Immersion, near-drowning and drowning

Manner of death determination in a case of gastric mucosal tears

Gastric tears are rarely described in the forensic pathological literature, although they can lead to a fatal acute exsanguination. Such lesions can arise from several conditions leading to an increased intragastric pressure, such as Mallory Weiss syndrome, cardiopulmonary resuscitation, acute barotrauma and operative procedures, showing peculiar morphological features. We present a case of a 32-year-old drug addicted white woman found dead in a pool of blood in the house of her drug dealer, after taking a dose of intravenous heroin. At autopsy, abundant bloody gastric content and multiple and long gastric tears, extending from the cardias and fundus regions to the gastric corpus were observed; one of them involved the subserous region, resulting in a gastric wall rupture. The victim had no history of recent vomiting and of gastro-intestinal pathologies. Drugs and ethanol levels detected in the specimens of the victim were not consistent with lethal concentrations, thus the death was attributed to acute exsanguination. After reviewing the literature, it turned out that morphological aspects of the gastric tears, such as number, size and topographical distribution, observed at autopsy were atypical compared to those of typical gastric lacerations.

Habituation of the cold shock response: A systematic review and meta-analysis

Cold water immersion (CWI) evokes the life-threatening reflex cold shock response (CSR), inducing hyperventilation, increasing cardiac arrhythmias, and increasing drowning risk by impairing safety behaviour. Repeated CWI induces CSR habituation (i.e., diminishing response with same stimulus magnitude) after ∼4 immersions, with variation between studies. We quantified the magnitude and coefficient of variation (CoV) in the CSR in a systematic review and meta-analysis with search terms entered to Medline, SportDiscus, PsychINFO, Pubmed, and Cochrane Central Register. Random effects meta-analyses, including effect sizes (Cohen's d) from 17 eligible groups (k), were conducted for heart rate (HR, n = 145, k = 17), respiratory frequency (fR, n = 73, k = 12), minute ventilation (Ve, n = 106, k = 10) and tidal volume (Vt, n = 46, k=6). All CSR variables habituated (p < 0.001) with large or moderate pooled effect sizes: ΔHR -14 (10) bt. min-1 (d: -1.19); ΔfR -8 (7) br. min-1 (d: -0.78); ΔVe, -21.3 (9.8) L. min-1 (d: -1.64); ΔVt -0.4 (0.3) L -1. Variation was greatest in Ve (control vs comparator immersion: 32.5&24.7%) compared to Vt (11.8&12.1%). Repeated CWI induces CSR habituation potentially reducing drowning risk. We consider the neurophysiological and behavioural consequences.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 3: Heat and cold tolerance during exercise

In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.

Treatment of Hypothermic Cardiac Arrest in the Pediatric Drowning Victim, a Case Report, and Systematic Review

OBJECTIVES

Drowning is the second leading cause of death in children. Extracorporeal membrane oxygenation (ECMO) has become the criterion standard therapy to resuscitate the hypothermic drowning victim in cardiac arrest. We present our own experience treating 5 children with hypothermic cardiac arrest in conjunction with a systematic review to analyze clinical features predictive of survival.

METHODS

Our search resulted in 55 articles. Inclusion criteria were as follows: (1) younger than 18 years, (2) ECMO therapy, and (3) drowning. Ten articles met our inclusion criteria. We included studies using both central and peripheral ECMO and salt or fresh water submersions. We compared clinical features of survivors to nonsurvivors.

RESULTS

A total of 29 patients from the 10 different studies met our criteria. Data analyzed included presenting cardiac rhythm, time to initiation of ECMO, submersion time, pH, potassium, lactate, duration of chest compressions, and survival. There was a significant increase in mortality for presenting rhythm of asystole and with hyperkalemia (P < 0.05).

CONCLUSIONS

Extracorporeal membrane oxygenation is an important resuscitation tool for the hypothermic drowning victim. Hyperkalemia and presenting cardiac rhythm correlate with survival although they are not reasons to end resuscitation. More studies are needed to compare the outcomes in using ECMO for the hypothermic drowning victim.

Thiazoline-related innate fear stimuli orchestrate hypothermia and anti-hypoxia via sensory TRPA1 activation

Thiazoline-related innate fear-eliciting compounds (tFOs) orchestrate hypothermia, hypometabolism, and anti-hypoxia, which enable survival in lethal hypoxic conditions. Here, we show that most of these effects are severely attenuated in transient receptor potential ankyrin 1 (Trpa1) knockout mice. TFO-induced hypothermia involves the Trpa1-mediated trigeminal/vagal pathways and non-Trpa1 olfactory pathway. TFOs activate Trpa1-positive sensory pathways projecting from trigeminal and vagal ganglia to the spinal trigeminal nucleus (Sp5) and nucleus of the solitary tract (NTS), and their artificial activation induces hypothermia. TFO presentation activates the NTS-Parabrachial nucleus pathway to induce hypothermia and hypometabolism; this activation was suppressed in Trpa1 knockout mice. TRPA1 activation is insufficient to trigger tFO-mediated anti-hypoxic effects; Sp5/NTS activation is also necessary. Accordingly, we find a novel molecule that enables mice to survive in a lethal hypoxic condition ten times longer than known tFOs. Combinations of appropriate tFOs and TRPA1 command intrinsic physiological responses relevant to survival fate.

As a Rare Reason of Alveolar Consolidation, Negative Pressure Pulmonary Edema: Case Report

In this paper we describe two cases with negative pressure pulmonary edema (NPPE). Excessive negative airway pressures against an obstructed airway has been reported to cause fluid filtration into alveoli and lung edema. The patients are generally young adults without any medical problems. The condition involves central interstitial area of both lungs and is treated by nonnvasive mechanical ventilation and corticosteroids.

The Mammalian Diving Response: Inroads to Its Neural Control

The mammalian diving response (DR) is a remarkable behavior that was first formally studied by Laurence Irving and Per Scholander in the late 1930s. The DR is called such because it is most prominent in marine mammals such as seals, whales, and dolphins, but nevertheless is found in all mammals studied. It consists generally of breathing cessation (apnea), a dramatic slowing of heart rate (bradycardia), and an increase in peripheral vasoconstriction. The DR is thought to conserve vital oxygen stores and thus maintain life by directing perfusion to the two organs most essential for life-the heart and the brain. The DR is important, not only for its dramatic power over autonomic function, but also because it alters normal homeostatic reflexes such as the baroreceptor reflex and respiratory chemoreceptor reflex. The neurons driving the reflex circuits for the DR are contained within the medulla and spinal cord since the response remains after the brainstem transection at the pontomedullary junction. Neuroanatomical and physiological data suggesting brainstem areas important for the apnea, bradycardia, and peripheral vasoconstriction induced by underwater submersion are reviewed. Defining the brainstem circuit for the DR may open broad avenues for understanding the mechanisms of suprabulbar control of autonomic function in general, as well as implicate its role in some clinical states. Knowledge of the proposed diving circuit should facilitate studies on elite human divers performing breath-holding dives as well as investigations on sudden infant death syndrome (SIDS), stroke, migraine headache, and arrhythmias. We have speculated that the DR is the most powerful autonomic reflex known.

Cardiac Arrest Secondary to Accidental Hypothermia: Who Should We Resuscitate?

Cardiac arrest with a degree of concurrent hypothermia is not a rare presentation. This presentation, often in remote areas, poses a challenge for the prehospital physician because the cause of the arrest will significantly alter decision making and prognostication. Survival from cardiac arrest secondary to accidental hypothermia is significantly greater than that of normothermic arrests when appropriate triage and management decisions are made. The complexity of this decision benefits from a specific algorithm to follow in the event of such a casualty presenting. This article systematically reviews the literature on cardiac arrest secondary to accidental hypothermia and provides recommendations in addition to a novel algorithm to aid the responding prehospital clinician in deciding if a hypothermic resuscitation standard operating procedure should be implemented.

Successful resuscitation after drowning with severe hypernatraemia and prolonged time to return of spontaneous circulation

We describe the successful resuscitation of a 23-year-old previously healthy man who had drowned. After prolonged submersion, hypothermia, severe hypernatraemia, a prolonged time to return of spontaneous circulation was possible using a combination of extracorporal life support and early continuous veno-venous haemofiltration. This combination of clinical circumstances is rarely associated with positive outcomes, but this case demonstrates the utility of extracorporeal life support and haemofiltration in patients drowned in saltwater.

Cold Water Immersion Syndrome and Whitewater Recreation Fatalities

Sudden death during whitewater recreation often occurs through understandable mechanisms such as underwater entrapment or trauma, but poorly defined events are common, particularly in colder water. These uncharacterized tragedies are frequently called flush drownings by whitewater enthusiasts. We believe the condition referred to as cold water immersion syndrome may be responsible for some of these deaths. Given this assumption, the physiologic alterations contributing to cold water immersion syndrome are reviewed with an emphasis on those factors pertinent to flush drowning.

Aquatic Orthopaedic Injuries

Extremity injuries sustained in aquatic environments require unique considerations compared with injuries sustained on land. Knowledge of these considerations is becoming more important as aquatic recreational activities increase in popularity. Aquatic injuries may occur through mechanical contact with a variety of different objects or surfaces, such as a recreational device or watercraft part, or may occur through contact with marine animals. Marine animal injuries can be further categorized into bites, stings, or blunt contact, as well as venomous or nonvenomous, distinctions that should be used to guide clinical management. Numerous instances of retained foreign bodies after marine animal stings exist, which can result in infection and prolonged envenomization; thus, radiographic examination should be routinely performed in aquatic sting injuries to prevent these harmful sequelae. Any aquatic injury resulting in an open wound has an increased risk for infection, and prophylactic antibiotics must be given with consideration for the unique microbiologic flora of the aquatic environment.

Management of accidental hypothermia: A narrative review

A narrative review is presented on the diagnosis, treatment and management of accidental hypothermia. Although all these processes form a continuum, for descriptive purposes in this manuscript the recommendations are organized into the prehospital and in-hospital settings. At prehospital level, it is advised to: a) perform high-quality cardiopulmonary resuscitation for cardiac arrest patients, regardless of body temperature; b) establish measures to minimize further cooling; c) initiate rewarming; d) prevent rescue collapse and continued cooling (afterdrop); and (e) select the appropriate hospital based on the clinical and hemodynamic situation of the patient. Extracorporeal life support has revolutionized rewarming of the hemodynamically unstable victim or patients suffering cardiac arrest, with survival rates of up to 100%. The new evidences indicate that the management of accidental hypothermia has evolved favorably, with substantial improvement of the final outcomes.

Accidental Drowning: The Importance of Early Measures of Resuscitation for a Successful Outcome

CASE REPORT

The case of a drowning teenager is described involving application of cardiopulmonary resuscitation (CPR) by an untrained rescuer in the field and fast transport to a hospital enabling a positive resuscitation outcome despite an underorganized emergency medical service in a rural area. In our case hypoxia led to extended functional disorders of the cardiovascular system, which fully recovered after adequate therapy.

CONCLUSION

Knowledge about BLS measures by ordinary citizens, together with continuous education of health professionals concerning modern techniques of CPR, is crucial for increasing the number of patients surviving after cardiac arrest.

Potential technique for improving the survival of victims of tsunamis

We investigated a method for surviving tsunamis that involved the use of personal flotation devices (PFDs). In our work, we succeeded in numerically demonstrating that the heads of all the dummies wearing PFDs remained on the surface and were not dragged underwater after the artificial tsunami wave hit them. In contrast, the heads of all the dummies not wearing PFDs were drawn underwater immediately; these dummies were subsequently entrapped in a vortex. The results of our series of experiments are important as a first step to preventing the tragedies caused by tsunamis.

Therapeutic Hypothermia for Asphyxial Out-of-Hospital Cardiac Arrest Due to Drowning: A Systematic Review of Case Series and Case Reports

The objective of this review was to summarize published evidence of the effectiveness of therapeutic hypothermia in patients with drowning-associated asphyxial out-of-hospital cardiac arrest (OHCA) and to explore any preliminary favorable factors in the management of therapeutic hypothermia to improve survival and neurological outcome. Drowning may result in asphyxial OHCA or hypothermic OHCA, but the former does not provide any potential neuroprotective effect as the latter may do. Electronic literature searches of Ovid Medline, Embase, Cochrane Library, and Scopus were performed for all years from inception to July 2016. Primary studies in the form of case reports, letters to the editor, and others with higher quality are included, but guidelines, reviews, editorials, textbook chapters, conference abstracts, and nonhuman studies are excluded. Non-English articles are excluded. Relevant studies are then deemed eligible if the drowning OHCA patient's initial temperature was above 28°C, which implies asphyxial cardiac arrest, and intentional therapeutic hypothermia was instituted. Because of the narrow scope of interest and strict definition of the condition, limited studies addressed it, and no randomized controlled trials (RCT) could be selected. Thirteen studies covering 35 patients are included. No quantitative synthesis, assessment of study quality, or assessment of bias was performed. It is conjectured that extended therapeutic hypothermia of 48-72 hours might help prevent reperfusion injury during the intermediate phase of postcardiac arrest care to benefit patients of drowning-associated asphyxial OHCA, but this finding only serves as preliminary observation for future research. No conclusive recommendation could be made regarding the duration of and the time of onset of therapeutic hypothermia. Future research should put effort on RCT, particularly the effect of extended duration of 48-72 hours. Important parameters should be reported in detail. Asphyxial and hypothermic OHCA should be differentiated.

Forensic Case Reports Presenting Immersion Pulmonary Edema as a Differential Diagnosis in Fatal Diving Accidents

Immersion Pulmonary Edema (IPE) reduces the transport of gases over the respiratory membrane due to edema in the interstitium and respiratory zones. IPE has previously been described in both swimmers and divers, with a few known fatal cases. We have reviewed 42 SCUBA and snorkeling-related drowning deaths, and through a thorough analysis of each case, including both diving physiology and forensic pathology, we present IPE as a differential diagnosis to drowning in four cases. Our findings propose that; absence of watery content in the stomach and conducting airways, and liquid filled lungs without hyperexpansion, may be compatible with IPE. We suggest that IPE should be considered in cases where witness testimony reveals; no obvious signs of aspiration and rapid respiratory deterioration despite continuous breathing through an appropriate air source. The diagnosis should be based on the overall impression, including both the autopsy findings and the circumstances regarding the accident.

Physiology Of Drowning: A Review

Drowning physiology relates to two different events: immersion (upper airway above water) and submersion (upper airway under water). Immersion involves integrated cardiorespiratory responses to skin and deep body temperature, including cold shock, physical incapacitation, and hypovolemia, as precursors of collapse and submersion. The physiology of submersion includes fear of drowning, diving response, autonomic conflict, upper airway reflexes, water aspiration and swallowing, emesis, and electrolyte disorders. Submersion outcome is determined by cardiac, pulmonary, and neurological injury. Knowledge of drowning physiology is scarce. Better understanding may identify methods to improve survival, particularly related to hot-water immersion, cold shock, cold-induced physical incapacitation, and fear of drowning.

Accidental hypothermia-an update : The content of this review is endorsed by the International Commission for Mountain Emergency Medicine (ICAR MEDCOM)

BACKGROUND

This paper provides an up-to-date review of the management and outcome of accidental hypothermia patients with and without cardiac arrest.

METHODS

The authors reviewed the relevant literature in their specialist field. Summaries were merged, discussed and approved to produce this narrative review.

RESULTS

The hospital use of minimally-invasive rewarming for non-arrested, otherwise healthy, patients with primary hypothermia and stable vital signs has the potential to substantially decrease morbidity and mortality for these patients. Extracorporeal life support (ECLS) has revolutionised the management of hypothermic cardiac arrest, with survival rates approaching 100 % in some cases. Hypothermic patients with risk factors for imminent cardiac arrest (temperature <28 °C, ventricular arrhythmia, systolic blood pressure <90 mmHg), and those who have already arrested, should be transferred directly to an ECLS-centre. Cardiac arrest patients should receive continuous cardiopulmonary resuscitation (CPR) during transfer. If prolonged transport is required or terrain is difficult, mechanical CPR can be helpful. Delayed or intermittent CPR may be appropriate in hypothermic arrest when continuous CPR is impossible. Modern post-resuscitation care should be implemented following hypothermic arrest. Structured protocols should be in place to optimise pre-hospital triage, transport and treatment as well as in-hospital management, including detailed criteria and protocols for the use of ECLS and post-resuscitation care.

CONCLUSIONS

Based on new evidence, additional clinical experience and clearer management guidelines and documentation, the treatment of accidental hypothermia has been refined. ECLS has substantially improved survival and is the treatment of choice in the patient with unstable circulation or cardiac arrest.

Drowning Injuries: Analysis of a Decennial Air Medical Rescue Center Experience

OBJECTIVE

Drowning is one of the leading injury death causes in younger children. Common intensive care measures seem not to improve neurologic outcome, and early prognostic options appear partially unreliable. Therefore, we evaluated a cohort of drowning patients cotreated by a helicopter emergency medical service regarding typical incident constellations, early and subsequent prognostic options, and relevant interventions.

METHODS

All patients prehospitally cotreated by helicopter emergency medical service "Christoph 4" in primary missions because of drowning incidents during a 10-year period were evaluated. Patient, prehospital, and clinical data were recorded retrospectively; correlations and prognostic values were evaluated with appropriate statistical tests.

RESULTS

Fifty-one patients were included. Various examination results (several vital, neurologic, and laboratory parameters) and sufficient prehospital first aid measures were significantly correlated with the final outcome (P < .05, respectively). Aspartate aminotransferase and alanine aminotransferase values precisely discriminated between the final outcome groups (P = .001 and area under the receiver operating characteristic curve = 1.0 in both cases).

CONCLUSION

Aspartate aminotransferase and alanine aminotransferase values were the most useful predictors of outcome in our study. Sufficient prehospital first aid measures were correlated with improved outcome. Regular first aider training is recommended.

Continuous venovenous hemofiltration decreases mortality and ameliorates acute lung injury in canine model of severe salt water drowning

Background

Pulmonary edema is an important cause of complications and death in severe drowning. Continuous veno-venous hemofiltration (CVVH) may reduce pulmonary edema and thus may be a treatment modality for severe sea water drowning resuscitation.

Methos

20 dogs were anesthetized and tracheally intubated. 10 ml/kg of sea water was infused into trachea in a minute. All animals developed signs of respiratory distress and severe hypoxia (PaO₂ < 40 mmHg) within 15 minutes after infusion. They were then mechanical ventilated and randomized to receive either CVVH (n = 10) or no additional treatment (control, n = 10) and followed over 4 hours. Arterial gas, hemodynamic parameters, and the levels of circulating inflammatory cytokines including interleukin 6 (IL-6), interleukin 8 (IL-8), and tumor necrosis factor α (TNFα) were determined. Additionally, blood endothelin and the levels of oxidative stress in lung were measured at sacrifice.

Results

5 animals in the control group (50 %) died within 4 hours after sea water aspiration, while 10 animals received CVVH all survived (p < 0.05). Importantly, CVVH significantly improved blood gas exchange as evidenced by higher PaO_2, normal oxygen saturation, and no carbon dioxide retention after 3 hour of CVVH, while also correcting against acidosis. Levels of circulating IL-6, IL-8, and TNFα were elevated in control but not in CVVH group (p < 0.01). CVVH also reduced plasma endothelin and alleviated oxidative stress. Histology examination further revealed reductions in pulmonary alveolar injury, blood congestion, and inflammation by CVVH.

Discussion and conclusions

CVVH decreased mortality and pulmonary injury and largely maintained hemodynamic and acid-base balance in animals with severe sea water drowning and thus, may be added as a new measure to aid in resuscitation from severe sea water drowning.

Trial registration

Animal protocol number: FZG0001859 http://www.fzzyy.com.

[Drowning versus cardiac ischemia: Cardiac arrest of an 11-year-old boy at a swimming lake]

This report describes a case of sudden cardiac arrest and subsequent attempted cardiopulmonary resuscitation of an 11-year-old child on the shores of a swimming lake. Reports of eyewitnesses excluded the obviously suspected diagnosis of a drowning accident. The result of the autopsy was sudden cardiac death due to a congenital coronary anomaly (abnormal left coronary artery, ALCA). Favored by vigorous physical activity, this anomaly can lead to malignant arrhythmias because the ectopic coronary artery with its intramural course through the aortic wall is compressed during every systole. This pathology was not known to the boy or his family; in fact he liked sports but had suffered of a syncope once which was not followed up. Without a strong suspicion it is difficult to diagnose a coronary artery anomaly and it is often missed even in college athletes. Tragically, sudden cardiac arrest may be the first symptom of an undiagnosed abnormal coronary artery. Following syncope or chest pain during exercise with a normal electrocardiogram (ECG) cardiac imaging, such as computed tomography (CT) or angiography should be initiated in order to enable surgical repair of an abnormal coronary artery.

The Millennium child with autism: early childhood trajectories for health, education and economic wellbeing

OBJECTIVE

Most of what we know about children with autism spectrum disorder (ASD) is based on post-diagnostic, retrospective, self-select studies. Oftentimes, there is no direct comparison between trajectories of children with ASD and children without ASD.

METHODS

To circumvent both of these problems, the present secondary data analysis utilised a large-scale longitudinal general population survey of children born in the year 2000 (i.e. the Millennium Cohort Study; MCS; n = 18,522). Bi-annual MCS data were available from five data sweeps (children aged 9 months to 11 years of age).

RESULTS

Pre-diagnostic data showed early health problems differentiated children later diagnosed with autism from non-diagnosed peers. Prevalence was much higher than previously estimated (3.5% for 11-year olds). Post-diagnosis, trajectories deteriorated significantly for the children with ASD and their families in relation to education, health and economic wellbeing.

CONCLUSION

These findings raise many issues for service delivery and the rights of persons with disabilities and their families.

A systematic review protocol for measuring comorbidity in inpatient rehabilitation for non-traumatic brain injury

BACKGROUND

Comorbidity can affect health-care utilization and outcomes, and the results and interpretation of risk adjustment studies that attempt to predict rehabilitation utilization and outcomes are influenced by the choice of comorbidity measurement. Although the identification of an appropriate measurement has been conducted in some populations and outcomes, this information is currently lacking for the non-traumatic brain injury (nTBI) population in inpatient rehabilitation settings. As such, this is a systematic review protocol to survey the methods used to measure comorbidities in the rehabilitation setting for patients with nTBI.

METHODS/DESIGN

MEDLINE, MEDLINE In-Process, Embase, The Cochrane Database of Systematic Reviews, PsycINFO, and Health and Psychosocial Instruments will be systematically searched using the concepts 'nTBI,' 'comorbidity,' and 'rehabilitation.' Grey matters and the reference list of eligible articles will also be searched. Study selection will be performed independently by two reviewers based on predetermined eligibility criteria through two rounds of screening using, first, the title and abstract, followed by full-text. Extracted information will include study purpose, design, and setting; data source and type; outcomes variables; statistical methods; comorbidity measurement method, rationale, justification, or validation; and results involving comorbidity. The data will be tabulated and narratively synthesized. Meta-analyses will be performed if appropriate.

SYSTEMATIC REVIEW REGISTRATION

This protocol has not been registered with PROSPERO.

DISCUSSION

This protocol provides a systematic method for surveying current practice as well as monitoring the progress on comorbidity measurement methodology and effects of comorbidity on rehabilitation outcomes for patients with nTBI. The selection of an appropriate comorbidity measurement method has implications for the interpretation of both descriptive and risk adjustment studies, and thus, the validity of evidence used to inform planning and delivery of services.

A rare type of drowning with a latent period following surviving an episode of immersion

Drowning is a leading cause of accidental death worldwide and its diagnosis is an important part of forensic investigation. It is generally acknowledged that hypoxia due to airway obstruction by fluid is the primary mechanism of death in drowning. Drowned individuals are usually found dead in the water or show severe clinical signs once out of the water. However, sudden death due to drowning after a short period of recovery following immersion/submersion has rarely been reported. A case of a 40-year-old man who died suddenly due to severe pulmonary edema about 40 min after he was recovered from an episode of immersion is reported. We suspected delayed lung injury due to water aspiration as the prime cause of death. This rare type of drowning should be well recognized by a clinician or forensic pathologist.

Integrative physiological and behavioural responses to sudden cold-water immersion are similar in skilled and less-skilled swimmers

We examined the initial physiological responses and subsequent capacity to swim following cold-water immersion. An ecologically-valid model was used whereby immersion was sudden (<2s) and participants had to actively remain afloat. Participants (15 skilled swimmers, 17 less-skilled swimmers) undertook four experimental test sessions: a physiological test and a swimming test in both cold (10°C) water and temperate (27°C) water in a swimming flume (temperature order counter-balanced). For physiological testing, measures of brain perfusion [flow velocity (MCAv, Doppler) and oxygenation (NIRS)] and cardiorespiratory function [ventilation parameters and end-tidal PCO2 (PETCO2)] were recorded whilst treading water for 150s. The swimming test involved treading water (150s) before swimming at 60% (up to 120s) and 90% (to intolerance) of pre-determined maximum velocity. Multifactorial analysis revealed that swimming duration was influenced most heavily by water temperature, followed by respiratory variables and MCAv in the first 30s of immersion. The time course and severity of cold shock were similar in both groups (p=0.99), in terms of initial physiological changes (MCAv down ~20 ± 11%, respiratory frequency increased to 58 ± 18 breaths·min(-1), PETCO2 dropped to 12 ± 9 mmHg). Treading water following cold-water immersion increased MCAv by 30% above resting values despite maintained cold-shock-induced hyperventilation. In comparison to temperate water, swimming capacity was also reduced similarly between groups in the cold (i.e., distance decreased by 34 ± 26% skilled; 41 ± 33% less-skilled, p=0.99). These integrative findings verify that sudden cold-water immersion followed by physical activity leads to similar physiological responses in humans when contrasting between skilled and less-skilled swimmers.

Time course of physiological and psychological responses in humans during a 20-day severe-cold-acclimation programme

The time course of physiological and psychological markers during cold acclimation (CA) was explored. The experiment included 17 controlled (i.e., until the rectal temperature reached 35.5°C or 170 min had elapsed; for the CA-17 session, the subjects (n = 14) were immersed in water for the same amount of time as that used in the CA-1 session) head-out water immersions at a temperature of 14°C over 20 days. The data obtained in this study suggest that the subjects exhibited a thermoregulatory shift from peripheral-to-central to solely central input thermoregulation, as well as from shivering to non-shivering thermogenesis throughout the CA. In the first six CA sessions, a hypothermic type of acclimation was found; further CA (CA-7 to CA-16) led to a transitional shift to a hypothermic–insulative type of acclimation. Interestingly, when the subjects were immersed in water for the same time as that used in the CA-1 session (CA-17), the CA led to a hypothermic type of acclimation. The presence of a metabolic type of thermogenesis was evident only under thermoneutral conditions. Cold-water immersion decreased the concentration of cold-stress markers, reduced the activity of the innate immune system, suppressed specific immunity to a lesser degree and yielded less discomfort and cold sensation. We found a negative correlation between body mass index and Δ metabolic heat production before and after CA.

The mammalian diving response: an enigmatic reflex to preserve life?

The mammalian diving response is a remarkable behavior that overrides basic homeostatic reflexes. It is most studied in large aquatic mammals but is seen in all vertebrates. Pelagic mammals have developed several physiological adaptations to conserve intrinsic oxygen stores, but the apnea, bradycardia, and vasoconstriction is shared with those terrestrial and is neurally mediated. The adaptations of aquatic mammals are reviewed here as well as the neural control of cardiorespiratory physiology during diving in rodents.

Out-of-hospital cardiac arrest due to drowning among children and adults from the Utstein Osaka Project

BACKGROUND

Children have better outcomes after out-of-hospital cardiac arrest (OHCA) than adults. However, little is known about the difference in outcomes between children and adults after OHCA due to drowning.

OBJECTIVES

The aim of this study is to assess the outcome after OHCA due to drowning between children and adults. Our hypothesis is that outcomes after OHCA due to drowning would be in better among children (<18 years old) compared with adults (≥18 years old).

METHOD

This prospective population-based, observational study included all emergency medical service-treated OHCA due to drowning in Osaka, Japan, between 1999 and 2010 (excluding 2004). Outcomes were evaluated between younger children (0-4 years old), older children (5-17 years old), and adults (≥18 years old). Major outcome measures were one-month survival and neurologically favorable one-month survival defined as cerebral performance category 1 or 2. Multivariate logistic regression analyses were used to account for potential confounders.

RESULTS

During the study period, 66,716 OHCAs were documented, and resuscitation was attempted for 62,048 patients (1300 children [2%] and 60,748 adults [98%]). Among these OHCAs, 1737 (3% of OHCAs) were due to drowning (36 younger children [2%], 32 older children [2%], and 1669 adults [96%]). The odds of one-month survival were significantly higher for younger children (28% [10/36]; adjusted odds ratio [AOR], 20.20 [95% confidence interval {CI} 7.45-54.78]) and older children (9% [3/32]; AOR, 4.47 [95% CI 1.04-19.27]) when compared with adults (2% [28/1669]). However, younger children (6% [2/36]; AOR, 5.23 [95% CI 0.52-51.73]) and older children (3% [1/32]; AOR, 2.53 [95% CI 0.19-34.07]) did not have a higher odds of neurologically favorable outcome than adults (1% [11/1669]).

CONCLUSION

In this large OHCA registry, children had better one-month survival rates after OHCA due to drowning compared with adults. Most survivors in all groups had unfavorable neurological outcomes.

A proposed decision-making guide for the search, rescue and resuscitation of submersion (head under) victims based on expert opinion

There is some confusion, and consequent variation in policy, between the agencies responsible for the search, rescue and resuscitation of submersion victims regarding the likelihood of survival following a period of submersion. The aim of this work was to recommend a decision-making guide for such victims. This guidance was arrived at by a review of the relevant literature and specific case studies, and a "consensus" meeting on the topic. The factors found to be important for determining the possibility of prolonged survival underwater were: water temperature; salinity of water; duration of submersion; and age of the victim. Of these, only water temperature and duration are sufficiently clear to form the basis of guidance in this area. It is concluded that if water temperature is warmer than 6°C, survival/resuscitation is extremely unlikely if submerged longer than 30 min. If water temperature is 6°C or below, survival/resuscitation is extremely unlikely if submerged longer than 90 min.

Cardiorespiratory and neural consequences of rats brought past their aerobic dive limit

The mammalian diving response is a dramatic autonomic adjustment to underwater submersion affecting heart rate, arterial blood pressure, and ventilation. The bradycardia is known to be modulated by the parasympathetic nervous system, arterial blood pressure is modulated via the sympathetic system, and still other circuits modulate the respiratory changes. In the present study, we investigate the submergence of rats brought past their aerobic dive limit, defined as the diving duration beyond which blood lactate concentration increases above resting levels. Hemodynamic measurements were made during underwater submergence with biotelemetric transmitters, and blood was drawn from cannulas previously implanted in the rats' carotid arteries. Such prolonged submersion induces radical changes in blood chemistry; mean arterial PCO(2) rose to 62.4 Torr, while mean arterial PO(2) and pH reached nadirs of 21.8 Torr and 7.18, respectively. Despite these radical changes in blood chemistry, the rats neither attempted to gasp nor breathe while underwater. Immunohistochemistry for Fos protein done on their brains revealed numerous Fos-positive profiles. Especially noteworthy were the large number of immunopositive profiles in loci where presumptive chemoreceptors are found. Despite the activation of these presumptive chemoreceptors, the rats did not attempt to breathe. Injections of biotinylated dextran amine were made into ventral parts of the medullary dorsal horn, where central fibers of the anterior ethmoidal nerve terminate. Labeled fibers coursed caudal, ventral, and medial from the injection to neurons on the ventral surface of the medulla, where numerous Fos-labeled profiles were seen in the rats brought past their aerobic dive limit. We propose that this projection inhibits the homeostatic chemoreceptor reflex, despite the gross activation of chemoreceptors.

Combat-associated drowning

BACKGROUND

The purpose of this article is to describe the clinical course and outcome of drowning cases related to current US military combat operations.

METHODS

This retrospective case series spans December 2002 to January 2009 of survivors transferred to an echelon IV military trauma center in Europe serving as the primary evacuation hub for ongoing combat operations. Patient demographics and the situational and clinical findings at the initial drowning scene were reviewed. A comprehensive analysis of care as each patient transitioned through the combat theater to the echelon IV trauma center in Europe was performed.

RESULTS

Overall, mortality was 37.5% mortality rate (3 of 8 patients). Advanced modes of respiratory support such as high-frequency ventilation, airway pressure release ventilation, and extracorporeal membrane oxygenation were required in a majority of the cohort (6 of 8 patients). Limited-duration vasopressor infusions (7 of 8 patients) were also required to ensure adequate end-organ perfusion. Glasgow Coma Scale (GCS) scores and the need for cardiopulmonary resuscitation (CPR) at the scene of injury were associated with eventual patient mortality (100% mortality for an initial GCS score of 3 and 75% mortality for on-scene CPR). Survivor long-term morbidity was often related to the sequelae of acute respiratory distress syndrome and hypoxic encephalopathy.

CONCLUSION

Drowning associated with combat operations was associated with severe acute respiratory distress syndrome and cardiovascular shock. GCS score and the need for CPR at the scene of injury were associated with eventual mortality because of anoxic brain injury in all cases.

Outcome of 12 drowned children with attempted resuscitation on cardiopulmonary bypass: An analysis of variables based on the “Utstein Style for Drowning”

BACKGROUND

In 2003, the International Liaison Committee on Resuscitation (ILCOR) published the "Utstein Style for Drowning" (USFD) to advance knowledge on the epidemiology, treatment, and outcome prediction after drowning. Applying the USFD and evaluating its data template for outcome analysis, we report here on the largest study published thus far of drowned children (age 0-14) who underwent attempted resuscitation on cardiopulmonary bypass (CPB).

METHODS

We conducted a retrospective review of all drowned children admitted to Göttingen University Hospital between 1/1987 and 12/2005 in sustained cardiopulmonary arrest and resuscitation with CPB. We correlated eight outcome-affecting USFD variables and four additional variables not included in the USFD with potential impact on outcome to four outcome groups: survival, non-survival, survival with full recovery, and failed resuscitation.

RESULTS

Out of 12 children (aged 22 months to 7.5 years), 5 survived to hospital discharge and 7 died in hospital. Two survivors recovered fully and three remained in a vegetative state. In two patients, resuscitation on CPB failed. Both children who fully recovered, compared to the 10 others, had relatively low serum K+ concentrations (2.6 and 3.7 mmol/l versus 5.8+/-3.8 mmol/l [mean+/-S.D.; n=10]), a relatively slow rewarming speed (1.9 and 1.2 degrees C/h versus 3.4+/-1.8 degrees C/h), were female (all three girls survived), received early basic life support (BLS) and showed idioventricular bradycardia. Both children with failed resuscitation had severe hyperkalaemia (11.7 and 13.3 mmol/l versus 10 others, 4.0+/-1.5 mmol/l), were relatively rapidly rewarmed (6.9 and 4.0 degrees C/h versus 10 others, 2.61+/-1.32 degrees C/h), male, and in asystole. We identified no outcome trends for age, pH, or water and core temperatures.

CONCLUSIONS

Most variables relevant for outcome in drowned children can be documented with the use of the USFD. Additional variables not included in the USFD that have emerged from this study and may predict outcome include serum K+ concentration, rewarming speed, and initial cardiac rhythm.