Heat-related illness: a hot topic in critical care

Heat acclimation alleviates the heat stress-induced impairment of vascular endothelial cells

Heat acclimation (HA) is found to help decrease the incidence of heat-related illnesses such as heat syncope and exertional heat stroke. However, the response of vascular endothelial cells to HA remain to be elucidated. In this study, mouse brain microvascular endothelial cells (bEnd.3), human umbilical vein endothelial cells (HUVEC), and human aortic endothelial cells (HAEC) were selected. The cells were first subjected to HA at 40 ℃ for 2 h per day for 3 days, and then subjected to heat stress at 43 ℃ for 2 h or 4 h. After heat stress, HA-pretreated cells showed a significant increase in cell viability, cell integrity, a decrease in the proportion of S phase cells, cell apoptosis, and cytoskeletal shrinkage compared with the cells without HA pretreatment. Additionally, the expression of VEGF, ICAM-1, iNOS and EPO in HA-pretreated cells significantly increased. We also presented evidence that HA upregulated HSP70 and bcl-2, while downregulated p-p53 and bax. Notably, the suppression of HSP70 expression attenuated the protective role of heat acclimation. Furthermore, HA mitigated injuries in vital organs of mice exposed to heat stress. Conclusively, these findings indicated the HA can increase the vitality of vascular endothelial cells after heat stress, partially restore the function of vascular endothelial cells, and this protective effect may be related to the upregulation of HSP70 expression.

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.

Diagnosing and managing heat exhaustion: insights from a systematic review of cases in the desert climate of Mecca

Heat exhaustion (HE) is a common, yet obscure, heat-related illness that affects millions of people yearly and its burden is projected to rise due to climate change. A comprehensive literature synthesis is lacking despite previous studies on various HE aspects. This systematic review aims to fill this gap by identifying and synthesizing available evidence on the risk factors, symptoms, biomarkers, treatment options, and outcomes for HE. The review focused on HE during the Muslim (Hajj) pilgrimage where the condition is endemic. We conducted a structured search of MEDLINE/PubMed, Embase, Web of Science Core Collection, SCOPUS, and CINAHL databases. We summarized the data from eligible studies and synthesized them in narrative form using pooled descriptive statistics. Ten studies were included between 1980 and 2019, reporting over 1,194 HE cases. HE cases presented with elevated core temperature (up to 40°C) and mainly affected older males from the Middle East and North Africa region, with overweight individuals at a higher risk. Clinical symptoms included hyperventilation, fatigue, dizziness, headaches, nausea, and vomiting, but not central nervous system disturbances. HE was associated with cardiac stress, and with water, electrolyte, and acid-base alterations. Cooling and hydration therapy were the primary management strategies, leading to a low mortality rate (pooled case fatality rate=0.11 % [95 % CI: 0.01, 0.3]). Most cases recovered within a few hours without complications. HE is associated with cardiac stress and changes in homeostasis, leading to distinct clinical symptoms. Early diagnosis and treatment of HE are crucial in reducing the risk of complications and mortality. The review provides insights into the pathophysiology and outcomes of HE, adding to the scarce literature on the subject. Prospero registration number: CRD42022325759.

Risk factors for heat-related illnesses during the Hajj mass gathering: an expert review

Human exposure to a hot environment may result in various heat-related illnesses (HRIs), which range in severity from mild and moderate forms to life-threatening heatstroke. The Hajj is one of the largest annual mass gatherings globally and has historically been associated with HRIs. Hajj attracts over two million Muslim pilgrims from more than 180 countries to the holy city of Makkah, Kingdom of Saudi Arabia. Several modifiable and non-modifiable factors render Hajj pilgrims at increased risk of developing HRIs during Hajj. These include characteristics of the Hajj, its location, population, and rituals, as well as pilgrims' knowledge of HRIs and their attitude and behavior. Makkah is characterized by a hot desert climate and fluctuating levels of relative humidity. Pilgrims are very diverse ethnically and geographically, with different adaptations to heat. Significant proportions of the Hajj population are elderly, obese, and with low levels of fitness. In addition, many have underlying health conditions and are on multiple medications that can interfere with thermoregulation. Other factors are inherent in the Hajj and its activities, including crowding, physically demanding outdoor rituals, and a high frequency of infection and febrile illness. Pilgrims generally lack awareness of HRIs, and their uptake of preventive measures is variable. In addition, many engage in hazardous behaviors that increase their risk of HRIs. These include performing rituals during the peak sunshine hours with no sun protection and with suboptimal sleep, nutrition, and hydration, while neglecting treatment for their chronic conditions. HRIs preventive plans for Hajj should incorporate measures to address the aforementioned factors to reduce the burden of these illnesses in future Hajj seasons. Lessons from the Hajj can be used to inform policy making and HRIs preventive measures in the general population worldwide.

Heat-Related Illness in Emergency and Critical Care: Recommendations for Recognition and Management with Medico-Legal Considerations

Hyperthermia is an internal body temperature increase above 40.5 °C; normally internal body temperature is kept constant through natural homeostatic mechanisms. Heat-related illnesses occur due to exposure to high environmental temperatures in conditions in which an organism is unable to maintain adequate homeostasis. This can happen, for example, when the organism is unable to dissipate heat adequately. Heat dissipation occurs through evaporation, conduction, convection, and radiation. Heat disease exhibits a continuum of signs and symptoms ranging from minor to major clinical pictures. Minor clinical pictures include cramps, syncope, edema, tetany, and exhaustion. Major clinical pictures include heatstroke and life-threatening heat stroke and typically are expressed in the presence of an extremely high body temperature. There are also some categories of people at greater risk of developing these diseases, due to exposure in particular geographic areas (e.g., hot humid environments), to unchangeable predisposing conditions (e.g., advanced age, young age (i.e., children), diabetes, skin disease with reduced sweating), to modifiable risk factors (e.g., alcoholism, excessive exercise, infections), to partially modifiable risk factors (obesity), to certain types of professional activity (e.g., athletes, military personnel, and outdoor laborers) or to the effects of drug treatment (e.g., beta-blockers, anticholinergics, diuretics). Heat-related illness is largely preventable.

Using Esophageal Temperature Management to Treat Severe Heat Stroke: A Case Report

BACKGROUND: Exertional heat stroke (EHS) is defined by a core body temperature that exceeds 40°C with associated central nervous system dysfunction, skeletal muscle injury, and multiple organ damage. The most important initial focus of treatment involves reduction of patient temperature. First approaches to achieve temperature reduction often include ice packs, water blankets, and cold intravenous fluid administration. When these measures fail, more advanced temperature management methods may be deployed but often require surgical expertise. Esophageal temperature management (ETM) has recently emerged as a new temperature management modality in which an esophageal heat transfer device replaces the standard orogastric tube routinely placed after endotracheal intubation and adds a temperature modulation capability. The objective of this case study is to report the first known use of ETM driven by bedside nursing staff in the treatment of EHS. METHOD: An ETM device was placed after endotracheal intubation in a 28-year-old man experiencing EHS over a 5-day course of treatment. RESULTS: Because the ETM device was left in place, when the patient experienced episodes of increasing temperature as high as 39.1°C, which required active cooling, nursing staff were able to immediately adjust the external heat exchange unit settings to achieve aggressive cooling at bedside. CONCLUSION: This nurse-driven technology offers a new means to rapidly deploy cooling to critically ill patients without needing to implement advanced surgical approaches or obstruct access to the patient, freeing the provider to continue optimal care in high-morbidity conditions.

Heat related illnesses. Review of an ongoing challenge

Climate change is the most challenging natural calamity of chronic nature that presents intense episodes of heat waves, and events. Effects of heat waves and increasing average temperature on heat-related illnesses (HRIs) demand a review of existing preventive and treatment strategies to direct future research. Heat-related illnesses are presented as minor to severe life-threatening conditions. Despite the understanding of the pathophysiology of HRI, pharmacological interventions are limited. Prevention is the best strategy against HRI. There is a dearth of epidemiological studies that reviewed the effect of pharmacological interventions on mortality, and there remains a need to identify critical key components other than inflammatory modulators, which can be targeted to decrease HRI.

Expert consensus on the diagnosis and treatment of heat stroke in China

Heat stroke (HS) is a fatal disease caused by thermal damage in the body, and it has a very high mortality rate. In 2015, the People's Liberation Army Professional Committee of Critical Care Medicine published the first expert consensus on HS in China, Expert consensus on standardized diagnosis and treatment for heat stroke. With an increased understanding of HS and new issues that emerged during the HS treatment in China in recent years, the 2015 consensus no longer meet the requirements for HS prevention and treatment. It is necessary to update the consensus to include the latest research evidence and establish a new consensus that has broader coverage, is more practical and is more in line with China's national conditions. This new expert consensus includes new concept of HS, recommendations for laboratory tests and auxiliary examinations, new understanding of diagnosis and differential diagnosis, On-site emergency treatment and In-hospital treatment, translocation of HS patients and prevention of HS.

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.

Evaluation of a Novel Classification of Heat-Related Illnesses: A Multicentre Observational Study (Heat Stroke STUDY 2012)

The Japanese Association for Acute Medicine Committee recently proposed a novel classification system for the severity of heat-related illnesses. The illnesses are simply classified into three stages based on symptoms and management or treatment. Stages I, II, and III broadly correspond to heat cramp and syncope, heat exhaustion, and heat stroke, respectively. Our objective was to examine whether this novel severity classification is useful in the diagnosis by healthcare professionals of patients with severe heat-related illness and organ failure. A nationwide surveillance study of heat-related illnesses was conducted between 1 June and 30 September 2012, at emergency departments in Japan. Among the 2130 patients who attended 102 emergency departments, the severity of their heat-related illness was recorded for 1799 patients, who were included in this study. In the patients with heat cramp and syncope or heat exhaustion (but not heat stroke), the blood test data (alanine aminotransferase, creatinine, blood urea nitrogen, and platelet counts) for those classified as Stage III were significantly higher than those of patients classified as Stage I or II. There were no deaths among the patients classified as Stage I. This novel classification may avoid underestimating the severity of heat-related illness.

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.

Sodium tanshinone IIA sulfonate suppresses heat stress-induced endothelial cell apoptosis by promoting NO production through upregulating the PI3K/AKT/eNOS pathway

Heat shock is a life-threatening disease involving systematic inflammation that is closely related to endothelial injury and can lead to multiple organ dysfunction syndrome. Sodium tanshinone IIA sulfonate (STS) has various functions in the vascular endothelium. In the present study, STS is presented to suppress heat stress‑induced apoptosis of human umbilical vein endothelial cells (HUVECs) and high ambient temperature‑induced systematic inflammation in Sprague Dawley rats. In addition, the STS apoptosis‑suppression mechanism was explored. The results presented in the present study demonstrated that the PI3K/AKT pathway was stimulated by STS treatment and that eNOS phosphorylation at Ser‑1177 was also upregulated, resulting in increased nitric oxide production in HUVECs under heat stress. Using specific inhibitors, the authors confirmed that STS‑induced endothelial nitric oxide synthase (eNOS) phosphorylation at Ser‑1177 was activated by protein kinase B phosphorylation at Ser‑473, involving activation of phosphatidylinositol‑3 kinase (PI3K). The results suggested that STS suppresses heat stress‑induced apoptosis of HUVECs via the PI3K/AKT/eNOS pathway and may be used in heat shock treatment as a vascular endothelial protection mechanism.

Potential of in vivo real-time gastric gas profiling: a pilot evaluation of heat-stress and modulating dietary cinnamon effect in an animal model

Gastroenterologists are still unable to differentiate between some of the most ordinary disorders of the gut and consequently patients are misdiagnosed. We have developed a swallowable gas sensor capsule for addressing this. The gases of the gut are the by-product of the fermentation processes during digestion, affected by the gut state and can consequently provide the needed information regarding the health of the gut. Here we present the first study on gas sensor capsules for revealing the effect of a medical supplement in an animal (pig) model. We characterise the real-time alterations of gastric-gas in response to environmental heat-stress and dietary cinnamon and use the gas profiles for understanding the bio-physiological changes. Under no heat-stress, feeding increases gastric CO₂ concentration, while dietary cinnamon reduces it due to decrease in gastric acid and pepsin secretion. Alternatively, heat-stress leads to hyperventilation in pigs, which reduces CO₂ concentration and with the cinnamon treatment, CO₂ diminishes even more, resulting in health improvement outcomes. Overall, a good repeatability in gas profiles is also observed. The model demonstrates the strong potential of real-time gas profiler in providing new physiological information that will impact understanding of therapeutics, presenting a highly reliable device for monitoring/diagnostics of gastrointestinal disorders.

Predictive Factors for Hospitalization of Patients with Heat Illness in Yamaguchi, Japan

The objective of the study was to investigate the predictive factors for the hospitalization of patients who presented with mild to moderate heat illness at an emergency department. We conducted a retrospective survey of hospitals with an emergency department in Yamaguchi Prefecture, Japan. The survey questionnaire entries included patient age, sex, use of an ambulance, vital signs, blood examination conducted at the emergency department, the length of hospitalization, and outcome. We analyzed the predictive factors for hospitalization in patients with heat illness. A total of 127 patients were analyzed. Of these, 49 (37%) were admitted, with 59% discharged on the day following admission. In univariate analysis, the following inpatient characteristics were predictive for hospitalization: old age, low Glasgow Coma Scale score, elevated body temperature, increased serum C-reactive protein, and increased blood urea nitrogen. In logistic regression multivariate analysis, the following were predictive factors for hospitalization: age of ≥ 65 years (odds ratio (OR) 4.91; 95% confidence interval (CI) 1.42–17.00), body temperature (OR 1.97; 95% CI 1.14–3.41), Glasgow Coma Scale (OR 0.40; 95% CI 0.16–0.98), and creatinine (OR 2.92; 95% CI 1.23–6.94). The results suggest that the elderly with hyperthermia, disturbance of consciousness, and elevated serum creatinine have an increased risk for hospitalization with heat illness.

Dexamethasone improves heat stroke-induced multiorgan dysfunction and damage in rats

Dexamethasone (DXM) is known as an immunosuppressive drug used for inflammation control. In the present study, we attempted to examine whether DXM administration could attenuate the hypercoagulable state and the overproduction of pro-inflammatory cytokines, improve arterial hypotension, cerebral ischemia and damage, and vital organ failure in a rat model of heat stroke. The results indicated that all the rats suffering from heat stroke showed high serum levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), accompanied with increased prothrombin time, activated partial thromboplastin time and D-D dimer, and decreased protein C. During the induction period of heat stroke, plasma levels of blood urea nitrogen (BUN), creatinine, glutamic oxaloacetic transaminase (SGOT), glutamic pyruvic transaminase (SGPT), and alkaline phosphatase (ALP), were consistently increased. High striatal levels of glycerol, glutamate, and lactate/pyruvate were simultaneously detected. On the contrary, the mean arterial pressure, plasma levels of interleukin-10 (IL-10), and local cerebral blood flow at the striatum were all decreased. Importantly, intravenous administration of DXM substantially ameliorated the circulatory dysfunction, systematic inflammation, hypercoagulable state, cerebral ischemia and damage during the induction period of heat stroke. These findings demonstrated that DXM may be an alternative therapy that can ameliorate heat stroke victims by attenuating activated coagulation, systemic inflammation, and vital organ ischemia/injury during heat stroke.