A Randomized Controlled Trial of Aspirin and Exertional Heat Stress Activation of Platelets in Firefighters during Exertion in Thermal Protective Clothing

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.

Hemostatic Responses to Multiple Bouts of Firefighting Activity: Female vs. Male Differences in a High Demand, High Performance Occupation

While the fire service has long been a male-dominated occupation, women's participation in this strenuous, high risk, high performance activity has increased in recent years. Firefighting induces significant cardiovascular strain, including hemostatic disruption; however, the effect of sex on hemostatic responses has not been investigated despite evidence that there are sex-related differences in hemostatic variables at rest and following exercise. Thus, we investigated hemostatic responses in age- and BMI-matched male and female firefighters who performed 3-4 evolutions of firefighting drills over a 3 h period. Venous blood samples were collected before and after the firefighting training drills and hemostatic variables were assessed. Firefighting significantly increased platelet count and factor VIII, tissue plasminogen activator (t-PA) antigen, and t-PA activity, and decreased activated partial thromboplastin time and plasminogen activator inhibitor (PAI-1) activity. Females had lower values for epinephrine-induced platelet closure time, antithrombin III, PAI-1 activity, and PAI-1 antigen. There were no interactions between sex and time for any variables assessed. In conclusion, multiple bouts of firefighting activity resulted in a procoagulatory state. Although there were sex differences for several hemostatic variables, male and female firefighters did not differ in their hemostatic response to multiple bouts of firefighting.

The effect of personal protective equipment on thermal stress: An experimental study on firefighters

BACKGROUND

Various parameters can affect the performance of firefighters. Thermal stress in firefighters is one of the most important harmful factors, which causes impaired performance and subsequent occupational accidents. Therefore, this study aimed to evaluate the effect of personal protective equipment (PPE) on thermal stress in firefighters.

MATERIALS AND METHODS

This descriptive-analytical cross-sectional study was performed on 30 firefighters. Heart rate, metabolism and temperature parameters were measured with and without using PPE in a simulated standard chamber. Then, the two indices of predicted mean vote (PMV) and predicted percentage dissatisfied (PPD) were calculated. Data analysis was performed using SPSS version 22.0.

RESULTS

The results showed that PPE-induced weight directly increased heart rate and indirectly led to an increase in metabolism and temperature as well as significant changes in PMV and PPD indices (p < 0.001). In addition, our results showed that the effect of thermal resistance of clothing (Clo) on PMV and PPD indices was very high (p < 0.001).

CONCLUSION

The findings of the study indicated that heat stress in firefighters is influenced by PPE weight and thermal resistance of clothing. Therefore, cooling vests can be used to reduce the thermal stress induced by temperature rise resulted from metabolism, PPE weight and thermal resistance of clothing. Reduced thermal stress will lead to the cooling of body temperature to acceptable levels of PMV and PPD.

Postural stability pattern as an important safety factor of firefighters

BACKGROUND

Firefighting is a hazardous profession that involves high fall risk and is crucial component for the safety of people.

OBJECTIVE

The aim of this study was to identify factors that impact on postural stability patterns of firefighters.

METHODS

The study examined 177 Polish firefighters from the National Firefighting and Rescue System (NFRS) aged 31.9±10.1 years, with body height of 179.6±5.93, body mass of 83.9±11.0 and BMI of 26.0±3.03. Postural stability was evaluated by means of the Balance System SD (Biodex USA) set at the level 12 of instability, in a sportswear, bunker gear, with and without visual input. The fall risk test (FRI) was also performed. Four indices were analysed: overall stability index (OSI), anterior-posterior stability index (APSI), medial-lateral stability index (MLSI), and fall risk index (FRI).

RESULTS

Mean results for fall risk index (FRI) were in the normal range for all age groups regardless of the type of clothing the firefighters were wearing. Individual results obtained in the fall risk test, 128 firefighters were in the normal range for their age, furthermore, 10 firefighters obtained better results than the normal range, 34 firefighters had worse results and 5 people failed to complete the test. Postural stability with eyes closed was found to decline with age. Wearing bunker gear did not have an effect on postural stability.

CONCLUSIONS

Balance tests should be integrated into the firefighting training routines in order to improve balance and support fall prevention. Exercises with reduced visual input should also be incorporated into the training methodology.

Accuracy of Tympanic Temperature Measurement in Firefighters Completing a Simulated Structural Firefighting Task

INTRODUCTION

In the course of their duties, firefighters risk heat stroke and other medical conditions due to exertion in high-temperature environments. Infrared tympanic temperature measurement (TTym) is often used by Emergency Medical Services (EMS) to assess the core body temperature of firefighters. The accuracy of TTym in this setting has been called into question. Hypothesis/Problem This study aimed to examine the accuracy of TTym for core body temperature assessment at emergency firefighting events compared with gastrointestinal temperature measurement (TGI) as measured by ingestible thermometers.

METHODS

Forty-five (42 male, three female) professional urban firefighters from an Australian fire service completed two 20-minute work periods in a 100°C (± 5°C) heat chamber while wearing personal protective clothing (PPC) and breathing apparatus (weighing approximately 22 kg). Measurements were taken immediately before entering, and on exiting, the heat chamber. Tympanic temperature was assessed by an infrared tympanic thermometer and TGI was measured by ingestible sensor and radio receiver.

RESULTS

Complete data were available for 37 participants. Participant temperatures were higher on exiting the heat chamber than at baseline (TTym: 35.9°C (SD=0.7) vs 37.5°C (SD=0.8); TGI: 37.2°C (SD=0.4) vs 38.6°C (SD=0.5)). Tympanic temperature underestimated TGI on average by 1.3°C (SD=0.5) before entering the chamber and by 1.0°C (SD=0.8) following the exercise. Using pooled data, the average underestimation was 1.2°C (SD=0.7).

CONCLUSION

Tympanic thermometers cause an unreliable measure of core body temperature for firefighters engaged in fire suppression activities. Accurate and practical measures of core body temperature are required urgently.

Review of Burn Research for Year 2014

Management of burn injuries requires treatments and interventions from many disciplines. Worldwide, burn patients suffer from physical and psychological challenges that impact their lives socially and economically. In this review, we will highlight a handful of the numerous articles published in multiple areas of burn care. The areas of burn care addressed in the article are: epidemiology; burn resuscitation, critical care, and infection; nutrition and metabolism; pain and rehabilitation; prevention and firefighter safety; psychology; and reconstruction and wounds.

Effect of Aspirin Supplementation on Hemostatic Responses in Firefighters Aged 40 to 60 Years

Sudden cardiovascular events account for approximately 45% to 50% of all duty-related deaths among firefighters and a disproportionate number of these fatalities occur after strenuous fire suppression activities. The purpose of this study was to evaluate the effect of acute and chronic aspirin supplementation on hemostatic function before and after live firefighting activities in older firefighters. A double-blind, crossover design included 4 treatments: a 2-week aspirin/placebo treatment ("chronic") and a single prefirefighting aspirin/placebo treatment ("acute"). Hemostatic function was assessed in 24 male firefighters (mean age = 48.2 ± 5.9 years) immediately before and after 18 minutes of live-fire firefighting activity. An acute bout of firefighting activity significantly decreased platelet aggregation time and decreased activated partial thromboplastin time. Compared with placebo, acute aspirin supplementation resulted in a significant increase in epinephrine closure time, which was further augmented by chronic supplementation. Aspirin supplementation had no effect on coagulatory or fibrinolytic factors. Our findings suggest that an acute bout of firefighting leads to increased coagulatory potential in older firefighters. In conclusion, aspirin supplementation had an antiplatelet effect that decreased platelet aggregability at rest and after an acute bout of firefighting compared with placebo.

Medical Monitoring During Firefighter Incident Scene Rehabilitation

OBJECTIVE

The objective of this study was to retrospectively investigate aspects of medical monitoring, including medical complaints, vital signs at entry, and vital sign recovery, in firefighters during rehabilitation following operational firefighting duties.

RESULTS

Incident scene rehabilitation logs obtained over a 5-year span that included 53 incidents, approximately 40 fire departments, and more than 530 firefighters were reviewed. Only 13 of 694 cases involved a firefighter reporting a medical complaint. In most cases, vital signs were similar between firefighters who registered a complaint and those who did not. On average, heart rate was 104 ± 23 beats·min(-1), systolic blood pressure was 132 ± 17 mmHg, diastolic blood pressure was 81 ± 12 mmHg, and respiratory rate was 19 ± 3 breaths·min(-1) upon entry into rehabilitation. At least two measurements of heart rate, systolic blood pressure, diastolic blood pressure, and respiratory rate were obtained for 365, 383, 376, and 160 cases, respectively. Heart rate, systolic and diastolic blood pressures, and respiratory rate decreased significantly (p < 0.001) during rehabilitation. Initial vital signs and changes in vital signs during recovery were highly variable.

CONCLUSIONS

Data from this study indicated that most firefighters recovered from the physiological stress of firefighting without any medical complaint or symptoms. Furthermore, vital signs were within fire service suggested guidelines for release within 10 or 20 minutes of rehabilitation. The data suggested that vital signs of firefighters with medical symptoms were not significantly different from vital signs of firefighters who had an unremarkable recovery.

Emergency Incident Rehabilitation: Resource Document to the Position Statement of the National Association of EMS Physicians

Position Statement: Emergency Incident Rehabilitation The National Association of EMS Physicians® believes that: Emergency operations and training conducted while wearing protective clothing and respirators is physiologically and cognitively demanding. The heat stress and fatigue created by working in protective clothing and respirators creates additional risk of illness/injury for the public safety provider. Emergency incident rehabilitation provides a structured rest period for rehydration and correction of abnormal body core temperature following work in protective clothing and respirators. Emergency incident rehab should be conducted at incidents (e.g. fireground, hazardous materials, and heavy rescue emergencies) and trainings involving activities that may lead to exceeding safe levels of physical and mental exertion. Emergency incident rehabilitation is incident care, not fitness for duty, and meant to reduce physiologic strain and prepare the responder to return to duty at the current incident and for the remainder of the shift. EMS should play a role in emergency incident rehabilitation with providers trained to understand the physiologic response of healthy individuals to environmental, exertional, and cognitive stress and implement appropriate mitigation strategies. An appropriately qualified physician should have oversight over the creation and implementation of emergency incident rehabilitation protocols and may be separate from the roles and responsibilities of the occupational medicine physician. There are no peer-reviewed data related to cold weather rehabilitation. Future studies should address this limitation to the literature.

Water immersion for post incident cooling of firefighters; a review of practical fire ground cooling modalities

Rapidly cooling firefighters post emergency response is likely to increase the operational effectiveness of fire services during prolonged incidents. A variety of techniques have therefore been examined to return firefighters core body temperature to safe levels prior to fire scene re-entry or redeployment. The recommendation of forearm immersion (HFI) in cold water by the National Fire and Protection Association preceded implementation of this active cooling modality by a number of fire services in North America, South East Asia and Australia. The vascularity of the hands and forearms may expedite body heat removal, however, immersion of the torso, pelvis and/or lower body, otherwise known as multi-segment immersion (MSI), exposes a greater proportion of the body surface to water than HFI, potentially increasing the rates of cooling conferred. Therefore, this review sought to establish the efficacy of HFI and MSI to rapidly reduce firefighters core body temperature to safe working levels during rest periods. A total of 38 studies with 55 treatments (43 MSI, 12 HFI) were reviewed. The core body temperature cooling rates conferred by MSI were generally classified as ideal (n = 23) with a range of ~0.01 to 0.35 °C min(-1). In contrast, all HFI treatments resulted in unacceptably slow core body temperature cooling rates (~0.01 to 0.05 °C min(-1)). Based upon the extensive field of research supporting immersion of large body surface areas and comparable logistics of establishing HFI or MSI, it is recommended that fire and rescue management reassess their approach to fireground rehabilitation of responders. Specifically, we question the use of HFI to rapidly lower firefighter core body temperature during rest periods. By utilising MSI to restore firefighter Tc to safe working levels, fire and rescue services would adopt an evidence based approach to maintaining operational capability during arduous, sustained responses. While the optimal MSI protocol will be determined by the specifics of an individual response, maximising the body surface area immersed in circulated water of up to 26 °C for 15 min is likely to return firefighter Tc to safe working levels during rest periods. Utilising cooler water temperatures will expedite Tc cooling and minimise immersion duration.

Effects of Low-Dose Aspirin Therapy on Thermoregulation in Firefighters

BACKGROUND

Heart attack is the most common cause of line-of-duty death in the fire service. Daily aspirin therapy is a preventative measure used to reduce the morbidity of heart attacks but may decrease the ability to dissipate heat by reducing skin blood flow.

METHODS

In this double-blind, placebo-controlled, crossover study, firefighters were randomized to receive 14 days of therapy (81-mg aspirin or placebo) before performing treadmill exercise in thermal-protective clothing in a hot room [38.8 ± 2.1°C, 24.9 ± 9.1% relative humidity (RH)]. Three weeks without therapy was provided before crossing to the other arm. Firefighters completed a baseline skin blood-flow assessment via laser Doppler flowmetry; skin was heated to 44°C to achieve maximal cutaneous vasodilation. Skin blood flow was measured before and after exercise in a hot room, and at 0 minutes, 10 minutes, 20 minutes, and 30 minutes of recovery under temperature conditions (25.3 ± 1.2°C, 40.3 ± 13.7% RH). Platelet clotting time was assessed before drug administration, and before and after exercise.

RESULTS

Fifteen firefighters completed the study. Aspirin increased clotting time before and after exercise compared with placebo (p = 0.003). There were no differences in absolute skin blood flow between groups (p = 0.35). Following exercise, cutaneous vascular conductance (CVC) was 85 ± 42% of maximum in the aspirin and 76 ± 37% in the placebo groups. The percentage of maximal CVC did not differ by treatment before or after recovery. Neither maximal core body temperature nor heart rate responses to exercise differed between trials.

CONCLUSION

There were no differences in skin blood flow during uncompensable heat stress following exercise after aspirin or placebo therapy.

Immune and inflammatory responses of Australian firefighters after repeated exposures to the heat

When firefighters work in hot conditions, altered immune and inflammatory responses may increase the risk of a cardiac event. The present study aimed to establish the time course of such responses. Forty-two urban firefighters completed a repeat work protocol in a heat chamber (100 ± 5°C). Changes to leukocytes, platelets, TNFα, IL-6, IL-10, LPS and CRP were evaluated immediately post-work and also after 1 and 24 h of rest. Increases in core temperatures were associated with significant increases in leukocytes, platelets and TNFα directly following work. Further, platelets continued to increase at 1 h (+31.2 ± 31.3 × 10(9) l, p < 0.01) and remained elevated at 24 h (+15.9 ± 19.6 × 10(9) l, p < 0.01). Sustained increases in leukocytes and platelets may increase the risk of cardiac events in firefighters when performing repeat work tasks in the heat. This is particularly relevant during multi-day deployments following natural disasters. Practitioner Summary: Firefighters regularly re-enter fire affected buildings or are redeployed to further operational tasks. Should work in the heat lead to sustained immune and inflammatory changes following extended rest periods, incident controllers should plan appropriate work/rest cycles to minimise these changes and any subsequent risks of cardiac events.

Effect of aspirin on acute changes in peripheral arterial stiffness and endothelial function following exertional heat stress in firefighters: The factorial group results of the Enhanced Firefighter Rehab Trial

Peripheral arterial stiffness and endothelial function, which are independent predictors of cardiac events, are abnormal in firefighters. We examined the effects of aspirin on peripheral arterial stiffness and endothelial function in firefighters. Fifty-two firefighters were randomized to receive daily 81 mg aspirin or placebo for 14 days before treadmill exercise in thermal protection clothing, and a single dose of 325 mg aspirin or placebo immediately following exertion. Peripheral arterial augmentation index adjusted for a heart rate of 75 (AI75) and reactive hyperemia index (RHI) were determined immediately before, and 30, 60, and 90 minutes after exertion. Low-dose aspirin was associated with lower AI75 (-15.25±9.25 vs -8.08±10.70, p=0.014) but not RHI. On repeated measures analysis, treatment with low-dose aspirin before, but not single-dose aspirin after exertion, was associated with lower AI75 following exertional heat stress (p=0.018). Low-dose aspirin improved peripheral arterial stiffness and wave reflection but not endothelial function in firefighters.

Exertional Heat Illness: Emerging Concepts and Advances in Prehospital Care

Exertional heat illness is a classification of disease with clinical presentations that are not always diagnosed easily. Exertional heat stroke is a significant cause of death in competitive sports, and the increasing popularity of marathons races and ultra-endurance competitions will make treating many heat illnesses more common for Emergency Medical Services (EMS) providers. Although evidence is available primarily from case series and healthy volunteer studies, the consensus for treating exertional heat illness, coupled with altered mental status, is whole body rapid cooling. Cold or ice water immersion remains the most effective treatment to achieve this goal. External thermometry is unreliable in the context of heat stress and direct internal temperature measurement by rectal or esophageal probes must be used when diagnosing heat illness and during cooling. With rapid recognition and implementation of effective cooling, most patients suffering from exertional heat stroke will recover quickly and can be discharged home with instructions to rest and to avoid heat stress and exercise for a minimum of 48 hours; although, further research pertaining to return to activity is warranted.

PryorRR,RothRN,SuyamaJ,HostlerD.Exertional heat illness: emerging concepts and advances in prehospital care.Prehosp Disaster Med.2015;30(3):19.

Effect of cycling in the heat for 164 km on procoagulant and fibrinolytic parameters

PURPOSE

We assessed the impact of completing the Hotter'n Hell Hundred (HHH), an annual 164 km road cycling event performed in a hot environment, on hemostatic balance in men.

METHODS

Sixteen men who completed the ride in <6 h were included in this study. Plasma samples were collected on that morning of the ride (PRE) and immediately on the completion of the ride (IP). Primary hemostasis was assessed by platelet count and von Willebrand factor antigen (vWF:Ag). Coagulation was assessed by measuring prothrombin fragment 1 + 2 (PTF 1 + 2) and thrombin-antithrombin complex (TAT), whereas fibrinolysis was assessed by plasminogen activator inhibitor antigen (PAI-1 Ag), tissue plasminogen activator (tPA Ag), and D-Dimer analyses.

RESULTS

Compared to PRE, increases (p < 0.001) were observed at IP for platelets (39 %), vWF:Ag (65 %), PTF 1 + 2 (47 %), TAT (81 %), tPA Ag (231 %), PAI-1 Ag (148 %), and D-Dimer (54 %). PRE PAI-1 Ag concentrations were directly related to BMI and waist circumference (p < 0.05). D-Dimer concentrations at IP correlated positively with age (p < 0.05).

CONCLUSIONS

Completing the HHH activated the coagulation and fibrinolytic systems in balance. Age was positively correlated with IP D-Dimer concentrations. Additionally, participants displaying a larger BMI and waist circumference exhibited a positive correlation with PRE PAI-1 Ag concentrations.

What does it cost to prevent on-duty firefighter cardiac events? A content valid method for calculating costs

Cardiac arrest is a leading cause of mortality among firefighters. We sought to develop a valid method for determining the costs of a workplace prevention program for firefighters. In 2012, we developed a draft framework using human resource accounting and in-depth interviews with experts in the firefighting and insurance industries. The interviews produced a draft cost model with 6 components and 26 subcomponents. In 2013, we randomly sampled 100 fire chiefs out of >7,400 affiliated with the International Association of Fire Chiefs. We used the Content Validity Index (CVI) to identify the content valid components of the draft cost model. This was accomplished by having fire chiefs rate the relevancy of cost components using a 4-point Likert scale (highly relevant to not relevant). We received complete survey data from 65 fire chiefs (65% response rate). We retained 5 components and 21 subcomponents based on CVI scores ≥0.70. The five main components include, (1) investment costs, (2) orientation and training costs, (3) medical and pharmaceutical costs, (4) education and continuing education costs, and (5) maintenance costs. Data from a diverse sample of fire chiefs has produced a content valid method for calculating the cost of a prevention program among firefighters.