pH, salt content, and presence of organic and inorganic substances—influences bacterial growth as well Implicated organisms include aerobic gramnegative bacteria, such as Enterobacter spp., Klebsiella spp., and Pseudomonas spp., as well as gram-positive bacteria, including Streptococcus pneumoniae and Staphylococcus aureus Oropharyngeal flora, as well as pathogens present in the body of water that the child drowned in, have been implicated in drowningassociated pneumonia.32,33 There have been reports of multidrugresistant bacteria34 and fungal pneumonia as well The diagnosis of pneumonia is based on clinical parameters such as fever, leukocytosis, and new infiltrates on chest radiographs When pneumonia is suspected, respiratory cultures are a valuable tool to guide antimicrobial therapy Understanding the alterations in pulmonary mechanics is important in order to provide the necessary support in the least injurious fashion Predominant manifestations are those of ARDS complicating the drowning event Although pulmonary involvement is often bilateral and diffuse, there is considerable inhomogeneity, with some areas more affected than others Overall, lung compliance is reduced, necessitating higher inflation pressures to maintain adequate tidal volume (Vt) Low Vt at low FRC leads to a vicious cycle of atelectasis, decreased compliance, and further reduction in Vt Critical opening pressure necessary to begin alveolar inflation is increased Appropriate positive endexpiratory pressure (PEEP) needs to be administered to maintain the necessary FRC for adequate oxygenation and ventilation above the critical opening pressure Airway resistance is relatively less affected or only minimally elevated unless there is airway obstruction from aspirated debris Time constant, a product of compliance and resistance, reflects the time needed for pressure equilibration between the proximal airway and alveoli to occur In ARDS, time constant is decreased, allowing for quicker approximation of pressures at these sites during the inspiratory and expiratory phases of the mechanical ventilation Relatively large Vt (10–12 mL/kg) is associated with greater ventilator-associated lung injury in ARDS, whereas smaller Vt (6 mL/kg) is associated with less volutrauma Because of the short time constant, prolongation of inspiratory time to improve oxygenation and increasing the respiratory rate for CO2 elimination often are effective options during mechanical ventilation A more detailed description of management of ARDS in drowning appears later in this chapter Cardiovascular Effects Profound cardiovascular instability is often encountered after a severe drowning event, which poses an immediate threat to survival after the initial rescue The hypoxemia that occurs due to ventilation-perfusion mismatch can cause life-threatening CHAPTER 115 Drowning dysrhythmias, such as ventricular tachycardia, ventricular fibrillation, and asystole The two determinants of O2 delivery—namely, cardiac output and arterial O2 content—can be adversely affected by the drowning event A decrease in Pao2, if sufficiently severe, decreases O2 saturation and therefore arterial O2 content This decrease in arterial O2 content can cause a decrease in myocardial O2 delivery, which contributes to worsening cardiac output and decreased myocardial perfusion pressure Smooth muscle contraction banding in the media of major coronary arteries and local ventricular myocytes with focal myocardial necrosis have been described after a drowning episode.35,36 Cytosolic calcium overload and O2-derived free radicals have also been implicated in the mechanism of myocardial injury after resuscitation following cardiac arrest.37 Cardiogenic shock may result from hypoxic damage to the myocardium Metabolic acidosis may further impair myocardial performance Additionally, therapeutic application of PEEP decreases venous return and right and left ventricular preload Right ventricular afterload is also increased by structural pulmonary microvascular damage and humoral inflammatory mediators involved in ARDS The right ventricle is anatomically designed to tolerate increased preload, but it is not as tolerant of high pressures and afterload as the left ventricle If pulmonary hypertension is severe enough, left ventricular preload further decreases owing to right ventricular failure These factors, as well as the excessive permeability of pulmonary and systemic capillaries, result in hypovolemia and decreased left ventricular filling pressures The end result is that of inadequate supply of O2 to tissues to meet their metabolic demands Central Nervous System Effects Owing to a lack of metabolic substrate reserves, the brain depends on continuous O2 delivery Metabolic failure can begin within seconds after an immediate disruption in circulation Hypoxia, if sufficiently prolonged, causes profound disturbances of central nervous system (CNS) function The severity of brain injury depends on the magnitude and duration of hypoxemia and cerebral hypoperfusion, as well as on mechanisms of secondary brain injury The most important components of brain-specific management include prompt rescue, early and successful resuscitation, and mitigation of secondary injuries Following restoration of adequate cerebral O2 delivery after the initial hypoxemia and/or hypoperfusion after drowning, there are several mechanisms of secondary brain injury at the tissue, synaptic, and cellular level At the tissue level, increased intracranial pressure (ICP) and alterations in cerebral blood flow (CBF) can adversely impact local tissue O2 delivery At the synaptic level, the excitotoxic neurotransmitter glutamate can cause an imbalance in the neuronal supply and demand Delayed neuronal death occurs owing to cellular responses to hypoxia and subsequent reperfusion, leading to complex pathways of pro-survival and pro-death signals Intracellularly, accumulation of cytosolic calcium, neuronal energy failure associated with DNA damage and repair, and generation of O2-free radicals can all contribute to secondary neuronal death There are several developmental factors that render the neurologic effects of pediatric cardiac arrest different from that of adults Brain injury from sudden cardiac arrest, which more commonly occurs in adults, results when CBF suddenly stops In contrast, brain injury from drowning, along with most causes of pediatric cardiac arrest, is caused by asphyxia Cerebral O2 delivery continues for some time and progressively decreases because of hypoxemia 1341 and decreased CBF Cardiac arrest may occur but is usually preceded by this period of decreased O2 delivery Neurologic injury is similar to that of other causes of pediatric asphyxia, including foreign body airway obstruction, apnea, asthma, and suffocation Approximately 46% of all children with cardiopulmonary arrest survive to hospital discharge38 and only 38% if the arrest occurred outside the hospital.39 Studies in humans and animals indicate that there are several developmental differences in excitotoxic pathways In the neonatal period, there is increased vulnerability to N-methyl-d-aspartate receptor activation40 and glutamate toxicity,41 as well as heightened capability for apoptosis, which, albeit an important process of normal brain development, may render the immature brain vulnerable to neuronal loss after an insult.42 In addition, a developmental difference exists in CBF after cardiac arrest In adult models of cardiac arrest, global hyperemia is present for 15 to 30 minutes after return of spontaneous circulation (ROSC) followed by delayed hypoperfusion that persists for several hours In an immature animal model of a brief asphyxial cardiac arrest, hyperemia was observed for 10 minutes after ROSC followed by restoration of baseline CBF, whereas prolonged cardiac arrest was followed by hypoperfusion and blood pressure–dependent CBF.43 Effects on Other Organ Systems Drowning victims are at significant risk for the development of hypoxemia and/or ischemia, particularly in the face of cardiac or respiratory arrest These factors increase the risk for multiple-organ dysfunction syndrome (MODS) In addition to neurologic injury and acute lung injury, hepatic and renal injuries have been observed Typpo and colleagues reported on the incidence of MODS on day in children admitted to the PICU.44 Of the 18% of children who developed MODS on the first day, 30% to 35% had an unfavorable neurologic outcome In 2015, Mtaweh et al reported on the patterns of MODS in children after drowning.45 Pediatric Logistic Organ Dysfunction Score-1 (PELOD-1) and Pediatric Multiple Organ Dysfunction Score (P-MODS) were calculated for the first 24 hours of admission Of the 60 children, 39 (65%) were in respiratory arrest and 21 (35%) were in cardiac arrest at the scene Seventeen of 60 patients had severe neurologic injury Of the children who developed MODS, approximately half had been in respiratory or cardiac arrest Children who had been in cardiac arrest had much more significant organ dysfunction, which included neurologic, respiratory, hepatic, and renal systems Of those children who developed acute kidney injury (3 in 60), one child required continuous renal replacement therapy and hemodialysis Mammalian Diving Reflex A certain degree of protection against hypoxia in drowning may occur in the form of a response similar to the diving reflex observed in seals and other air-breathing diving mammals While the heart, brain, and lungs remain adequately perfused, blood flow to tissues resistant to hypoxia (i.e., gastrointestinal tract, skin, and muscle) is markedly reduced Significant bradycardia occurs with a reduction in cardiac output The mammalian diving reflex acts as an O2-conserving adaptation in response to submersion It has been proposed that this reflex is most active in infancy and is potentiated by fear and low water temperature.46 A combination of marked bradycardia and impalpable pulses resulting from vasoconstriction may make the victim appear dead at a time when ... for the third leading cause of worldwide unintentional injury death.8 In the United States, drowning is the leading cause of death in children ages to 14 years.9 Further stratifying this age... in fresh water This is likely related to the disruption of surfactant noted in freshwater drowning Karch demonstrated marked changes in the pulmonary vasculature in rabbits within 30 minutes... and acidosis ensue and, when sufficiently severe, result in lessening of laryngospasm, and breathing of liquid into the lungs The amount of liquid aspirated varies considerably among the victims