Association Between Platelet Levels on Admission and 90-day Mortality in Patients With Exertional Heatstroke, a 10 Years Cohort Study

Heat stress-induced platelet dysfunction is associated with loss of fibrinogen and is improved by fibrinogen supplementation

INTRODUCTION

Heatstroke is a critical heat-related condition characterized by coagulopathy and multiple organ dysfunction. One of the most severe complications of heatstroke is disseminated intravascular coagulation. This condition manifests as excessive clot formation and bleeding that are primarily due to platelet depletion and dysfunction. Fibrinogen plays a crucial role in hemostasis because it links integrin αIIbβ3 on adjacent platelets, thereby promoting the platelet activation and aggregation necessary for clot formation. However, reduced fibrinogen levels may impair the formation of the initial platelet plug and increase the risk of bleeding. The current study explored the effect of fibrinogen on platelet dysfunction in a heatstroke model.

MATERIALS AND METHODS

Male Wistar rats were subjected to heat stress, and subsequent changes in hemodynamic, biochemical, and coagulation parameters were analyzed. Platelet viability, aggregation, adhesion, spreading and fibrin clot retraction were assessed.

RESULTS

The rats with heatstroke exhibited a variety of clinical symptoms, including hypotension, tachycardia, multiple organ dysfunction, and coagulopathy. Platelet viability in the heatstroke group was comparable to that in the healthy control group. However, the heatstroke group exhibited significant reductions in plasma fibrinogen levels and platelet aggregation, adhesion, spreading, and fibrin clot retraction. Notably, fibrinogen supplementation markedly augmented the aggregation responses of platelets in the heatstroke group. The impairment of platelet adhesion, spreading, and fibrin clot retraction in the rats with heatstroke was partially ameliorated by fibrinogen supplementation.

CONCLUSIONS

An early use of fibrinogen replacement may serve as a therapeutic intervention to alleviate platelet hyporeactivity and prevent the complications in patients with heatstroke.

Heatstroke Comorbid with SARS-CoV-2 Infection: A Case Report and Literature Review

Background

Hyperthermia and multiple organ dysfunction syndrome (MODS) are the main characteristics of heatstroke and COVID-19. Differentiating between these illnesses is crucial during a summer COVID-19 pandemic, but cases of heatstroke comorbid with COVID-19 are rarely reported.

Case description

We report the first case of heatstroke comorbid with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection in a 52-year-old male. After receiving intravenous antibiotics, organ protection measures, and treatment for coagulation disorders, his fever and coma resolved. However, he developed dyspnea and cerebral hemorrhage after several days. This patient experienced a multi-pathogen pulmonary infection and an intractable coagulopathy that ultimately resulted in MODS and death.

Conclusion

The combination of heatstroke and SARS-CoV-2 infection exacerbated inflammation, immune abnormalities, and coagulation disorders. The interaction between inflammation and coagulation disturbances contributed to the underlying mechanism in this case, highlighting the importance of early anti-infection, treatment for coagulopathy, immune regulation, and organ protection as crucial interventions.

Thromboinflammation and microcirculation damage in heatstroke

Rising temperatures associated with climate change have significantly increased the risk of heatstroke. Unfortunately, the trend is anticipated to persist and increasingly threaten vulnerable populations, particularly older adults. According to Japan's environment ministry, over 1000 people died from heatstroke in 2021, and 86% of deaths occurred in those above 65. Since the precise mechanism of heatstroke is not fully understood, we examined the pathophysiology by focusing on the microcirculatory derangement. Online search of published medical literature through MEDLINE and Web of Science using the term "heatstroke," "heat-related illness," "inflammation," "thrombosis," "coagulation," "fibrinolysis," "endothelial cell," and "circulation." Articles were chosen for inclusion based on their relevance to heatstroke, inflammation, and thrombosis. Reference lists were reviewed to identify additional relevant articles. Other than preexisting conditions (genetic background, age, etc.), factors such as hydration status, acclimatization, dysregulated coagulation, and inflammation are the additional major factors that promote tissue malcirculation in heatstroke. The fundamental pathophysiologic mechanisms significantly overlap with those seen in the systemic inflammatory response to sepsis, and as a result, coagulation-predominant coagulopathy develops during heat stress. Although a bleeding tendency is not common, bleeding frequently occurs in the microcirculation, causing additional injury. Sterile inflammation is mediated by proinflammatory cytokines, chemokines, and other humoral mediators in concert with cellular factors, including monocytes, neutrophils, platelets, and endothelial cells. Excess inflammation results in inflammatory cell death, including pyroptosis and necroptosis, and the release of danger signals that further propagate systemic inflammation and coagulopathy. Consequently, thromboinflammation is the critical factor that induces microcirculatory disturbance in heatstroke.

A newly proposed heatstroke-induced coagulopathy score in patients with heat illness: A multicenter retrospective study in China

PURPOSE

In patients with heatstroke, disseminated intravascular coagulation (DIC) is associated with greater risk of in-hospital mortality. However, time-consuming assays or a complex diagnostic system may delay immediate treatment. Therefore, the present study proposes a new heatstroke-induced coagulopathy (HIC) score in patients with heat illness as an early warning indicator for DIC.

METHODS

This retrospective study enrolled patients with heat illness in 24 Chinese hospitals from March 2021 to May 2022. Patients under 18 years old, with a congenital clotting disorder or liver disease, or using anticoagulants were excluded. Data were collected on demographic characteristics, routine blood tests, conventional coagulation assays and biochemical indexes. The risk factors related to coagulation function in heatstroke were identified by regression analysis, and used to construct a scoring system for HIC. The data of patients who met the diagnostic criteria for HIC and International Society on Thrombosis and Haemostasis defined-DIC were analyzed. All statistical analyses were performed using SPSS 26.0.

RESULTS

The final analysis included 302 patients with heat illness, of whom 131 (43.4%) suffered from heatstroke, including 7 death (5.3%). Core temperature (OR = 1.681, 95% CI 1.291 - 2.189, p < 0.001), prothrombin time (OR = 1.427, 95% CI 1.175 - 1.733, p < 0.001) and D-dimer (OR = 1.242, 95% CI 1.049 - 1.471, p = 0.012) were independent risk factors for heatstroke, and therefore used to construct an HIC scoring system because of their close relation with abnormal coagulation. A total score ≥ 3 indicated HIC, and HIC scores correlated with the score for International Society of Thrombosis and Hemostasis -DIC (r = 0.8848, p < 0.001). The incidence of HIC (27.5%) was higher than that of DIC (11.2%) in all of 131 heatstroke patients. Meanwhile, the mortality rate of HIC (19.4%) was lower than that of DIC (46.7%). When HIC developed into DIC, parameters of coagulation dysfunction changed significantly: platelet count decreased, D-dimer level rose, and prothrombin time and activated partial thromboplastin time prolonged (p < 0.05).

CONCLUSIONS

The newly proposed HIC score may provide a valuable tool for early detection of HIC and prompt initiation of treatment.

Construction and Validation of the Nomogram Based on von Willebrand Factor Predicting Mortality in Patients with Heatstroke

Heatstroke (HS), a severe condition, can develop multiple organ dysfunction syndrome and death. However, at present, no early reliable index exists for risk stratification and prognosis. von Willebrand factor (vWF), a marker of vascular endothelial injury, is a key regulatory target of inflammation and coagulation, which is closely associated with the pathogenesis of HS. vWF was reported as a prognostic marker in several infectious and noninfectious severe illness such as COVID-19, sepsis, and trauma. Although early increased level of vWF is seen in HS, the relationship between vWF and mortality is to be elucidated. Clinical data of patients with HS in a tertiary hospital were recorded and analyzed. It was shown that plasma vWF concentrations at admission were significantly increased in the nonsurvivors (351% ± 105%) compared with survivors (278% ± 104%, p = 0.021). After multivariate logistic regression analysis it was shown that vWF (odds ratio [OR] = 1.010; 95% confidence interval [CI], 1.002-1.18; p = 0.017), hemoglobin (Hb) (OR = 0.954; 95% CI, 0.931-0.979; p < 0.001), and hematocrit (HCT) in blood (OR = 0.859; 95% CI, 0.790-0.934; p < 0.001) were independent factors of in-hospital mortality in HS. The nomogram based on vWF and Hb was constructed in patients with HS. The area under curve under the receiver operating characteristic of this prediction model was 0.860 (95% CI, 0.773-0.923) and cutoff was 0.15, with Youden index 0.5840, which were not significantly different to sequential organ failure assessment (p = 0.0644), Acute Physiology and Chronic Health Evaluation II (APACHE II) (p = 0.7976), and systemic inflammatory response syndrome (SIRS) scores (p = 0.3274). The prediction model that integrated vWF and Hb showed a better predicting efficiency than single variable, and a higher specificity (81.48%) than APACHE II (72.84%) and SIRS (72.84%) scores. In summary, vWF, as an independent risk factor for in-hospital mortality, combined with Hb, could effectively prognosis the mortality in HS patients at early stage.

The role of platelets in heat-related illness and heat-induced coagulopathy

Heat-related illness is becoming more problematic due to ongoing global warming. Heat-related injury causes systemic inflammation and coagulopathy, due to leukocyte, platelet, and vascular endothelial cell activation and injury. Hyperthermia directly modulates platelet function and can induce cellular damage. Meanwhile, heat also affects platelet function via activated coagulation, excess inflammation, production of cytokines, and heat shock proteins. Aberrant hyperthermia-induced interactions between leukocytes and endothelial cells are also involved in platelet regulation. Heat-induced coagulopathy commonly progresses to disseminated intravascular coagulation (DIC), leading to multiple organ failure and in some cases enhanced bleeding. Consequently, platelet count, prothrombin time, and DIC score are useful for evaluating the severity of heat-related illness in addition to other organ damage markers such as Glasgow Coma Scale, creatinine, and bilirubin. Despite the increasing risk, therapeutic modalities targeting platelets are limited and no established therapy exists. In this review, we summarize the current knowledge about the role of platelets in the pathogenesis, diagnosis, and management of heat-related illness.

Nomogram for predicting disseminated intravascular coagulation in heatstroke patients: A 10 years retrospective study

Background

Disseminated intravascular coagulation (DIC) can lead to multiple organ failure and death in patients with heatstroke. This study aimed to identify independent risk factors of DIC and construct a predictive model for clinical application.

Methods

This retrospective study included 87 patients with heatstroke who were treated in the intensive care unit of our hospital from May 2012 to October 2022. Patients were divided into those with DIC (n = 23) or without DIC (n = 64). Clinical and hematological factors associated with DIC were identified using a random forest model, least absolute shrinkage and selection operator (LASSO) regression and support vector machine-recursive feature elimination (SVM-RFE). Overlapping factors were used to develop a nomogram model, which was diagnostically validated. Survival at 30 days after admission was compared between patients with or without DIC using Kaplan-Meier analysis.

Results

Random forest, LASSO, and SVM-RFE identified a low maximum amplitude, decreased albumin level, high creatinine level, increased total bilirubin, and aspartate transaminase (AST) level as risk factors for DIC. Principal component analysis confirmed that these independent variables differentiated between patients who experienced DIC or not, so they were used to construct a nomogram. The nomogram showed good predictive power, with an area under the receiver operating characteristic curve of 0.976 (95% CI 0.948–1.000) and 0.971 (95% CI, 0.914–0.989) in the internal validation. Decision curve analysis indicated clinical utility for the nomogram. DIC was associated with significantly lower 30 days survival for heatstroke patients.

Conclusion

A nomogram incorporating coagulation-related risk factors can predict DIC in patients with heatstroke and may be useful in clinical decision-making.

Inflammation, coagulation, and cellular injury in heat-induced shock

BACKGROUND

The number of heatstroke victims hit record numbers in 2022 as global warming continues. In heat-induced injuries, circulatory shock is the most severe and deadly complication. This review aims to examine the mechanisms and potential approaches to heat-induced shock and the life-threatening complications of heatstroke.

METHODS

A computer-based online search was performed using the PubMed database and Web of Science database for published articles concerning heatstroke, shock, inflammation, coagulopathy, endothelial cell, cell death, and heat shock proteins.

RESULTS

Dehydration and heat-induced cardiomyopathy were reported as the major causes of heat-induced shock, although other heat-induced injuries are also involved in the pathogenesis of circulatory shock. In addition to dehydration, the blood volume decreases considerably due to the increased vascular permeability as a consequence of endothelial damage. Systemic inflammation is induced by factors that include elevated cytokine and chemokine levels, dysregulated coagulation/fibrinolytic responses, and the release of damage-associated molecular patterns (DAMPs) from necrotic cell death that cause distributive shock. The cytoprotective heat shock proteins can also facilitate circulatory disturbance under excess heat stress.

CONCLUSIONS

Multiple mechanisms are involved in the pathogenesis of heat-induced shock. In addition to dehydration, heat stress-induced cardiomyopathy due to the thermal damage of mitochondria, upregulated inflammation via damage-associated molecular patterns released from oncotic cells, unbalanced coagulation/fibrinolysis, and endothelial damage are the major factors that are related to circulatory shock.