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.

Methods for improving thermal tolerance in military personnel prior to deployment

Acute exposure to heat, such as that experienced by people arriving into a hotter or more humid environment, can compromise physical and cognitive performance as well as health. In military contexts heat stress is exacerbated by the combination of protective clothing, carried loads, and unique activity profiles, making them susceptible to heat illnesses. As the operational environment is dynamic and unpredictable, strategies to minimize the effects of heat should be planned and conducted prior to deployment. This review explores how heat acclimation(HA) prior to deployment may attenuate the effects of heat by initiating physiological and behavioural adaptations to more efficiently and effectively protect thermal homeostasis, thereby improving performance and reducing heat illness risk. HA usually requires access to heat chamber facilities and takes weeks to conduct, which can often make it impractical and infeasible, especially if there are other training requirements and expectations. Recent research in athletic populations has produced protocols that are more feasible and accessible by reducing the time taken to induce adaptations, as well as exploring new methods such as passive HA. These protocols use shorter HA periods or minimise additional training requirements respectively, while still invoking key physiological adaptations, such as lowered core temperature, reduced heart rate and increased sweat rate at a given intensity. For deployments of special units at short notice(< 1 day) it might be optimal to use heat re-acclimation to maintain an elevated baseline of heat tolerance for long periods in anticipation of such an event. Methods practical for military groups are yet to be fully understood, therefore further investigation into the effectiveness of HA methods is required to establish the most effective and feasible approach to implement them within military groups.

An acute naproxen dose does not affect core temperature or Interleukin-6 during cycling in a hot environment

Non-steroidal anti-inflammatory drugs’anti-pyretic and anti-inflammatory effects has led some individuals to theorize these medications may blunt core body temperature(Tc)increases during exercise.We utilized a double-blind,randomized,and counterbalanced cross-over design to examine the effects of a 24-h naproxen dose(3–220 mg naproxen pills)and placebo(0 mg naproxen)on Tc and plasma interleukin-6(IL-6)concentrations during cycling in a hot or ambient environment.Participants(n=11;6 male,5 female;age=27.8±6.5 years,weight=79.1±17.9 kg,height=177±9.5 cm)completed 4 conditions:1)placebo and ambient(Control);2)placebo and heat(Heat);3)naproxen and ambient(Npx);and 4)naproxen and heat(NpxHeat).Dependent measures were taken before,during,and immediately after 90 min of cycling and then 3 h after cycling.Overall,Tc significantly increased pre-(37.1±0.4℃)to post-cycling(38.2±0.3℃,F_(1.7,67.3)=150.5,p<0.001)and decreased during rest(37.0±0.3℃,F_(2.0,81.5)=201.6,p<0.001).Rate of change or maximum Tc were not significantly different between conditions.IL-6 increased pre-(0.54±0.06 pg/ml)to post-exercise(2.46±0.28 pg/ml,p<0.001)and remained significantly higher than pre-at 3 h post-(1.17±0.14 pg/ml,95%CI=-1.01 to-0.23,p=0.001).No significant IL-6 differences occurred between conditions.A 24-h,over-the-counter naproxen dose did not significantly affect Tc or IL-6 among males and females cycling in hot or ambient environments.