BACKGROUND AND OBJECTIVE:Heat-related illnesses can range from mild to severe, potentially causing death or disability. Central nervous system abnormalities are crucial clinical indicators, yet their relationships with outcomes remain unclear. We aimed to investigate this association using a Japanese nationwide database. METHODS:This study analysed data from the Heatstroke Study database (2017-2021) which included adult Japanese patients with heat-related illnesses. Acute neurological symptoms (Glasgow Coma Scale (GCS) <14 and/or seizures) were the primary exposure. Outcomes included in-hospital mortality and unfavourable functional outcomes (modified Rankin Scale (mRS) ≥3). Adjusted ORs with 95% CIs were estimated using multivariable logistic regression, adjusting for age, sex, preadmission mRS, Charlson Comorbidity Index, occurrence situation, body temperature and systolic blood pressure. RESULTS:Among 2961 patients (median age 73.0 years, 69.4% were male), the in-hospital mortality was 5.4% (160/2961). The observed mortality was 10.9% (142/1303) in patients with acute neurological symptoms and 1.1% (18/1658) in patients without symptoms. Unfavourable functional outcomes occurred in 42.2% (455/1078) of patients with acute neurological symptoms and 10.4% (155/1492) of patients without symptoms. After adjustment, acute neurological symptoms were found to be significantly associated with in-hospital mortality (adjusted OR 7.33, 95% CI 4.50 to 12.64) and unfavourable functional outcomes (adjusted OR 5.15, 95% CI 4.14 to 6.44). A dose-dependent relationship was observed between GCS severity and mortality, with GCS 3-8 showing the highest risk compared with GCS 14-15 (adjusted OR 12.23, 95% CI 7.42 to 21.17). CONCLUSION:Acute neurological symptoms, particularly impaired consciousness, were independently associated with mortality and unfavourable outcomes in heat-related illnesses. These findings emphasise the importance of neurological symptoms in severity classification for heat-related illnesses.

Heat-related illnesses are a serious public health concern and are exacerbated by global warming. Wet-Bulb Globe Temperature (WBGT) is widely used as a heat stress indicator, but its clinical impact remains unclear. This study aimed to investigate the association between hourly variations in WBGT and the incidence of hospitalizations for heat-related illness in Japan using a nationwide database. By incorporating individual-level clinical data and performing stratified analyses, we sought to provide a more granular understanding of how heat exposure affects the risk of heat-related illness requiring hospitalization. We conducted a time-stratified, case-crossover study using data collected from July to September in 2020 and 2021 in the Heatstroke STUDY registry. The inclusion criteria were patients registered in the Heatstroke STUDY registry, specifically hospitalized patients with heat-related illness who were transported to participating hospitals during the study period. Hourly WBGT values were assigned based on the nearest monitoring station to each hospital. Conditional logistic regression and distributed lag models were used to estimate associations between WBGT and the risk of hospitalization. A total of 1,653 heat-related illness hospitalizations were analyzed. The mean patient age was 67.9 years; 67.6

OBJECTIVE:Children are particularly vulnerable to heat-related illnesses due to their unique physiological and behavioral characteristics. Understanding the epidemiology and clinical features of heat-related illnesses in children is crucial for guiding targeted preventive measures and management strategies. This descriptive study aims to investigate the characteristics of pediatric patients with heat-related illness who were transferred to emergency departments in Japan. METHODS:This study was a secondary analysis of the Heatstroke Study, led by the Heatstroke and Hypothermia Surveillance Committee of the Japanese Association for Acute Medicine. This study included pediatric patients (<18 years) with heat-related illness transferred to emergency departments in the summer from 2017 to 2021. We summarized the circumstances of onset, clinical characteristics, and outcomes. RESULTS:Of the 3,154 registered patients, 146 children were included. Of them, 60% were male, with a median age of 15 years (interquartile range, 13-16 years). The most cases occurred in August (47%), and most (80%) were associated with sports activities and with outdoor settings (70%). Cases with a body temperature above 40 °C were rare (3%). Most cases were admitted to hospitals (75% to the general ward and 16% to the intensive care unit), and patients admitted to intensive care unit had altered consciousness with increased serum creatinine. There were two cases of mortality, both of which were out-of-hospital cardiac arrest. CONCLUSION:Most pediatric cases with heat-related illness were middle or high school students, occurred in August, and were related to outdoor sports activity. Patients admitted to hospitals suffered altered consciousness, dehydration, and acute kidney injury.

Rapid assessment of severity is crucial for timely intervention and improved patient outcomes in heatstroke (HS). However, existing biomarkers are limited in their accuracy and accessibility in ER settings. A prospective pilot study was conducted to assess urinary liver fatty acid-binding protein (L-FABP) levels using a point-of-care testing (POCT) upon HS. Severity was estimated using initial Sequential Organ Failure Assessment (SOFA) scores, and outcomes were measured using modified Rankin Scale (mRS) scores. In 78 severe HS patients, semi-quantitative L-FABP measurements were performed in ER and patients were divided as P-group (positive group, L-FABP ≧ 12.5 ng/mL on POCT) and N-group (negative group: L-FABP < 12.5ng/mL, on POCT). urinary L-FABP concentrations were also measured on admission, with a median concentration of 48.3 ng/mL. The positive correlation was observed between urinary L-FABP concentration and pulse rate (r = 0.300, P < 0.01) and lactate (r = 0.259, P < 0.01). The POCT of L-FABP showed promise in predicting severity, as indicated by higher concentrations in patients with higher initial SOFA scores. Furthermore, the comparison between semi-quantitative POCT measurements and urine concentrations of L-FABP measured by enzyme-linked immunosorbent assay (ELISA) revealed significant differences among three POCT groups (POC Range < 12.5 ng/ml, 12.6–100 ng/ml, and 55 > 100 ng/ml, P = 0.001). Additionally, patients in the POCT positive group had significantly worse outcomes at discharge compared to the negative group, although this difference diminished over time. The study demonstrates the feasibility and potential utility of POCT for initial L-FABP in estimating severity in HS patients. This rapid and accessible testing method may aid in early field triage and intervention, ultimately improving patient outcomes in the management of HS.

Aim:This study aimed to experimentally verify the safety and effectiveness of evaporative plus convective cooling used in heat stroke treatment using a doll simulating a patient with heat stroke. Methods:Evaporative plus convective cooling was simulated by blowing air through a fan (speed: approximately 1.0 or 2.5 m/s) and using normal (20°C) or slightly warm (40°C) water on a doll whose surface body temperature was set at 40°C. We measured the change in surface body temperature using a surface heater attached to the back of the doll's chest cover and observed aerosol generation (size: ≥5 μm) using a particulate visualization system. Three particle counters were placed to measure the generated particles that were not captured by the particulate visualization system. Results:The cooling effect of the 2.5 m/s wind speed was greater than that of the 1.0 m/s wind speed. No particles >0.5 μm were observed, and no aerosol particles were generated. Conclusions:Our results thus suggested that wind force has a significant effect, and there was no risk of aerosol-related viral infection in evaporative plus convective cooling. However, this does not rule out the risk of droplet infection.

AbstractRecently, patients with out-of-hospital cardiac arrest (OHCA) refractory to conventional resuscitation have started undergoing extracorporeal cardiopulmonary resuscitation (ECPR). However, the mortality rate of these patients remains high. This study aimed to clarify whether a center ECPR volume was associated with the survival rates of adult patients with OHCA resuscitated using ECPR. This was a secondary analysis of a retrospective multicenter registry study, the SAVE-J II study, involving 36 participating institutions in Japan. Centers were divided into three groups according to the tertiles of the annual average number of patients undergoing ECPR: high-volume (≥ 21 sessions per year), medium-volume (11–20 sessions per year), or low-volume (< 11 sessions per year). The primary outcome was survival rate at the time of discharge. Patient characteristics and outcomes were compared among the three groups. Moreover, a multivariable-adjusted logistic regression model was applied to study the impact of center ECPR volume. A total of 1740 patients were included in this study. The center ECPR volume was strongly associated with survival rate at the time of discharge; furthermore, survival rate was best in high-volume compared with medium- and low-volume centers (33.4%, 24.1%, and 26.8%, respectively; P = 0.001). After adjusting for patient characteristics, undergoing ECPR at high-volume centers was associated with an increased likelihood of survival compared to middle- (adjusted odds ratio 0.657; P = 0.003) and low-volume centers (adjusted odds ratio 0.983; P = 0.006). The annual number of ECPR sessions was associated with favorable survival rates and lower complication rates of the ECPR procedure.Clinical trial registration: https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000041577 (unique identifier: UMIN000036490).

AimThe study aimed to determine the current status of face mask use, deep body temperature measurement, and active cooling in patients suffering from heat stroke and heat exhaustion in Japan.MethodsThis was a prospective, observational, multicenter study using data from the Heatstroke STUDY 2020–2021, a nationwide periodical registry of heat stroke and heat exhaustion patients. Based on the Bouchama heatstroke criteria, we classified the patients into two groups: severe and mild‐to‐moderate. We compared the outcomes between the two groups and reclassified them into two subgroups according to the severity of the illness, deep body temperature measurements, and face mask use. Cramer's V was used to determine the effect sizes for a comparison between groups.ResultsAlmost all patients in this study were categorized as having degree III based on the Japanese Association for Acute Medicine heatstroke criteria (JAAM‐HS). However, the severe group was significantly worse than the mild‐to‐moderate group in outcomes like in‐hospital death and modified Rankin Scale scores, when discharged. Heat strokes had significantly higher rates of active cooling and lower mortality rates than heat stroke‐like illnesses. Patients using face masks often use them during labor, sports, and other exertions, had less severe conditions, and were less likely to be young male individuals.ConclusionsIt is suggested that severe cases require a more detailed classification of degree III in the JAAM‐HS criteria, and not measuring deep body temperature could have been a factor in the nonperformance of active cooling and worse outcomes.

Both coronavirus disease 2019 (COVID-19) and heat stroke have symptoms of fever or hyperthermia and the difficulty in distinguishing them could lead to a strain on emergency medical care. To mitigate the potential confusion that could arise from actions for preventing both COVID-19 spread and heat stroke, particularly in the context of record-breaking summer season temperatures, this work offers new knowledge and evidence that address concerns regarding indoor ventilation and indoor temperatures, mask wearing and heat stroke risk, and the isolation of older adults. Specifically, the current work is the second edition to the previously published guidance for handling heat stroke during the COVID-19 pandemic, prepared by the "Working group on heat stroke medical care during the COVID-19 epidemic," composed of members from four organizations in different medical and related fields. The group was established by the Japanese Association for Acute Medicine Heatstroke and Hypothermia Surveillance Committee. This second edition includes new knowledge, and conventional evidence gleaned from a primary selection of 60 articles from MEDLINE, one article from Cochrane, 13 articles from Ichushi, and a secondary/final selection of 56 articles. This work summarizes the contents that have been clarified in the prevention and treatment of infectious diseases and heat stroke to provide guidance for the prevention, diagnosis, and treatment of heat stroke during the COVID-19 pandemic.

Background The conflicting results of previous analyses about hypothermia management in patients with out-of-hospital cardiopulmonary arrest have hindered the establishment of a uniform standard temperature setting for temperature control. This study investigated and compared the clinical outcomes of hypothermic (target temperature: 32–34°C) and normothermic (35–36°C) management of out-of-hospital cardiac arrest (OHCA) patients, treated with extracorporeal cardiopulmonary resuscitation (ECPR).Methods This secondary analysis of the SAVE-J II study, a retrospective, multicenter, registry study involving 36 participating institutions in Japan, was undertaken, and ECPR patients with a suspected cardiac etiology were included in this cohort. The primary outcome was survival at hospital discharge. Favorable neurological outcomes (5-point Glasgow-Pittsburgh Cerebral Performance Categories 1–2) constituted the secondary outcome. Multivariable logistic analysis, which was adjusted for potential confounders, was performed for the primary and secondary outcomes.Results Of the 949 participants of this study, 57% underwent hypothermic management. A total favorable neurological outcome at hospital discharge was identified in 164 patients (17%), and the survival rate was 35%. In multivariable analysis, with the primary and secondary endpoints as each dependent variable, and gender, age, witness, bystander CPR, electrocardiogram, low flow time, and causative disease as categorical covariates, hypothermic management compared to normothermic management in OHCA patients treated with ECPR, was not significantly associated with a favorable neurological outcome (adjusted odds ratio (aOR): 1.22: 95% CI: 0.85–1.74), but was associated with survival (aOR: 1.74: 95% CI: 1.31–2.32).Conclusions Compared to normothermic management, hypothermic management of OHCA patients treated with ECPR was not significantly associated with a favorable neurological outcome, but was associated with survival at hospital discharge.### Competing Interest StatementThe authors have declared no competing interest.### Funding StatementThis work was supported by the Japan Society for the Promotion of Science KAKENHI to JK(JP19K18365) and YK (JP19K09419). The funding organization did not play any role in the study; the views expressed in this paper do not reflect the views of the Ministry.### Author DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:The SAVE-J II Study was approved by the institutional review board of Kagawa University (approval number: 2018-110). For all participating centers, the requirement for patient consent was waived because of the retrospective nature of the study. The study was approved by the Teikyo University School of Medicine Research Ethics Committee (approval number: 23-005).I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).YesI have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.YesThe data that support the findings of this study are available from the corresponding author upon reasonable request.The data that support the findings of this study are available from the corresponding author upon reasonable request.

We previously developed a risk assessment tool to predict outcomes after heat-related illness (J-ERATO score), which consists of six binary prehospital vital signs. We aimed to evaluate the ability of the score to predict clinical outcomes for hospitalized patients with heat-related illnesses. In a nationwide, prospective, observational study, adult patients hospitalized for heat-related illnesses were registered. A binary logistic regression model and receiver operating characteristic (ROC) curve analysis were used to assess the relationship between the J-ERATO and survival at hospital discharge as a primary outcome. Among eligible patients, 1244 (93.0%) survived to hospital discharge. Multivariable logistic regression analysis revealed that the J-ERATO was an independent predictor for survival to discharge (adjusted odds ratio [OR] 0.47; 95% confidence interval [CI] 0.37-0.59) and occurrence of disseminated intravascular coagulation (DIC) on day 1 (adjusted OR 2.07; 95% CI 1.73-2.49). ROC analyses revealed an optimal J-ERATO cut-off of 5 for prediction of mortality at discharge (area under the curve [AUC] 0.742; 95% CI 0.691-0.787) and DIC development on day 1 (AUC 0.723; 95% CI 0.684-0.758). The J-ERATO obtained before transportation could be helpful in predicting the severity and mortality of hospitalized patients with heat-related illnesses.

Abstract Background The number of traffic fatalities is declining in Japan; however, a large proportion of head injuries are still attributable to traffic accidents. Severe head trauma may cause progressive and devastating coagulopathy owing to exacerbated coagulation and fibrinolysis, which results in massive bleeding and poor patient outcomes. D-dimer is a fibrinolytic marker, which remarkably increases in severe coagulopathy due to the exacerbated fibrinolytic system. Because the degree of coagulopathy is associated with patient outcomes, the D-dimer level is a useful prognostic predictor in patients with head trauma. However, the usefulness of D-dimer in cases of head trauma caused by road traffic accidents remains inadequately explored. In this study, we investigated the relationship between D-dimer levels and outcomes in head injuries caused by traffic accidents. Methods We extracted data on traffic injuries from Japan Neuro-Trauma Data Bank Project 2015, which is a prospective multicenter registry of head injuries. The analysis included 335 individuals with no missing data. The outcome variable was the score of the Glasgow Outcome Scale (GOS), a neurological outcome index. The participants were categorized into the favorable outcome (GOS score ≥ 4) and poor outcome (GOS score ≤ 3) groups. The serum D-dimer levels at the time of admission were divided into four categories at the quartiles, and the reference category was less than the first quartile (< 17.4 µg/mL). We performed a logistic regression analysis with GOS as the dependent variable and D-dimer as a predictor and performed a multivariate analysis that was adjusted for 10 physiological parameters. Results In the univariate analysis, all groups with serum D-dimer values ≥ 17.4 μg/dL showed significantly poorer outcomes than those of the reference group. In the multivariate analysis, after adjusting for other factors, D-dimer levels ≥ 89.3 μg/dL were an independent predictor of poor outcome. Conclusion After adjusting for physiological parameters, high serum D-dimer levels can be an independent factor for predicting neurological prognosis in head trauma caused by road traffic accidents.

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.

Abstract Background The prevalence of extracorporeal cardiopulmonary resuscitation (ECPR) in patients with out-of-hospital cardiac arrest (OHCA) has been increasing rapidly worldwide. However, guidelines or clinical studies do not provide sufficient data on ECPR practice. The aim of this study was to provide real-world data on ECPR for patients with OHCA, including details of complications. Methods We did a retrospective database analysis of observational multicenter cohort study in Japan. Adult patients with OHCA of presumed cardiac etiology who received ECPR between 2013 and 2018 were included. The primary outcome was favorable neurological outcome at hospital discharge, defined as a cerebral performance category of 1 or 2. Results A total of 1644 patients with OHCA were included in this study. The patient age was 18–93 years (median: 60 years). Shockable rhythm in the initial cardiac rhythm at the scene was 69.4%. The median estimated low flow time was 55 min (interquartile range: 45–66 min). Favorable neurological outcome at hospital discharge was observed in 14.1% of patients, and the rate of survival to hospital discharge was 27.2%. The proportions of favorable neurological outcome at hospital discharge in terms of shockable rhythm, pulseless electrical activity, and asystole were 16.7%, 9.2%, and 3.9%, respectively. Complications were observed during ECPR in 32.7% of patients, and the most common complication was bleeding, with the rates of cannulation site bleeding and other types of hemorrhage at 16.4% and 8.5%, respectively. Conclusions In this large cohort, data on the ECPR of 1644 patients with OHCA show that the proportion of favorable neurological outcomes at hospital discharge was 14.1%, survival rate at hospital discharge was 27.2%, and complications were observed during ECPR in 32.7%.

Aim: This study aimed to investigate the relationship between transient return of spontaneous circulation (ROSC) before extracorporeal membrane oxygenation (ECMO) initiation and outcomes in out-of-hospital cardiac arrest (OHCA) patients, who were resuscitated with extracorporeal cardiopul-monary resuscitation (ECPR).Methods: This study was a secondary analysis of the SAVE-J II study, which was a retrospective multicentre registry study involving 36 participating institutions in Japan. We classified patients into two groups according to the presence or absence of transient ROSC before ECMO initiation. Tran-sient ROSC was defined as any palpable pulse of >= 1 min before ECMO initiation. The primary outcome was favourable neurological outcomes (cerebral performance categories 1-2).Results: Of 2,157 patients registered in the SAVE-J II study, 1,501 met the study inclusion criteria; 328 (22%) experienced transient ROSC before ECMO initiation. Patients with transient ROSC had better outcomes than those without ROSC (favourable neurological outcome, 26% vs 12%, P < 0.001; survival to hospital discharge, 46% vs 24%, respectively; P < 0.001). A Kaplan-Meier plot showed better survival in the transient ROSC group (log-rank test, P < 0.001). In multiple logistic analyses, transient ROSC was significantly associated with favourable neurological outcomes and survival (favourable neurological outcomes, adjusted odds ratio, 3.34 [95% confidence interval, 2.35-4.73]; survival, adjusted odds ratio, 3.99 [95% confidence interval, 2.95-5.40]).Conclusions: In OHCA patients resuscitated with ECPR, transient ROSC before ECMO initiation was associated with favourable outcomes. Hence, transient ROSC is a predictor of improved outcomes after ECPR.

Heatstroke is a life-threatening event that affects people worldwide. Currently, there are no established tools to predict the outcomes of heatstroke. Although the Sequential Organ Failure Assessment (SOFA) score is a promising tool for judging the severity of critically ill patients. Therefore, in this study, we investigated whether the SOFA score could predict the outcome of patients hospitalized with severe heatstroke, including the classical and exertional types, by using data from a Japanese nationwide multicenter observational registry. We performed retrospective subanalyses of the Japanese Association for Acute Medicine heatstroke registry, 2019. Adults with a SOFA score ≥ 1 hospitalized for heatstroke were analyzed. We analyzed data for 225 patients. Univariate and multivariable analyses showed a significant difference in the SOFA score between non-survivors and survivors in classical and exertional heatstroke cases. The area under the receiver operating characteristic curve were 0.863 (classical) and 0.979 (exertional). The sensitivity and specificity of SOFA scores were 50.0% and 97.5% (classical), 66.7% and 97.5% (exertional), respectively, at a cutoff of 12.5, and 35.0% and 98.8% (classical), 33.3% and 100.0% (exertional), respectively, at a cutoff of 13.5. This study revealed that the SOFA score may predict mortality in patients with heatstroke and might be useful for assessing prognosis.

Recently, a letter to the editor was published to comment on the 5A score which is the prediction model for accidental hypothermia patients comparing the HOPE score. In this letter, we responded to the comments to clarify the difference between the 5A score and the HOPE score.

Aim To assess heat stroke and heat exhaustion occurrence and response during the coronavirus disease 2019 pandemic in Japan. Methods This retrospective, multicenter, registry‐based study describes and compares the characteristics of patients between the months of July and September in 2019 and 2020. Factors affecting heat stroke and heat exhaustion were statistically analyzed. Cramér’s V was calculated to determine the effect size for group comparisons. We also investigated the prevalence of mask wearing and details of different cooling methods. Results No significant differences were observed between 2019 and 2020. In both years, in‐hospital mortality rates just exceeded 8%. Individuals >65 years old comprised 50% of cases and non‐exertional onset (office work and everyday life) comprised 60%–70%, respectively. The recommendations from the Working Group on Heat Stroke Medicine given during the coronavirus disease pandemic in 2019 had a significant impact on the choice of cooling methods. The percentage of cases, for which intravascular temperature management was performed and cooling blankets were used increased, whereas the percentage of cases in which evaporative plus convective cooling was performed decreased. A total of 49 cases of heat stroke in mask wearing were reported. Conclusion Epidemiological assessments of heat stroke and heat exhaustion did not reveal significant changes between 2019 and 2020. The findings suggest that awareness campaigns regarding heat stroke prevention among the elderly in daily life should be continued in the coronavirus disease 2019 pandemic. In the future, it is also necessary to validate the recommendations of the Working Group on Heatstroke Medicine.

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.

Body cooling is recommended for patients with heat stroke and heat exhaustion. However, differences in the outcomes of patients who do or do not receive active cooling therapy have not been determined. The best available evidence supporting active cooling is based on a case series without comparison groups; thus, the effectiveness of this method in improving patient prognoses cannot be appropriately quantified. Therefore, we compared the outcomes of heat stroke patients receiving active cooling with those of patients receiving rehydration-only therapy. This prospective observational multicenter registry-based study of heat stroke and heat exhaustion patients was conducted in Japan from 2010 to 2019. The patients were stratified into the "severe" group or the "mild-to-moderate" group, per clinical findings on admission. After conducting multivariate logistic regression analyses, we compared the prognoses between patients who received "active cooling + rehydration" and patients who received "rehydration only," with in-hospital death as the endpoint. Sex, age, onset situation (i.e., exertional or non-exertional), core body temperature, liver damage, renal dysfunction, and disseminated intravascular coagulation were considered potential covariates. Among those who received active cooling and rehydration-only therapy, the in-hospital mortality rates were 21.5% and 35.5%, respectively, for severe patients (n = 231) and 3.9% and 5.7%, respectively, for mild-to-moderate patients (n = 578). Rehydration-only therapy was associated with a higher in-hospital mortality in patients with severe heat illness (adjusted odds ratio [aOR], 3.29; 95% confidence interval [CI], 1.21-8.90), whereas the cooling methods were not associated with lower in-hospital mortality in patients with mild-to-moderate heat illness (aOR, 2.22; 95% CI, 0.92-5.84). Active cooling was associated with lower in-hospital mortality only in the severe group. Our results indicated that active cooling should be recommended as an adjunct to rehydration-only therapy for patients with severe heat illness.