The 12-lead electrocardiographic findings in hypothermia include the presence of J waves; prolongation of the PR, QRS, and QT intervals; and atrial and ventricular dysrhythmias. Among these findings, the J wave, known as the Osborn wave, is considered pathognomonic. In 1953, the J wave was reported as a specific response to hypothermia in dogs, representing the current at the site of injury instead of a widening of the QRS complex that occurs caused by a conduction delay. The J wave is often accompanied by ventricular fibrillation. For the past 28 years, it was assumed that the hypothermia-induced J wave was mediated by the transient outward current. However, it was recently been reported that the J waves in some patients with hypothermia can be considered delayed conduction-related waveforms. Here, we present a case of hypothermia-induced J waves together with giant R waves, which have not been previously reported during hypothermia, augmented by short RR intervals arising from premature atrial contractions. Our observations indicate that the underlying mechanism for the genesis of J waves is indeed conduction delay and not transient outward currents.

Death from general hypothermia is one of the leading causes in the structure of violent death in the Russian Federation.
OBJECTIVE: To clarify and supplement the complex of differential diagnostic macro- and microscopic signs of a fatal acute general cold trauma received when person is in the air and water.
METHODS: The conclusions of forensic medical experts on the bodies of people who died from hypothermia in the air and in water (by 150 observations) were analyzed. Methods of descriptive statistics, calculation of the frequency ratio of signs\' occurrence were used.
RESULTS: The article provides quantitative assessment of occurrence (detection) rate of diagnostically significant signs established with the help of traditional methods of expert examination. A new classification of diagnostic death signs from hypothermia taking into account their differential diagnostic significance and reflecting the conditions of a person\'s stay in the air and water in the pre-mortem and post-mortem periods, as well as terminal period mechanisms is proposed.
CONCLUSIONS: The established complexes of signs provide an objective basis for determining death cause in non-obvious conditions when cold exposure is expected to be one of the most damaging factors.
В Российской Федерации смерть от общего переохлаждения организма занимает одно из ведущих мест в структуре насильственной смерти.
UNASSIGNED: Уточнить и дополнить комплекс дифференциально-диагностических макро- и микроскопических признаков смертельной острой общей холодовой травмы, полученной в условиях нахождения человека на воздухе и в воде.
UNASSIGNED: Проанализированы заключения судебно-медицинских экспертов в отношении трупов людей, умерших от переохлаждения на воздухе и в воде (по 150 наблюдений). Применяли методы описательной статистики, вычисление соотношения частот встречаемости признаков.
UNASSIGNED: Дана количественная оценка частоты встречаемости (выявляемости) диагностически значимых признаков, устанавливаемых с помощью традиционных методов экспертного исследования. Предложена новая классификация диагностических признаков смерти от переохлаждения, учитывающая их дифференциально-диагностическую значимость и отражающая условия пребывания человека на воздухе или водной среде в премортальном и постмортальном периоде, а также механизмы терминального периода.
UNASSIGNED: Установленные комплексы признаков представляют объективную основу для установления причины смерти в условиях неочевидности, когда одним из повреждающих факторов предполагается холодовое воздействие.

BACKGROUND: In out-of-hospital cardiac arrest (OHCA) patients with extracorporeal cardiopulmonary resuscitation (ECPR), the association between low-flow time and outcomes in accidental hypothermia (AH) patients compared to those of patients without AH has not been fully investigated.
METHODS: This was a secondary analysis of the retrospective multicenter registry in Japan. We enrolled patients aged ≥ 18 years who had been admitted to the emergency department for OHCA and had undergone ECPR between January, 2013 and December, 2018. AH was defined as an arrival body temperature below 32 °C. The primary outcome was survival to discharge. Cubic spline analyses were performed to assess the non-linear associations between low-flow time and outcomes stratified by the presence of AH. We also analyzed the interaction between low-flow time and the presence of AH.
RESULTS: Of 1252 eligible patients, 105 (8.4%) and 1147 (91.6%) were in the AH and non-AH groups, respectively. Median low-flow time was 60 (47-79) min in the AH group and 51 (42-62) min in the non-AH group. The survival discharge rates in the AH and non-AH groups were 44.8% and 25.4%, respectively. The cubic spline analyses showed that survival discharge rate remained constant regardless of low-flow time in the AH group. Conversely, a decreasing trend was identified in the survival discharge rate with longer low-flow time in the non-AH group. The interaction analysis revealed a significant interaction between low-flow time and AH in survival discharge rate (p for interaction = 0.048).
CONCLUSIONS: OHCA patients with arrival body temperature < 32 °C who had received ECPR had relatively good survival outcomes regardless of low-flow time, in contrast to those of patients without AH.

Victims of severe accidental hypothermia are frequently treated with catecholamines to counteract the hemodynamic instability associated with hypothermia-induced cardiac contractile dysfunction. However, we previously reported that the inotropic effects of epinephrine are diminished after hypothermia and rewarming (H/R) in an intact animal model. Thus, the goal of this study was to investigate the effects of Epi treatment on excitation-contraction coupling in isolated rat cardiomyocytes after H/R. In adult male rats, cardiomyocytes isolated from the left ventricle were electrically stimulated at 0.5 Hz and evoked cytosolic [Ca2+] and contractile responses (sarcomere length shortening) were measured. In initial experiments, the effects of varying concentrations of epinephrine on evoked cytosolic [Ca2+] and contractile responses at 37 °C were measured. In a second series of experiments, cardiomyocytes were cooled from 37 °C to 15 °C, maintained at 15 °C for 2 h, then rewarmed to 37 °C (H/R protocol). Immediately after rewarming, the effects of epinephrine treatment on evoked cytosolic [Ca2+] and contractile responses of cardiomyocytes were determined. At 37 °C, epinephrine treatment increased both cytosolic [Ca2+] and contractile responses of cardiomyocytes in a concentration-dependent manner peaking at 25-50 nM. The evoked contractile response of cardiomyocytes after H/R was reduced while the cytosolic [Ca2+] response was slightly elevated. The diminished contractile response of cardiomyocytes after H/R was not mitigated by epinephrine (25 nM) and epinephrine treatment reduced the exponential time decay constant (Tau), but did not increase the cytosolic [Ca2+] response. We conclude that epinephrine treatment does not mitigate H/R-induced contractile dysfunction in cardiomyocytes.

UNASSIGNED: Hypothermia is associated with poor prognosis in patients with sepsis. However, no studies have explored the correlation between the severity of hypothermia and prognosis.
UNASSIGNED: Using data from the Japanese accidental hypothermia network registry (J-Point registry), we examined adult patients aged ≥18 years with infectious diseases whose initial body temperature was ≤35°C from April 1, 2011 to March 31, 2016, in 12 centers. Patients were divided into three groups according to their body temperature: Tertile 1 (T1) (32.0-35.0°C), Tertile 2 (T2) (28.0-31.9°C), and Tertile 3 (T3) (<28.0°C). In-hospital mortality was employed as a metric to assess outcomes. We conducted a multivariate logistic regression analysis to investigate the relationship between the three categories and the occurrence of in-hospital mortality.
UNASSIGNED: A total of 572 patients were registered, and 170 eligible patients were identified. Of these patients, 55 were in T1 (32.0-35.0°C), 76 in T2 (28.0-31.9°C), and 39 in T3 (<28.0°C) groups. The overall in-hospital mortality rate in accidental hypothermia (AH) patients with infectious diseases was 34.1%. The in-hospital mortality rates in the T1, T2, and T3 groups were 34.5%, 36.8%, and 28.2%, respectively. The multivariable analysis demonstrated no significant differences regarding in-hospital mortality among the three groups (T2 vs. T1, adjusted odds ratio [OR]: 1.29; 95% confidence interval [CI]: 0.58-2.89 and T3 vs. T1, adjusted OR: 0.83; 95% CI: 0.30-2.31).
UNASSIGNED: In this multicenter retrospective observational study, hypothermia severity was not associated with in-hospital mortality in AH patients with infectious diseases.

BACKGROUND: Use of a vapor barrier in the prehospital care of cold-stressed or hypothermic patients aims to reduce evaporative heat loss and accelerate rewarming. The application of a vapor barrier is recommended in various guidelines, along with both insulating and wind/waterproof layers and an active external rewarming device; however, evidence of its effect is limited. This study aimed to investigate the effect of using a vapor barrier as the inner layer in the recommended \"burrito\" model for wrapping hypothermic patients in the field.
METHODS: In this, randomized, crossover field study, 16 healthy volunteers wearing wet clothing were subjected to a 30-minute cooling period in a snow chamber before being wrapped in a model including an active heating source either with (intervention) or without (control) a vapor barrier. The mean skin temperature, core temperature, and humidity in the model were measured, and the shivering intensity and thermal comfort were assessed using a subjective questionnaire. The mean skin temperature was the primary outcome, whereas humidity and thermal comfort were the secondary outcomes. Primary outcome data were analyzed using analysis of covariance (ANCOVA).
RESULTS: We found a higher mean skin temperature in the intervention group than in the control group after approximately 25 min (p < 0.05), and this difference persisted for the rest of the 60-minute study period. The largest difference in mean skin temperature was 0.93 °C after 60 min. Humidity levels outside the vapor barrier were significantly higher in the control group than in the intervention group after 5 min. There were no significant differences in subjective comfort. However, there was a consistent trend toward increased comfort in the intervention group compared with the control group.
CONCLUSIONS: The use of a vapor barrier as the innermost layer in combination with an active external heat source leads to higher mean skin rewarming rates in patients wearing wet clothing who are at risk of accidental hypothermia.
BACKGROUND: ClinicalTrials.gov identifier: NCT05779722.

Hypothermia is defined as a significant drop in core body temperature below 35°C (95°F). It is traditionally staged as mild, moderate, severe, and profound at temperatures of 35°C to 32°C (95°F to 89.6°F), 32°C to 28°C (89.6°F to 82.4°F), <28°C (<82.4°F), and <24°C (75.2°F), respectively. It can also be classified into the same stages by clinical presentations. We present a patient that fits into two different stages based on core body temperature and clinical presentation.  A 58-year-old homeless male with a history of seizures and alcohol use presented via emergency medical services after spending the night outside and uncovered with a core body temperature of 25.1°C (77.1°F) via a urinary bladder thermometer, meeting criteria for severe, near profound, hypothermia. However, he was alert and communicating, shivering, with tachycardia, tachypnea, normal oxygen saturation, and elevated blood pressure, suggestive of mild hypothermia clinically. Passive and active external and internal rewarming were utilized to treat, with the removal of wet clothing, forced air patient warming system, warm blankets, and warm lactated ringers given intravenously. He was soon transferred to the intensive care unit and first returned to normothermic levels after approximately 10 hours from presentation. An electrocardiogram was obtained after resolution of shivering and revealed atrial fibrillation without Osborn waves. He remained in the hospital for the following week to treat his atrial fibrillation, hypothermia-induced rhabdomyolysis, and alcohol withdrawal. He was discharged without neurologic deficits and medically stable with appropriate resources.  This case demonstrates a unique presentation of severe hypothermia. To our knowledge, there has not been a reported case of severe hypothermia that does not involve severe central nervous system depression, severe slowing of vitals, and/or comatose status. These clinical symptoms normally begin during moderate hypothermic levels near 32°C (89.6°F), yet our patient presented without any central nervous system depression and with accelerated vitals that are more consistent with mild hypothermia yet had a core temperature of 25.1°C (77.1°F). Treatment was dictated by his core body temperature rather than clinical presentation. Because of this incongruence between symptoms and true severity of disease in hypothermia, we recommend diagnosis and treatment of hypothermia always be confirmed and based on core body temperature via a low-reading thermometer instead of clinical presentation alone.

BACKGROUND: Accidental hypothermia is common in all trauma patients and contributes to the lethal diamond, increasing both morbidity and mortality. In hypotensive shock, fluid resuscitation is recommended using fluids with a temperature of 37-42°, as fluid temperature can decrease the patient\'s body temperature. In Sweden, virtually all prehospital services use preheated fluids. The aim of the present study was to investigate how the temperature of preheated infusion fluids is affected by the ambient temperatures and flow rates relevant for prehospital emergency care.
METHODS: In this experimental simulation study, temperature changes in crystalloids preheated to 39 °C were evaluated. The fluid temperature changes were measured both in the infusion bag and at the patient end of the infusion system. Measurements were conducted in conditions relevant to prehospital emergency care, with ambient temperatures varying between - 4 and 28 °C and flow rates of 1000 ml/h and 6000 ml/h, through an uninsulated infusion set at a length of 175 cm.
RESULTS: The flow rate and ambient temperature affected the temperature in the infusion fluid both in the infusion bag and at the patient end of the system. A lower ambient temperature and lower flow rate were both associated with a greater temperature loss in the infusion fluid.
CONCLUSIONS: This study shows that both a high infusion rate and a high ambient temperature are needed if an infusion fluid preheated to 39 °C is to remain above 37 °C when it reaches the patient using a 175-cm-long uninsulated infusion set. It is apparent that the lower the ambient temperature, the higher the flow rate needs to be to limit temperature loss of the fluid.

The HOPE score (https://www.hypothermiascore.org) is a validated instrument for estimating the survival probability of patients in hypothermic cardiac arrest with ECLS rewarming. It is based on six patient characteristics: sex, age, mechanism of hypothermia, duration of cardiopulmonary resuscitation, serum potassium and temperature. The HOPE score provides a reliable estimate of survival probability that can be used to decide whether to rewarm a patient. In the initial publication of the HOPE score, a cutoff of 10% was proposed, below which a patient would not be rewarmed. This choice was tentative and subject to debate. In this paper, we examine the implications of this choice on the proportions of false positives (i.e., rewarmed patient who ends up dying) and false negatives (i.e., non-rewarmed patients who would have survived if rewarmed), and we provide approximate formulas to obtain upper bounds for these proportions as a function of the cutoff chosen. In particular, the choice of a 10% cutoff will result in a proportion of FP of less than 40% and a proportion of FN of less than 0.5% in many practical situations.

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