Elevation of cardiac troponin I during non-exertional heat-related illnesses in the context of a heatwave

One day of environment-induced heat stress damages the murine myocardium

The physiological consequences of environment-induced heat stress (EIHS), caused by prolonged exposure to excess heat and humidity, are largely unknown. The purpose of this investigation was to determine the extent to which EIHS alters cardiac health. We hypothesized that 24 h of EIHS would cause cardiac injury and cellular dysfunction in a murine EIHS model. To test this hypothesis, 7-wk-old female mice were housed under thermoneutral (TN) conditions (n = 12; 31.2 ± 1.01°C, 35 ± 0.7% humidity) or EIHS conditions (n = 14; 37.6 ± 0.01°C, 42.0 ± 0.06% humidity) for 24 h. Environment-induced heat stress increased rectal temperature by 2.1°C (P < 0.01) and increased subcutaneous temperature by 1.8°C (P < 0.01). Body weight was decreased by 10% (P = 0.03), heart weight/body weight was increased by 26% (P < 0.01), and tissue water content was increased by 11% (P < 0.05) in EIHS compared with TN. In comparison with TN, EIHS increased protein abundance of heat shock protein (HSP) 27 by 84% (P = 0.01); however, HSPs 90, 60, 70, and phosphorylated HSP 27 were similar between groups. Histological inspection of the heart revealed that EIHS animals had increased myocyte vacuolation in the left ventricle (P = 0.01), right ventricle (P < 0.01), and septum (P = 0.01) compared with TN animals. Biochemical indices are suggestive of mitochondrial remodeling, increased autophagic flux, and robust activation of endoplasmic reticulum stress in hearts from EIHS mice compared with TN mice. These data demonstrate that 1 day of EIHS is sufficient to induce myocardial injury and biochemical dysregulation.NEW & NOTEWORTHY The consequences of prolonged environment-induced heat stress (EIHS) on heart health are largely unknown. We discovered that a 24-h exposure to environmental conditions sufficient to cause EIHS resulted in cardiac edema and histopathologic changes in the right and left ventricles. Furthermore, among other biochemical changes, EIHS increased autophagic flux and caused endoplasmic reticulum stress. These data raise the possibility that thermic injury, even when insufficient to cause heat stroke, can damage the myocardium.

Is heat wave a predictor of diarrhoea in Dhaka, Bangladesh? A time-series analysis in a South Asian tropical monsoon climate

While numerous studies have assessed the association between temperature and diarrhoea in various locations, evidence of relationship between heat wave and diarrhoea is scarce. We defined elevated daily mean and maximum temperature over the 95th and 99th percentiles lasting for at least one day between March to October 1981-2010 as TAV95 and TAV99 and D95 and D99 heat wave, respectively. We investigated the association between heat wave and daily counts of hospitalisations for all-cause diarrhoea in Dhaka, Bangladesh using time series regression analysis employing constrained distributed lag-linear models. Effects were assessed for all ages and children aged under 5 years of age. Diarrhoea hospitalisation increased by 6.7% (95% CI: 4.6%- 8.9%), 8.3% (3.7-13.1), 7.0 (4.8-9.3) and 7.4 (3.1-11.9) in all ages on a TAV95, TAV99, D95 and D99 heat wave day, respectively. These effects were more pronounced for under-5 children with an increase of 13.9% (95% CI: 8.3-19.9), 24.2% (11.3-38.7), 17.0 (11.0-23.5) and 19.5 (7.7-32.6) in diarrhoea hospitalisations on a TAV95, TAV99, D95 and D99 heat wave day, respectively. At lags of 3 days, we noticed a negative association indicating a 'harvesting' effect. Our findings suggest that heat wave was a significant risk factor for diarrhoea hospitalisation in Dhaka. Further research is needed to elucidate the causal pathways and identify the preventive measures necessary to mitigate the impacts of heat waves on diarrhoea. Given that no heat wave definitions exist for Dhaka, these results may help to define heat waves for Dhaka and trigger public health interventions including heat alerts to prevent heat-related morbidity in Dhaka, Bangladesh.

Heat stroke with significantly elevated troponin and dynamic ECG changes: Myocardial infarction or myocardial injury?

We described an 82-year-old man who was taken to our emergency department after being found unconscious. His electrocardiogram (ECG) showed ST-segment elevation in leads V4-V6 and cardiac troponin I (cTnI) was abnormally elevated. In addition to ECG and cTnI changes, this patient was combined with unconsciousness, high fever, abnormal liver function, acute renal failure, and rhabdomyolysis. The initial diagnosis was heat stroke, so cooling measures were initiated immediately, but a concurrent myocardial infarction was suspected. Meanwhile, emergency coronary angiography was performed, but no severe coronary stenosis or thrombosis was found. We first evaluated quantitative flow ratio (QFR) and coronary angiography-derived index of microvascular resistance (ca-IMR) in patients with heat stroke. Ca-IMR was 260 mmHg*s/m in the left circumflex artery, indicating the presence of coronary microvascular dysfunction (CMD). After several days of treatment, the patient recovered from multiple organ damage. Therefore, ECG and troponin results should be interpreted carefully in patients with high fever and coma during high temperature seasons.

Cardiovascular magnetic resonance feature tracking derived strain analysis can predict return to training following exertional heatstroke

BACKGROUND

Exertional heatstroke (EHS) is increasingly common in young trained soldiers. However, prognostic markers in EHS patients remain unclear. The objective of this study was to evaluate cardiovascular magnetic resonance (CMR) feature tracking derived left ventricle (LV) strain as a biomarker for return to training (RTT) in trained soldiers with EHS.

METHODS

Trained soldiers (participants) with EHS underwent CMR cine sequences between June 2020 and August 2023. Two-dimensional (2D) LV strain parameters were derived. At 3 months after index CMR, the participants with persistent cardiac symptoms including chest pain, dyspnea, palpitations, syncope, and recurrent heat-related illness were defined as non-RTT. Multivariable logistic regression analysis was used to develop a predictive RTT model. The performance of different models was compared using the area under curve (AUC).

RESULTS

A total of 80 participants (median age, 21 years; interquartile range (IQR), 20-23 years) and 27 health controls (median age, 21 years; IQR, 20-22 years) were prospectively included. Of the 77 participants, 32 had persistent cardiac symptoms and were not able to RTT at 3 months follow-up after experiencing EHS. The 2D global longitudinal strain (GLS) was significantly impaired in EHS participants compared to the healthy control group (-15.8 ± 1.7% vs -16.9 ± 1.2%, P = 0.001), which also showed significant statistical differences between participants with RTT and non-RTT (-15.0 ± 3.5% vs -16.5 ± 1.4%, P < 0.001). 2D-GLS (≤ -15.0%) (odds ratio, 1.53; 95% confidence interval: 1.08, 2.17; P = 0.016) was an independent predictor for RTT even after adjusting known risk factors. 2D-GLS provided incremental prognostic value over the clinical model and conventional CMR parameters model (AUCs: 0.72 vs 0.88, P = 0.013; 0.79 vs 0.88, P = 0.023; respectively).

CONCLUSION

Two-dimensional global longitudinal strain (≤ -15.0%) is an incremental prognostic CMR biomarker to predict RTT in soldiers suffering from EHS.

Management of Heat-Related Illness and Injury in the ICU: A Concise Definitive Review

OBJECTIVES

The increasing frequency of extreme heat events has led to a growing number of heat-related injuries and illnesses in ICUs. The objective of this review was to summarize and critically appraise evidence for the management of heat-related illnesses and injuries for critical care multiprofessionals.

DATA SOURCES

Ovid Medline, Embase, Cochrane Clinical Trials Register, Cumulative Index to Nursing and Allied Health Literature, and ClinicalTrials.gov databases were searched from inception through August 2023 for studies reporting on heat-related injury and illness in the setting of the ICU.

STUDY SELECTION

English-language systematic reviews, narrative reviews, meta-analyses, randomized clinical trials, and observational studies were prioritized for review. Bibliographies from retrieved articles were scanned for articles that may have been missed.

DATA EXTRACTION

Data regarding study methodology, patient population, management strategy, and clinical outcomes were qualitatively assessed.

DATA SYNTHESIS

Several risk factors and prognostic indicators for patients diagnosed with heat-related illness and injury have been identified and reported in the literature. Effective management of these patients has included various cooling methods and fluid replenishment. Drug therapy is not effective. Multiple organ dysfunction, neurologic injury, and disseminated intravascular coagulation are common complications of heat stroke and must be managed accordingly. Burn injury from contact with hot surfaces or pavement can occur, requiring careful evaluation and possible excision and grafting in severe cases.

CONCLUSIONS

The prevalence of heat-related illness and injury is increasing, and rapid initiation of appropriate therapies is necessary to optimize outcomes. Additional research is needed to identify effective methods and strategies to achieve rapid cooling, the role of immunomodulators and anticoagulant medications, the use of biomarkers to identify organ failure, and the role of artificial intelligence and precision medicine.

The pathogenesis and therapeutic strategies of heat stroke-induced myocardial injury

Heat stroke (HS) is a febrile illness characterized by an elevation in the core body temperature to over 40°C, accompanied by central nervous system impairment and subsequent multi-organ dysfunction syndrome. In recent years, the mortality rate from HS has been increasing as ambient temperatures continue to rise each year. The cardiovascular system plays an important role in the pathogenesis process of HS, as it functions as one of the key system for thermoregulation and its stability is associated with the severity of HS. Systemic inflammatory response and endothelial cell damage constitute pivotal attributes of HS, other factors such as ferroptosis, disturbances in myocardial metabolism and heat shock protein dysregulation are also involved in the damage to myocardial tissue in HS. In this review, a comprehensively detailed description of the pathogenesis of HS-induced myocardial injury is provided. The current treatment strategies and the promising therapeutic targets for HS are also discussed.

Multiparametric cardiac magnetic resonance reveals persistent myocardial inflammation in patients with exertional heat illness

OBJECTIVES

To explore the clinical potential of multiparametric cardiac magnetic resonance (CMR) in evaluating myocardial inflammation in patients with exertional heat illness (EHI).

METHODS

This prospective study enrolled 28 males with EHI (18 patients with exertional heat exhaustion (EHE) and 10 with exertional heat stroke (EHS)) and 18 age-matched male healthy controls (HC). All subjects underwent multiparametric CMR, and 9 patients had follow-up CMR measurements 3 months after recovery from EHI. CMR-derived left ventricular geometry, function, strain, native T1, extracellular volume (ECV), T2, T2*, and late gadolinium enhancement (LGE) were obtained and compared among different groups.

RESULTS

Compared with HC, EHI patients showed increased global ECV, T2, and T2* values (22.6% ± 4.1 vs. 19.7% ± 1.7; 46.8 ms ± 3.4 vs. 45.1 ms ± 1.2; 25.5 ms ± 2.2 vs. 23.8 ms ± 1.7; all p < 0.05). Subgroup analysis showed that ECV was higher in the EHS patients than those in EHE and HC groups (24.7% ± 4.9 vs. 21.4% ± 3.2, 24.7% ± 4.9 vs. 19.7% ± 1.7; both p < 0.05). Repeated CMR measurements at 3 months after baseline CMR showed persistently higher ECV than HC (p = 0.042).

CONCLUSIONS

With multiparametric CMR, EHI patients demonstrated increased global ECV, T2, and persistent myocardial inflammation at 3-month follow-up after EHI episode. Therefore, multiparametric CMR might be an effective method in evaluating myocardial inflammation in patients with EHI.

CLINICAL RELEVANCE STATEMENT

This study showed persistent myocardial inflammation after an exertional heat illness (EHI) episode demonstrated by multiparametric CMR, which is a potential promising method to evaluate the severity of myocardial inflammation and guide return to work, play, or duty in EHI patients.

KEY POINTS

• EHI patients showed an increased global extracellular volume (ECV), late gadolinium enhancement, and T2 value, indicating myocardial edema and fibrosis. • ECV was higher in the exertional heat stroke patients than exertional heat exhaustion and healthy control groups (24.7% ± 4.9 vs. 21.4% ± 3.2, 24.7% ± 4.9 vs. 19.7% ± 1.7; both p < 0.05). • EHI patients showed persistent myocardial inflammation with higher ECV than healthy controls 3 months after index CMR (22.3% ± 2.4 vs. 19.7% ± 1.7, p = 0.042).

Onset of cardiovascular drift during progressive heat stress in young adults (PSU HEAT project)

With climate change, humans are at a greater risk for heat-related morbidity and mortality, often secondary to increased cardiovascular strain associated with an elevated core temperature (Tc). Critical environmental limits (i.e., the upper limits of compensable heat stress) have been established based on Tc responses for healthy, young individuals. However, specific environmental limits for the maintenance of cardiovascular homeostasis have not been investigated in the context of thermal strain during light activity. Therefore, the purposes of this study were to 1) identify the specific environmental conditions (combinations of ambient temperature and water vapor pressure) at which cardiovascular drift [i.e., a continuous rise in heart rate (HR)] began to occur and 2) compare those environments to the environmental limits for the maintenance of heat balance. Fifty-one subjects (27 F; 23 ± 4 yr) were exposed to progressive heat stress across a wide range of environmental conditions in an environmental chamber at two low metabolic rates reflecting minimal activity (MinAct; 159 ± 34 W) or light ambulation (LightAmb; 260 ± 55 W). Whether systematically increasing ambient temperature or humidity, the onset of cardiovascular drift occurred at lower environmental conditions compared with Tc inflection points at both intensities (P < 0.05). Furthermore, the time at which cardiovascular drift began preceded the time of Tc inflection (MinAct P = 0.01; LightAmb P = 0.0002), and the difference in time between HR and Tc inflection points did not differ (MinAct P = 0.08; LightAmb P = 0.06) across environmental conditions for either exercise intensity. These data suggest that even in young adults, increases in cardiovascular strain precede the point at which heat stress becomes uncompensable during light activity.NEW & NOTEWORTHY To our knowledge, this study is the first to 1) identify the specific combinations of temperature and humidity at which an increase in cardiovascular strain (cardiovascular drift) occurs and 2) compare those environments to the critical environmental limits for the maintenance of heat balance. We additionally examined the difference in time between the onset of increased cardiovascular strain and uncompensable heat stress. We show that an increase in cardiovascular strain systematically precedes sustained heat storage in young adults.

Myocardial structure and functional alterations in a preclinical model of exertional heat stroke

AIM

Relatively little information is available about the effect of an acute exertional heat stroke (EHS) on myocardium structure and function. Herein, we used a survival male rat model of EHS to answer the question.

MAIN METHODS

Adult male Wistar rats underwent forced treadmill running at a 36 °C room temperature and 50 % relative humidity until EHS onset, characterized by hyperthermia and collapse. All rats that were followed for 14 days survived. Injury severity scores of both gastrocnemius and myocardium were determined histologically. Following an EHS event, pathological echocardiography, skeletal muscle and myocardial damage scores and indicators, myocardial fibrosis, hypertrophy, and autophagy were elucidated.

KEY FINDINGS

Rats with EHS onset displayed skeletal muscle damage, elevated serum levels of skeletal muscle indicators (e.g., creatinine kinase, myoglobin, and potassium) and myocardial injury indicators (e.g., cardiac troponin I, creatinine kinase, and lactate dehydrogenase) returning to homeostasis within 3 days post-EHS. However, EHS-induced myocardial damage, pathological echocardiography, myocardial fibrosis, hypertrophy, and deposited misfolded proteins lasted up to 14 days post-EHS at least.

SIGNIFICANCE

First, we provide evidence to confirm that despite the apparent return to homeostasis, underlying processes may still be ongoing after EHS onset. Second, we provide several key findings emphasizing the pathophysiology and risk factors of EHS, highlighting gaps in knowledge with the aim of stimulating future studies.

Biomarkers of heatstroke-induced organ injury and repair

NEW FINDINGS

What is the topic of this review? The status and potential role of novel biological markers (biomarkers) that can help identify the patients at risk of organ injury or long-term complications following heatstroke. What advances does it highlight? Numerous biomarkers were identified related to many aspects of generalized heatstroke-induced cellular injury and tissue damage, and heatstroke-provoked cardiovascular, renal, cerebral, intestinal and skeletal muscle injury. No novel biomarkers were identified for liver or lung injury.

ABSTRACT

Classic and exertional heatstroke cause acute injury and damage across numerous organ systems. Moreover, heatstroke survivors may sustain long-term neurological, cardiovascular and renal complications with a persistent risk of death. In this context, biomarkers, defined as biological samples obtained from heatstroke patients, are needed to detect early organ injury, and predict outcomes to develop novel organ preservation therapeutic strategies. This narrative review provides preliminary insights that will guide the development and future utilization of these biomarkers. To this end, we have identified numerous biomarkers of widespread heatstroke-associated cellular injury, tissue damage and repair (extracellular heat shock proteins 72 and 60, high mobility group box protein 1, histone H3, and interleukin-1α), and other organ-specific biomarkers including those related to the cardiovascular system (cardiac troponin I, endothelium-derived factors, circulation endothelial cells, adhesion molecules, thrombomodulin and von Willebrand factor antigen), the kidneys (plasma and urinary neutrophil gelatinase-associated lipocalin), the intestines (intestinal fatty acid-binding protein 2), the brain (serum S100β and neuron-specific enolase) and skeletal muscle (creatine kinase, myoglobin). No specific biomarkers have been identified so far for liver or lung injury in heatstroke. Before translating the identified biomarkers into clinical practice, additional preclinical and clinical prospective studies are required to further understand their clinical utility, particularly for the biomarkers related to long-term post-heatstroke health outcomes.

A Case of Heat Exhaustion Masquerading as ST-Elevation Myocardial Infarction

Heat-related illnesses (HRIs) are characterized by hyperthermia, neurological dysfunction, and multiorgan damage. Cardiac dysfunction has been reported, but ST-elevation with a rise in cardiac markers suggesting acute coronary syndrome has been infrequently reported. Data from the middle east in particular is lacking. This is a case of a 43-year-old male patient from the United Arab Emirates diagnosed with acute inferior ST-elevation myocardial infarction necessitating cath lab activation revealing normal coronary arteries. Echocardiography did not show evidence of wall motion abnormalities. After reviewing his clinical presentation, he was diagnosed with heat exhaustion complicated by rhabdomyolysis and acute kidney injury. The patient fully recovered with intensive medical care. This case showed that the electrocardiographic changes and elevation of cardiac markers do not reflect true cardiac ischemia but rather a pathophysiological response to HRI. Previously published reports were scarce and showed conflicting results due to the heterogenicity of cases and methods as well as the lack of angiographic documentation of coronary pathology. This case report demonstrates the importance of early recognition and timely management of HRI cases with an unusual presentation that mimics myocardial infarction, especially in countries with high ambient temperatures during the summer seasons.

Aging Hearts in a Hotter, More Turbulent World: The Impacts of Climate Change on the Cardiovascular Health of Older Adults

PURPOSE OF REVIEW

Climate change has manifested itself in multiple environmental hazards to human health. Older adults and those living with cardiovascular diseases are particularly susceptible to poor outcomes due to unique social, economic, and physiologic vulnerabilities. This review aims to summarize those vulnerabilities and the resultant impacts of climate-mediated disasters on the heart health of the aging population.

RECENT FINDINGS

Analyses incorporating a wide variety of environmental data sources have identified increases in cardiovascular risk factors, hospitalizations, and mortality from intensified air pollution, wildfires, heat waves, extreme weather events, rising sea levels, and pandemic disease. Older adults, especially those of low socioeconomic status or belonging to ethnic minority groups, bear a disproportionate health burden from these hazards. The worldwide trends responsible for global warming continue to worsen climate change-mediated natural disasters. As such, additional investigation will be necessary to develop personal and policy-level interventions to protect the cardiovascular wellbeing of our aging population.

Classic and exertional heatstroke

In the past two decades, record-breaking heatwaves have caused an increasing number of heat-related deaths, including heatstroke, globally. Heatstroke is a heat illness characterized by the rapid rise of core body temperature above 40 °C and central nervous system dysfunction. It is categorized as classic when it results from passive exposure to extreme environmental heat and as exertional when it develops during strenuous exercise. Classic heatstroke occurs in epidemic form and contributes to 9-37% of heat-related fatalities during heatwaves. Exertional heatstroke sporadically affects predominantly young and healthy individuals. Under intensive care, mortality reaches 26.5% and 63.2% in exertional and classic heatstroke, respectively. Pathological studies disclose endothelial cell injury, inflammation, widespread thrombosis and bleeding in most organs. Survivors of heatstroke may experience long-term neurological and cardiovascular complications with a persistent risk of death. No specific therapy other than rapid cooling is available. Physiological and morphological factors contribute to the susceptibility to heatstroke. Future research should identify genetic factors that further describe individual heat illness risk and form the basis of precision-based public health response. Prioritizing research towards fundamental mechanism and diagnostic biomarker discovery is crucial for the design of specific management approaches.

The Cardiovascular System in Heat Stroke

In June 2021, western Canada experienced an unprecedented heat wave, breaking dozens of temperature records. As a result, the region had a significant uptick in sudden deaths, emergency department visits, and hospital admissions. Under thermal stress, the human body achieves heat dissipation through evaporation of sweat and increased cutaneous blood flow. When these mechanisms are overwhelmed, the core body temperature rises, which leads to heat stroke, a life-threatening syndrome of hyperthermia and central nervous system dysfunction in the setting of an environmental thermal load. Heat dissipation relies on an intact cardiovascular system to dilate cutaneous vasculature and increase cardiac output. Individuals with impaired cardiovascular function have a limited ability to increase stroke volume, cardiac output, and blood flow to the skin, increasing the risk of heat stroke. In turn, these patients, whose cardiac condition is already compromised, are susceptible to cardiovascular complications of heat stroke, including arrhythmias, myocardial ischemia, heart failure, shock, and sudden death. Indeed, the majority of excess deaths during heat waves are cardiovascular in origin, highlighting the impact the cardiovascular system has on the development of heat stroke, and vice versa. This review summarizes the current understanding of the interaction between the cardiovascular system and heat stroke, including the pathophysiology, cardiovascular complications, and treatment.

Clinical characteristics and risk factors of male exertional heatstroke in patients with myocardial injury: an over 10-year retrospective cohort study

BACKGROUND

Heatstrokes are a serious threat to human health, particularly the cardiovascular system. Understanding the clinical features and risk factors related to death in patients with myocardial injury (MI) complicated by heat stroke is crucial.

METHOD

This study included the baseline data of all patients with severe heatstroke between October 2008 and May 2019.

RESULTS

Of the 162 patients enrolled, 75 (46.3%) were in the MI group and 87 (53.7%) were in the non-MI group. A significant difference was noted in 90-day survival between the two groups even after correction for Age, Acute Physiology, and Chronic Health Evaluation II (APACHE II) scores, Sequential Organ Failure Assessment (SOFA) scores, Glasgow Coma Score (GCS), and activated partial thromboplastin time (before correction (p < .001; after correction, p = .023). Survival analysis showed that the 90-day survival time of patients with MI was shorter than that of patients without MI (p < .001). The area under the receiver operating characteristic (ROC) curve for predicting mortality based on the SOFA score was 92.8% (95% CI 0.847-1.000, p < .001), the optimal cutoff value was 7.5, the sensitivity was 91.7%, and the specificity was 94.6%.

CONCLUSION

Patients with heatstroke having MI had more severe clinical conditions, 90-day mortality was significantly increased, and the survival time was shortened. A high SOFA score is an independent risk factor for death in patients with heatstroke having MI, with an optimal cutoff value of 7.5, sensitivity of 91.7%, and specificity of 94.6%.

Physiological factors characterizing heat-vulnerable older adults: A narrative review

More frequent and intense periods of extreme heat (heatwaves) represent the most direct challenge to human health posed by climate change. Older adults are particularly vulnerable, especially those with common age-associated chronic health conditions (e.g., cardiovascular disease, hypertension, obesity, type 2 diabetes, chronic kidney disease). In parallel, the global population is aging and age-associated disease rates are on the rise. Impairments in the physiological responses tasked with maintaining homeostasis during heat exposure have long been thought to contribute to increased risk of health disorders in older adults during heatwaves. As such, a comprehensive overview of the provisional links between age-related physiological dysfunction and elevated risk of heat-related injury in older adults would be of great value to healthcare officials and policy makers concerned with protecting heat-vulnerable sectors of the population from the adverse health impacts of heatwaves. In this narrative review, we therefore summarize our current understanding of the physiological mechanisms by which aging impairs the regulation of body temperature, hemodynamic stability and hydration status. We then examine how these impairments may contribute to acute pathophysiological events common during heatwaves (e.g., heatstroke, major adverse cardiovascular events, acute kidney injury) and discuss how age-associated chronic health conditions may exacerbate those impairments. Finally, we briefly consider the importance of physiological research in the development of climate-health programs aimed at protecting heat-vulnerable individuals.

Establishment and effectiveness evaluation of a scoring system for exertional heat stroke by retrospective analysis

BACKGROUND

Heat stroke (HS) is a serious, life-threatening disease. However, there is no scoring system for HS so far. This research is to establish a scoring system that can quantitatively assess the severity of exertional heat stroke (EHS).

METHODS

Data were collected from a total of 170 exertional heat stroke (EHS) patients between 2005 and 2016 from 52 hospitals in China. Univariate statistical methods and comparison of the area under the receiver operating characteristic (ROC) curve (AUC) were used to screen exertional heat stroke score (EHSS) parameters, including but not limited body temperature (T), Glasgow Coma Scale (GCS) and others. By comparing the sizes of the AUCs of the APACHE II, SOFA and EHSS assessments, the effectiveness of EHSS in evaluating the prognosis of EHS patients was verified.

RESULTS

Through screening with a series of methods, as described above, the present study determined 12 parameters - body temperature (T), GCS, pH, lactate (Lac), platelet count (PLT), prothrombin time (PT), fibrinogen (Fib), troponin I (TnI), aspartate aminotransferase (AST), total bilirubin (TBIL), creatinine (Cr) and acute gastrointestinal injury (AGI) classification - as EHSS parameters. It is a 0-47 point system designed to reflect increasing severity of heat stroke. Low (EHSS< 20) and high scores (EHSS> 35) showed 100% survival and 100% mortality, respectively. We found that AUCEHSS > AUCSOFA > AUCAPACHE II.

CONCLUSION

A total of 12 parameters - T, GCS, pH, Lac, PLT, PT, Fib, TnI, AST, TBIL, Cr and gastrointestinal AGI classification - are the EHSS parameters with the best effectiveness in evaluating the prognosis of EHS patients. As EHSS score increases, the mortality rate of EHS patients gradually increases.

Long-Term Cardiovascular Diseases of Heatstroke: A Delayed Pathophysiology Outcome

Heatstroke, defined as an elevated core body temperature above 40°C accompanied by altered mental status (e.g., confusion, disorientation, seizure and coma), is the most severe and life-threatening condition in the spectrum of heat-related illnesses. Heatstroke patients may present with multi-organ dysfunction, but with rapid cooling and organ failure management, a full recovery often occurs within weeks. Long-term impairment is rare, with neurological impairment occurring most frequently. Despite an abundance of research on the persistent neurological and hepatic impairments, our knowledge of the long-term cardiovascular events in patients with heatstroke history is poor. We wondered whether heatstroke leads to cardiovascular diseases long after full recovery. Using Pubmed, Web of Science and Scopus, we gathered cohort studies looking at cardiovascular disease incidence or mortality as an outcome, including heatstroke animal studies. Based on the available literature, we found that a history of heatstroke is associated with an increased risk of cardiovascular diseases, including ischemic heart disease, heart failure and atrial fibrillation. Delayed metabolic disturbances occurring in exertional heatstroke mice are linked to the formation of atherosclerosis and the development of heart failure. These processes provide potential pathophysiological pathways leading to ischemic heart disease and heart failure in heatstroke patients. Our findings may massively impact our understanding of heatstroke recovery and the follow up of heatstroke patients. Therefore larger, more adequately powered cohort studies with cardiovascular disease as an outcome, in tandem with animal studies examining the underlying pathophysiology, are required to confirm or reject these findings and answer the proposed questions.

Performance of quick sequential organ failure assessment (qSOFA) score for prognosis of heat-related hospitalized patients

BACKGROUND

Heat-related illnesses pose significant threats to human health.

OBJECTIVES

(1) To evaluate the use of qSOFA score for prognosis of heat-related hospitalized patients; and (2) identify other predictors for patient prognosis.

METHODS

Using 28-day mortality as the primary endpoint, a retrospective, observational study of patients hospitalized between June 2013 and September 2018 was conducted.

RESULTS

The qSOFA score from 84 patients was identified as an independent predictor of patient prognosis. The area under the receiver operating characteristic curves for qSOFA score was 0.702, and a sensitivity of 100.00% and a specificity of 47.06% were found for qSOFA score greater than or equal to 2. Other predictors included bilirubin, urea nitrogen, and troponin I levels.

CONCLUSIONS

qSOFA score can be used as a parameter to distinguish patients with severe heat-related illness prior to further clinical analyses. In addition to that, multiple organ impairment should be considered when assessing patient prognosis.

Mechanism underlying the negative inotropic effect in rat left ventricle in hyperthermia: the role of TRPV1

We have previously reported that the negative inotropic effects of hyperthermia (42 °C) on left ventricular (LV) mechanoenergetics using the excised, cross-circulated rat heart model. Here, we investigated the role of TRPV1 on LV mechanoenergetics in hyperthermia. We analyzed the LV end-systolic pressure–volume relation (ESPVR) and the linear relation between the myocardial oxygen consumption per beat (VO₂) and the systolic pressure–volume area (PVA; a total mechanical energy per beat) during infusion of capsazepine (CPZ) in hyperthermia, or capsaicin (Cap) under 300 bpm pacing. LV ESP decreased in each LV volume and the resultant downward-shift of LV ESPVR was suppressed by CPZ infusion in hyperthermia-hearts. In Cap-treated hearts, LV ESPVR shifted downward from the control ESPVR, similar to hyperthermia-hearts. The slopes of VO₂–PVA relationship were unchanged. The VO₂ intercepts in hyperthermia-hearts did not decrease because of decreased E–C coupling VO₂, and inversely increased basal metabolic VO₂, which was suppressed by CPZ, though the VO₂ intercepts in Cap-treated hearts significantly decreased. The levels of phosphorylated phospholamban at serine 16 decreased significantly in hyperthermia-hearts, as well as Cap-treated hearts. These results indicate that a Cap-induced decrease in the LV contractility, like in cases of hyperthermia, are due to the down-regulation of the total calcium handling in E–C coupling, suggesting that negative inotropic effect in hyperthermia-heart is, at least in part, mediated through TRPV1 signaling pathway.

Time course determination of the effects of rapid and gradual cooling after acute hyperthermia on body temperature and intestinal integrity in pigs

Rapid cooling after acute hyperthermia may cause a sustained increase in body temperature and exacerbate intestinal damage in pigs. Therefore, the study objective was to evaluate the temporal effects of rapid and gradual cooling on body temperature response and intestinal integrity after acute hyperthermia in pigs. In three repetitions, 54 pigs [83.3 ± 6.7 kg initial body weight (BW)], balanced by sex were exposed to thermoneutral conditions for 6 h (TN; n = 6 pigs/repetition; 21.1 ± 2.0°C), or heat stress conditions (HS; 39.3 ± 1.6°C) for 3 h, followed by a 3 h recovery period of gradual cooling [HSGC; n = 6 pigs/repetition; gradual decrease from HS to TN conditions] or rapid cooling [HSRC; n = 6 pigs/repetition; rapid TN exposure and cold water (4.0°C) dousing every 30 min for 1.5 h]. Feed was withheld throughout the entire 6 h period, but water was provided ad libitum. Gastrointestinal (T_GI) and rectal (T_R) temperatures were recorded every 15 min during the HS and recovery periods. Six pigs per repetition (n = 2/treatment) were euthanized and jejunal and ileal samples were collected for histology immediately after (d 0), 2 d after, and 4 d after the recovery period. Data were analyzed using PROC MIXED in SAS 9.4. Overall, rapid cooling reduced T_R and T_GI (P < 0.01; 0.95°C and 0.74°C, respectively) compared to gradual cooling. Jejunal villus height was reduced overall (P = 0.02; 14.01%) in HSGC compared to HSRC and TN pigs. Jejunal villus height-to-crypt depth ratio was reduced overall (P = 0.05; 16.76%) in HSGC compared to TN pigs. Ileal villus height was reduced overall (P < 0.01; 16.95%) in HSGC compared to HSRC and TN pigs. No other intestinal morphology differences were detected. In summary, HSRC did not cause a sustained increase in body temperature and did not negatively impact biomarkers of intestinal integrity in pigs.

Short-term effects of ambient air pollution and outdoor temperature on biomarkers of myocardial damage, inflammation and oxidative stress in healthy adults

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The mechanisms whereby ambient air pollution and temperature changes promote cardiac events remain incompletely described. Seventy-three nonsmoking healthy adults (mean age 23.3, SD 5.4 years) were followed with up to four repeated visits across 15 months in Beijing in 2014–2016. Biomarkers relevant to myocardial damage (high-sensitivity cardiac troponin I [hs-cTnI]), inflammation (growth differentiation factor-15 [GDF-15]), and oxidative stress (8-hydroxy-2′-deoxyguanosine [8-OHdG]) were measured at each visit, while ambient air pollution and temperature were monitored throughout the study. Linear mixed-effects models coupled with distributed lag nonlinear models were used to assess the impacts of each exposure measure on study outcomes. During follow-up, average daily concentrations of fine particulate matter and outdoor temperature were 62.9 µg/m³ (8.1–331.0 µg/m³) and 10.1 °C (−6.5°C to 29.5°C). Serum hs-cTnI levels were detectable in 18.2% of blood samples, with 27.4% of individuals having ≥1 detectable values. Higher levels of ambient particulates and gaseous pollutants (per interquartile range) up to 14 days before clinical visits were associated with significant alterations in hs-cTnI levels of 22.9% (95% CI, 6.4, 39.4) to 154.7% (95% CI, 94.4, 215.1). These changes were accompanied by elevations of circulating GDF-15 and urinary 8-OHdG levels. Both low (5th percentile, −2.5 °C) and high (95th percentile, 24.8°C) outdoor temperatures, with breakpoint at ~13.0°C as the reference level, were also associated with elevations of hs-cTnI levels. Short-term exposure to ambient air pollution and temperature was associated with cardiac troponin, a biomarker of myocardial damage, along with increased inflammation and oxidative stress responses. These findings extend our understanding of the biological mechanisms linking pervasive environmental exposure to adverse cardiac events.

Salidroside pretreatment protects against myocardial injury induced by heat stroke in mice

Objective

To explore the protective effects and mechanisms of salidroside on myocardial injury induced by heat stroke (HS) in mice.

Methods

We pretreated mice with salidroside for 1 week and then established an HS model by exposure to 41.2°C for 1 hour. We then examined the effects of salidroside on survival. We also assessed the severity of cardiac injury by pathology, and analyzed changes in levels of myocardial injury markers, inflammatory cytokines, and oxidative stress.

Results

Salidroside pretreatment significantly reduced HS-induced mortality and improved thermoregulatory function. Salidroside also provided significant protection against HS-induced myocardial damage, and decreased the expression levels of cardiac troponin I, creatine kinase-MB, and lactate dehydrogenase. Moreover, salidroside attenuated HS-induced changes in the inflammation markers tumor necrosis factor-α, interleukin (IL)-6, and IL-10, and down-regulated the oxidative stress response indicated by thiobarbituric acid reactant substances, malondialdehyde, reduced glutathione, and superoxide dismutase.

Conclusions

Salidroside pretreatment protected against HS-induced myocardial damage, potentially via a mechanism involving anti-inflammatory and anti-oxidative effects.

Effect of prealbumin level on mortality in heatstroke patients

This study investigated whether serum prealbumin level is associated with mortality in heatstroke patients. A retrospective study of 102 heatstroke patients admitted to the ICU in the Affiliated Changzhou No. 2 People's Hospital of Nanjing Medical University from June 2010 to November 2017 was performed they were divided into normal serum prealbumin group (n=79) and low prealbumin group (n=23) according to the difference in PA expression. The clinical data, laboratory inspection data, invasive positive pressure ventilation (IPPV), co-infection, shock and length of ICU stay during the ICU were compared between the two groups of patients. The study endpoints, deaths at admission, were recorded, and the survival curve plotted. Cox regression analysis was performed based on the clinical data of patients, and ROC curve plotted based on Cox multivariate independent prognostic indicators. There were significant differences in clinical variables PLT, ALT, AST, TBIL, ALB, TCH, LDH, TNI, BNP, creatinine, PT, APTT, FBG and D-dimer (P<0.05). The incidence of infection, shock and IPPV was significantly lower in normal serum prealbumin group of patients than those in low prealbumin group (P<0.05). There was a statistically significant difference in short-term survival rate between the groups of patients (χ²=29.101, P<0.001). Prognostic factors for heatstroke patients were IPPV, heart rate, WBC count, PLT count, ALB, PA, TBIL, LDH, CPK, Cr, PCT, PT, APTT, D-dimer, co-infection and shock at admission. Independent prognostic-related factors for heatstroke patients were IPPV, PA level, PLT level, ALB level, CPK level and PT level. When prealbumin <17.95 mg/dl was used as the death threshold for predicting at 28 days, the sensitivity was 77.8%, and the specificity was 85.7%. Significantly associated with the prognosis of heatstroke patients, prealbumin level can be used as an important predictive indicator of the disease progression and worse clinical outcomes.

Pathophysiology of heatstroke in dogs - revisited

Heatstroke results from a failure to dissipate accumulated heat during exposure to hot environments, or during strenuous physical exercise under heat stress. It is characterized by core body temperatures > 41°C, with central nervous system dysfunction. Functional morphology and thermoregulatory effectors differences between dogs and humans may require special heatstroke protective adaptations in dogs, however, the risk factors for developing heatstroke are similar in both. In dogs, these include hot, especially highly humid environments, excessive physical activity, obesity, large (>15 kg) body weight, being of certain breed (e.g., Labrador retrievers and brachycephalic breeds), upper airway obstruction and prolonged seizures. Lack of acclimation to heat and physical fitness decreases the survival of heat stroked dogs. At the systemic level, blood pooling within the large internal organs (e.g., spleen, liver) is a major contributor to the development of shock and consequent intestinal ischemia, hypoxia and endothelial hyperpermeability, commonly occurring in heatstroke patients. Evoked serious complications include rhabdomyolysis, acute kidney injury, acute respiratory distress syndrome and ultimately, sepsis and disseminated intravascular coagulation. The most common clinical signs in dogs include acute collapse, tachypnea, spontaneous bleeding, shock signs and mental abnormalities, including depression, disorientation or delirium, seizures, stupor and coma. In such dogs, presence of peripheral blood nucleated red blood cells uniquely occurs, and is a highly sensitive diagnostic and prognostic biomarker. Despite early, appropriate body cooling, and intensive supportive treatment, with no available specific treatment to ameliorate the severe inflammatory and hemostatic derangements, the mortality rate is around 50%, similar to that of human heatstroke victims. This review discusses the pathophysiology of canine heatstroke from a veterinarian's point of view, integrating new and old studies and knowledge.

Spontaneously hypertensive rats are sensitive to thoracic aorta damage induced by a hot and humid environment

The purpose of this study was to investigate the effect of a hot and humid environment on thoracic aorta damage in spontaneously hypertensive rats (SHRs). Wistar-Kyoto (WKY) rats were randomly divided into three groups (n=8 in each group): Control group (WKY-CN), heat exposure for 8 h group (WKY-8) and heat exposure for 24 h group (WKY-24). The CN group was exposed to room temperature (24°C); WKY-8 and WKY-24 group were exposed to heat (32°C) and 65% relative humidity for 8 and 24 h, respectively. Accordingly, SHRs were randomly divided into three groups (n=8 each group): SHR-CN, SHR-8 and SHR-24. After 7 days of heat exposure, the weight, food consumption and blood pressure of rats was measured. Noradrenaline (NA)-induced contraction of aorta rings was measured using an organ bath system, and vascular morphology was observed. Expression levels of apoptotic genes and proteins in the thoracic aorta were also measured. The experimental results indicated that, in the heat exposure environment, rat food intake was reduced. Rat weight was significantly increased in all groups except SHR-24 (all P<0.01 except SHR-8, P<0.05). Heat exposure significantly increased the blood pressure of rats in the WKY-24 (P<0.01 for systolic; P<0.05 for diastolic), SHR-8 and SHR-24 (all P<0.01) groups. This effect was more notable in SHR compared with WKY. NA-induced contraction of aorta rings significantly increased in the SHR-CN group, compared with the WKY-CN group (P<0.01). Heat exposure significantly elevated the NA-induced contraction in both 8 h groups compared with the CN groups (P<0.01). This effect was accompanied by structural damage to the thoracic aorta and increased expression of apoptotic genes and proteins. In conclusion, thoracic aorta damages in SHRs were more sensitive to heat exposure. The enhanced NA-induced contraction may have partly been due to increased apoptosis in the thoracic aorta.

Point-of-care cardiac troponin test accurately predicts heat stroke severity in rats

Heat stroke (HS) remains a significant public health concern. Despite the substantial threat posed by HS, there is still no field or clinical test of HS severity. We suggested previously that circulating cardiac troponin (cTnI) could serve as a robust biomarker of HS severity after heating. In the present study, we hypothesized that (cTnI) point-of-care test (ctPOC) could be used to predict severity and organ damage at the onset of HS. Conscious male Fischer 344 rats (n = 16) continuously monitored for heart rate (HR), blood pressure (BP), and core temperature (Tc) (radiotelemetry) were heated to maximum Tc (Tc,Max) of 41.9 ± 0.1°C and recovered undisturbed for 24 h at an ambient temperature of 20°C. Blood samples were taken at Tc,Max and 24 h after heat via submandibular bleed and analyzed on ctPOC test. POC cTnI band intensity was ranked using a simple four-point scale via two blinded observers and compared with cTnI levels measured by a clinical blood analyzer. Blood was also analyzed for biomarkers of systemic organ damage. HS severity, as previously defined using HR, BP, and recovery Tc profile during heat exposure, correlated strongly with cTnI (R(2) = 0.69) at Tc,Max. POC cTnI band intensity ranking accurately predicted cTnI levels (R(2) = 0.64) and HS severity (R(2) = 0.83). Five markers of systemic organ damage also correlated with ctPOC score (albumin, alanine aminotransferase, blood urea nitrogen, cholesterol, and total bilirubin; R(2) > 0.4). This suggests that cTnI POC tests can accurately determine HS severity and could serve as simple, portable, cost-effective HS field tests.

Heat waves, aging, and human cardiovascular health

This brief review is based on a President's Lecture presented at the Annual Meeting of the American College of Sports Medicine in 2013. The purpose of this review was to assess the effects of climate change and consequent increases in environmental heat stress on the aging cardiovascular system. The earth's average global temperature is slowly but consistently increasing, and along with mean temperature changes come increases in heat wave frequency and severity. Extreme passive thermal stress resulting from prolonged elevations in ambient temperature and prolonged physical activity in hot environments creates a high demand on the left ventricle to pump blood to the skin to dissipate heat. Even healthy aging is accompanied by altered cardiovascular function, which limits the extent to which older individuals can maintain stroke volume, increase cardiac output, and increase skin blood flow when exposed to environmental extremes. In the elderly, the increased cardiovascular demand during heat waves is often fatal because of increased strain on an already compromised left ventricle. Not surprisingly, excess deaths during heat waves 1) occur predominantly in older individuals and 2) are overwhelmingly cardiovascular in origin. Increasing frequency and severity of heat waves coupled with a rapidly growing at-risk population dramatically increase the extent of future untoward health outcomes.

The impact of heat on mortality and morbidity in the Greater Metropolitan Sydney Region: a case crossover analysis

BACKGROUND

This study examined the association between unusually high temperature and daily mortality (1997-2007) and hospital admissions (1997-2010) in the Sydney Greater Metropolitan Region (GMR) to assist in the development of targeted health programs designed to minimise the public health impact of extreme heat.

METHODS

Sydney GMR was categorized into five climate zones. Heat-events were defined as severe or extreme. Using a time-stratified case-crossover design with a conditional logistic regression model we adjusted for influenza epidemics, public holidays, and climate zone. Odds ratios (OR) and 95% confidence intervals were estimated for associations between daily mortality and hospital admissions with heat-event days compared to non-heat event days for single and three day heat-events.

RESULTS

All-cause mortality overall had similar magnitude associations with single day and three day extreme and severe events as did all cardiovascular mortality. Respiratory mortality was associated with single day and three day severe events (95th percentile, lag0: OR = 1.14; 95%CI: 1.04 to 1.24). Diabetes mortality had similar magnitude associations with single day and three day severe events (95th percentile, lag0: OR = 1.22; 95%CI: 1.03 to 1.46) but was not associated with extreme events. Hospital admissions for heat related injuries, dehydration, and other fluid disorders were associated with single day and three day extreme and severe events. Contrary to our findings for mortality, we found inconsistent and sometimes inverse associations for extreme and severe events with cardiovascular disease and respiratory disease hospital admissions. Controlling for air pollutants did not influence the mortality associations but reduced the magnitude of the associations with hospital admissions particularly for ozone and respiratory disease.

CONCLUSIONS

Single and three day events of unusually high temperatures in Sydney are associated with similar magnitude increases in mortality and hospital admissions. The trend towards an inverse association between cardio-vascular admissions and heat-events and the strong positive association between cardio-vascular mortality and heat-events suggests these events may lead to a rapid deterioration in persons with existing cardio-vascular disease resulting in death. To reduce the adverse effects of high temperatures over multiple days, and less extreme but more frequent temperatures over single days, targeted public health messages are critical.

Heat waves, incidence of infectious gastroenteritis, and relapse rates of inflammatory bowel disease: a retrospective controlled observational study

OBJECTIVES

The objective of this study was to evaluate the effect of heat waves on flares of inflammatory bowel disease (IBD) and infectious gastroenteritis (IG).

METHODS

In this retrospective controlled observational study, data from 738 IBD and 786 IG patients admitted to the University Hospital of Zurich in the years 2001-2005, as well as from 506 other noninfectious chronic intestinal inflammations, which were used as control, were collected. Climate data were obtained from the Swiss Federal Office for Meteorology and Climatology.

RESULTS

The presence of a heat wave increased the risk of IBD flares by 4.6% (95% confidence interval (CI): 1.6-7.4%, P=0.0035) and of IG flares by 4.7% (95% CI: 1.8-7.4%, P=0.0020) for every additional day within a heat wave period. In the control group there was no significant effect (95% CI: -6.2-2.9%, P=0.53). Screening of alternative forms for the effect of heat waves suggested that for IG the effect is strongest when lagged by 7 days (risk increase per day: 7.2%, 95% CI: 4.6-9.7%, P<0.0001), whereas for IBD no such transformation was required. Other formulations with additive effects, interactions between heat waves and time of the year, and additional adjustments for daily average temperature did not show any improvement in model fit.

CONCLUSIONS

In this retrospective controlled observational study, we found a substantial increase in hospital admissions because of flares of IBD and IG during heat wave periods. Whereas the effect on IG is strongest with a delay of 7 days, the effect on IBD flares is immediate, suggesting different mechanisms.

The effects of temperature on heat-related illness according to the characteristics of patients during the summer of 2012 in the Republic of Korea

Objectives

This study was conducted to investigate the relationship between heat-related illnesses developed in the summer of 2012 and temperature.

Methods

The study analyzed data generated by a heat wave surveillance system operated by the Korea Centers for Disease Control and Prevention during the summer of 2012. The daily maximum temperature, average temperature, and maximum heat index were compared to identify the most suitable index for this study. A piecewise linear model was used to identify the threshold temperature and the relative risk (RR) above the threshold temperature according to patient characteristics and region.

Results

The total number of patients during the 3 months was 975. Of the three temperature indicators, the daily maximum temperature showed the best goodness of fit with the model. The RR of the total patient incidence was 1.691 (1.641 to 1.743) per 1℃ after 31.2℃. The RR above the threshold temperature of women (1.822, 1.716 to 1.934) was greater than that of men (1.643, 1.587 to 1.701). The threshold temperature was the lowest in the age group of 20 to 64 (30.4℃), and the RR was the highest in the ≥65 age group (1.863, 1.755 to 1.978). The threshold temperature of the provinces (30.5℃) was lower than that of the metropolitan cities (32.2℃). Metropolitan cities at higher latitudes had a greater RR than other cities at lower latitudes.

Conclusions

The influences of temperature on heat-related illnesses vary according to gender, age, and region. A surveillance system and public health program should reflect these factors in their implementation.

Serum sodium abnormalities during nonexertional heatstroke: incidence and prognostic values

BACKGROUND

Although heatstroke is often associated with dehydration, the clinical significance of serum sodium abnormalities in patients with heat-related illness during heat wave has been poorly documented.

METHOD

We evaluated 1263 patients (age, 82±15 years; body temperature, 40.1°C+1.2°C) admitted to emergency departments during the August 2003 heat wave in Paris, having a core temperature greater than 38.5°C and measurement of serum sodium concentrations. Patients were classified according to our previously described risk score of death.

RESULTS

Hyponatremia (<135 mmol/L) was reported in 409 (32%) and hypernatremia (>145 mmol/L) in 220 patients (17%). One-year survival was significantly decreased in patients with hypernatremia (45%; P=.004) but not in those with hyponatremia (58%; P=.86) as compared with patients with serum sodium concentration in the reference range (57%). Using Cox regression, only hypernatremia was an independent prognostic factor (hazard ratio, 1.35; 95% confidence interval, 1.09-1.36) when risk score was taken into account. Using logistic regression, 2 variables were independently associated with hyponatremia (heatstroke severity score and blood urea nitrogen-creatinine ratio<100). Conversely, 5 variables were independently associated with hypernatremia (living in an institution, dementia, serum creatinine>120 μmol/L, a blood urea nitrogen-creatinine ratio >100, and absence of long-term diuretic intake).

CONCLUSIONS

Serum sodium abnormalities are frequently observed in patients with a nonexertional heatstroke during heat wave; however, only hypernatremia should be considered as an independent risk factor of death. Rapid measurement of serum sodium concentration is mandatory to appropriately guide electrolyte resuscitation.