Accidental hypothermia

New Evidence of Tiger Subspecies Differentiation and Environmental Adaptation: Comparison of the Whole Genomes of the Amur Tiger and the South China Tiger

Simple Summary

Tigers are top predators and umbrella protectors, vital to the stability of ecosystems. The South China tiger has been declared extinct in the wild and only exists in captivity. The Chinese government is actively promoting the reintroduction of the South China tiger into the wild. The future of the wild population of the Amur tiger in China is not optimistic, and the recovery of the population is an essential task for the conservation of the Amur tiger. The recovery of the population is not only a macroscopic problem but also a significant study of molecular ecology. We used high-throughput sequencing technology to study the differences in adaptive selection between Amur tigers and South China tigers. Significant genetic differences were found between the Amur tiger and the South China tiger based on a principal component analysis and phylogenetic tree. We identified functional genes and regulatory pathways related to reproduction, disease, predation, and metabolism and characterized functional genes related to survival in the wild, such as smell, vision, muscle, and predatory ability. The data also provide new evidence for the adaptation of Amur tigers to cold environments. PRKG1 is involved in temperature regulation in a cold climate. FOXO1 and TPM4 regulate body temperature to keep it constant. The research also provides a molecular basis for future tiger conservation.

Abstract

Panthera tigris is a top predator that maintains the integrity of forest ecosystems and is an integral part of biodiversity. No more than 400 Amur tigers (P. t. altaica) are left in the wild, whereas the South China tiger (P. t. amoyensis) is thought to be extinct in the wild, and molecular biology has been widely used in conservation and management. In this study, the genetic information of Amur tigers and South China tigers was studied by whole-genome sequencing (WGS). A total of 647 Gb of high-quality clean data was obtained. There were 6.3 million high-quality single-nucleotide polymorphisms (SNPs), among which most (66.3%) were located in intergenic regions, with an average of 31.72% located in coding sequences. There were 1.73 million insertion-deletions (InDels), among which there were 2438 InDels (0.10%) in the coding region, and 270 thousand copy number variations (CNVs). Significant genetic differences were found between the Amur tiger and the South China tiger based on a principal component analysis and phylogenetic tree. The linkage disequilibrium analysis showed that the linkage disequilibrium attenuation distance of the South China tiger and the Amur tiger was almost the same, whereas the r² of the South China tiger was 0.6, and the r² of the Amur tiger was 0.4. We identified functional genes and regulatory pathways related to reproduction, disease, predation, and metabolism and characterized functional genes related to survival in the wild, such as smell, vision, muscle, and predatory ability. The data also provide new evidence for the adaptation of Amur tigers to cold environments. PRKG1 is involved in temperature regulation in a cold climate. FOXO1 and TPM4 regulate body temperature to keep it constant. Our results can provide genetic support for precise interspecies conservation and management planning in the future.

Association between stress hyperglycemia on admission and unfavorable neurological outcome in OHCA patients receiving ECPR

BACKGROUND

Stress hyperglycemia is a normal response to stress and has been associated with outcomes in out-of-hospital cardiac arrest (OHCA) patients. However, this association remained unknown in OHCA patients receiving extracorporeal cardiopulmonary resuscitation (ECPR). This study aimed to examine the association between degree of stress hyperglycemia on admission and neurological outcomes at discharge in OHCA patients receiving ECPR.

PATIENTS AND METHODS

This was a retrospective cohort study of adult OHCA patients receiving ECPR between 2011 and 2021. Patients were classified into three groups: absence of stress hyperglycemia (blood glucose level on admission < 200 mg/dL), moderate stress hyperglycemia (200-299 mg/dL), and severe stress hyperglycemia (≥ 300 mg/dL). The primary outcome was unfavorable neurological outcome (Cerebral Performance Category: 3-5) at discharge.

RESULTS

This study included 160 patients; unfavorable neurological outcomes totaled 79.4% (n = 127). There were 23, 52, and 85 patients in the absence, moderate, and severe stress hyperglycemia groups, respectively. Of each group, unfavorable neurological outcomes constituted 91.3%, 71.2%, and 81.2%, respectively. Multivariable analysis showed that, compared with moderate stress hyperglycemia, absence of stress hyperglycemia on admission was significantly associated with unfavorable neurological outcome at discharge (odds ratio [OR], 4.70; 95% confidence interval [CI], 1.07-33.35; p = 0.039).

CONCLUSION

Compared with moderate stress hyperglycemia on admission, absence of stress hyperglycemia showed significant association with unfavorable neurological outcome at discharge in OHCA patients receiving ECPR.

Barriers to body temperature monitoring among prehospital personnel: a qualitative study using the modified nominal group technique

OBJECTIVES

To identify and explore barriers that healthcare professionals working as prehospital care (PHC) providers at the University Hospital of North Norway experience with temperature monitoring and discover solutions to these problems.

STUDY DESIGN

Qualitative study using the modified nominal group technique.

MATERIALS AND METHODS

14 experienced healthcare professionals working in air and ground emergency medical services were invited to the study. Initially, each participant was asked to suggest through email topics of importance regarding barriers to prehospital thermometry. Afterwards, they received a list of all disparate topics and were asked to individually rank them by importance. The top-ranked topics were discussed in a consensus meeting. The meeting was audio-recorded and a transcript was written and then analysed through an inductive thematic analysis.

RESULTS

13 participants accepted the invitation. 63 suggestions were reduced to 24 disparate topics after removal of duplicates. Twelve highly ranked topics were discussed during the consensus meeting. Thematic analysis revealed 47 codes that were grouped together into six overarching themes, of which four described challenges to monitoring and two described potential solutions: equipment dissatisfaction, little focus on patient temperature, fear of iatrogenic complications, thermometry subordinated, more focus on temperature and simplification of thermometry.

CONCLUSION

To increase the frequency of temperature measurement on correct indication, we suggest introducing PHC protocols that specify patients and conditions where an accurate temperature measurement should have high priority. Furthermore, there is a profound need for more suitable techniques for temperature monitoring in the prehospital setting.

External validation of 5A score model for predicting in-hospital mortality among the accidental hypothermia patients: JAAM-Hypothermia study 2018-2019 secondary analysis

BACKGROUND

The 5A score including five components "Age, Activities of daily living, Arrest, Acidemia and Albumin" was developed as an easy-to-use screening tool for predicting in-hospital mortality among patients with accidental hypothermia. However, the external validity of the 5A score has not yet been evaluated. We aimed to perform an external validation of the 5A score model.

METHOD

This secondary analysis of the multicenter, prospective cohort Japanese Association for Acute Medicine-Hypothermia Study (2018-2019), which was conducted at 87 and 89 institutions throughout Japan, collected data from December 2018 to February 2019 and from December 2019 to February 2020. Adult accidental hypothermia patients whose body temperature was 35 °C or less were included in this analysis. The probability of in-hospital mortality was calculated using a logistic regression model of the 5A score. The albumin was not recorded in this database; thus, it was imputed by estimation. Predictions were compared with actual observations to evaluate the calibration of the model. Furthermore, decision-curve analysis was used to evaluate the clinical usefulness.

RESULTS

Of the 1363 patients registered in the database, data of 1139 accidental hypothermia patients were included for analysis. The median [interquartile range] age was 79 [68-87] years, and there were 625 men (54.9%) in the study cohort. The predicted probability and actual observation by risk groups produced the following results: low 7% (5.4-8.6), mild 19.1% (17.4-20.8), moderate 33.2% (29.9-36.5), and high 61.9% (55.9-67.9) predicted risks, and the low 12.4% (60/483), mild 17.7% (59/334), moderate 32.6% (63/193), and high 69% (89/129) observed mortality. These results indicated that the model was well calibrated. Decision-curve analysis visually indicated the clinical utility of the 5A score model.

CONCLUSION

This study indicated that the 5A score model using estimated albumin value has external validity in a completely different dataset from that used for the 5A model development. The 5A score is potentially helpful to predict the mortality risk and may be one of the valuable information for discussing the treatment strategy with patients and their family members.

Protein dynamics of human serum albumin at hypothermic temperatures investigated by temperature jump

Human serum albumin (HSA) is the most abundant protein in human plasma. Most protein dynamics studies of HSA have been performed above the hyperthermia temperature (>42 °C), so information on the dynamics under hypothermic conditions (<35 °C) is lacking. In this work, a tryptophan-based fluorescence temperature jump system was employed to investigate the thermally-induced dynamic process of HSA at a physiological concentration of ca. 45 mg mL^-1 and pH = ca. 7 upon an instantaneous temperature increase from 25 °C to 30-43 °C. The observed kinetics manifested a three-state consecutive feature, . Upon analysis with the Arrhenius model, the rate coefficients k₁ and k₂ manifested piecewise temperature dependence, and the turning-point temperature was found to be ca. 34 °C, coinciding with the upper bound of hypothermic temperature. Meanwhile, the corresponding activation energies of the transitions at 34-43 °C were lower than those at 30-34 °C, suggesting that protein conformational adjustments at 34-43 °C were more feasible than those at hypothermic temperatures. These observations provided a fresh viewpoint on the relationship between the energetics of protein dynamics and the apparent functioning of a given protein at the molecular level.

Enhanced Blood Clotting After Rewarming From Experimental Hypothermia in an Intact Porcine Model

Introduction: Due to functional alterations of blood platelets and coagulation enzymes at low temperatures, excessive bleeding is a well-recognized complication in victims of accidental hypothermia and may present a great clinical challenge. Still, it remains largely unknown if hemostatic function normalizes upon rewarming. The aim of this study was to investigate effects of hypothermia and rewarming on blood coagulation in an intact porcine model.

Methods: The animals were randomized to cooling and rewarming (n = 10), or to serve as normothermic, time-matched controls (n = 3). Animals in the hypothermic group were immersion cooled in ice water to 25°C, maintained at 25°C for 1 h, and rewarmed to 38°C (normal temperature in pigs) using warm water. Clotting time was assessed indirectly at different temperatures during cooling and rewarming using a whole blood coagulometer, which measures clotting time at 38°C.

Results: Cooling to 25°C led to a significant increase in hemoglobin, hematocrit and red blood cell count, which persisted throughout rewarming. Cooling also caused a transiently decreased white blood cell count that returned to baseline levels upon rewarming. After rewarming from hypothermia, clotting time was significantly shortened compared to pre-hypothermic baseline values. In addition, platelet count was significantly increased.

Discussion/Conclusion: We found that clotting time was significantly reduced after rewarming from hypothermia. This may indicate that rewarming from severe hypothermia induces a hypercoagulable state, in which thrombus formation is more likely to occur.

Hypothermia Induced Impairment of Platelets: Assessment With Multiplate vs. ROTEM—An In Vitro Study

Introduction: This experimental in vitro study aimed to identify and characterize hypothermia-associated coagulopathy and to compare changes in mild to severe hypothermia with the quantitative measurement of rotational thromboelastometry (ROTEM) and multiple-electrode aggregometry (MULTIPLATE).

Methods: Whole blood samples from 18 healthy volunteers were analyzed at the target temperatures of 37, 32, 24, 18, and 13.7°C with ROTEM (ExTEM, InTEM and FibTEM) and MULTIPLATE using the arachidonic acid 0.5 mM (ASPI), thrombin receptor-activating peptide-6 32 µM (TRAP) and adenosine diphosphate 6.4 µM (ADP) tests at the corresponding incubating temperatures for coagulation assessment.

Results: Compared to baseline (37°C) values ROTEM measurements of clotting time (CT) was prolonged by 98% (at 18°C), clot formation time (CFT) was prolonged by 205% and the alpha angle dropped to 76% at 13.7°C (p < 0.001). At 24.0°C CT was prolonged by 56% and CFT by 53%. Maximum clot firmness was only slightly reduced by ≤2% at 13.7°C. Platelet function measured by MULTIPLATE was reduced with decreasing temperature (p < 0.001): AUC at 13.7°C −96% (ADP), −92% (ASPI) and −91% (TRAP).

Conclusion: Hypothermia impairs coagulation by prolonging coagulation clotting time and by decreasing the velocity of clot formation in ROTEM measurements. MULTIPLATE testing confirms a linear decrease in platelet function with decreasing temperatures, but ROTEM fails to adequately detect hypothermia induced impairment of platelets.

Successful Pre-Rewarming Resuscitation after Cardiac Arrest in Severe Hypothermia: A Retrospective Cohort Study from the International Hypothermia Registry

The aim of our study is to investigate successful pre-rewarming resuscitation after hypothermic cardiac arrest (HCA). The hypothermic heart may be insensitive to defibrillation when core temperature is below 30 °C and after successful defibrillation, sinus rhythm often returns into ventricular fibrillation. Recurrent defibrillation attempts may induce myocardial injury. Discrepancy exists concerning pre-rewarming defibrillation between the guidelines of the European Resuscitation Council and American Heart Association. The International Hypothermia Registry (IHR) gathers hypothermia cases. The primary outcome was survival. Secondary outcomes were the characteristics of defibrillation, the effect of Adrenaline administration under 30 °C, and the duration of CPR. Of the 239 patients, eighty-eight were in cardiac arrest at arrival of the rescue team. Successful pre-rewarming resuscitation was obtained in 14 patients. The outcome showed: seven deaths, one vegetative state, two patients with reversible damage, and four patients with full recovery. A total of five patients had a shockable rhythm, and defibrillation was successful in four patients. The response rate to Adrenaline was reported as normal in six patients. There were no statistically significant differences in the presence of a shockable rhythm, the success of defibrillation, and the effect on Adrenaline administration between the survivors and non-survivors. Successful resuscitation in severe hypothermia is possible before active rewarming and arrival in the hospital, thus improving the chance of survival.

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.

Evaluation and Management of Watercraft-Related Injuries for Acute Care Surgeons: Towards Improving Care and Implementing Effective Public Health Prevention Policies

Boating has exposed humans to elemental hazards for centuries. What was once a lifelong craft and time-honored skillset is now, with modern technology, a popular recreational activity. Boating safety has inherent limitations and has been historically challenging to enforce. These circumstances have given way to a rising number of watercraft-associated injuries and fatalities. This review aims to investigate the diagnosis, work-up, and management of watercraft-related injuries, including blunt mechanisms, propeller wounds, water-force trauma, associated marine infections, and submersion injuries, as well as outline gaps in current public health policy on watercraft injuries, potential interventions, and available solutions. Motorboats and personal watercraft differ in size, power modality, and differential risk for injury. Accidents aboard watercraft often share commonalities with motor vehicles and motorcycles, namely: rapid deceleration, ejection, and collision with humans. The complexity of care is added by the austere environment in which many watercraft accidents occur, as well as the added morbidity of drowning and hypothermia. Wounds can also become infected by marine organisms, which require wound care and antimicrobial therapy specific to the aquatic environment in which the injury occurred. The treatment of these patients can be further exacerbated by the prolonged transportation times due to complicated water rescue. There are many measures that can prevent or abate watercraft injuries, but inconsistent regulations and enforcement may impair the success of these interventions. Further research is needed to identify possible solutions to common causes of watercraft injuries, such as inconsistent lifejacket use and bow riding.

Characteristics of antipsychotic drug-induced hypothermia in psychogeriatric inpatients

OBJECTIVE

Hypothermia is a potentially lethal adverse reaction to typical and atypical antipsychotic drugs (APD). Among predisposing factors are advanced age and comorbid somatic diseases. The aim of this study was to assess the incidence of hypothermia and quantify risk factors.

METHOD

Charts of N = 3002 psychogeriatric inpatients were screened for incidence of hypothermia (body core temperature <35.0°C). The frequency of hypothermia was compared between patients treated with versus without APD and, within the sample of APD-treated patients, for (1) specific APD, (2) sex, (3) main diagnosis, and (4) age.

RESULTS

N = 54 cases (2.6%) of hypothermia occurred in APD-treated patients and 12 cases (1.3%) in non-APD-treated patients (p = 0.024). In APD-treated patients, only male sex (p = 0.038) and pipamperone were associated with a higher incidence of hypothermia (p = 0.0017). Whereas the main diagnosis delirium showed a trend to significance, age did not correlate with hypothermia.

CONCLUSION

Medication with pipamperone was associated with an increased risk of hypothermia. The advanced age of our sample might as well explain the high incidence of hypothermia within our sample and the failure to detect high age as a risk factor due to a ceiling effect.

How to Survive 33 min after the Umbilical of a Saturation Diver Severed at a Depth of 90 msw?

In 2012, a severe accident happened during the mission of a professional saturation diver working at a depth of 90 m in the North Sea. The dynamic positioning system of the diver support vessel crashed, and the ship drifted away from the working place, while one diver’s umbilical became snagged on a steel platform and was severed. After 33 min, he was rescued into the diving bell, without exhibiting any obvious neurological injury. In 2019, the media and a later ‘documentary’ film suggested that a miracle had happened to permit survival of the diver once his breathing gas supply was limited to only 5 min. Based on the existing data and phone calls with the diver concerned (Dc), the present case report tries to reconstruct, on rational grounds, how Dc could have survived after he was cut off from breathing gas, hot water, light and communication while 90 m deep at the bottom of the sea. Dc carried bail-out heliox (86/14) within two bottles (2 × 12 L × 300 bar: 7200 L). Calculating Dc’s varying per-minute breathing gas consumption over time, both the decreased viscosity of the helium mix and the pressure-related increase in viscosity did not exhibit a breathing gas gap. Based on the considerable respiratory heat loss, the core temperature was calculated to be as low as 28.8 °C to 27.2 °C after recovery in the diving bell. In accordance with the literature, such values would be associated with impaired or lost consciousness, respectively. Relocating Dc on the drilling template by using a remotely operated vehicle (ROV), the transport of the victim to the bell and subsequent care in the hyperbaric chamber must be regarded as exemplary. We conclude that, based on rational arguments and available literature data, Dc’s healthy survival is not a miracle, as it can be convincingly explained by means of reliable data. Remaining with a breathing gas supply sufficient for five minutes only would not have ended in a miracle but would have ended in death by suffocation. Nevertheless, survival of such an accident may appear surprising, and probably the limit for a healthy outcome was very close. We conclude, in addition, that highly effective occupational safety measures, in particular the considerable bail-out heliox reserve, secured the healthy survival. Nevertheless, the victim’s survival is likely to be due to his excellent diving training, together with many years of diving routine. The rescue action of the second diver and Dc’s retrieval by the ROV operator are also suggestive of the behavior of carefully selected crew members with the high degree of professional qualification needed to correctly function in a hostile environment.

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.

Clinical relevance of impaired consciousness in accidental hypothermia: a Japanese multicenter retrospective study

Aim

This study aimed to investigate the association between level of impaired consciousness and severe hypothermia (<28°C) and to evaluate the association between level of impaired consciousness and inhospital mortality among accidental hypothermia patients.

Methods

This was a multicenter retrospective study using the J‐Point registry database, which includes data regarding patients whose core body temperature was 35.0°C or less and who were treated as accidental hypothermia in emergency departments between April 1, 2011 and March 31, 2016. We estimated adjusted odds ratios of the level of impaired consciousness for severe hypothermia less than 28°C and inhospital mortality using a logistic regression model.

Results

The study included 505 of 572 patients in the J‐Point registry. Relative to mildly impaired consciousness (Glasgow Coma Scale [GCS] 13–15), the adjusted odds ratios for severe hypothermia less than 28°C were: moderate (GCS 9–12), 3.26 (95% confidence interval [CI], 1.69–6.25); and severe (GCS < 9), 4.68 (95% CI, 2.40–9.14). Relative to mildly impaired consciousness (GCS 13–15), the adjusted odds ratios for inhospital mortality were: moderate (GCS9–12), 1.65 (95% CI, 0.95–2.88); and severe (GCS < 9), 2.10 (95% CI, 1.17–3.78).

Conclusion

The level of impaired consciousness in patients with accidental hypothermia was associated with severe hypothermia and inhospital mortality.

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.

Soluble thrombomodulin ameliorates aberrant hemostasis after rewarming in a rat accidental hypothermia model

BACKGROUND

Accidental hypothermia (AH) sometimes leads to coagulation disorder, especially in severe AH. We previously demonstrated that intrasplenic platelet activation caused aberrant hemostasis and thrombus formation after rewarming in a murine AH model. However, no study has focused on the appropriate management of platelets causing coagulation activation after rewarming of AH. We investigated whether or not recombinant soluble thrombomodulin (rTM) can suppress thrombosis formation after rewarming using a rat AH model.

METHODS

Wistar rats were exposed to an ambient temperature of -20 °C under general anesthesia until their rectal temperature decreased to 26 °C. The Hypo group rats (n = 5) were immediately euthanized, while the Hypo/Re group (n = 5) and rTM group rats (n = 5), which were administered rTM (1 mg/kg) via the tail vein, were rewarmed until the rectal temperature returned to 34 °C and then euthanized 6 h later. Tissue and blood samples were collected from all rats for histopathological and coagulation analyses at euthanasia.

RESULTS

There was no significant change in the D-dimer level in the Hypo group rats, while the D-dimer level was significantly elevated at 6 h after rewarming in the Hypo/Re group rats (P = 0.015), and histopathology detected both fibrin and platelets in the renal glomerulus. However, the rTM group rats did not show any elevation of the D-dimer levels at 6 h after rewarming, and no fibrin was noted on histopathology.

CONCLUSIONS

rTM may be useful as an appropriate anticoagulant in cases of aberrant hemostasis after rewarming of AH.

Resuscitation from severe accidental hypothermia by active core rewarming via an indwelling peritoneal dialysis catheter

Accidental hypothermia is a life-threatening medical condition, which requires the appropriate rewarming strategy with careful monitoring. Active core rewarming is often necessary in the management of severe hypothermia. However, especially in the emergent clinical setting, immediate establishment of a reliable route for active core rewarming is difficult. Severe accidental hypothermia in patients dependent on peritoneal dialysis or combination of hemodialysis with peritoneal dialysis is extremely rare, and the ideal rewarming procedure for these patients is unclear. To our knowledge, this is the first case report illustrating the application of an indwelling peritoneal dialysis catheter to active core rewarming in the management of severe accidental hypothermia. A 64-year-old female with type 1 diabetes and end-stage renal disease (ESRD) on combination of hemodialysis with peritoneal dialysis was delivered to our hospital due to severe accidental hypothermia. On presentation, she was unresponsive and her core temperature was 22.8 °C. Since rewarming by an electric blanket and warmed saline infusion was ineffective, infusion of warmed peritoneal dialysis solution via an indwelling peritoneal dialysis catheter was performed in the emergency room. In the next few hours, her body temperature recovered to normal level, and she regained consciousness. During resuscitation, complications related to rewarming, such as arrhythmia or hypotension, were not observed. She was discharged without any sequelae. Indwelling peritoneal dialysis catheters, if available, could be utilized as the safe and reliable route for active core rewarming in ESRD patients.

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.

Blowing Hot and Cold: Body Temperature and the Microbiome

The intestinal microbiome influences host health, and its responsiveness to diet and disease is increasingly well studied. However, our understanding of the factors driving microbiome variation remain limited. Temperature is a core factor that controls microbial growth, but its impact on the microbiome remains to be fully explored. Although commonly assumed to be a constant 37°C, normal body temperatures vary across the animal kingdom, while individual body temperature is affected by multiple factors, including circadian rhythm, age, environmental temperature stress, and immune activation. Changes in body temperature via hypo- and hyperthermia have been shown to influence the gut microbiota in a variety of animals, with consistent effects on community diversity and stability. It is known that temperature directly modulates the growth and virulence of gastrointestinal pathogens; however, the effect of temperature on gut commensals is not well studied. Further, body temperature can influence other host factors, such as appetite and immunity, with indirect effects on the microbiome. In this minireview, we discuss the evidence linking body temperature and the intestinal microbiome and their implications for microbiome function during hypothermia, heat stress, and fever.

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.

Successful Non-Extracorporeal Rewarming from Hypothermic Cardiac Arrest: 2 Cases

Accidental hypothermia (core temperature <35°C) is a complication in persons who have fallen into crevasses; hypothermic cardiac arrest is the most serious complication. Extracorporeal life support (ECLS) is the optimal method for rewarming hypothermic cardiac arrest patients, but it may not be readily available and non-ECLS rewarming may be required. We report the medical course of 2 patients with hypothermic cardiac arrest, each of whom had fallen into a crevasse. They were treated successfully with non-ECLS rewarming using peritoneal and thoracic lavage. We discuss non-ECLS treatment options for hypothermic cardiac arrest and describe successful non-ECLS rewarming in an outlying hospital without ECLS rewarming capability in the Grossglockner region of Austria in 1990 and 2003. Both patients survived neurologically intact. Non-ECLS rewarming in a trauma center without ECLS capabilities is feasible and can result in a good outcome when ECLS is not available. The best non-ECLS rewarming method for hypothermic cardiac arrest patients has not yet been established. Non-ECLS rewarming should be adapted to local capabilities. To obtain more robust evidence, it seems reasonable to pool data on the treatment and outcome of non-ECLS rewarming in hypothermic cardiac arrest patients.

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.

On-Site Medical Management of Avalanche Victims-A Narrative Review

Avalanche accidents are common in mountain regions and approximately 100 fatalities are counted in Europe each year. The average mortality rate is about 25% and survival chances are mainly determined by the degree and duration of avalanche burial, the patency of the airway, the presence of an air pocket, snow characteristics, and the severity of traumatic injuries. The most common cause of death in completely buried avalanche victims is asphyxia followed by trauma. Hypothermia accounts for a minority of deaths; however, hypothermic cardiac arrest has a favorable prognosis and prolonged resuscitation and extracorporeal rewarming are indicated. In this article, we give an overview on the pathophysiology and on-site management of avalanche victims.

Accidental hypothermia: characteristics, outcomes, and prognostic factors-A nationwide observational study in Japan (Hypothermia study 2018 and 2019)

Aim

This study describes the clinical characteristics and outcomes as well as the prognostic factors of patients with accidental hypothermia (AH) using Japan’s nationwide registry data.

Methods

The Hypothermia study 2018 and 2019, which included patients aged 18 years or older with a body temperature of 35°C or less, was a multicenter registry conducted at 87 and 89 institutions throughout Japan, with data collected from December 2018 to February 2019 and December 2019 to February 2020, respectively.

Results

In total, 1363 patients were enrolled in the registry, of which 1194 were analyzed in this study. The median (interquartile range) age was 79 (68–87) years, and the median (interquartile range) body temperature at the emergency department was 30.8°C (28.4–33.6°C). Forty‐three percent of patients with AH had a mild condition, 35.2% moderate, and 21.9% severe. AH occurred in an indoor setting in 73.4% and was caused by acute medical illness in 49.3% of patients. A total of 101 (8.5%) patients suffered from cardiopulmonary arrest on arrival at the hospital. The overall 30‐day mortality rate was 24.5%, the median (interquartile range) intensive care unit stay was 4 (2–7) days, and the median (interquartile range) hospital stay was 13 (4–27) days. In the multivariable logistic analysis, the prognostic factors were age (≥75 years old), male, activities of daily living (needing total assistance), cause of AH (trauma, alcohol), Glasgow Coma Scale score, and potassium level (>5.5 mEq/L).

Conclusion

The mortality rate of AH was 24.5% in Japan. The prognostic factors developed in this study may be useful for the early prediction, prevention, and awareness of severe AH.

Association between frailty and mortality among patients with accidental hypothermia: a nationwide observational study in Japan

BACKGROUND

Frailty has been associated with a risk of adverse outcomes, and mortality in patients with various conditions. However, there have been few studies on whether or not frailty is associated with mortality in patients with accidental hypothermia (AH). In this study, we aim to determine this association in patients with AH using Japan's nationwide registry data.

METHODS

The data from the Hypothermia STUDY 2018&19, which included patients of ≥18 years of age with a body temperature of ≤35 °C, were obtained from a multicenter registry for AH conducted at 120 institutions throughout Japan, collected from December 2018 to February 2019 and December 2019 to February 2020. The clinical frailty scale (CFS) score was used to determine the presence and degree of frailty. The primary outcome was the comparison of mortality between the frail and non-frail patient groups.

RESULTS

In total, 1363 patients were included in the study, of which 920 were eligible for the analysis. The 920 patients were divided into the frail patient group (N = 221) and non-frail patient group (N = 699). After 30-days of hospitalization, 32.6% of frail patients and 20.6% of non-frail patients had died (p < 0.001). Frail patients had a significantly higher risk of 90-day mortality (Hazard ratio [HR], 1.64; 95% confidence interval [CI], 1.25-2.17; p < 0.001). Based on the Cox proportional hazards analysis using multiple imputation, after adjustment for age, potassium level, lactate level, pH value, sex, CPK level, heart rate, platelet count, location of hypothermia incidence, and rate of tracheal intubation, the HR was 1.69 (95% CI, 1.25-2.29; p < 0.001).

CONCLUSIONS

This study showed that frailty was associated with mortality in patients with AH. Preventive interventions for frailty may help to avoid death caused by AH.

Effects of rewarming with extracorporeal membrane oxygenation to restore oxygen transport and organ blood flow after hypothermic cardiac arrest in a porcine model

We recently documented that cardiopulmonary resuscitation (CPR) generates the same level of cardiac output (CO) and mean arterial pressure (MAP) during both normothermia (38 °C) and hypothermia (27 °C). Furthermore, continuous CPR at 27 °C provides O₂ delivery (ḊO₂) to support aerobic metabolism throughout a 3-h period. The aim of the present study was to investigate the effects of extracorporeal membrane oxygenation (ECMO) rewarming to restore ḊO₂ and organ blood flow after prolonged hypothermic cardiac arrest. Eight male pigs were anesthetized and immersion cooled to 27 °C. After induction of hypothermic cardiac arrest, CPR was started and continued for a 3-h period. Thereafter, the animals were rewarmed with ECMO. Organ blood flow was measured using microspheres. After cooling with spontaneous circulation to 27 °C, MAP and CO were initially reduced to 66 and 44% of baseline, respectively. By 15 min after the onset of CPR, there was a further reduction in MAP and CO to 42 and 25% of baseline, respectively, which remained unchanged throughout the rest of 3-h CPR. During CPR, ḊO₂ and O₂ uptake (V̇O₂) fell to critical low levels, but the simultaneous small increase in lactate and a modest reduction in pH, indicated the presence of maintained aerobic metabolism. Rewarming with ECMO restored MAP, CO, ḊO₂, and blood flow to the heart and to parts of the brain, whereas flow to kidneys, stomach, liver and spleen remained significantly reduced. CPR for 3-h at 27 °C with sustained lower levels of CO and MAP maintained aerobic metabolism sufficient to support ḊO₂. Rewarming with ECMO restores blood flow to the heart and brain, and creates a "shockable" cardiac rhythm. Thus, like continuous CPR, ECMO rewarming plays a crucial role in "the chain of survival" when resuscitating victims of hypothermic cardiac arrest.

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.

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020)

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020), a Japanese-specific set of clinical practice guidelines for sepsis and septic shock created as revised from J-SSCG 2016 jointly by the Japanese Society of Intensive Care Medicine and the Japanese Association for Acute Medicine, was first released in September 2020 and published in February 2021. An English-language version of these guidelines was created based on the contents of the original Japanese-language version. The purpose of this guideline is to assist medical staff in making appropriate decisions to improve the prognosis of patients undergoing treatment for sepsis and septic shock. We aimed to provide high-quality guidelines that are easy to use and understand for specialists, general clinicians, and multidisciplinary medical professionals. J-SSCG 2016 took up new subjects that were not present in SSCG 2016 (e.g., ICU-acquired weakness [ICU-AW], post-intensive care syndrome [PICS], and body temperature management). The J-SSCG 2020 covered a total of 22 areas with four additional new areas (patient- and family-centered care, sepsis treatment system, neuro-intensive treatment, and stress ulcers). A total of 118 important clinical issues (clinical questions, CQs) were extracted regardless of the presence or absence of evidence. These CQs also include those that have been given particular focus within Japan. This is a large-scale guideline covering multiple fields; thus, in addition to the 25 committee members, we had the participation and support of a total of 226 members who are professionals (physicians, nurses, physiotherapists, clinical engineers, and pharmacists) and medical workers with a history of sepsis or critical illness. The GRADE method was adopted for making recommendations, and the modified Delphi method was used to determine recommendations by voting from all committee members.As a result, 79 GRADE-based recommendations, 5 Good Practice Statements (GPS), 18 expert consensuses, 27 answers to background questions (BQs), and summaries of definitions and diagnosis of sepsis were created as responses to 118 CQs. We also incorporated visual information for each CQ according to the time course of treatment, and we will also distribute this as an app. The J-SSCG 2020 is expected to be widely used as a useful bedside guideline in the field of sepsis treatment both in Japan and overseas involving multiple disciplines.

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.

Hypothermia in Trauma

Hypothermia in trauma patients is a common condition. It is aggravated by traumatic hemorrhage, which leads to hypovolemic shock. This hypovolemic shock results in a lethal triad of hypothermia, coagulopathy, and acidosis, leading to ongoing bleeding. Additionally, hypothermia in trauma patients can deepen through environmental exposure on the scene or during transport and medical procedures such as infusions and airway management. This vicious circle has a detrimental effect on the outcome of major trauma patients. This narrative review describes the main factors to consider in the co-existing condition of trauma and hypothermia from a prehospital and emergency medical perspective. Early prehospital recognition and staging of hypothermia are crucial to triage to proper care to improve survival. Treatment of hypothermia should start in an early stage, especially the prevention of further cooling in the prehospital setting and during the primary assessment. On the one hand, active rewarming is the treatment of choice of hypothermia-induced coagulation disorder in trauma patients; on the other hand, accidental or clinically induced hypothermia might improve outcomes by protecting against the effects of hypoperfusion and hypoxic injury in selected cases such as patients suffering from traumatic brain injury (TBI) or traumatic cardiac arrest.

Treatment of Cardiovascular Dysfunction With PDE5-Inhibitors - Temperature Dependent Effects on Transport and Metabolism of cAMP and cGMP

Introduction

Cardiovascular dysfunction is a potentially lethal complication of hypothermia. Due to a knowledge gap, pharmacological interventions are not recommended at core temperatures below 30°C. Yet, further cooling is induced in surgical procedures and survival of accidental hypothermia is reported after rewarming from below 15°C, advocating a need for evidence-based treatment guidelines. In vivo studies have proposed vasodilation and afterload reduction through arteriole smooth muscle cGMP-elevation as a favorable strategy to prevent cardiovascular dysfunction in hypothermia. Further development of treatment guidelines demand information about temperature-dependent changes in pharmacological effects of clinically relevant vasodilators.

Materials and Methods

Human phosphodiesterase-enzymes and inverted erythrocytes were utilized to evaluate how vasodilators sildenafil and vardenafil affected cellular efflux and enzymatic breakdown of cAMP and cGMP, at 37°C, 34°C, 32°C, 28°C, 24°C, and 20°C. The ability of both drugs to reach their cytosolic site of action was assessed at the same temperatures. IC₅₀- and K_i-values were calculated from dose–response curves at all temperatures, to evaluate temperature-dependent effects of both drugs.

Results

Both drugs were able to reach the intracellular space at all hypothermic temperatures, with no reduction compared to normothermia. Sildenafil IC₅₀ and K_i-values increased during hypothermia for enzymatic breakdown of both cAMP (IC₅₀: 122 ± 18.9 μM at 37°C vs. 269 ± 14.7 μM at 20°C, p < 0.05) and cGMP (IC₅₀: 0.009 ± 0.000 μM at 37°C vs. 0.024 ± 0.004 μM at 32°C, p < 0.05), while no significant changes were detected for vardenafil. Neither of the drugs showed significant hypothermia-induced changes in IC₅₀ and K_i–values for inhibition of cellular cAMP and cGMP efflux.

Conclusion

Sildenafil and particularly vardenafil were ableto inhibit elimination of cGMP down to 20°C. As the cellular effects of these drugs can cause afterload reduction, they show potential in treating cardiovascular dysfunction during hypothermia. As in normothermia, both drugs showed higher selectivity for inhibition of cGMP-elimination than cAMP-elimination at low core temperatures, indicating that risk for cardiotoxic side effects is not increased by hypothermia.

Smart textiles for personalized thermoregulation

Thermoregulation has substantial implications for human health. Traditional central space heating and cooling systems are less efficient due to wasted energy spent on the entire building and ignore individual thermophysiological comfort. Emerging textiles based on innovations in materials chemistry and physics, nanoscience, and nanotechnology have now facilitated thermoregulation in a far more personalized and energy-saving manner. In this tutorial review, we discuss the latest technological advances in thermoregulatory textiles. First, we outline the basic mechanisms behind the physiological chemistry processes for both internal and external thermoregulation in the human body. Then, we systematically elaborate on typical smart passive and active thermoregulatory textiles considering current working mechanisms, materials engineering towards practical applications. In light of burgeoning commercial trends, we offer important insights into green chemistry for the sustainable development of smart thermoregulatory textiles. Prospectively, we propose an autonomous textile thermoregulation system that could intelligently provide personalized thermophysiological comfort in a self-adaptive manner in the era of Internet of Things (IoT). The discussion of interdisciplinary interactions of energy, environmental science, and nanotechnology in this review will further promote development of the thermoregulatory textile field in both academia and industry, ultimately realizing personalized thermoregulation and a sustainable energy future.

Water Temperature Variability Is Associated with Neurologic Outcomes in Out-of-Hospital Cardiac Arrest Survivors Who Underwent Targeted Temperature Management at 33°C

We examined the association between variability in body temperature (BT) and water temperature (WT) during the maintenance period of targeted temperature management (TTM) and neurologic outcomes in out-of-hospital cardiac arrest (OHCA) survivors. Adult (≥18 years), comatose OHCA survivors who underwent TTM at 33°C between October 2015 and December 2019 were included. We collected data on BT and WT recorded every minute during the TTM maintenance period. Temperature variability was measured as the standard deviation of BT and WT during the 33°C maintenance period. The primary outcome was a poor neurologic outcome, defined as a cerebral performance category scale 3-5 at 6 months. Of the 154 included patients, 96 (62.3%) had poor outcomes. The BT variability in the poor outcome group was lower than that in the good outcome group (0.16°C [0.13-0.27°C] vs. 0.13°C [0.11-0.18°C]). In addition, the WT variability during the maintenance period in the poor outcome group was lower than that in the good outcome group (2.24°C [1.80-3.96°C] vs. 1.77°C [1.26-2.32°C]). In the multivariate analysis, WT variability (odds ratio 0.508; 95% confidence interval, 0.295-0.874; p = 0.014) was independently associated with poor neurologic outcome. BT variability and cooling beyond 33.0°C ± 1.0°C were not associated with poor neurologic outcomes. WT variability during the maintenance period was independently associated with neurologic outcomes in OHCA survivors who underwent TTM at 33°C. In addition, overcooling or undercooling during the maintenance period was not associated with neurologic outcomes.

Repolarization and ventricular arrhythmia during targeted temperature management post cardiac arrest

BACKGROUND

Targeted temperature management (TTM) following out-of-hospital cardiac arrest (OHCA) prolongs the QT-interval but our knowledge of different temperatures and risk of arrhythmia is incomplete.

OBJECTIVE

To assess whether the QTc, QT-peak (QTp) and T-peak to T-end interval (TpTe) may be useful markers of ventricular arrhythmia in contemporary post cardiac arrest treatment.

METHODS

An ECG-substudy of the TTM-trial (TTM at 33 °C vs. 36 °C) with serial ECGs from 680 (94%) patients. Bazett's (B) and Fridericia's (F) formula were used for heart rate correction of the QT, QTp and TpTe. Ventricular arrhythmia (VT/VF) were registered during the first three days of post cardiac arrest care.

RESULTS

The QT, QTc and QTp intervals were prolonged more at 33 °C compared to 36 °C and restored to similar and lower levels after rewarming. The TpTe-interval remained between 92-100 ms throughout TTM in both groups. The QTc intervals were associated with ventricular arrhythmia, but not after adjustment for cardiac arrest characteristics. The QTp-interval was not associated with risk of ventricular arrhythmia. Heart rate corrected TpTe-intervals were associated with higher risk of arrhythmia (Odds ratio (OR): TpTe(B): 1.12 (1.02-1.23, p = 0.01 TpTe(F): 1.12 (1.02-1.23, p = 0.02) per 20 ms). Further a prolonged TpTe-interval ≥ 90 ms was consistently associated with higher risk (OR_adjusted: TpTe(B): 2.05 (1.25-3.37), p < 0.01, TpTe(F): 2.14 (1.32-3.49), p < 0.01).

CONCLUSIONS

TTM prolongs the QT-interval by prolongation of the QTp-interval without association to increased risk. The TpTe-interval is not significantly affected by core temperature, but heart rate corrected TpTe intervals are robustly associated with risk of ventricular arrhythmia.

TRIAL REGISTRATION

The TTM-trial is registered and accessible at ClinicalTrials.gov (Identifier: NCT01020916).

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.

Hypothermia causes platelet activation in the human spleen

BACKGROUND

Accidental hypothermia results in various dysfunctions in the human body. Additionally, coagulation disorder can lead to a life-threatening condition. We previously demonstrated that platelets stored in the spleen were activated and thus triggered coagulation disorder in a mouse model of hypothermia. In the present study, we wanted to investigate if this phenomenon in mice also occurs in humans as a reaction to hypothermia.

METHODS

We analyzed splenic tissue collected from 22 deceased subjects who have died from hypothermia. These samples were compared with 22 control cases not exposed to cold environment. We performed immunohistochemical staining for CD61 (a marker of all platelets) and CD62P (a marker of activated platelets). We also evaluated the morphology of platelets in the spleen with scanning electron microscopy.

RESULTS

Immunohistochemical analysis revealed no significant changes in the amounts of CD61-positive platelets between the hypothermia and control cases. However, the hypothermia cases contained abundant CD62P-positive platelets compared with those of the control cases. Immunohistochemical analysis also revealed that the activated platelets formed aggregates and adhered to splenic sinusoidal endothelial cells in the hypothermia cases. However, we observed no significant fibrin formation around the activated platelets.

CONCLUSIONS

Hypothermia resulted in splenic platelet activation, which may be used as a postmortem marker of hypothermia. The release of activated platelets from the spleen into to circulation upon rewarming may promote coagulation disturbances.

Extracorporeal life support rewarming rate is associated with survival with good neurological outcome in accidental hypothermia

OBJECTIVES

Favourable outcomes have been demonstrated after extracorporeal life support (ECLS) facilitated rewarming for severe accidental hypothermia. The clinical impact of varying rewarming rates however is unclear. We sought to quantify the change in the probability of good neurological outcome with ECLS rewarming rate and identify the optimal rewarming rate threshold.

METHODS

We performed a secondary analysis of the International ACcidental Hypothermia Extracorporeal Life Support Collaborators, an individual patient data data set (n = 658) for ECLS-assisted rewarming for accidental hypothermia. The independent variable of interest was rewarming rate. The primary outcome was survival with good neurological status. We applied an adjusted marginal effects model to quantify the probability of good neurological outcome over clinically observed rewarming rates. We examined strata defined by sex, initial potassium level and history of asphyxiation.

RESULTS

Of 658 cases, the median age and initial core temperature were 36 years (22-55) and 24.5°C (22.1-26.2) respectively; 190 (29%) were female, and 547 (83%) had a non-perfusing initial cardiac rhythm. The mean rewarming rate was 7.0°C/h. The median ECLS duration was 5.8 h (range: 0.5-158 h). The overall survival was 46% (n = 303/658), and good neurological outcome was 40% (n = 265/658). The median intensive care unit and hospital length of stay was 5 days (range: 1-35 days) and 18 days (range: 1-106 days), respectively. Marginal effects analysis demonstrated a 1.9% decrease in the probability of survival with good neurological outcome for each 1°C/h increase in rewarming. Across the reported range of rewarming rates (0.05-30.8°C/h), the probability of good neurological outcome declined from 49.6% to 4.1% for an average patient. The relationship was similar within various subgroups. The optimal cut-off threshold for the rate of rewarming to distinguish between a good and poor neurological outcome was ≤5.0°C/h.

CONCLUSIONS

Among cases with severe accidental hypothermia treated with ECLS, slower rewarming rates are associated with improved survival with good neurological outcomes. Slow rewarming, at rates ≤5.0°C/h, may improve clinical outcomes.

[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).

Resuscitation of Severe Accidental Hypothermia to Normal Neurologic Outcome With Use of Extracorporeal Membrane Oxygenation

Accidental hypothermia is a condition associated with significant morbidity and mortality. A 48-year-old male with a history of alcohol use disorder and optic neuropathy presented to the emergency department after being found unresponsive with an unknown downtime. One hundred four minutes passed from resuscitation, to pre-hospital discovery, until cannulation with extracorporeal membrane oxygenation. Here, a rare case of successful resuscitation of a profoundly hypothermic patient to normal neurologic outcome is presented.

Accidental hypothermia in Denmark: A nationwide cohort study of incidence and outcomes

OBJECTIVES

To investigate the incidence of accidental hypothermia (AH) in a nationwide registry and the associated outcomes.

DESIGN

Nationwide retrospective cohort study PARTICIPANTS AND SETTINGS: All patients at least 18 years old, admitted to hospitals in Denmark with a diagnosis of AH, with an International Classification of Diseases, 10th edition code of T689, from January 1996 to November 2016. Other recorded diagnoses were included in the analyses.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome was 1-year mortality.

RESULTS

During the inclusion period, 5242 patients were admitted with a diagnosis of AH, corresponding to a mean annual incidence of 4.4±1.2 (range by calendar year: 2.9-6.4) per 100 000 inhabitants. A total of 2230 (43%) had AH recorded as the primary diagnosis without any recorded secondary diagnoses (primary AH), 1336 (25%) had AH recorded as the primary diagnosis with other recorded secondary diagnoses (AH+2° diagnosis), and 1676 (32%) had AH recorded as a secondary diagnosis with another recorded primary diagnosis (1° diagnosis+AH). Alcohol intoxication was the most common diagnosis associated with AH. Overall 1-year mortality was 27%. In patients with primary AH, 1-year mortality was 22%, compared with 26% in patients with secondary AH type I, and 35% in patients with secondary AH type II (p_log-rank<0.001).

CONCLUSIONS

The present study investigated the incidence of AH, associated comorbidities and mortality after AH in Denmark from 1995 to 2016. The diagnosis is associated with a high comorbidity burden and a considerable 1-year mortality. In the high proportion of patients with associated comorbidities, establishing whether AH or the comorbidities are the drivers of mortality remains difficult. This complicates our understanding of AH and makes it difficult to find modifiable factors associated with both AH and outcomes. Future prospective studies are needed elucidate the causal relationship between AH and associated comorbidities.

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.

The use of minimal invasive extracorporeal circulation for rewarming after accidental hypothermia and circulatory arrest

BACKGROUND

Extracorporeal cardiopulmonary resuscitation has become a recommended treatment option for patients with severe hypothermia with cardiac arrest. Minimal invasive extracorporeal circulation (MiECC) may offer advantages over the current standard extracorporeal membrane oxygenation (ECMO).

METHODS

Retrospective cohort analysis of hospital database for patients with accidental hypothermia and extracorporeal rewarming with MiECC admitted between 2010 and 2019.

RESULTS

Overall, six of 17 patients survived to hospital discharge. Eleven patients suffered accidental hypothermia in an alpine and six in an urban setting. Sixteen patients arrived at the hospital under ongoing cardiopulmonary resuscitation (CPR). CPR time was 90 minutes (0-150). Four patients survived from an alpine setting and two from an urban setting with CPR duration of 90 minutes (0-150) and 85 minutes (25-100), respectively. Asphyctic patients tended to have lower survival (one of seven patients). Two patients of six with major trauma survived.

CONCLUSION

MiECC for extracorporeal rewarming from severe accidental hypothermia is a feasible alternative to ECMO, with comparable survival rates.

[Spontaneous periodic hypothermia syndrome: A systematic review of the literature]

INTRODUCTION

Periodic spontaneous hypothermia syndrome (PSHS), also known as hypersudation-hypothermia syndrome, is a rare condition characterised by the occurrence of paroxysmal attacks of spontaneous hypothermia occurring without age limit. Few studies have attempted to synthesise the available data on PSHS. The objective of this study was to summarize the literature on this condition.

METHODS

A literature review was conducted using the Pubmed and ScienceDirect databases. Cases from a registry of PSHS initiated at the CHU of Saint-Étienne were added to the analysis. For each clinical case, clinical, biological and morphological data as well as therapeutic management and evolution were collected.

RESULTS

Seventy-one cases of PSHS were collected. The median age at symptom onset was 21.5 years. The clinical sign most frequently associated with hypothermia was the presence of hyperhidrosis. The triad of hypothermia-hypersudation-agenesis of the corpus callosum was present in 35.7% of cases.

CONCLUSION

PSHS remains a poorly known cause of hypothermia, without consensual therapeutic options. The need to better describe cases and obtain more long-term data will allow a better definition and knowledge of this syndrome.

Episodic headache with spontaneous hypothermia reveal Shapiro's syndrome variant with effectiveness of clonidine therapy

BACKGROUND

Episodic headache with spontaneous hypothermia constitute an uncommon association and is not well recognized in the International Classification of Headache Disorders (ICHD-3). Spontaneous periodic hypothermia, also called Shapiro's syndrome, is a rare disease characterized by hypothermia attacks associated or not with hyperhidrosis without any triggering factor.

CASE PRESENTATION

We report a rare case of Shapiro's syndrome variantrevealed by episodes of headache with spontaneous hypothermia witheffectiveness of clonidine therapy in a 76-year-old Parkinson's disease woman.

CONCLUSIONS

In the literature, apart from Shapiro's syndrome, headache withhypothermia seem to occur very rarely. In our case,these symptoms may be considered as a very rare non-motor fluctuation ofParkinson's disease.

Concentrations of Ca, Mg, P, Prostaglandin E2 in Bones and Parathyroid Hormone; 1,25-dihydroxyvitamin D3; 17-β-estradiol; Testosterone and Somatotropin in Plasma of Aging Rats Subjected to Physical Training in Cold Water

Exposure to low temperatures can be considered a stressor, which when applied for a specific time can lead to adaptive reactions. In our study we hypothesized that cold, when applied to the entire body, may be a factor that positively modifies the aging process of bones by improving the mechanisms related to the body's mineral balance. Taking the above into account, the aim of the study was to determine the concentration of calcium (Ca), magnesium (Mg), and phosphorus (P) in bones, and to examine bone density and concentrations of the key hormones for bone metabolism, namely parathyroid hormone (PTH), somatotropin (GH), 1,25-dihydroxyvitamin D3, 17-β estradiol, testosterone (T) in plasma, and prostaglandin E2 (PGE2) in the bone of aging rats subjected to physical training in cold water. The animals in the experiment were subjected to a series of swimming sessions for nine weeks. Study group animals (male and female respectively) performed swimming training in cold water at 5 ± 2 °C and in water with thermal comfort temperature (36 ± 2 °C). Control animals were kept in a sedentary condition. Immersion in cold water affects bone mineral metabolism in aging rats by changing the concentration of Ca, Mg, and P in the bone, altering bone mineral density and the concentration of key hormones involved in the regulation of bone mineral metabolism. The effect of cold-water immersion may be gender-dependent. In females, it decreases Ca and Mg content in bones while increasing bone density and 17-β estradiol and 1,25-dihydroxyvitamin D3 levels, and with a longer perspective in aging animals may be positive not only for bone health but also other estrogen-dependent tissues. In males, cold water swimming decreased PTH and PGE2 which resulted in a decrease in phosphorus content in bones (with no effect on bone density), an increase in 1,25-dihydroxyvitamin D3, and increase in T and GH, and may have positive consequences especially in bones and muscle tissue for the prevention of elderly sarcopenia.

Maintaining intravenous volume mitigates hypothermia-induced myocardial dysfunction and accumulation of intracellular Ca2

NEW FINDINGS

What is the central question of this study? Detailed guidelines for volume replacement to counteract hypothermia-induced intravascular fluid loss are lacking. Evidence suggests colloids might have beneficial effects compared to crystalloids. Are central haemodynamic function and level of hypothermia-induced calcium overload, as a marker of cardiac injury, restored by fluid substitution during rewarming, and are colloids favourable to crystalloids? What is the main finding and its importance? Infusion with crystalloid or dextran during rewarming abolished post-hypothermic cardiac dysfunction, and partially mitigated myocardial calcium overload. The effects of volume replacement to support haemodynamic function are comparable to those using potent cardio-active drugs. These findings underline the importance of applying intravascular volume replacement to maintain euvolaemia during rewarming.

ABSTRACT

Previous research exploring pathophysiological mechanisms underlying circulatory collapse after rewarming victims of severe accidental hypothermia has documented post-hypothermic cardiac dysfunction and hypothermia-induced elevation of intracellular Ca²⁺ concentration ([Ca²⁺ ]_i ) in myocardial cells. The aim of the present study was to examine if maintaining euvolaemia during rewarming mitigates cardiac dysfunction and/or normalizes elevated myocardial [Ca²⁺ ]_i . A total of 21 male Wistar rats (300 g) were surface cooled to 15°C, then maintained at 15°C for 4 h, and subsequently rewarmed to 37°C. The rats were randomly assigned to one of three groups: (1) non-intervention control (n = 7), (2) dextran treated (i.v. 12 ml/kg dextran 70; n = 7), or (3) crystalloid treated (24 ml/kg 0.9% i.v. saline; n = 7). Infusions occurred during the first 30 min of rewarming. Arterial blood pressure, stroke volume (SV), cardiac output (CO), contractility (dP/dt_max ) and blood gas changes were measured. Post-hypothermic changes in [Ca²⁺ ]_i were measured using the method of radiolabelled Ca²⁺ (⁴⁵ Ca²⁺ ). Untreated controls displayed post-hypothermic cardiac dysfunction with significantly reduced CO, SV and dP/dt_max . In contrast, rats receiving crystalloid or dextran treatment showed a return to pre-hypothermic control levels of CO and SV after rewarming, with the dextran group displaying significantly better amelioration of post-hypothermic cardiac dysfunction than the crystalloid group. Compared to the post-hypothermic increase in myocardial [Ca²⁺ ]_i in non-treated controls, [Ca²⁺ ]_i values with crystalloid and dextran did not increase to the same extent after rewarming. Volume replacement with crystalloid or dextran during rewarming abolishes post-hypothermic cardiac dysfunction, and partially mitigates the hypothermia-induced elevation of [Ca²⁺ ]_i .

Na+/Ca2+ exchanger mediates cold Ca2+ signaling conserved for temperature-compensated circadian rhythms

Circadian rhythms are based on biochemical oscillations generated by clock genes/proteins, which independently evolved in animals, fungi, plants, and cyanobacteria. Temperature compensation of the oscillation speed is a common feature of the circadian clocks, but the evolutionary-conserved mechanism has been unclear. Here, we show that Na⁺/Ca²⁺ exchanger (NCX) mediates cold-responsive Ca²⁺ signaling important for the temperature-compensated oscillation in mammalian cells. In response to temperature decrease, NCX elevates intracellular Ca²⁺, which activates Ca²⁺/calmodulin-dependent protein kinase II and accelerates transcriptional oscillations of clock genes. The cold-responsive Ca²⁺ signaling is conserved among mice, Drosophila, and Arabidopsis The mammalian cellular rhythms and Drosophila behavioral rhythms were severely attenuated by NCX inhibition, indicating essential roles of NCX in both temperature compensation and autonomous oscillation. NCX also contributes to the temperature-compensated transcriptional rhythms in cyanobacterial clock. Our results suggest that NCX-mediated Ca²⁺ signaling is a common mechanism underlying temperature-compensated circadian rhythms both in eukaryotes and prokaryotes.

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.