“Nobody is dead until warm and dead”: Prolonged resuscitation is warranted in arrested hypothermic victims also in remote areas – A retrospective study from northern Norway

Environmental Hypothermia

Although a rare diagnosis in the Emergency Department, hypothermia affects patients in all environments, from urban to mountainous settings. Classic signs of death cannot be interpreted in the hypothermic patient, thus resulting in the mantra, "No one is dead until they're warm and dead." This comprehensive review of environmental hypothermia covers the clinical significance and pathophysiology of hypothermia, pearls and pitfalls in the prehospital management of hypothermia (including temperature measurement techniques and advanced cardiac life support deviations), necessary Emergency Department diagnostics, available rewarming modalities including extracorporeal life support, and criteria for termination of resuscitation.

Avalanche burial pathophysiology - a unique combination of hypoxia, hypercapnia and hypothermia

For often unclear reasons, the survival times of critically buried avalanche victims vary widely from minutes to hours. Individuals can survive and sustain organ function if they can breathe under the snow and maintain sufficient delivery of oxygen and efflux of carbon dioxide. We review the physiological responses of humans to critical avalanche burial, a model which shares similarities and differences with apnoea and accidental hypothermia. Within a few minutes of burial, an avalanche victim is exposed to hypoxaemia and hypercapnia, which have important effects on the respiratory and cardiovascular systems and pose a major threat to the central nervous system. As burial time increases, an avalanche victim also develops hypothermia. Despite progressively reduced metabolism, reduced oxygen and increased carbon dioxide tensions may exacerbate the pathophysiological consequences of hypothermia. Hypercapnia seems to be the main cause of cardiovascular instability, which, in turn, is the major reason for reduced cerebral oxygenation despite reductions in cerebral metabolic activity caused by hypothermia. 'Triple H syndrome' refers to the interaction of hypoxia, hypercapnia and hypothermia in a buried avalanche victim. Future studies should investigate how the respiratory gases entrapped in the porous snow structure influence the physiological responses of buried individuals and how haemoconcentration, blood viscosity and cell deformability affect blood flow and oxygen delivery. Attention should also be devoted to identifying strategies to prolong avalanche survival by either mitigating hypoxia and hypercapnia or reducing core temperature so that neuroprotection occurs before the onset of cerebral hypoxia.

Delayed Rewarming Thrombocytopenia: A Suggested Preventable and Treatable Cause of Rewarming Deaths

The lack of a consensus of accepted prognostic factors in hypothermia suggests an additional factor has been overlooked. Delayed rewarming thrombocytopenia (DRT) is a novel candidate for such a role. At body temperature, platelets undergoing a first stage of aggregation are capable of progression to a second irreversible stage of aggregation. However, we have shown that the second stage of aggregation does not occur below 32°C and that this causes the first stage to become augmented (first-stage platelet hyperaggregation). In aggregometer studies performed below 32°C, the use of quantities of ADP that cause a marked first-stage hyperaggregation can cause an augmented second-stage activation of the platelets during rewarming (second-stage platelet hyperaggregation). In vivo, after 24 hours of hypothermia, platelets on rewarming seem to undergo second-stage hyperaggregation, from ADP released from erythrocytes, leading to life-threatening thrombocytopenia. This hyperaggregation is avoidable if heparin is given before the hypothermia or if aspirin, alcohol or platelet transfusion is given during the hypothermia before reaching 32°C on rewarming. Many of the open questions existing in this field are explained by DRT. Prevention and treatment of DRT could be of significant value in preventing rewarming deaths and some cases of rescue collapse. Performing platelet counts during rewarming will demonstrate potentially fatal thrombocytopenia and enable treatment with platelet infusions aspirin or alcohol.

Wilderness Medical Society Clinical Practice Guidelines for Prevention and Management of Avalanche and Nonavalanche Snow Burial Accidents: 2024 Update

To provide guidance to the general public, clinicians, and avalanche professionals about best practices, the Wilderness Medical Society convened an expert panel to revise the evidence-based guidelines for the prevention, rescue, and resuscitation of avalanche and nonavalanche snow burial victims. The original panel authored the Wilderness Medical Society Practice Guidelines for Prevention and Management of Avalanche and Nonavalanche Snow Burial Accidents in 2017. A second panel was convened to update these guidelines and make recommendations based on quality of supporting evidence.

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.

Hypothermia: Beyond the Narrative Review-The Point of View of Emergency Physicians and Medico-Legal Considerations

Hypothermia is a widespread condition all over the world, with a high risk of mortality in pre-hospital and in-hospital settings when it is not promptly and adequately treated. In this review, we aim to describe the main specificities of the diagnosis and treatment of hypothermia through consideration of the physiological changes that occur in hypothermic patients. Hypothermia can occur due to unfavorable environmental conditions as well as internal causes, such as pathological states that result in reduced heat production, increased heat loss or ineffectiveness of the thermal regulation system. The consequences of hypothermia affect several systems in the body-the cardiovascular system, the central and peripheral nervous systems, the respiratory system, the endocrine system and the gastrointestinal system-but also kidney function, electrolyte balance and coagulation. Once hypothermia is recognized, prompt treatment, focused on restoring body temperature and supporting vital functions, is fundamental in order to avert preventable death. It is important to also denote the fact that CPR has specificities related to the unique profile of hypothermic patients.

Extracorporeal cardiopulmonary resuscitation for hypothermic refractory cardiac arrests in urban areas with temperate climates

BACKGROUND

Accidental hypothermia designates an unintentional drop in body temperature below 35 °C. There is a major risk of ventricular fibrillation below 28 °C and cardiac arrest is almost inevitable below 24 °C. In such cases, conventional cardiopulmonary resuscitation is often inefficient. In urban areas with temperate climates, characterized by mild year-round temperatures, the outcome of patients with refractory hypothermic out-of-hospital cardiac arrest (OHCA) treated with extracorporeal cardiopulmonary resuscitation (ECPR) remains uncertain.

METHODS

We conducted a retrospective monocentric observational study involving patients admitted to a university hospital in Paris, France. We reviewed patients admitted between January 1, 2011 and April 30, 2022. The primary outcome was survival at 28 days with good neurological outcomes, defined as Cerebral Performance Category 1 or 2. We performed a subgroup analysis distinguishing hypothermic refractory OHCA as either asphyxic or non-asphyxic.

RESULTS

A total of 36 patients were analysed, 15 of whom (42%) survived at 28 days, including 13 (36%) with good neurological outcomes. Within the asphyxic subgroup, only 1 (10%) patient survived at 28 days, with poor neurological outcomes. A low-flow time of less than 60 min was not significantly associated with good neurological outcomes (P = 0.25). Prehospital ECPR demonstrated no statistically significant difference in terms of survival with good neurological outcomes compared with inhospital ECPR (P = 0.55). Among patients treated with inhospital ECPR, the HOPE score predicted a 30% survival rate and the observed survival was 6/19 (32%).

CONCLUSION

Hypothermic refractory OHCA occurred even in urban areas with temperate climates, and survival with good neurological outcomes at 28 days stood at 36% for all patients treated with ECPR. We found no survivors with good neurological outcomes at 28 days in submersed patients.

Using point-of-care testing for adult patients with out-of-hospital cardiac arrest resuscitated at the emergency department to predict return of spontaneous circulation: Development and external validation of POC-ED-ROSC model

BACKGROUND AND IMPORTANCE

Most prediction models, like return of spontaneous circulation (ROSC) after cardiac arrest (RACA) or Utstein-based (UB)-ROSC score, were developed for prehospital settings to predict the probability of ROSC in patients with out-of-hospital cardiac arrest (OHCA). A prediction model has been lacking for the probability of ROSC in patients with OHCA at emergency departments (EDs).

OBJECTIVE

In the present study, a point-of-care (POC) testing-based model, POC-ED-ROSC, was developed and validated for predicting ROSC of OHCA at EDs.

DESIGN, SETTINGS AND PARTICIPANTS

Prospectively collected data for adult OHCA patients between 2015 and 2020 were analysed. POC blood gas analysis obtained within 5 min of ED arrival was used.

OUTCOMES MEASURE AND ANALYSIS

The primary outcome was ROSC. In the derivation cohort, multivariable logistic regression was used to develop the POC-ED-ROSC model. In the temporally split validation cohort, the discriminative performance of the POC-ED-ROSC model was assessed using the area under the receiver operating characteristic (ROC) curve (AUC) and compared with RACA or UB-ROSC score using DeLong test.

MAIN RESULTS

The study included 606 and 270 patients in the derivation and validation cohorts, respectively. In the total cohort, 471 patients achieved ROSC. Age, initial cardiac rhythm at ED, pre-hospital resuscitation duration, and POC testing-measured blood levels of lactate, potassium and glucose were significant predictors included in the POC-ED-ROSC model. The model was validated with fair discriminative performance (AUC: 0.75, 95% confidence interval [CI]: 0.69-0.81) with no significant differences from RACA (AUC: 0.68, 95% CI: 0.62-0.74) or UB-ROSC score (AUC: 0.74, 95% CI: 0.68-0.79).

CONCLUSION

Using only six easily accessible variables, the POC-ED-ROSC model can predict ROSC for OHCA resuscitated at ED with fair accuracy.

Functional recovery after accidental deep hypothermic cardiac arrest: Comparison of different cardiopulmonary bypass rewarming strategies

Introduction: Using a porcine model of accidental immersion hypothermia and hypothermic cardiac arrest (HCA), the aim of the present study was to compare effects of different rewarming strategies on CPB on need for vascular fluid supply, level of cardiac restitution, and cerebral metabolism and pressures.

Materials and Methods: Totally sixteen healthy, anesthetized castrated male pigs were immersion cooled to 20°C to induce HCA, maintained for 75 min and then randomized into two groups: 1) animals receiving CPB rewarming to 30°C followed by immersion rewarming to 36°C (CPB₃₀, n = 8), or 2) animals receiving CPB rewarming to 36°C (CPB₃₆, n = 8). Measurements of cerebral metabolism were collected using a microdialysis catheter. After rewarming to 36°C, surviving animals in both groups were further warmed by immersion to 38°C and observed for 2 h.

Results: Survival rate at 2 h after rewarming was 5 out of 8 animals in the CPB₃₀ group, and 8 out of 8 in the CPB₃₆ group. All surviving animals displayed significant acute cardiac dysfunction irrespective of rewarming method. Differences between groups in CPB exposure time or rewarming rate created no differences in need for vascular volume supply, in variables of cerebral metabolism, or in cerebral pressures and blood flow.

Conclusion: As 3 out of 8 animals did not survive weaning from CPB at 30°C, early weaning gave no advantages over weaning at 36°C. Further, in surviving animals, the results showed no differences between groups in the need for vascular volume replacement, nor any differences in cerebral blood flow or pressures. Most prominent, after weaning from CPB, was the existence of acute cardiac failure which was responsible for the inability to create an adequate perfusion irrespective of rewarming strategy.

Autoregulation of Cerebral Blood Flow During 3-h Continuous Cardiopulmonary Resuscitation at 27°C

Introduction: Victims of accidental hypothermia in hypothermic cardiac arrest (HCA) may survive with favorable neurologic outcome if early and continuous prehospital cardiopulmonary resuscitation (CPR) is started and continued during evacuation and transport. The efficacy of cerebral autoregulation during hypothermic CPR is largely unknown and is aim of the present experiment. Methods: Anesthetized pigs (n = 8) were surface cooled to HCA at 27°C before 3 h continuous CPR. Central hemodynamics, cerebral O₂ delivery (DO₂) and uptake (VO₂), cerebral blood flow (CBF), and cerebral perfusion pressure (CPP) were determined before cooling, at 32°C and at 27°C, then at 15 min after the start of CPR, and hourly thereafter. To estimate cerebral autoregulation, the static autoregulatory index (sARI), and the CBF/VO₂ ratio were determined. Results: After the initial 15-min period of CPR at 27°C, cardiac output (CO) and mean arterial pressure (MAP) were reduced significantly when compared to corresponding values during spontaneous circulation at 27°C (-66.7% and -44.4%, respectively), and remained reduced during the subsequent 3-h period of CPR. During the first 2-h period of CPR at 27°C, blood flow in five different brain areas remained unchanged when compared to the level during spontaneous circulation at 27°C, but after 3 h of CPR blood flow in 2 of the 5 areas was significantly reduced. Cooling to 27°C reduced cerebral DO₂ by 67.3% and VO₂ by 84.4%. Cerebral VO₂ was significantly reduced first after 3 h of CPR. Cerebral DO₂ remained unaltered compared to corresponding levels measured during spontaneous circulation at 27°C. Cerebral autoregulation was preserved (sARI > 0.4), at least during the first 2 h of CPR. Interestingly, the CBF/VO₂ ratio during spontaneous circulation at 27°C indicated the presence of an affluent cerebral DO₂, whereas after CPR, the CBF/VO₂ ratio returned to the level of spontaneous circulation at 38°C. Conclusion: Despite a reduced CO, continuous CPR for 3 h at 27°C provided sufficient cerebral DO₂ to maintain aerobic metabolism and to preserve cerebral autoregulation during the first 2-h period of CPR. This new information supports early start and continued CPR in accidental hypothermia patients during rescue and transportation for in hospital rewarming.

[Medical liability and criminal law in emergency medicine]

Medical liability is booming. Malpractice can entail both civil and criminal consequences. Besides financial and custodial penalties, at worst the license to practice medicine can be withdrawn. Physicians owe their patients a treatment according to current standards. Furthermore, physicians are obliged to fulfill their duty of care. Nevertheless, the patient's right of self-determination must not be violated. Especially in emergency situations, physicians have to focus on taking protective measures in order to avert further dangers to the health of patients. This article analyses common pitfalls in emergency medical treatment with respect to the legal aspects.

Physiological Changes in Subjects Exposed to Accidental Hypothermia: An Update

Background

Accidental hypothermia (AH) is an unintended decrease in body core temperature (BCT) to below 35°C. We present an update on physiological/pathophysiological changes associated with AH and rewarming from hypothermic cardiac arrest (HCA).

Temperature Regulation and Metabolism

Triggered by falling skin temperature, Thyrotropin-Releasing Hormone (TRH) from hypothalamus induces release of Thyroid-Stimulating Hormone (TSH) and Prolactin from pituitary gland anterior lobe that stimulate thyroid generation of triiodothyronine and thyroxine (T4). The latter act together with noradrenaline to induce heat production by binding to adrenergic β3-receptors in fat cells. Exposed to cold, noradrenaline prompts degradation of triglycerides from brown adipose tissue (BAT) into free fatty acids that uncouple metabolism to heat production, rather than generating adenosine triphosphate. If BAT is lacking, AH occurs more readily.

Cardiac Output

Assuming a 7% drop in metabolism per °C, a BCT decrease of 10°C can reduce metabolism by 70% paralleled by a corresponding decline in CO. Consequently, it is possible to maintain adequate oxygen delivery provided correctly performed cardiopulmonary resuscitation (CPR), which might result in approximately 30% of CO generated at normal BCT.

Liver and Coagulation

AH promotes coagulation disturbances following trauma and acidosis by reducing coagulation and platelet functions. Mean prothrombin and partial thromboplastin times might increase by 40-60% in moderate hypothermia. Rewarming might release tissue factor from damaged tissues, that triggers disseminated intravascular coagulation. Hypothermia might inhibit platelet aggregation and coagulation.

Kidneys

Renal blood flow decreases due to vasoconstriction of afferent arterioles, electrolyte and fluid disturbances and increasing blood viscosity. Severely deranged renal function occurs particularly in the presence of rhabdomyolysis induced by severe AH combined with trauma.

Conclusion

Metabolism drops 7% per °C fall in BCT, reducing CO correspondingly. Therefore, it is possible to maintain adequate oxygen delivery after 10°C drop in BCT provided correctly performed CPR. Hypothermia may facilitate rhabdomyolysis in traumatized patients. Victims suspected of HCA should be rewarmed before being pronounced dead. Rewarming avalanche victims of HCA with serum potassium > 12 mmol/L and a burial time >30 min with no air pocket, most probably be futile.

Effects of Carbon Dioxide and Temperature on the Oxygen-Hemoglobin Dissociation Curve of Human Blood: Implications for Avalanche Victims

Completely avalanche-buried patients are frequently exposed to a combination of hypoxia and hypercapnia with a risk of normothermic cardiac arrest. Patients with a long burial time and an air pocket are exposed to a combination of hypoxia, hypercapnia, and hypothermia which may lead to the development of the “triple H syndrome”. This specific combination has several pathophysiological implications, particularly on the cardiovascular system and oxygen transport (oxygen supply and oxygen consumption). To examine the effects on hemoglobin oxygen affinity, we investigated venous blood samples from 15 female and 15 male healthy subjects. In a factorial design of four different carbon dioxide partial pressure (PCO2) levels (20, 40, 60, and 80 mmHg) and five different temperature levels (13.7°C, 23°C, 30°C, 37°C, and 42°C), 30 unbuffered whole blood samples were analyzed in a newly developed in vitro method for high-throughput oxygen dissociation curve (ODC) measurements. P50s, Hill coefficients, CO2-Bohr coefficients, and temperature coefficients were analyzed using a linear mixed model (LMM). Mean P50 at baseline (37°C, 40 mmHg PCO2) was 27.1 ± 2.6 mmHg. Both CO2-Bohr (p < 0.001) and temperature coefficients (p < 0.001) had a significant effect on P50. The absolute CO2 effect was still pronounced at normothermic and febrile temperatures, whereas at low temperatures, the relative CO2 effect (expressed by CO2-Bohr coefficient; p < 0.001, interaction) was increased. The larger impact of PCO2 on oxygen affinity at low temperature may be caused by the competition of 2,3-BPG with PCO2 and the exothermic binding characteristic of 2,3-BPG. In a model of an avalanche burial, based on published data of CO2 levels and cooling rates, we calculated the resulting P50 for this specific condition based on the here-reported PCO2 and temperature effect on ODC. Depending on the degree of hypercapnia and hypothermia, a potentially beneficial increase in hemoglobin oxygen affinity in the hypoxic condition might ensue.

2021 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations: Summary From the Basic Life Support; Advanced Life Support; Neonatal Life Support; Education, Implementation, and Teams; First Aid Task Forces; and the COVID-19 Working Group

The International Liaison Committee on Resuscitation initiated a continuous review of new, peer-reviewed published cardiopulmonary resuscitation science. This is the fifth annual summary of the International Liaison Committee on Resuscitation International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations; a more comprehensive review was done in 2020. This latest summary addresses the most recently published resuscitation evidence reviewed by International Liaison Committee on Resuscitation task force science experts. Topics covered by systematic reviews in this summary include resuscitation topics of video-based dispatch systems; head-up cardiopulmonary resuscitation; early coronary angiography after return of spontaneous circulation; cardiopulmonary resuscitation in the prone patient; cord management at birth for preterm and term infants; devices for administering positive-pressure ventilation at birth; family presence during neonatal resuscitation; self-directed, digitally based basic life support education and training in adults and children; coronavirus disease 2019 infection risk to rescuers from patients in cardiac arrest; and first aid topics, including cooling with water for thermal burns, oral rehydration for exertional dehydration, pediatric tourniquet use, and methods of tick removal. Members from 6 International Liaison Committee on Resuscitation task forces have assessed, discussed, and debated the quality of the evidence, according to the Grading of Recommendations Assessment, Development, and Evaluation criteria, and their statements include consensus treatment recommendations or good practice statements. Insights into the deliberations of the task forces are provided in Justification and Evidence-to-Decision Framework Highlights sections. In addition, the task forces listed priority knowledge gaps for further research.

[Medical liability and criminal law in emergency medicine]

Medical liability is booming. Malpractice can entail both civil and criminal consequences. Besides financial and custodial penalties, at worst the license to practice medicine can be withdrawn. Physicians owe their patients a treatment according to current standards. Furthermore, physicians are obliged to fulfill their duty of care. Nevertheless, the patient's right of self-determination must not be violated. Especially in emergency situations, physicians have to focus on taking protective measures in order to avert further dangers to the health of patients. This article analyses common pitfalls in emergency medical treatment with respect to the legal aspects.

2021 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations: Summary From the Basic Life Support; Advanced Life Support; Neonatal Life Support; Education, Implementation, and Teams; First Aid Task Forces; and the COVID-19 Working Group

The International Liaison Committee on Resuscitation initiated a continuous review of new, peer-reviewed published cardiopulmonary resuscitation science. This is the fifth annual summary of the International Liaison Committee on Resuscitation International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations; a more comprehensive review was done in 2020. This latest summary addresses the most recently published resuscitation evidence reviewed by International Liaison Committee on Resuscitation task force science experts. Topics covered by systematic reviews in this summary include resuscitation topics of video-based dispatch systems; head-up cardiopulmonary resuscitation; early coronary angiography after return of spontaneous circulation; cardiopulmonary resuscitation in the prone patient; cord management at birth for preterm and term infants; devices for administering positive-pressure ventilation at birth; family presence during neonatal resuscitation; self-directed, digitally based basic life support education and training in adults and children; coronavirus disease 2019 infection risk to rescuers from patients in cardiac arrest; and first aid topics, including cooling with water for thermal burns, oral rehydration for exertional dehydration, pediatric tourniquet use, and methods of tick removal. Members from 6 International Liaison Committee on Resuscitation task forces have assessed, discussed, and debated the quality of the evidence, according to the Grading of Recommendations Assessment, Development, and Evaluation criteria, and their statements include consensus treatment recommendations or good practice statements. Insights into the deliberations of the task forces are provided in Justification and Evidence-to-Decision Framework Highlights sections. In addition, the task forces listed priority knowledge gaps for further research.

Pediatric Hypothermia: An Ambiguous Issue

Hypothermia in pediatrics is mainly about small body size. The key thermal factor here is the large surface-to-volume ratio. Although small mammals, including human infants and children, are adapted to higher heat losses through their elevated metabolic rate and thermogenic capacity, they are still at risk of hypothermia because of a small regulatory range and an impending metabolic exhaustion. However, some small mammalian species (hibernators) use reduced metabolic rates and lowered body temperatures as adaptations to impaired energy supply. Similar to nature, hypothermia has contradictory effects in clinical pediatrics as well: In neonates, it is a serious risk factor affecting respiratory adaptation in term and developmental outcome in preterm infants. On the other hand, it is an important self-protective response to neonatal hypoxia and an evidence-based treatment option for asphyxiated babies. In children, hypothermia first enabled the surgical repair of congenital heart defects and promotes favorable outcome after ice water drowning. Yet, it is also a major threat in various prehospital and clinical settings and has no proven therapeutic benefit in pediatric critical care. All in all, pediatric hypothermia is an ambiguous issue whose harmful or beneficial effects strongly depend on the particular circumstances.

Intensive care with extracorporeal membrane oxygenation rewarming in accident severe hypothermia (ICE-CRASH) study: a protocol for a multicentre prospective, observational study in Japan

INTRODUCTION

Accidental hypothermia (AH) is a rare but critical disease, leading to death in severe cases. In recent decades, extracorporeal membrane oxygenation (ECMO) has been successfully used to rewarm hypothermic patients with cardiac arrest or circulation instability. However, data on the efficacy of rewarming using ECMO for patients with AH are limited. Therefore, a large-scale, multicentre, prospective study is warranted. The primary objective of this study will be to clarify the effectiveness of rewarming using ECMO for patients with AH. Our secondary objectives will be to compare the incidence of adverse effects between ECMO rewarming and non-ECMO rewarming and to identify the most appropriate management of ECMO for AH.

METHODS AND ANALYSES

The Intensive Care with ExtraCorporeal membrane oxygenation Rewarming in Accidentally Severe Hypothermia study is taking place in 35 tertiary emergency medical facilities in Japan. The inclusion criteria are patients ≥18 years old with a body temperature ≤32°C. We will include patients with AH who present to the emergency department from December 2019 to March 2022. The research personnel at each hospital will collect several variables, including patient demographics, rewarming method, ECMO data and complications. Our primary outcome is to compare the 28-day survival rate between the ECMO and non-ECMO (other treatments) groups among patients with severe AH. Our secondary outcomes are to compare the following values between the ECMO and non-ECMO groups: length of stay in the intensive-care unit and complications. Furthermore, in patients with cardiac arrest, the Cerebral Performance Category score at discharge will be compared between both groups.

ETHICS AND DISSEMINATION

This study received research ethics approval from Asahikawa Medical University (18194 and 19115). The study was approved by the institutional review board of each hospital, and the requirement for informed consent was waived due to the observational nature of the study.

TRIAL REGISTRATION NUMBER

UMIN000036132.

Rewarming With Closed Thoracic Lavage Following 3-h CPR at 27°C Failed to Reestablish a Perfusing Rhythm

Introduction: Previously, we showed that the cardiopulmonary resuscitation (CPR) for hypothermic cardiac arrest (HCA) maintained cardiac output (CO) and mean arterial pressure (MAP) to the same reduced level during normothermia (38°C) vs. hypothermia (27°C). In addition, at 27°C, the CPR for 3-h provided global O₂ delivery (DO₂) to support aerobic metabolism. The present study investigated if rewarming with closed thoracic lavage induces a perfusing rhythm after 3-h continuous CPR at 27°C.

Materials and Methods: Eight male pigs were anesthetized, and immersion-cooled. At 27°C, HCA was electrically induced, CPR was started and continued for a 3-h period. Thereafter, the animals were rewarmed by combining closed thoracic lavage and continued CPR. Organ blood flow was measured using microspheres.

Results: After cooling with spontaneous circulation to 27°C, MAP and CO were initially reduced by 37 and 58% from baseline, respectively. By 15 min after the onset of CPR, MAP, and CO were further reduced by 58 and 77% from baseline, respectively, which remained unchanged throughout the rest of the 3-h period of CPR. During CPR at 27°C, DO₂ and O₂ extraction rate (VO₂) fell to critically low levels, but the simultaneous small increase in lactate and a modest reduction in pH, indicated the presence of maintained aerobic metabolism. During rewarming with closed thoracic lavage, all animals displayed ventricular fibrillation, but only one animal could be electro-converted to restore a short-lived perfusing rhythm. Rewarming ended in circulatory collapse in all the animals at 38°C.

Conclusion: The CPR for 3-h at 27°C managed to sustain lower levels of CO and MAP sufficient to support global DO₂. Rewarming accidental hypothermia patients following prolonged CPR for HCA with closed thoracic lavage is not an alternative to rewarming by extra-corporeal life support as these patients are often in need of massive cardio-pulmonary support during as well as after rewarming.

Physiological Impact of Hypothermia: The Good, the Bad and the Ugly

Hypothermia is defined as a core body temperature of < 35°C, and as body temperature is reduced the impact on physiological processes can be beneficial or detrimental. The beneficial effect of hypothermia enables circulation of cooled experimental animals to be interrupted for 1-2 h without creating harmful effects, while tolerance of circulation arrest in normothermia is between 4 and 5 min. This striking difference has attracted so many investigators, experimental as well as clinical, to this field, and this discovery was fundamental for introducing therapeutic hypothermia in modern clinical medicine in the 1950's. Together with the introduction of cardiopulmonary bypass, therapeutic hypothermia has been the cornerstone in the development of modern cardiac surgery. Therapeutic hypothermia also has an undisputed role as a protective agent in organ transplantation and as a therapeutic adjuvant for cerebral protection in neonatal encephalopathy. However, the introduction of therapeutic hypothermia for organ protection during neurosurgical procedures or as a scavenger after brain and spinal trauma has been less successful. In general, the best neuroprotection seems to be obtained by avoiding hyperthermia in injured patients. Accidental hypothermia occurs when endogenous temperature control mechanisms are incapable of maintaining core body temperature within physiologic limits and core temperature becomes dependent on ambient temperature. During hypothermia spontaneous circulation is considerably reduced and with deep and/or prolonged cooling, circulatory failure may occur, which may limit safe survival of the cooled patient. Challenges that limit safe rewarming of accidental hypothermia patients include cardiac arrhythmias, uncontrolled bleeding, and "rewarming shock".

Management of hypothermic submersion associated cardiac arrest in a 5-year-old child: A case report

We report a case of severe accidental hypothermia (core body temperature of 26.8 °C) in a five-year-old boy due to submersion in freezing lake water. The child was brought to the hospital intubated, in cardiac arrest rhythm of pulseless electrical activity and with dilated and nonreactive pupils. We continued with cardiopulmonary resuscitation and administrated adrenaline in boluses (10 μg/kg) and infusion (0.2 μg/kg/min). Spontaneous circulation returned after 50 minutes. Rewarming was performed with minimally invasive techniques. Post resuscitation he was admitted to the intensive care unit, where he required venovenous extracorporeal membrane oxygenation due to respiratory failure. He was discharged from the hospital neurologically intact and without organ damage on day 17 post arrest.

Hypothermic Cardiac Arrest - Retrospective cohort study from the International Hypothermia Registry

AIM

The International Hypothermia Registry (IHR) was created to increase knowledge of accidental hypothermia, particularly to develop evidence-based guidelines and find reliable outcome predictors. The present study compares hypothermic patients with and without cardiac arrest included in the IHR.

METHODS

Demographic, pre-hospital and in-hospital data, method of rewarming and outcome data were collected anonymously in the IHR between 2010 and 2020.

RESULTS

Two hundred and one non-consecutive cases were included. The major causeof hypothermia was mountain accidents, predominantly in young men. Hypothermic Cardiac Arrest (HCA) occurred in 73 of 201 patients. Core temperature was significantly lower in the patients in cardiac arrest (25.0 vs. 30.0 °C, p < 0.001). One hundred and fifteen patients were rewarmed externally (93% with ROSC), 53 by extra-corporeal life support (ECLS) (40% with ROSC) and 21 with invasive internal techniques (71% with ROSC). The overall survival rate was 95% for patients with preserved circulation and 36% for those in cardiac arrest. Witnessed cardiac arrest and ROSC before rewarming were positive outcome predictors, asphyxia, coagulopathy, high potassium and lactate negative outcome predictors.

CONCLUSIONS

This first analysis of 201 IHR patients with moderate to severe accidental hypothermia shows an excellent 95% survival rate for patients with preserved circulation and 36% for HCA patients. Witnessed cardiac arrest, restoration of spontaneous circulation, low potassium and lactate and absence of asphyxia were positive survival predictors despite hypothermia in young, healthy adults after mountaineering accidents. However, accidental hypothermia is a heterogenous entity that should be considered in both treatment strategies and prognostication.

[Paediatric Life Support]

The European Resuscitation Council (ERC) Paediatric Life Support (PLS) guidelines are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations of the International Liaison Committee on Resuscitation (ILCOR). This section provides guidelines on the management of critically ill or injured infants, children and adolescents before, during and after respiratory/cardiac arrest.

Rewarming From Hypothermic Cardiac Arrest Applying Extracorporeal Life Support: A Systematic Review and Meta-Analysis

Introduction: This systematic review and meta-analysis aims at comparing outcomes of rewarming after accidental hypothermic cardiac arrest (HCA) with cardiopulmonary bypass (CPB) or/and extracorporeal membrane oxygenation (ECMO). Material and Methods: Literature searches were limited to references with an abstract in English, French or German. Additionally, we searched reference lists of included papers. Primary outcome was survival to hospital discharge. We assessed neurological outcome, differences in relative risks (RR) of surviving, as related to the applied rewarming technique, sex, asphyxia, and witnessed or unwitnessed HCA. We calculated hypothermia outcome prediction probability score after extracorporeal life support (HOPE) in patients in whom we found individual data. P < 0.05 considered significant. Results: Twenty-three case observation studies comprising 464 patients were included in a meta-analysis comparing outcomes of rewarming with CPB or/and ECMO. One-hundred-and-seventy-two patients (37%) survived to hospital discharge, 76 of 245 (31%) after CPB and 96 of 219 (44 %) after ECMO; 87 and 75%, respectively, had good neurological outcomes. Overall chance of surviving was 41% higher (P = 0.005) with ECMO as compared with CPB. A man and a woman had 46% (P = 0.043) and 31% (P = 0.115) higher chance, respectively, of surviving with ECMO as compared with CPB. Avalanche victims had the lowest chance of surviving, followed by drowning and people losing consciousness in cold environments. Assessed by logistic regression, asphyxia, unwitnessed HCA, male sex, high initial body temperature, low pH and high serum potassium (s-K+) levels were associated with reduced chance of surviving. In patients displaying individual data, overall mean predictive surviving probability (HOPE score; n = 134) was 33.9 ± 33.6% with no significant difference between ECMO and CPB-treated patients. We also surveyed 80 case reports with 96 victims of HCA, who underwent resuscitation with CPB or ECMO, without including them in the meta-analysis. Conclusions: The chance of surviving was significantly higher after rewarming with ECMO, as compared to CPB, and in patients with witnessed compared to unwitnessed HCA. Avalanche victims had the lowest probability of surviving. Male sex, high initial body temperature, low pH, and high s-K+ were factors associated with low surviving chances.

Accidental hypothermia: Factors related to a prolonged hospital stay - A nationwide observational study in Japan

BACKGROUND

The incidence of accidental hypothermia (AH) is low, and the length of hospital stay in patients with AH remains poorly understood. The present study explored which factors were related to prolonged hospitalization among patients with AH using Japan's nationwide registry data.

METHODS

The data from the Hypothermia STUDY 2018, which included patients ≥18 years old with a body temperature ≤ 35 °C, were obtained from a multicenter registry for AH conducted at 89 institutions throughout Japan, collected from December 1, 2018, to February 28, 2019. The patients were divided into a "short-stay patients" group (within 7 days) and "long-stay patients" group (more than 7 days). A logistic regression analysis after multiple imputation was performed to obtain odds ratios (ORs) for prolonged hospitalization with age, frailty, location, causes underlying the hypothermia, temperature, pH, potassium level, and disseminated intravascular coagulation (DIC) score as independent variables.

RESULTS

In total, 656 patients were included in the study, of which 362 were eligible for the analysis. The median length of hospital stay was 17 days. Of the 362 patients, 265 (73.2%) stayed in the hospital for more than 7 days. The factors associated with prolonged hospitalization were frailty (OR, 2.11; 95% confidence interval [CI], 1.09-4.10; p = 0.027), the occurrence of indoor (OR, 3.20; 95% CI, 1.58-6.46; p = 0.001), alcohol intoxication (OR, 0.17; 95% CI, 0.05-0.56; p = 0.004), pH (OR, 0.07; 95% CI, 0.01-0.76; p = 0.029), potassium level (OR, 1.36; 95% CI, 1.00-1.85; p = 0.048), and DIC score (OR, 1.54; 95% CI, 1.13-2.10; p = 0.006).

CONCLUSIONS

Frailty, indoor situation, alcohol intoxication, pH value, potassium level, and DIC score were factors contributing to prolonged hospitalization in patients with AH. Preventing frailty may help reduce the length of hospital stay in patients with AH. In addition, measuring the pH value and potassium level by an arterial blood gas analysis at the ED is recommended for the early evaluation of AH.

European Resuscitation Council Guidelines 2021: Paediatric Life Support

These European Resuscitation Council Paediatric Life Support (PLS) guidelines, are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the management of critically ill infants and children, before, during and after cardiac arrest.

Resuscitation and emergency care in drowning: A scoping review

BACKGROUND

The ILCOR Basic Life Support Task Force and the international drowning research community considered it timely to undertake a scoping review of the literature to identify evidence relating to the initial resuscitation, hospital-based interventions and criteria for safe discharge related to drowning.

METHODS

Medline, PreMedline, Embase, Cochrane Reviews and Cochrane CENTRAL were searched from 2000 to June 2020 to identify relevant literature. Titles and abstracts and if necessary full text were reviewed in duplicate. Studies were eligible for inclusion if they reported on the population (adults and children who are submerged in water), interventions (resuscitation in water/boats, airway management, oxygen administration, AED use, bystander CPR, ventilation strategies, ECMO, protocols for hospital discharge (I), comparator (standard care) and outcomes (O) survival, survival with a favourable neurological outcome, CPR quality, physiological end-points).

RESULTS

The database search yielded 3242 references (Medline 1104, Pre-Medline 202, Embase 1722, Cochrane reviews 12, Cochrane CENTRAL 202). After removal of duplicates 2377 papers were left for screening titles and abstracts. In total 65 unique papers were included. The evidence identified was from predominantly high-income countries and lacked consistency in the populations, interventions and outcomes reported. Clinical studies were exclusively observational in nature.

CONCLUSION

This scoping review found that there is very limited evidence from observational studies to inform evidence based clinical practice guidelines for drowning. The review highlights an urgent need for high quality research in drowning.

Unrecognized platelet physiology is the cause of rewarming deaths in accidental hypothermia and neonatal cold injury

BACKGROUND

The lack of improvement in prognosis of accidental hypothermia and neonatal cold injury suggests that a major cause of mortality has not been appreciated.

AIM OF THE ARTICLE

To show that thrombocytopenia that deepens on rewarming under certain conditions is that missing factor.

SCIENTIFIC BASIS

Below 34 °C the first stage of aggregation is accentuated, the platelets are more sensitive to ADP and aggregation studies show an increased response "first stage hyper aggregation". We have confirmed that the irreversible second stage of platelet aggregation does not occur below 34 °C. On rewarming, the first stage of aggregation is followed by disaggregation. When platelets are warmed to 34 °C the potential exists for the platelets to undergo an irreversible second stage of aggregation "second stage platelet hyper aggregation" that can cause a further drop in platelet count and a bleeding diathesis. This only occurs if the platelets have been sufficiently primed when cold and may not be appreciated if platelet counts are not followed.

SIGNIFICANCE OF THIS DATA AND CORRELATION WITH THE LITERATURE

This thesis explains many other open questions. Why has the overall prognosis remained without improvement over the last half century? Why hypothermic cardiac surgery is free of this problem? Why the depth of hypothermia is alone not prognostic? Has following platelet counts been associated with improved prognosis? Why cardiac arrest does not affect prognosis? Why some patients die suddenly after recovering from hypothermia? Why are so many different rewarming techniques used? Why is the prognosis better in hypothermic suicide attempts? What is the pathophysiological explanation for reversible sequestration of platelets to the liver and spleen in hypothermia? Is DIC (diffuse intravascular coagulation) a problem in hypothermia? And how this new approach could improve prognosis?

CONCLUSION

Prognosis can be improved by following platelet counts during rewarming. In patients with prolonged hypothermia, this will show a life-threatening drop in such counts easily treated by platelet infusion.

Adult Basic Life Support: International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations

This 2020 International Consensus on Cardiopulmonary Resuscitation (CPR) and Emergency Cardiovascular Care Science With Treatment Recommendations on basic life support summarizes evidence evaluations performed for 20 topics that were prioritized by the Basic Life Support Task Force of the International Liaison Committee on Resuscitation. The evidence reviews include 16 systematic reviews, 3 scoping reviews, and 1 evidence update. Per agreement within the International Liaison Committee on Resuscitation, new or revised treatment recommendations were only made after a systematic review.

Systematic reviews were performed for the following topics: dispatch diagnosis of cardiac arrest, use of a firm surface for CPR, sequence for starting CPR (compressions-airway-breaths versus airway-breaths-compressions), CPR before calling for help, duration of CPR cycles, hand position during compressions, rhythm check timing, feedback for CPR quality, alternative techniques, public access automated external defibrillator programs, analysis of rhythm during chest compressions, CPR before defibrillation, removal of foreign-body airway obstruction, resuscitation care for suspected opioid-associated emergencies, drowning, and harm from CPR to victims not in cardiac arrest.

The topics that resulted in the most extensive task force discussions included CPR during transport, CPR before calling for help, resuscitation care for suspected opioid-associated emergencies, feedback for CPR quality, and analysis of rhythm during chest compressions. After discussion of the scoping reviews and the evidence update, the task force prioritized several topics for new systematic reviews.

Adult Basic Life Support: 2020 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations

This2020 International Consensus on Cardiopulmonary Resuscitation(CPR)and Emergency Cardiovascular Care Science With Treatment Recommendationson basic life support summarizes evidence evaluations performed for 22 topics that were prioritized by the Basic Life Support Task Force of the International Liaison Committee on Resuscitation. The evidence reviews include 16 systematic reviews, 5 scoping reviews, and 1 evidence update. Per agreement within the International Liaison Committee on Resuscitation, new or revised treatment recommendations were only made after a systematic review.

Systematic reviews were performed for the following topics: dispatch diagnosis of cardiac arrest, use of a firm surface for CPR, sequence for starting CPR (compressions-airway-breaths versus airway-breaths-compressions), CPR before calling for help, duration of CPR cycles, hand position during compressions, rhythm check timing, feedback for CPR quality, alternative techniques, public access automated external defibrillator programs, analysis of rhythm during chest compressions, CPR before defibrillation, removal of foreign-body airway obstruction, resuscitation care for suspected opioid-associated emergencies, drowning, and harm from CPR to victims not in cardiac arrest.

The topics that resulted in the most extensive task force discussions included CPR during transport, CPR before calling for help, resuscitation care for suspected opioid-associated emergencies, feedback for CPR quality, and analysis of rhythm during chest compressions. After discussion of the scoping reviews and the evidence update, the task force prioritized several topics for new systematic reviews.

Outcomes of patients suffering unwitnessed hypothermic cardiac arrest rewarmed with extracorporeal life support: A systematic review

Prolonged cardiac arrest (CA) may lead to neurologic deficit in survivors. Good outcome is especially rare when CA was unwitnessed. However, accidental hypothermia is a very specific cause of CA. Our goal was to describe the outcomes of patients who suffered from unwitnessed hypothermic cardiac arrest (UHCA) supported with Extracorporeal Life Support (ECLS). We included consecutive patients' cohorts identified by systematic literature review concerning patients suffering from UHCA and rewarmed with ECLS. Patients were divided into four subgroups regarding the mechanism of cooling, namely: air exposure; immersion; submersion; and avalanche. A statistical analysis was performed in order to identify the clinical parameters associated with good outcome (survival and absence of neurologic impairment). A total of 221 patients were included into the study. The overall survival rate was 27%. Most of the survivors (83%), had no neurologic deficit. Asystole was the presenting CA rhythm in 48% survivors, of which 79% survived with good neurologic outcome. Variables associated with survival included the following: female gender (P < .001); low core temperature (P = .005); non-asphyxia-related mechanism of cooling (P < .001); pulseless electrical activity as an initial rhythm (P < .001); high blood pH (P < .001); low lactate levels (P = .003); low serum potassium concentration (P < .001); and short resuscitation duration (P = .004). Severely hypothermic patients with unwitnessed CA may survive with good neurologic outcome, including those presenting as asystole. The initial blood pH, potassium, and lactate concentration may help predict outcome in hypothermic CA.

Predictive accuracy of biomarkers for survival among cardiac arrest patients with hypothermia: a prospective observational cohort study in Japan

Background

There is limited information on the predictive accuracy of commonly used predictors, such as lactate, pH or serum potassium for the survival among out-of-hospital cardiac arrest (OHCA) patients with hypothermia. This study aimed to identify the predictive accuracy of these biomarkers for survival among OHCA patients with hypothermia.

Methods

In this retrospective analysis, we analyzed the data from a multicenter, prospective nationwide registry among OHCA patients transported to emergency departments in Japan (the JAAM-OHCA Registry). We included all adult (≥18 years) OHCA patients with hypothermia (≤32.0 °C) who were registered from June 2014 to December 2017 and whose blood test results on hospital arrival were recorded. We calculated the predictive accuracy of pH, lactate, and potassium for 1-month survival.

Results

Of the 34,754 patients in the JAAM-OHCA database, we included 754 patients from 66 hospitals. The 1-month survival was 5.8% (44/754). The areas under the curve of the predictors and 95% confidence interval were as follows: pH 0.829 [0.767–0.877] and lactate 0.843 [0.793–0.882]. On setting the cutoff points of 6.9 in pH and 120 mg/dL (13.3 mmol/L) in lactate, the predictors had a high sensitivity (lactate: 0.91; pH 0.91) and a low negative likelihood ratio (lactate: 0.14; pH 0.13), which are suitable to exclude survival to 1 month. Furthermore, in additional analysis that included only the patients with potassium values available, a cutoff point of 7.0 (mmol/L) for serum potassium had high sensitivity (0.96) and a low negative likelihood ratio (0.09).

Conclusion

This study indicated the predictive accuracy of serum lactate, pH, and potassium for 1-month survival among adult OHCA patients with hypothermia. These biomarkers may help define a more appropriate resuscitation strategy.

Extracorporeal Membrane Oxygenation for Respiratory Failure

This review focuses on the use of veno-venous extracorporeal membrane oxygenation for respiratory failure across all blood flow ranges. Starting with a short overview of historical development, aspects of the physiology of gas exchange (i.e., oxygenation and decarboxylation) during extracorporeal circulation are discussed. The mechanisms of phenomena such as recirculation and shunt playing an important role in daily clinical practice are explained.Treatment of refractory and symptomatic hypoxemic respiratory failure (e.g., acute respiratory distress syndrome [ARDS]) currently represents the main indication for high-flow veno-venous-extracorporeal membrane oxygenation. On the other hand, lower-flow extracorporeal carbon dioxide removal might potentially help to avoid or attenuate ventilator-induced lung injury by allowing reduction of the energy load (i.e., driving pressure, mechanical power) transmitted to the lungs during mechanical ventilation or spontaneous ventilation. In the latter context, extracorporeal carbon dioxide removal plays an emerging role in the treatment of chronic obstructive pulmonary disease patients during acute exacerbations. Both applications of extracorporeal lung support raise important ethical considerations, such as likelihood of ultimate futility and end-of-life decision-making. The review concludes with a brief overview of potential technical developments and persistent challenges.

Study of the Effects of 3 h of Continuous Cardiopulmonary Resuscitation at 27°C on Global Oxygen Transport and Organ Blood Flow

Aims

Complete restitution of neurologic function after 6 h of pre-hospital resuscitation and in-hospital rewarming has been reported in accidental hypothermia patients with cardiac arrest (CA). However, the level of restitution of circulatory function during long-lasting hypothermic cardiopulmonary resuscitation (CPR) remains largely unknown. We compared the effects of CPR in replacing spontaneous circulation during 3 h at 27°C vs. 45 min at normothermia by determining hemodynamics, global oxygen transport (DO₂), oxygen uptake (VO₂), and organ blood flow.

Methods

Anesthetized pigs (n = 7) were immersion cooled to CA at 27°C. Predetermined variables were compared: (1) Before cooling, during cooling to 27°C with spontaneous circulation, after CA and subsequent continuous CPR (n = 7), vs. (2) before CA and during 45 min CPR in normothermic pigs (n = 4).

Results

When compared to corresponding values during spontaneous circulation at 38°C: (1) After 15 min of CPR at 27°C, cardiac output (CO) was reduced by 74%, mean arterial pressure (MAP) by 63%, DO₂ by 47%, but organ blood flow was unaltered. Continuous CPR for 3 h maintained these variables largely unaltered except for significant reduction in blood flow to the heart and brain after 3 h, to the kidneys after 1 h, to the liver after 2 h, and to the stomach and small intestine after 3 h. (2) After normothermic CPR for 15 min, CO was reduced by 71%, MAP by 54%, and DO₂ by 63%. After 45 min, hemodynamic function had deteriorated significantly, organ blood flow was undetectable, serum lactate increased by a factor of 12, and mixed venous O₂ content was reduced to 18%.

Conclusion

The level to which CPR can replace CO and MAP during spontaneous circulation at normothermia was not affected by reduction in core temperature in our setting. Compared to spontaneous circulation at normothermia, 3 h of continuous resuscitation at 27°C provided limited but sufficient O₂ delivery to maintain aerobic metabolism. This fundamental new knowledge is important in that it encourages early and continuous CPR in accidental hypothermia victims during evacuation and transport.

Wilderness Medical Society Clinical Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2019 Update

To provide guidance to clinicians, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for the out-of-hospital evaluation and treatment of victims of accidental hypothermia. The guidelines present the main diagnostic and therapeutic modalities and provide recommendations for the management of hypothermic patients. The panel graded the recommendations based on the quality of supporting evidence and a balance between benefits and risks/burdens according to the criteria published by the American College of Chest Physicians. The guidelines also provide suggested general approaches to the evaluation and treatment of accidental hypothermia that incorporate specific recommendations. This is the 2019 update of the Wilderness Medical Society Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2014 Update.

Prognostic ability of the sequential organ failure assessment score in accidental hypothermia: a multi-institutional retrospective cohort study

Background

Severe accidental hypothermia (AH) is life threatening. Thus, prognostic prediction in AH is essential to rapidly initiate intensive care. Several studies on prognostic factors for AH are known, but none have been established. We clarified the prognostic ability of the Sequential Organ Failure Assessment (SOFA) score in comparison with previously reported prognostic factors among patients with AH.

Methods

The J-point registry database is a multi-institutional retrospective cohort study for AH in 12 Japanese emergency departments. From this registry, we enrolled patients who were treated at the intensive care unit (ICU) in various critical care medical centers. In-hospital mortality was the primary outcome. We investigated the discrimination ability of each candidate prognostic factor and the in-hospital mortality by applying the logistic regression models with areas under the receiver operating characteristic curve (AUROC) with 95% confidence interval (CI).

Results

Of the 572 patients with AH registered in the J-point registry, 220 were eligible for the analyses. The in-hospital mortality was 23.2%. The AUROC of the SOFA score (0.80; 95% CI: 0.72–0.86) was the highest among all factors. The other factors were serum potassium (0.65; 95% CI: 0.55–0.73), lactate (0.67; 95% CI: 0.57–0.75), quick SOFA (qSOFA) (0.55; 95% CI: 0.46–0.65), systemic inflammatory response syndrome (SIRS) (0.60; 95% CI: 0.50–0.69), and 5A severity scale (0.77; 95% CI: 0.68–0.84).

Discussion

Although serum potassium and lactate had relatively good discrimination ability as mortality predictors, the SOFA score had slightly better discrimination ability. The reason is that lactate and serum potassium were mainly reflected by the hemodynamic state; conversely, the SOFA score is a comprehensive score of organ failure, basing on six different scores from the respiratory, cardiovascular, hepatic, coagulation, renal, and neurological systems. Meanwhile, the qSOFA and SIRS scores underestimated the severity, with low discrimination abilities for mortality.

Conclusions

The SOFA score demonstrated better discrimination ability as a mortality predictor among all known prognostic factors in patients with AH.

Injury coding in a national trauma registry: a one-year validation audit in a level 1 trauma centre

Background

Hospitals must improve patient safety and quality continuously. Clinical quality registries can drive such improvement. Trauma registries code injuries according to the Abbreviated Injury Scale (AIS) and benchmark outcomes based on the Injury Severity Score (ISS) and New ISS (NISS). The primary aim of this study was to validate the injury codes and severities registered in a national trauma registry. Secondarily, we aimed to examine causes for missing and discordant codes, to guide improvement of registry data quality.

Methods

We conducted an audit and established an expert coder group injury reference standard for patients met with trauma team activation in 2015 in a Level 1 trauma centre. Injuries were coded according to the AIS. The audit included review of all data in the electronic health records (EHR), and new interpretation of all images in the picture archiving system. Validated injury codes were compared with the codes registered in the registry. The expert coder group’s interpretations of reasons for discrepancies were categorised and registered. Inter-rater agreement between registry data and the reference standard was tested with Bland–Altman analysis.

Results

We validated injury data from 144 patients (male sex 79.2%) with median age 31 (inter quartile range 19–49) years. The total number of registered AIS codes was 582 in the registry and 766 in the reference standard. All injuries were concordantly coded in 62 (43.1%) patients. Most non-registered codes (n = 166 in 71 (49.3%) patients) were AIS 1, and information in the EHR overlooked by registrars was the dominating cause. Discordant coding of head injuries and extremity fractures were the most common causes for 157 discordant AIS codes in 74 (51.4%) patients. Median ISS (9) and NISS (12) for the total population did not differ between the registry and the reference standard.

Conclusions

Concordance between the codes registered in the trauma registry and the reference standard was moderate, influencing individual patients’ injury codes validity and ISS/NISS reliability. Nevertheless, aggregated median group ISS/NISS reliability was acceptable.

Engineering Human Stasis for Long-Duration Spaceflight

Suspended animation for deep-space travelers is moving out of the realm of science fiction. Two approaches are considered: the first elaborates the current medical practice of therapeutic hypothermia; the second invokes the cascade of metabolic processes naturally employed by hibernators. We explore the basis and evidence behind each approach and argue that mimicry of natural hibernation will be critical to overcome the innate limitations of human physiology for long-duration space travel.

Cut-off values of serum potassium and core temperature at hospital admission for extracorporeal rewarming of avalanche victims in cardiac arrest: A retrospective multi-centre study

AIM

Evidence of existing guidelines for the on-site triage of avalanche victims is limited and adherence suboptimal. This study attempted to find reliable cut-off values for the identification of hypothermic avalanche victims with reversible out-of-hospital cardiac arrest (OHCA) at hospital admission. This may enable hospitals to allocate extracorporeal life support (ECLS) resources more appropriately while increasing the proportion of survivors among rewarmed victims.

METHODS

All avalanche victims with OHCA admitted to seven centres in Europe capable of ECLS from 1995 to 2016 were included. Optimal cut-off values, for parameters identified by logistic regression, were determined by means of bootstrapping and exact binomial distribution and served to calculate sensitivity, rate of overtriage, positive and negative predictive values, and receiver operating curves.

RESULTS

In total, 103 avalanche victims with OHCA were included. Of the 103 patients 61 (58%) were rewarmed by ECLS. Six (10%) of the rewarmed patients survived whilst 55 (90%) died. We obtained optimal cut-off values of 7 mmol/L for serum potassium and 30 °C for core temperature.

CONCLUSION

For in-hospital triage of avalanche victims admitted with OHCA, serum potassium accurately predicts survival. The combination of the cut-offs 7 mmol/L for serum potassium and 30 °C for core temperature achieved the lowest overtriage rate (47%) and the highest positive predictive value (19%), with a sensitivity of 100% for survivors. The presence of vital signs at extrication is strongly associated with survival. For further optimisation of in-hospital triage, larger datasets are needed to include additional parameters.

Cortical Thickness and Cognitive Performance After Out-of-Hospital Cardiac Arrest

BACKGROUND

Cognitive impairment is common in long-term survivors of out-of-hospital cardiac arrest (OHCA) but corresponding neuroimaging data are lacking.

OBJECTIVES

This study explored the relationship among the cortical brain structure, cognitive performance, and clinical variables after OHCA.

METHODS

Three months after resuscitation, 13 OHCA survivors who had recovered from a coma to living independently and 19 healthy controls were assessed by cerebral magnetic resonance imaging and neuropsychological tests quantifying memory, fine-motor coordination, and attention/executive functions. Cortical thickness (Cth) and surface area (SA) were compared between groups and analyzed for relationships with cognitive performance as well as the clinical variables of coma duration and the time to return of spontaneous circulation (ROSC). All analyses were controlled for age and sex.

RESULTS

Analyses of SA revealed no significant differences. Compared with controls, survivors had significantly reduced memory and fine-motor coordination and significantly thinner cortex in large clusters in the frontal, parietal, and inferior temporal cortices, with additional regions in the left occipital lobe and the left temporal lobe. Widespread thinner cortical regions were significantly associated with decreased memory performance in survivors when compared with those in controls and were significantly associated with an increased time to ROSC and increased coma duration in the OHCA group. Increased coma duration, but not increased time to ROSC, was significantly correlated with cognitive test performance.

CONCLUSIONS

The results suggest that widespread Cth reductions correspond to the cognitive impairments observed after OHCA. Neuroimaging studies of long-term OHCA survivors are warranted to guide the development of diagnostics and treatment options.

Hypothermia outcome prediction after extracorporeal life support for hypothermic cardiac arrest patients: An external validation of the HOPE score

AIMS

The HOPE score, based on covariates available at hospital admission, predicts the probability of in-hospital survival after extracorporeal life support (ECLS) rewarming of a given hypothermic cardiac arrest patient with accidental hypothermia. Our goal was to externally validate the HOPE score.

METHODS

We included consecutive hypothermic arrested patients who underwent rewarming with ECLS. The sample comprised 122 patients. The six independent predictors of survival included in the HOPE score were collected for each patient: age, sex, mechanism of hypothermia, core temperature at admission, serum potassium level at admission and duration of CPR. The primary outcome parameter was survival to hospital discharge.

RESULTS

Overall, 51 of the 122 included patients survived, resulting in an empirical (global) probability of survival of 42% (95% CI = [33-51%]). This was close to the average HOPE survival probability of 38% calculated for patients from the validation cohort, while the Hosmer-Lemeshow test comparing empirical and HOPE (i.e. estimated) probabilities of survival was not significant (p = 0.08), suggesting good calibration. The corresponding area under the receiver operating characteristic curve was 0.825 (95% CI = [0.753-0.897]), confirming the excellent discrimination of the model. The negative predictive value of a HOPE score cut-off of <0.10 was excellent (97%).

CONCLUSIONS

This study provides the first external validation of the HOPE score reaching good calibration and excellent discrimination. Clinically, the prediction of the HOPE score remains accurate in the validation sample. The HOPE score may replace serum potassium in the future as the triage tool when considering ECLS rewarming of a hypothermic cardiac arrest victim.

Extracorporeal membrane oxygenation for accidental deep hypothermia-current challenges and future perspectives

The incidence of accidental hypothermia (core temperature ≤35 °C) is difficult to estimate, as the affected population is heterogeneous. Both temperature and clinical presentation should be considered while determining severity, which is difficult in a prehospital setting. Extracorporeal rewarming is advocated for all Swiss Staging System class IV (hypothermic cardiac arrest) and class III (hypothermic cardiac instability) patients. Veno-arterial extracorporeal membrane oxygenation (ECMO) is the method of choice, as it not only allows a gradual, controlled increase of core body temperature, but also provides respiratory and hemodynamic support during the unstable period of rewarming and reperfusion. This poses difficulties with the coordination of patient management, as usually only cardiac referral centers can deliver such advanced treatment. Further special considerations apply to subgroups of patients, including drowning or avalanche victims. The principle of ECMO implantation in severely hypothermic patients is no different from any other indication, although establishing vascular access in a timely manner during ongoing resuscitation and maintaining adequate flow may require modification of the operating technique, as well as aggressive fluid resuscitation. Further studies are needed in order to determine the optimal rewarming rate and flow that would favor brain and lung protection. Recent analysis shows an overall survival rate of 40.3%, while additional prognostic factors are being sought for determining those patients in whom the treatment is futile. New cannulas, along with ready-to-use ECMO sets, are being developed that would enable easy, safe and efficient out-reach ECMO implantation, thus shortening resuscitation times. Moreover, national guidelines for the management of accidental hypothermia are needed in order that all patients that would benefit from extracorporeal rewarming would be provided with such treatment. In this perspective article, we discuss burning problems in ECMO therapy in hypothermic patients, outlining the important research goals to improve the outcomes.