Clinical characteristics and outcomes of witnessed hypothermic cardiac arrest: A systematic review on rescue collapse

Clinical outcomes of challenging out-of-hospital hypothermia management: A retrospective assessment of DOKEI protocol

BACKGROUND

Accidental hypothermia (AH) is a major cause of death in mountainous areas globally, and the second highest of mountaineering deaths in Japan, accounting for 37 % in Hokkaido. Managing AH is a significant challenge, particularly when adverse weather complicates the application of recommended rewarming and rapid transfer. To address this, the Hokkaido Police Organization (DOKEI) AH protocol was applied in Hokkaido's remote areas from 2011 to 2022, integrating high-temperature active external rewarming (HT-AER) with on-site sustained treatment.

METHODS

This study retrospectively analyzed the rescue reports and hospital records of hypothermia patients treated postprotocol, excluding patients with cold exposure, undetectable vital signs at rescue, and inadequate documentation. Protocol adherence and outcomes-hypothermia stage, cardiocirculatory collapse, survival, and neurological status-were assessed.

RESULTS

Among the 60 protocol-treated patients (19-74 years, 85 % male), 14 had stage 2 hypothermia, and 3 had stage 3 hypothermia. HT-AER was applied in 96.7 % of the patients. A total of 98.3 % of patients improved before handover without cardiac arrest (CA) or extracorporeal life support (ECLS). Comparatively, ten preprotocol patients (18-60 years, 70 % male) had two CAs, one fatal and six with no improvement.

CONCLUSION

The DOKEI AH protocol demonstrates feasibility in managing stages 1-3 hypothermia, enhancing survival and neurological recovery, and can offer a vital option in challenging AH rescue scenarios.

The Outcome of Walking Cold Patients with Potential Mild Hypothermia to Safety-A Mountain Rescue Case Series

INTRODUCTION

Some experts recommend that ambulant hypothermic patients should be rewarmed, fed, and not permitted to exercise for 30 min because of concerns that afterdrop can cause cardiac instability. We investigated the outcome of ambulant hypothermic patients in a case series from mountain rescue teams in Great Britain.

METHODS

A questionnaire was used to collect information on a series of adult patients with a clinical diagnosis of mild hypothermia. All patients were alert on the AVPU scale and evacuated by walking from the mountain. The outcome measures were survival or a change in management because of medical deterioration during evacuation.

RESULTS

A series of 108 eligible cases were reported over a 5-year period. When rescuers arrived on the scene, 98 (91%) patients were stationary, and 10 (9%) were still mobile. Thirty-eight (39%) of the stationary cases were walked immediately off the mountain without any on-scene delay. In the remaining 60 (61%) stationary cases, the decision was taken to delay evacuation to provide food, drinks, and additional clothing. In 3 cases, the use of heat packs indicated an intention to actively rewarm. In cases where the on-scene time was reported, 27 (79%) were known to be mobile again within 20 min. All patients survived, and no adverse medical events occurred in all 108 cases.

CONCLUSIONS

In this study, no adverse events occurred because of immediate mobilization, suggesting that in these cases, there appears to be minimal risk of early activity.

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.

Predictors of cardiac arrest in severe accidental hypothermia

STUDY OBJECTIVE

To indicate predictors of witnessed hypothermic cardiac arrest.

METHODS

We conducted a retrospective analysis of 182 patients with severe accidental hypothermia (i.e., with core body temperature of ≤28 °C) who presented with preserved spontaneous circulation at first contact with medical services. We divided the study population into two groups: patients who suffered hypothermic cardiac arrest (HCA) at any time between encounter with medical service and restoration of normothermia, and those who did not sustain HCA. The analyzed outcome was the occurrence of cardiac arrest prior to achieving normothermia. Hemodynamic and biochemical parameters were analyzed with regard to their association with the outcome.

RESULTS

Fifty-two (29%) patients suffered HCA. In a univariable analysis, four variables were significantly associated with the outcome, namely heart rate (p < 0.001), systolic blood pressure (p = 0.03), ventricular arrhythmia (p = 0.001), and arterial oxygen partial pressure (p = 0.002). In the multivariable logistic regression the best model predicting HCA included heart rate, PaO2, and Base Excess (AUROC = 0.78). In prehospital settings, when blood gas analysis is not available, other multivariable model including heart rate and occurrence of ventricular arrhythmia (AUROC = 0.74) can be used. In this study population, threshold values of heart rate of 43/min, temperature-corrected PaO2 of 72 mmHg, and uncorrected PaO2 of 109 mmHg, presented satisfactory sensitivity and specificity for HCA prediction.

CONCLUSIONS

In patients with severe accidental hypothermia, the occurrence of HCA is associated with a lower heart rate, hypoxemia, ventricular arrhythmia, lower BE, and lower blood pressure. These parameters can be helpful in the early selection of high-risk patients and their allocation to extracorporeal rewarming facilities.

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.

Implementation of Extracorporeal CPR Programs for Out-of-Hospital Cardiac Arrest: Another Tale of Two County Hospitals

Extracorporeal cardiopulmonary resuscitation (ECPR) is a form of intensive life support that has seen increasing use globally to improve outcomes for patients who experience out-of-hospital cardiac arrest (OHCA). Hospitals with advanced critical care capabilities may be interested in launching an ECPR program to offer this support to the patients they serve; however, to do so, they must first consider the significant investment of resources necessary to start and sustain the program. The existing literature describes many single-center ECPR programs and often focuses on inpatient care and patient outcomes in hospitals with cardiac surgery capabilities. However, building a successful ECPR program and using this technology to support an individual patient experiencing refractory cardiac arrest secondary to a shockable rhythm depends on efficient out-of-hospital and emergency department (ED) management. This article describes the process of implementing 2 intensivist-led ECPR programs with limited cardiac surgery capability. We focus on emergency medical services and ED clinician roles in identifying patients, mobilizing resources, initiation and management of veno-arterial extracorporeal membrane oxygenation (VA-ECMO) in the ED, and ongoing efforts to improve ECPR program quality. Each center experienced a significant learning curve to reach goals of arrest-to-flow times of cannulation for ECPR. Building consensus from multidisciplinary stakeholders, including out-of-hospital stakeholders; establishing shared expectations of ECPR outcomes; and ensuring adequate resource support for ECPR activation were all key lessons in improving our ECPR programs.

Termination of Cardiopulmonary Resuscitation in Mountain Rescue: A Scoping Review and ICAR MedCom 2023 Recommendations

Lugnet, Viktor, Miles McDonough, Les Gordon, Mercedes Galindez, Nicolas Mena Reyes, Alison Sheets, Ken Zafren, and Peter Paal. Termination of cardiopulmonary resuscitation in mountain rescue: a scoping review and ICAR MedCom 2023 recommendations. High Alt Med Biol. 24:274-286, 2023. Background: In 2012, the International Commission for Mountain Emergency Medicine (ICAR MedCom) published recommendations for termination of cardiopulmonary resuscitation (CPR) in mountain rescue. New developments have necessitated an update. This is the 2023 update for termination of CPR in mountain rescue. Methods: For this scoping review, we searched the PubMed and Cochrane libraries, updated the recommendations, and obtained consensus approval within the writing group and the ICAR MedCom. Results: We screened a total of 9,102 articles, of which 120 articles met the inclusion criteria. We developed 17 recommendations graded according to the strength of recommendation and level of evidence. Conclusions: Most of the recommendations from 2012 are still valid. We made minor changes regarding the safety of rescuers and responses to primary or traumatic cardiac arrest. The criteria for termination of CPR remain unchanged. The principal changes include updated recommendations for mechanical chest compression, point of care ultrasound (POCUS), extracorporeal life support (ECLS) for hypothermia, the effects of water temperature in drowning, and the use of burial times in avalanche rescue.

Rewarming from unwitnessed hypothermic cardiac arrest with good neurological recovery using extracorporeal membrane oxygenation

A 26-year-old man, who was training in bad weather for a mountain ultramarathon, became hypothermic after running for 4 h. He deteriorated and was unable to continue. His running partner went for help. The man suffered an unwitnessed hypothermic cardiac arrest. The on-site management and evacuation are described and included the use of intermittent cardiopulmonary resuscitation and a mechanical device during transport. The patient was successfully resuscitated and rewarmed by Extracorporeal Membrane Oxygenation (ECMO) after more than 2 h of cardiopulmonary resuscitation. After 14 h of ECMO support and five days of ventilation, the patient subsequently made a good neurological recovery. At hospital discharge, he had normal cerebral function, and an improving peripheral polyneuropathy affecting distal limbs, with paraesthesia in both feet and reduced coordination and fine motor skills in both hands.

Extracorporeal Life Support for Recurrent Hypothermic Cardiac Arrest: A Case Report

Hypothermia-associated cardiac arrest (HACA) is a challenge for emergency physicians. Standard cardiopulmonary resuscitation (CPR) remains the primary intervention for the treatment of HACA, but extracorporeal life support (ECLS) may be needed as an adjunct to CPR. In this report, we present the case of an adult Asian patient who experienced two episodes of HACA at a two-year interval. In both episodes, the patient was treated with ECLS in addition to standard CPR. We discuss the fundamentals of HACA and how to safely and effectively incorporate ECLS into its management. No-flow time, age, comorbidities, and the cause of the cardiac arrest are criteria to consider when deciding on the duration of CPR and the intensity of the resources deployed. Hypothermia is a reversible cause of cardiac arrest, justifying prolonged CPR. According to the Hypothermia Outcome Prediction after ECLS (HOPE) score, active rewarming through ECLS is recommended. However, a history of cardiac arrest is rare and might be considered a severe comorbidity contraindicating ECLS use. Nevertheless, the indication is determined on a case-by-case basis.

The Role of Extracorporeal Membrane Oxygenation ECMO in Accidental Hypothermia and Rewarming in Out-of-Hospital Cardiac Arrest Patients-A Literature Review

Accidental hypothermia, defined as an unintentional drop of the body core temperature below 35 °C, is one of the causes of cardiocirculatory instability and reversible cardiac arrest. Currently, extracorporeal life support (ECLS) rewarming is recommended as a first-line treatment for hypothermic cardiac arrest patients. The aim of the ECLS rewarming is not only rapid normalization of core temperature but also maintenance of adequate organ perfusion. Veno-arterial extracorporeal membrane oxygenation (ECMO) is a preferred technique due to its lower anticoagulation requirements and potential to prolong circulatory support. Although highly efficient, ECMO is acknowledged as an invasive treatment option, requiring experienced medical personnel and is associated with the risk of serious complications. In this review, we aimed to discuss the clinical aspects of ECMO management in severely hypothermic cardiac arrest patients.

Hypothermic cardiac arrest patients admitted to hospital who were not rewarmed with extracorporeal life support: A retrospective study

Aims

Our goal was to study hypothermic cardiac arrest (CA) patients who were not rewarmed by Extracorporeal Life Support (ECLS) but were admitted to a hospital equipped for it. The focus was on whether the decisions of non-rewarming, meaning termination of resuscitation, were compliant with international guidelines based on serum potassium at hospital admission.

Methods

We retrospectively included all hypothermic CA who were not rewarmed, from three Swiss centers between 1st January 2000 and 2nd May 2021. Data were extracted from medical charts and assembled into two groups for analysis according to serum potassium. We identified the criteria used to terminate resuscitation. We also retrospectively calculated the HOPE score, a multivariable tool predicting the survival probability in hypothermic CA undergoing ECLS rewarming.

Results

Thirty-eight victims were included in the study. The decision of non-rewarming was compliant with international guidelines for 12 (33%) patients. Among the 36 patients for whom the serum potassium was measured at hospital admission, 24 (67%) had a value that - alone - would have indicated ECLS. For 13 of these 24 (54%) patients, the HOPE score was <10%, meaning that ECLS was not indicated. The HOPE estimation of the survival probabilities, when used with a 10% threshold, supported 23 (68%) of the non-rewarming decisions made by the clinicians.

Conclusions

This study showed a low adherence to international guidelines for hypothermic CA patients. In contrast, most of these non-rewarming decisions made by clinicians would have been compliant with current guidelines based on the HOPE score.

On-site treatment of avalanche victims: Scoping review and 2023 recommendations of the international commission for mountain emergency medicine (ICAR MedCom)

INTRODUCTION

The International Commission for Mountain Emergency Medicine (ICAR MedCom) developed updated recommendations for the management of avalanche victims.

METHODS

ICAR MedCom created Population Intervention Comparator Outcome (PICO) questions and conducted a scoping review of the literature. We evaluated and graded the evidence using the American College of Chest Physicians system.

RESULTS

We included 120 studies including original data in the qualitative synthesis. There were 45 retrospective studies (38%), 44 case reports or case series (37%), and 18 prospective studies on volunteers (15%). The main cause of death from avalanche burial was asphyxia (range of all studies 65-100%). Trauma was the second most common cause of death (5-29%). Hypothermia accounted for few deaths (0-4%).

CONCLUSIONS AND RECOMMENDATIONS

For a victim with a burial time ≤ 60 minutes without signs of life, presume asphyxia and provide rescue breaths as soon as possible, regardless of airway patency. For a victim with a burial time > 60 minutes, no signs of life but a patent airway or airway with unknown patency, presume that a primary hypothermic CA has occurred and initiate cardiopulmonary resuscitation (CPR) unless temperature can be measured to rule out hypothermic cardiac arrest. For a victim buried > 60 minutes without signs of life and with an obstructed airway, if core temperature cannot be measured, rescuers can presume asphyxia-induced CA, and should not initiate CPR. If core temperature can be measured, for a victim without signs of life, with a patent airway, and with a core temperature < 30 °C attempt resuscitation, regardless of burial duration.

Extrakorporale Reanimation – Kriterien, Bedingungen, Outcome

Für ausgewählte Patienten, in denen die konventionelle kardiopulmonale Reanimation (cCPR) erfolglos bleibt, sprechen die europäischen Leitlinien zur Reanimation 2021 erstmals eine Empfehlung zur extrakorporalen Reanimation (eCPR) als mögliche Rettungstherapie aus. Die eCPR wird im therapierefraktären Kreislaufstillstand etabliert, um Diagnostik und Therapie reversibler Ursachen, wie Herzinfarkt, Lungenembolie, akzidentielle Hypothermie, Intoxikationen mit herzwirksamen Substanzen und akute Hypoxie, zu ermöglichen. Selektionskriterien für eCPR umfassen prognostische Reanimationsfaktoren, wie beobachteter Kreislaufstillstand, Start von Reanimationsmaßnahmen in < 5 min, schockbarer Erstrhythmus, Zeichen effektiver cCPR wie Lebenszeichen während der Reanimation, anhaltendes Kammerflimmern, intermittierende Phasen von Spontankreislauf oder anhaltendes endtidales CO₂ > 10 mm Hg, Patientenalter und Gesundheitszustand. Die Zeitspanne vom Kreislaufstillstand bis zur eCPR ist eine der wichtigsten Determinanten für neurologisch gutes Überleben und sollte < 60 min liegen. Für die Einhaltung dieser Zielvorgabe muss eine entschlossene „Load-and-Go“-Strategie mit frühzeitiger Patientenselektion und raschem Transport unter mechanischer cCPR in ein eCPR-Zentrum verfolgt werden, oder es wird versucht, die eCPR präklinisch zum Einsatz zu bringen. Zwei randomisierte kontrollierte eCPR-Studien demonstrierten Überlebensraten von 43 % bzw. 31,5 % bei Patienten mit anhaltendem Kammerflimmern bzw. kardialem Kreislaufstillstand. Ob diese Ergebnisse außerhalb einzelner hochspezialisierter Zentren anwendbar sind, ist wie die Frage nach der besten präklinischen und innerklinischen Strategie Gegenstand zukünftiger Studien.

Accidental hypothermia: direct evidence for consciousness as a marker of cardiac arrest risk in the acute assessment of cold patients

Background

Rapid stratification of the risk of cardiac arrest is essential in the assessment of patients with isolated accidental hypothermia. Traditional methods based on measurement of core temperature are unreliable in the field. Behavioural observations have been used as predictors of core temperature and thus indirect predictors of cardiac arrest. This study aims to quantify the direct relationship between observed conscious level and cardiac arrest.

Methods

Retrospective case report analysis identified 114 cases of isolated accidental hypothermia meeting inclusion criteria. Level of consciousness in the acute assessment and management phase was classified using the AVPU system with an additional category of “Alert with confusion”; statistical analysis then related level of consciousness to incidence of cardiac arrest.

Results

All patients who subsequently suffered cardiac arrest showed some impairment of consciousness (p <  < .0001), and the risk of arrest increased directly with the level of impairment; none of the 33 fully alert patients arrested. In the lowest impairment category, Alert confused, a quarter of the 12 patients went on to arrest, while in the highest Unresponsive category, two thirds of the 43 patients arrested. Where core temperature was available (62 cases), prediction of arrest by consciousness level was at least as good as prediction from core temperature.

Conclusions

This study provides retrospective analytical evidence that consciousness level is a valid predictor of cardiac arrest risk in isolated accidental hypothermia; the importance of including confusion as a criterion is a new finding. This study suggests the use of consciousness alone may be at least as good as core temperature in cardiac arrest risk prediction. These results are likely to be of particular relevance to the management of accidental hypothermia in the pre-hospital and mass casualty environment, allowing for rapid and accurate triage of hypothermic patients.

Extracorporeal Life Support in Accidental Hypothermia with Cardiac Arrest-A Narrative Review

Severely hypothermic patients, especially suffering cardiac arrest, require highly specialized treatment. The most common problems affecting the recognition and treatment seem to be awareness, logistics, and proper planning. In severe hypothermia, pathophysiologic changes occur in the cardiovascular system leading to dysrhythmias, decreased cardiac output, decreased central nervous system electrical activity, cold diuresis, and noncardiogenic pulmonary edema. Cardiac arrest, multiple organ dysfunction, and refractory vasoplegia are indicative of profound hypothermia. The aim of these narrative reviews is to describe the peculiar pathophysiology of patients suffering cardiac arrest from accidental hypothermia. We describe the good chances of neurologic recovery in certain circumstances, even in patients presenting with unwitnessed cardiac arrest, asystole, and the absence of bystander cardiopulmonary resuscitation. Guidance on patient selection, prognostication, and treatment, including extracorporeal life support, is given.

Accidental Hypothermia: 2021 Update

Accidental hypothermia is an unintentional drop of core temperature below 35 °C. Annually, thousands die of primary hypothermia and an unknown number die of secondary hypothermia worldwide. Hypothermia can be expected in emergency patients in the prehospital phase. Injured and intoxicated patients cool quickly even in subtropical regions. Preventive measures are important to avoid hypothermia or cooling in ill or injured patients. Diagnosis and assessment of the risk of cardiac arrest are based on clinical signs and core temperature measurement when available. Hypothermic patients with risk factors for imminent cardiac arrest (temperature < 30 °C in young and healthy patients and <32 °C in elderly persons, or patients with multiple comorbidities), ventricular dysrhythmias, or systolic blood pressure < 90 mmHg) and hypothermic patients who are already in cardiac arrest, should be transferred directly to an extracorporeal life support (ECLS) centre. If a hypothermic patient arrests, continuous cardiopulmonary resuscitation (CPR) should be performed. In hypothermic patients, the chances of survival and good neurological outcome are higher than for normothermic patients for witnessed, unwitnessed and asystolic cardiac arrest. Mechanical CPR devices should be used for prolonged rescue, if available. In severely hypothermic patients in cardiac arrest, if continuous or mechanical CPR is not possible, intermittent CPR should be used. Rewarming can be accomplished by passive and active techniques. Most often, passive and active external techniques are used. Only in patients with refractory hypothermia or cardiac arrest are internal rewarming techniques required. ECLS rewarming should be performed with extracorporeal membrane oxygenation (ECMO). A post-resuscitation care bundle should complement treatment.

Cardiac arrest in special circumstances

PURPOSE OF REVIEW

European Resuscitation Council Guidelines for Cardiopulmonary Resuscitation prioritize treatments like chest compression and defibrillation, known to be highly effective for cardiac arrest from cardiac origin. This review highlights the need to modify this approach in special circumstances.

RECENT FINDINGS

Potentially reversible causes of cardiac arrest are clustered into four Hs and four Ts (Hypoxia, Hypovolaemia, Hyperkalaemia/other electrolyte disorders, Hypothermia, Thrombosis, Tamponade, Tension pneumothorax, Toxic agents). Point-of-care ultrasound has its role in identification of the cause and targeting treatment. Time-critical interventions may even prevent cardiac arrest if applied early. The extracorporeal CPR (eCPR) or mechanical CPR should be considered for bridging the period needed to reverse the precipitating cause(s). There is low quality of evidence available to guide the treatment in the majority of situations. Some topics (pulmonary embolism, eCPR, drowning, pregnancy and opioid toxicity) were included in recent ILCOR reviews and evidence updates but majority of recommendations is based on individual systematic reviews, scoping reviews, evidence updates and expert consensus.

SUMMARY

Cardiac arrests from reversible causes happen with lower incidence. Return of spontaneous circulation and neurologically intact survival can hardly be achieved without a modified approach focusing on immediate treatment of the underlying cause(s) of cardiac arrest.

ACSM Expert Consensus Statement: Injury Prevention and Exercise Performance during Cold-Weather Exercise

ABSTRACT

Cold injury can result from exercising at low temperatures and can impair exercise performance or cause lifelong debility or death. This consensus statement provides up-to-date information on the pathogenesis, nature, impacts, prevention, and treatment of the most common cold injuries.

Resuscitation of an Unconscious Victim of Accidental Hypothermia in 1805

In 1805, W.D., a 16-y-old boy, became hypothermic after he was left alone on a grounded boat in Leith Harbour, near Edinburgh, Scotland. He was brought to his own house and resuscitated with warm blankets, smelling salts, and massage by Dr. George Kellie. W.D. made an uneventful recovery. We discuss the pathophysiology and treatment of accidental hypothermia, contrasting treatment in 1805 with treatment today. W.D. was hypothermic when found by passersby. Although he appeared dead, he was rewarmed with help from Dr. Kellie and his assistants over 200 y ago using simple methods. One concept that has not changed is the critical importance of attempting resuscitation, even if it seems to be futile. Don't give up!

Cardiopulmonary resuscitation in special circumstances

Cardiopulmonary resuscitation prioritises treatment for cardiac arrests from a primary cardiac cause, which make up the majority of treated cardiac arrests. Early chest compressions and, when indicated, a defibrillation shock from a bystander give the best chance of survival with a good neurological status. Cardiac arrest can also be caused by special circumstances, such as asphyxia, trauma, pulmonary embolism, accidental hypothermia, anaphylaxis, or COVID-19, and during pregnancy or perioperatively. Cardiac arrests in these circumstances represent an increasing proportion of all treated cardiac arrests, often have a preventable cause, and require additional interventions to correct a reversible cause during resuscitation. The evidence for treating these conditions is mostly of low or very low certainty and further studies are needed. Irrespective of the cause, treatments for cardiac arrest are time sensitive and most effective when given early-every minute counts.

Prognosis of Hypothermic Patients Undergoing ECLS Rewarming-Do Alterations in Biochemical Parameters Matter?

Background: While ECLS is a highly invasive procedure, the identification of patients with a potentially good prognosis is of high importance. The aim of this study was to analyse changes in the acid-base balance parameters and lactate kinetics during the early stages of ECLS rewarming to determine predictors of clinical outcome. Methods: This single-centre retrospective study was conducted at the Severe Hypothermia Treatment Centre at John Paul II Hospital in Krakow, Poland. Patients ≥18 years old who had a core temperature (Tc) < 30 °C and were rewarmed with ECLS between December 2013 and August 2018 were included. Acid-base balance parameters were measured at ECLS implantation, at Tc 30 °C, and at 2 and 4 h after Tc 30 °C. The alteration in blood lactate kinetics was calculated as the percent change in serum lactate concentration relative to the baseline. Results: We included 50 patients, of which 36 (72%) were in cardiac arrest. The mean age was 56 ± 15 years old, and the mean Tc was 24.5 ± 12.6 °C. Twenty-one patients (42%) died. Lactate concentrations in the survivors group were significantly lower than in the non-survivors at all time points. In the survivors group, the mean lactate concentration decreased −2.42 ± 4.49 mmol/L from time of ECLS implantation until 4 h after reaching Tc 30 °C, while in the non-survivors’ group (p = 0.024), it increased 1.44 ± 6.41 mmol/L. Conclusions: Our results indicate that high lactate concentration is associated with a poor prognosis for hypothermic patients undergoing ECLS rewarming. A decreased value of lactate kinetics at 4 h after reaching 30 °C is also associated with a poor prognosis.

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.

Clinician miscalibration of survival estimate in hypothermic cardiac arrest: HOPE-estimated survival probabilities in extreme cases

AIM

Patients with hypothermic cardiac arrest may survive with an excellent outcome after extracorporeal life support rewarming (ECLSR). The HOPE (Hypothermia Outcome Prediction after ECLS) score is recommended to guide the in-hospital decision on whether or not to initiate ECLSR in patients in cardiac arrest following accidental hypothermia. We aimed to assess the HOPE-estimated survival probabilities for a set of survivors of hypothermic cardiac arrest who had extreme values for the variables included in the HOPE score.

METHODS

Survivors were identified and selected through a systematic literature review including case reports. We calculated the HOPE score for each patient who presented extraordinary clinical parameters.

RESULTS

We identified 12 such survivors. The HOPE-estimated survival probability was ≥10% for all (n = 11) patients for whom we were able to calculate the HOPE score.

CONCLUSION

Our study confirms the robustness of the HOPE score for outliers and thus further confirms its external validity. These cases also confirm that hypothermic cardiac arrest is a fundamentally different entity than normothermic cardiac arrest. Using HOPE for extreme cases may support the proper calibration of a clinician's prognosis and therapeutic decision based on the survival chances of patients with accidental hypothermic cardiac 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.

The efficiency of continuous renal replacement therapy for rewarming of patients in accidental hypothermia--An experimental study

Severe accidental hypothermia carries high mortality and morbidity and is often treated with invasive extracorporeal methods. Continuous veno-venous hemodiafiltration (CVVHDF) is widely available in intensive care units. We sought to provide theoretical basis for CVVHDF use in rewarming of hypothermic patients. CVVHDF system was used in the laboratory setting. Heat balance and transferred heat units were evaluated for the system without using blood. We used 5L of crystalloid solution at the temperature of approximately 25°C, placed in a thermally insulated tank (representing the "central compartment" of a hypothermic patient). Time of warming the central compartment from 24.9 to 30.0°C was assessed with different flow combinations: "blood" (central compartment fluid) 50 or 100 or 150 mL/min, dialysate solution 100 or 1500 mL/h, and substitution fluid 0 or 500 mL/h. The total circulation time was 1535 minutes. There were no differences between heat gain values on the filter depending on blood flow (P = .53) or dialysate flow (P = .2). The mean heating time for "blood" flow rates 50, 100, and 150 mL/min was 113.7 minutes (95% CI, 104.9-122.6 minutes), 83.3 minutes (95% CI, 76.2-90.3 minutes), and 74.7 minutes (95% CI, 62.6-86.9 minutes), respectively (P < .01). The respective median rewarming rate for different "blood" flows was 3.6°C/h (IQR, 3.0-4.2°C/h), 4.8 (IQR, 4.2-5.4°C/h), and 5.4 (IQR, 4.8-6.0°C/h), respectively (P < .01). The dialysate flow did not affect the warming rate. Based on our experimental model, CVVHDF may be used for extracorporeal rewarming, with the rewarming rates increasing achieved with higher blood flow rates.

[Cardiac arrest under special circumstances]

These guidelines of the European Resuscitation Council (ERC) Cardiac Arrest under Special Circumstances are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the modifications required for basic and advanced life support for the prevention and treatment of cardiac arrest under special circumstances; in particular, specific causes (hypoxia, trauma, anaphylaxis, sepsis, hypo-/hyperkalaemia and other electrolyte disorders, hypothermia, avalanche, hyperthermia and malignant hyperthermia, pulmonary embolism, coronary thrombosis, cardiac tamponade, tension pneumothorax, toxic agents), specific settings (operating room, cardiac surgery, cardiac catheterization laboratory, dialysis unit, dental clinics, transportation [in-flight, cruise ships], sport, drowning, mass casualty incidents), and specific patient groups (asthma and chronic obstructive pulmonary disease, neurological disease, morbid obesity, pregnancy).

Survival probability in avalanche victims with long burial (≥60 min): A retrospective study

BACKGROUND

The survival of completely buried victims in an avalanche mainly depends on burial duration. Knowledge is limited about survival probability after 60 min of complete burial.

AIM

We aimed to study the survival probability and prehospital characteristics of avalanche victims with long burial durations.

METHODS

We retrospectively included all completely buried avalanche victims with a burial duration of ≥60 min between 1997 and 2018 in Switzerland. Data were extracted from the registry of the Swiss Institute for Snow and Avalanche Research and the prehospital medical records of the physician-staffed helicopter emergency medical services. Avalanche victims buried for ≥24 h or with an unknown survival status were excluded. Survival probability was estimated by using the non-parametric Ayer-Turnbull method and logistic regression. The primary outcome was survival probability.

RESULTS

We identified 140 avalanche victims with a burial duration of ≥60 min, of whom 27 (19%) survived. Survival probability shows a slight decrease with increasing burial duration (23% after 60 min, to <6% after 1400 min, p = 0.13). Burial depth was deeper for those who died (100 cm vs 70 cm, p = 0.008). None of the survivors sustained CA during the prehospital phase.

CONCLUSIONS

The overall survival rate of 19% for completely buried avalanche victims with a long burial duration illustrates the importance of continuing rescue efforts. Avalanche victims in CA after long burial duration without obstructed airway, frozen body or obvious lethal trauma should be considered to be in hypothermic CA, with initiation of cardiopulmonary resuscitation and an evaluation for rewarming with extracorporeal life support.

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.

Impact of rescue collapse on mortality rate in severe accidental hypothermia: A matched-pair analysis

AIM

To assess the impact of the occurrence of cardiac arrest associated with initial management on the outcome of severely hypothermic patients who were rewarmed with Extracorporeal Life Support (ECLS).

METHODS

We collected the individual data of patients in a state of severe accidental hypothermia who were found with spontaneous circulation and rewarmed with ECLS, from cardiac surgery departments. Patients were divided into two groups: those with a subsequent cardiac arrest (RC group); and those with the retained circulation (HT3 group), and compared by using a matched-pair analysis. The mortality rates and the neurological status in survivors were compared as the main outcomes. The difference in the risk of death between the HT3 and RC groups was calculated.

RESULTS

A total of 124 patients were included into the study: 45 in the HT3 group and 79 in the RC group. The matched cohorts consisted of 45 HT3 patients and 45 RC patients. The mortality rate in both groups was 24% and 49% (p = 0.02) respectively; the relative risk of death was 2.0 (p = 0.02). ICU length of stay was significantly longer in the RC group (p < 0.001). Factors associated with survival in the HT3 group included patient age, rewarming rate, and blood BE; while in the RC group, patient age and lactate concentration.

CONCLUSIONS

The occurrence of rescue collapse is linked to a doubling of the risk of death in severely hypothermic patients. Procedures which are known as potential triggers of rescue collapse should be performed with special attention, including in conscious patients.

Extreme Cooling Rates in Avalanche Victims: Case Report and Narrative Review

Mittermair, Christof, Eva Foidl, Bernd Wallner, Hermann Brugger, and Peter Paal. Extreme cooling rates in avalanche victims: case report and narrative review. High Alt Med Biol. 22: 235-240, 2021. Background: We report a 25-year-old female backcountry skier who was buried by an avalanche during ascent. A cooling rate of 8.5°C/h from burial to hospital is the fastest reported in a person with persistent circulation. Methods: A case report according to the CARE guidelines is presented. A literature search with the keywords "avalanche" AND "hypothermia" was performed and yielded 96 results, and the last update was on October 25, 2020. A narrative review complements this work. Results: A literature search revealed four avalanche patients with extreme cooling rates (>5°/h). References of included articles were searched for further relevant studies. Nineteen additional pertinent articles were included. Overall, 32 studies were included in this work. Discussion: An avalanche patient cools in different phases, and every phase may have different cooling rates: (1) during burial, (2) with postburial exposure on-site, and (3) during transport. It is important to measure the core temperature correctly, ideally with an esophageal probe. Contributing factors to fast cooling are sweating, impaired consciousness, no shivering, wearing thin monolayer clothing and head and hands uncovered, an air pocket, and development of hypercapnia, being slender. Conclusions: Rescuers should be prepared to encounter severely hypothermic subjects (<30°C) even after burials of <60 minutes. Subjects rescued from an avalanche may cool extremely fast the more contributing factors for rapid cooling exist. After avalanche burial (≥60 minutes) and unwitnessed cardiac arrest, chances of neurologically intact survival are small and depend on rapid cooling and onset of severe hypothermia (<30°C) before hypoxia-induced cardiac arrest.

European Resuscitation Council Guidelines 2021: Cardiac arrest in special circumstances

These European Resuscitation Council (ERC) Cardiac Arrest in Special Circumstances guidelines are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the modifications required to basic and advanced life support for the prevention and treatment of cardiac arrest in special circumstances; specifically special causes (hypoxia, trauma, anaphylaxis, sepsis, hypo/hyperkalaemia and other electrolyte disorders, hypothermia, avalanche, hyperthermia and malignant hyperthermia, pulmonary embolism, coronary thrombosis, cardiac tamponade, tension pneumothorax, toxic agents), special settings (operating room, cardiac surgery, catheter laboratory, dialysis unit, dental clinics, transportation (in-flight, cruise ships), sport, drowning, mass casualty incidents), and special patient groups (asthma and COPD, neurological disease, obesity, pregnancy).

Clinical staging of accidental hypothermia: The Revised Swiss System: Recommendation of the International Commission for Mountain Emergency Medicine (ICAR MedCom)

Clinical staging of accidental hypothermia is used to guide out-of-hospital treatment and transport decisions. Most clinical systems utilize core temperature, by measurement or estimation, to stage hypothermia, despite the challenge of obtaining accurate field measurements. Recent studies have demonstrated that field estimation of core temperature is imprecise. We propose a revision of the original Swiss Staging system. The revised system uses the risk of cardiac arrest, instead of core temperature, to determine the staging level. Our revised system simplifies assessment by using the level of responsiveness, based on the AVPU scale, and by removing shivering as a stage-defining sign.

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.

Early risk stratification after resuscitation from cardiac arrest

Emergency clinicians often resuscitate cardiac arrest patients, and after acute resuscitation, clinicians face multiple decisions regarding disposition. Recent evidence suggests that out-of-hospital cardiac arrest patients with return of spontaneous circulation have higher odds of survival to hospital discharge, long-term survival, and improved functional outcomes when treated at centers that can provide advanced multidisciplinary care. For community clinicians, a high volume cardiac arrest center may be hours away. While current guidelines recommend against neurological prognostication in the first hours or days after return of spontaneous circulation, there are early findings suggestive of irrecoverable brain injury in which the patient would receive no benefit from transfer. In this Concepts article, we describe a simplified approach to quickly evaluate neurological status in cardiac arrest patients and identify findings concerning for irrecoverable brain injury. Characteristics of the arrest and resuscitation, initial neurological assessment, and brain computed tomography together can identify patients with high likelihood of irrecoverable anoxic injury. Patients who may benefit from centers with access to continuous electroencephalography are discussed. This approach can be used to identify patients who may benefit from rapid transfer to cardiac arrest centers versus those who may benefit from care close to home. Risk stratification also can provide realistic expectations for recovery to families.

Accidental hypothermic cardiac arrest and extracorporeal membrane oxygenation: a case report

BACKGROUND

Accidental hypothermic cardiac arrest, an involuntary drop in core body temperature resulting in cardiopulmonary arrest, is linked to 1500 deaths annually. We highlight the challenges with the treatment of accidental hypothermic cardiac arrest and describe improved preparations necessary for an integrated health system to care for similar patients.

CASE REPORT

Emergency medical services (EMS) were dispatched to a 34-year-old female who had been missing for several hours during a January snowfall. The patient was found unconscious over an embankment. The patient was found with a weak carotid pulse and two empty bottles of clozapine, an atypical antipsychotic. The EMS crew extricated the patient, performed a rapid trauma assessment, passive rewarming, and airway management. During transport, the patient suffered a ventricular fibrillation cardiac arrest, received defibrillation, and advanced life support measures. Resuscitative efforts continued in the emergency department while the treatment team addressed environmental exposure, assessed for traumatic injury and toxicologic exposure. On emergency department (ED) arrival, the patient's core temperature was 24°C, and despite aggressive resuscitation, the patient remained in cardiac arrest. The ED care team used extracorporeal membrane oxygenator (ECMO) and successfully resuscitated the patient with extracorporeal cardiopulmonary resuscitation. The patient achieved full neurologic recovery 15 days post-ED arrival.

CONCLUSION

This case highlights the importance of early recognition of accidental hypothermic cardiac arrest by EMS clinicians, rapid transport to a tertiary facility, and the timely application of active rewarming and in-hospital ECMO. Accidental hypothermic cardiac arrest is a reversible state; prompt and correct treatment allows for a high probability of a favorable neurologic outcome.

Therapeutic management of severe hypothermia with veno-arterial ECMO: where do we stand? Case report and review of the current literature

BACKGROUND

Severe accidental hypothermia is associated with high morbidity and mortality. Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) provides an efficient rewarming method with complete cardiopulmonary support. The use of VA-ECMO for this indication has greatly improved the vital and functional prognosis of patients.

CASE PRESENTATION

We report a case of a 46-year-old patient who was treated for severe hypothermia with a temperature of 22.4 °C along with initial cardiac arrest, whose progression was favorable after the implementation of VA-ECMO support. Two months after initial cardiac arrest, the patient was reassessed and showed signs of complete recovery with regard to his mental and physical capacities.

CONCLUSIONS

The recent international publications and groups of experts recommend the use of VA ECMO as the gold standard therapy to treat severe hypothermia. Therefore, it seems suitable to update the current knowledge on the topic by analysing the latest international publications. The performance of this technique calls into question ethical and economic factors. Two distinct medical teams tried to identify and regroup prognosis factors in predictive survival scores. They raise the question of the utility of these scores in clinical practice. Indeed, according to which survival rate should we proceed to prolonged resuscitation and implement VA-ECMO? Additional studies will be needed for external approval of these survival scores, and additional reflection by experts will be required.

A novel ECG-biomarker for cardiac arrest during hypothermia

Background

Treatment of arrhythmias evoked by accidental or therapeutic hypothermia and rewarming remains challenging. We aim to find an ECG-biomarker that can predict ventricular arrhythmias at temperatures occurring in therapeutic and accidental hypothermia.

Main body

Evaluation of ECG-data from accidental and therapeutic hypothermia patients and experimental data on ECG and ventricular fibrillation (VF) threshold in hypothermic New Zealand White Rabbits. VF threshold was measured in rabbit hearts cooled to moderate (31 °C) and severe (17 °C) hypothermia. QRS-interval divided by corrected QT-interval (QTc) was calculated at same temperatures. Clinical QRS/QTc data were obtained after a systematic literature review. Rabbit QRS/QTc values correlated with risk for VF (correlation coefficient: 0.97). Human QRS/QTc values from hypothermic patients, showed similar correlation with risk for ventricular fibrillation in the experimental data (correlation coefficient: 1.00).

Conclusions

These calculations indicate that QRS/QTc has potential as novel biomarker for predicting risk of hypothermia-induced cardiac arrest. Our findings apply both to victims of accidental hypothermia and to patients undergoing therapeutic hypothermia during surgery or after e.g. cardiac arrest.

Hypothermie accidentelle

L’hypothermie accidentelle est définie comme une baisse non intentionnelle de la température centrale du corps en dessous de 35 °C. La prévention de l’hypothermie est essentielle. La mesure de la température centrale est nécessaire au diagnostic d’hypothermie et permet d’en juger la sévérité. En présence de signes de vie, et en présence d’une hypothermie pure, l’instabilité hémodynamique apparente ne devrait en principe pas faire l’objet d’une prise en charge spécifique. Un risque d’arrêt cardiaque (AC) est présent si la température chute en dessous de 30–32 °C. En raison du risque d’AC, un patient hypotherme devrait bénéficier de l’application d’un monitoring avant toute mobilisation, laquelle devra être prudente. En cas d’AC, seule la mesure de la température oesophagienne est fiable. Si l’hypothermie est suspectée comme étant potentiellement responsable de l’AC du patient, celui-ci doit être transporté sous réanimation cardiopulmonaire vers un hôpital disposant d’une méthode de réchauffement par circulation extracorporelle (CEC). La valeur de la kaliémie ainsi que les autres paramètres à disposition (âge, sexe, valeur de la température corporelle, durée du low flow, présence d’une asphyxie) permettront de décider de l’indication d’une CEC de réchauffement. Le pronostic des patients victimes d’un AC sur hypothermie est potentiellement excellent, y compris sur le plan neurologique.

An evaluation of the Swiss staging model for hypothermia using hospital cases and case reports from the literature

BACKGROUND

The Swiss staging model for hypothermia uses clinical indicators to stage hypothermia and guide the management of hypothermic patients. The proposed temperature range for clinical stage 1 is < 35-32 °C, for stage 2 is < 32-28 °C, for stage 3 is < 28-24 °C, and for stage 4 is below 24 °C. Our previous study using 183 case reports from the literature showed that the measured temperature only corresponded to the clinical stage in the Swiss staging model in approximately 50% of cases. This study, however, included few patients with moderate hypothermia. We aimed to expand this database by adding cases of hypothermic patients admitted to hospital to perform a more comprehensive evaluation of the staging model.

METHODS

We retrospectively included patients aged ≥18 y admitted to hospital between 1.1.1994 and 15.7.2016 with a core temperature below 35 °C. We added the cases identified through our previously published literature review to estimate the percentage of those patients who were correctly classified and compare the theoretical with the observed temperature ranges for each clinical stage.

RESULTS

We included 305 cases (122 patients from the hospital sampling and the 183 previously published). Using the theoretically derived temperature ranges for clinical stages resulted in 185/305 (61%) patients being assigned to the correct temperature range. Temperature was overestimated using the clinical stage in 55/305 cases (18%) and underestimated in 65/305 cases (21%); important overlaps in temperature existed among the four stage groups. The optimal temperature thresholds for discriminating between the four stages (32.1 °C, 27.5 °C, and 24.1 °C) were close to those proposed historically (32 °C, 28 °C, and 24 °C).

CONCLUSIONS

Our results provide further evidence of the relationship between the clinical state of patients and their temperature. The historical proposed temperature thresholds were almost optimal for discriminating between the different stages. Adding overlapping temperature ranges for each clinical stage might help clinicians to make appropriate decisions when using clinical signs to infer temperature. An update of the Swiss staging model for hypothermia including our methodology and findings could positively impact clinical care and future research.