Efficacy of field treatments to reduce body core temperature in hyperthermic subjects

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.

Whole-body cooling effectiveness of cold intravenous saline following exercise hyperthermia: a randomized trial

INTRODUCTION

In some athletic, occupational, military and emergency settings, cold intravenous (IV) fluids are used to facilitate whole-body cooling in an effort to treat heat illness. This treatment has anecdotal support, but currently lacks evidence supporting it as a whole-body cooling modality. Other modalities may offer superior cooling rates, and thus, patient outcomes following treatment. We sought to evaluate cooling rates of cold-IV normal saline immediately following exercise-induced hyperthermia.

METHODS

Eight healthy participants (3 females; 25 ± 2y; 72.9 ± 10.9 kg) completed 2 trials in random order. Prior to exercise, participants provided a small urine sample to confirm hydration status via urine specific gravity. Wet bulb globe temperature (WBGT) was assessed throughout trials. In both trials, participants exercised outdoors until rectal temperature (Tre) reached ∼38.9 °C, or volitional exhaustion, and then were cooled. In cooling, participants received either cold-IV (∼5 °C 0.9% NaCl fluids) or no treatment (sat in the shade; passive). Throughout exercise and treatment, Tre and heart rate (HR) were monitored. During exercise and every 10 min throughout cooling, participants were asked to assess thermal sensation.

RESULTS

Hydration status (P = .847) was not significantly different prior to exercise between trials. WBGT throughout was not different between trials (P = .426). Maximum Tre reached was not different between cold-IV (38.88 ± 0.30 °C) and passive cooling (38.76 ± 0.28 °C) trials (P = .184). Mean cooling rate for cold-IV (0.039 ± 0.005 °C·min-1) was significantly greater than for passive cooling (0.028 ± 0.005 °C·min-1; P = .002). Tre throughout cooling was not different between trials (P = .707), but did decrease throughout (P = .008), regardless of trial. HR was decreased over time (P < .001), but cold-IV and passive cooling were not different throughout HR recovery (P = .141). Thermal sensation decreased throughout cooling (P < .001), but was not different between trials (p = .278).

CONCLUSION

Emergency medical personnel should adopt treatment protocols that employ documented effective treatments for exertional heat stroke. In isolation, our data casts significant doubt for the use of cold-IV saline infusion for whole-body cooling of hyperthermic individuals.

An assessment of the validity and reliability of the P022-P version of e-Celsius core temperature capsules

Core temperature monitoring is a research tool used in many studies, though most popularly, heat strain. Ingestible core temperature capsules are a non-invasive and increasingly popular choice for measuring core body temperature, particularly considering the well-established validation of capsule systems. A newer version of the e-Celsius ingestible core temperature capsule has been released since the preceding validation study resulting in a paucity of validated research for the current version of capsules, P022-P, used by researchers. Using a 1:1 ratio of propylene glycol to water in a circulating water bath, and a reference thermometer with resolution and uncertainty of 0.01 °C, we assessed the validity and reliability of 24 P022-P e-Celsius capsules in three groups of eight, at seven temperature plateaus between 35 °C, and 42 °C in a test-retest format. The systematic bias of these capsules across all 3360 measurements was found to be -0.038 °C ± 0.086 °C (p < .001), The TEST-RETEST evaluation revealed excellent reliability by way of a minute overall mean difference of 0.0095 °C ± 0.048 °C (p < .001), and an intraclass correlation coefficient of 1.00 for each of TEST and RETEST conditions. Although quite small, differences in systematic bias across temperature plateaus were observed for both the OVERALL bias-between 0.00066 °C and 0.041°C-and TEST/RETEST bias-between 0.00010 °C and 0.016 °C. We found that the new capsule version outperforms manufacturer guarantees, with half of the systematic bias observed in a validation study of the previous capsule version. Though these capsules tend to slightly underestimate temperature, we find they possess excellent validity and reliability between 35 °C and 42 °C.

Exertional heat stroke: An evidence based approach to clinical assessment and management

NEW FINDINGS

What is the topic of this review? The treatment of exertional heat stress, from initial field care through the return-to-activity decision, is reviewed. What advances does it highlight? Clinical assessment during field care using AVPU and vital signs to gauge recovery Approaches to field cooling and end of active cooling Shared clinical decision making for return to activity recommendations ABSTRACT: Exertional heat stroke (EHS) is a potentially fatal condition characterized by central nervous system dysfunction and body temperature often but not always >40°C that occurs in the context of physical work in warm or hot environments. In this paper, we review the continuum of care, from initial recognition and field care to transport and hospital care, and finally return to duty considerations. Morbidity and mortality can be greatly reduced if not eliminated with prompt recognition and aggressive cooling. If medical personnel are not present at point of collapse during or immediately following exercise, EHS should be the presumptive diagnosis until a formal diagnosis can be determined by qualified medical staff. EHS is the rare medical situation where initial treatment (cooling) takes precedence over transport to a medical facility, where advanced medical care may be required for severe EHS casualties. Recovery from EHS and return to activity is usually straightforward and unremarkable provided the casualty is rapidly cooled at time of collapse and adequate time is allowed for body healing. However, evidence-based data to guide return to activity following EHS is limited. Current research suggests that most individuals recover completely within a few weeks though some individuals may suffer prolonged sequalae and additional evaluation may be warranted, including heat tolerance testing. Several aspects of the care of the EHS casualty are based on best practices derived from personal experience and continued research is necessary to optimize evaluation and management. This article is protected by copyright. All rights reserved.

Roundtable on Preseason Heat Safety in Secondary School Athletics: Prehospital Care of Patients With Exertional Heat Stroke

OBJECTIVE

First, we will update recommendations for the prehospital management and care of patients with exertional heat stroke (EHS) in the secondary school setting. Second, we provide action items to aid clinicians in developing best-practice documents and policies for EHS. Third, we supply practical strategies clinicians can use to implement best practice for EHS in the secondary school setting.

DATA SOURCES

An interdisciplinary working group of scientists, physicians, and athletic trainers evaluated the current literature regarding the prehospital care of EHS patients in secondary schools and developed this narrative review. When published research was nonexistent, expert opinion and experience guided the development of recommendations for implementing life-saving strategies. The group evaluated and further refined the action-oriented recommendations using the Delphi method.

CONCLUSIONS

Exertional heat stroke continues to be a leading cause of sudden death in young athletes and the physically active. This may be partly due to the numerous barriers and misconceptions about the best practice for diagnosing and treating patients with EHS. Exertional heat stroke is survivable if it is recognized early and appropriate measures are taken before patients are transported to hospitals for advanced medical care. Specifically, best practice for EHS evaluation and treatment includes early recognition of athletes with potential EHS, a rectal temperature measurement to confirm EHS, and cold-water immersion before transport to a hospital. With planning, communication, and persistence, clinicians can adopt these best-practice recommendations to aid in the recognition and treatment of patients with EHS in the secondary school setting.

Cooling Between Exercise Bouts and Post-exercise With the Fan Cooling Jacket on Thermal Strain in Hot-Humid Environments

This study investigated the effects of cooling between exercise bouts and post-exercise with a commercially available fan cooling jacket on thermal and perceptual responses during and following exercise in hot-humid environments. Ten male athletes completed two 30 min cycling bouts at a constant workload (1.4 watts⋅kg^-1 of body mass) with a 5 min recovery period in between. Exercise was followed by a 10 min recovery period. In an environmental chamber (33°C, 65% relative humidity), participants performed two trials with (FCJ) or without (CON) the fan cooling jacket on a T-shirt during the 5 min inter-exercise and 10 min post-exercise recovery periods. Mean, chest and upper arm skin temperatures, and thermal sensation and comfort were lower in FCJ than CON trial during and following exercise (P < 0.05). Thigh and calf skin temperatures, infrared tympanic temperature and heart rate were lower in FCJ than CON trial during the experimental trials (P < 0.05). The rates of fall in mean, chest and upper arm skin temperatures, infrared tympanic temperature and thermal sensation and comfort were faster in FCJ than CON trial during both recovery periods (P < 0.05). There were faster rates of fall in thigh and calf skin temperatures and heart rate in FCJ than CON trial during the post-exercise recovery period (P < 0.05). No difference was observed between trials in the rating of perceived exertion (P > 0.05). This study indicates that cooling between exercise bouts and post-exercise with the fan cooling jacket would effectively mitigate thermal strain and perception/discomfort during and following exercise in hot-humid environments. This garment would reduce whole-body skin temperature quickly while promoting falls in lower-body as well as upper-body skin temperatures.

2020 International Consensus on First Aid Science With Treatment Recommendations

This is the summary publication of the International Liaison Committee on Resuscitation's 2020 International Consensus on First Aid Science With Treatment Recommendations. It addresses the most recent published evidence reviewed by the First Aid Task Force science experts. This summary addresses the topics of first aid methods of glucose administration for hypoglycemia; techniques for cooling of exertional hyperthermia and heatstroke; recognition of acute stroke; the use of supplementary oxygen in acute stroke; early or first aid use of aspirin for chest pain; control of life- threatening bleeding through the use of tourniquets, haemostatic dressings, direct pressure, or pressure devices; the use of a compression wrap for closed extremity joint injuries; and temporary storage of an avulsed tooth. Additional summaries of scoping reviews are presented for the use of a recovery position, recognition of a concussion, and 6 other first aid topics. The First Aid Task Force has assessed, discussed, and debated the certainty of evidence on the basis of Grading of Recommendations, Assessment, Development, and Evaluation criteria and present their consensus treatment recommendations with evidence-to-decision highlights and identified priority knowledge gaps for future research. The 2020 International Consensus on Cardiopulmonary Resuscitation (CPR) and Emergency Cardiovascular Care (ECC) Science With Treatment Recommendations (CoSTR) is the fourth in a series of annual summary publications from the International Liaison Committee on Resuscitation (ILCOR). This 2020 CoSTR for first aid includes new topics addressed by systematic reviews performed within the past 12 months. It also includes updates of the first aid treatment recommendations published from 2010 through 2019 that are based on additional evidence evaluations and updates. As a result, this 2020 CoSTR for first aid represents the most comprehensive update since 2010.

2020 International Consensus on First Aid Science With Treatment Recommendations

This is the summary publication of the International Liaison Committee on Resuscitation's 2020 International Consensus on First Aid Science With Treatment Recommendations. It addresses the most recent published evidence reviewed by the First Aid Task Force science experts. This summary addresses the topics of first aid methods of glucose administration for hypoglycemia; techniques for cooling of exertional hyperthermia and heatstroke; recognition of acute stroke; the use of supplementary oxygen in acute stroke; early or first aid use of aspirin for chest pain; control of life-threatening bleeding through the use of tourniquets, hemostatic dressings, direct pressure, or pressure devices; the use of a compression wrap for closed extremity joint injuries; and temporary storage of an avulsed tooth. Additional summaries of scoping reviews are presented for the use of a recovery position, recognition of a concussion, and 6 other first aid topics. The First Aid Task Force has assessed, discussed, and debated the certainty of evidence on the basis of Grading of Recommendations, Assessment, Development, and Evaluation criteria and present their consensus treatment recommendations with evidence-to-decision highlights and identified priority knowledge gaps for future research.

Are Recommended Heat Stroke Treatments Adequate for Australian Workers?

Workers that combine physical exertion with exposure to hot conditions are susceptible to heat-related illnesses, including heat stroke. Despite recognition of cold water immersion as the heat stroke treatment of choice in the peer-reviewed literature, it was not included within recommended treatments of leading Australian healthcare training organizations and was omitted from Safe Work Australia's recently updated 'Managing the risks of working in heat' guidance material. On this basis, the guidance material appears an opportunity lost to assist Australian industry transition their heat stroke management to reflect the evidence. It is recommended that Australian providers of healthcare training, and those reliant on such information, review the efficacy of their heat stroke treatments.

Keeping older individuals cool in hot and moderately humid conditions: wetted clothing with and without an electric fan

The present study evaluated whether wearing a water-soaked t-shirt, with or without electric fan use, mitigates thermal and cardiovascular strain in older individuals exposed to hot and moderately humid conditions. Nine healthy older individuals (68 ± 4 yr; five women) completed three 120-min heat exposures (42.4 ± 0.2°C, 34.2 ± 0.9% relative humidity) on separate days while wearing a dry t-shirt (CON), a t-shirt soaked with 500 ml of tap water (WET), or a t-shirt soaked with 500 ml of tap water while facing an electric fan (2.4 ± 0.4 m/s; WET+FAN). Measurements included core and skin temperatures, evaporative mass losses, heart rate, and blood pressure. In the WET condition, elevations in core temperature were attenuated compared with DRY from 30 to 120 min and compared with WET+FAN from 30 to 90 min (P < 0.05). Evaporative mass losses (inclusive of sweat and water losses from the shirt) were greatest in WET+FAN, followed by WET, and then DRY (P < 0.01). Sweat losses were lowest in WET, followed by DRY, and then WET+FAN (P < 0.01). Heart rate was lower only at 60 min in WET versus DRY (P = 0.01). No differences in mean arterial pressure were observed (P = 0.51). In conclusion, wearing a water-soaked t-shirt without, but not with, electric fan use is an effective heat management strategy to mitigate thermal strain and lower sweat losses in older individuals exposed to hot and moderately humid conditions.NEW & NOTEWORTHY In older individuals exposed to hot and moderately humid environments, electric fan use coupled with a water-soaked t-shirt exacerbates sweat losses without mitigating heat strain compared with a dry t-shirt. However, wearing a water-soaked t-shirt without fan use reduces sweat losses and attenuates heat strain compared with a dry t-shirt and a fan/water-soaked t-shirt combination. These findings suggest wearing a water-soaked t-shirt is an effective heat-management strategy for older individuals during heat waves when air conditioning is inaccessible.

Body cooling effects of immersion of the forearms in high-concentration artificial carbonic acid water at 25°C

BACKGROUND

This study examined the effects of immersion in stirred, high-concentration, artificial carbonic acid water on body cooling.

METHODS

Seven healthy male students (23 ± 2 years old) participated in the experiment. Signed informed consent was obtained from all subjects before the experiment. The subjects changed into shorts and T-shirts and entered an experimental room (with room temperature controlled at 30 °C and relative humidity maintained at 70%) at least 30 min before starting the experiment. After starting the experiment, the subjects were asked to rest on an exercise bike for 5 min and then pedal for 20 min. The exercise load was set to reach 50% of each subject's presumed maximum oxygen intake at 5 min after starting exercise. Subjects then continued pedaling for 1 min to cool down. After this exercise, subjects sat on a chair and immersed forearms in tap water or artificial carbonic acid water (CO2 water) at 25 °C for 20 min. During immersion, tap water or CO2 water was stirred slowly with a pump. After immersion, subjects rested for 10 min. Skin temperature and skin blood flow (left forearm), as well as heart rate and ear canal temperature, were measured continuously. Thermal sensation and thermal comfort were measured intermittently.

RESULTS

Skin blood flow of the immersed forearms was higher in CO2 water than in tap water during immersion. The blood flow in the last 5 min (average at rest was 100%) was significantly higher in CO2 water (290.85 ± 84.81%) than in tap water (104.80 ± 21.99%). Thermal sensation and thermal comfort were not different between conditions. Ear canal temperature significantly declined more in CO2 water (- 0.56 ± 0.31 °C) than in tap water (- 0.48 ± 0.30 °C) during immersion.

CONCLUSIONS

Our study suggests that immersion of the forearms in slowly stirred CO2 water at 25 °C reduces core temperature elevated by heat stress or exercise more effectively than does tap water at the same temperature. Immersion of the forearms in stirred CO2 water at 25 °C could be useful as a preventive measure against heat stroke from summer work or exercise.

First aid cooling techniques for heat stroke and exertional hyperthermia: A systematic review and meta-analysis

BACKGROUND

Heat stroke is an emergent condition characterized by hyperthermia (>40 °C/>104 °F) and nervous system dysregulation. There are two primary etiologies: exertional which occurs during physical activity and non-exertional which occurs during extreme heat events without physical exertion. Left untreated, both may lead to significant morbidity, are considered a special circumstance for cardiac arrest, and cause of mortality.

METHODS

We searched Medline, Embase, CINAHL and SPORTDiscus. We used Grading of Recommendations Assessment, Development and Evaluation (GRADE) methods and risk of bias assessments to determine the certainty and quality of evidence. We included randomized controlled trials, non-randomized trials, cohort studies and case series of five or more patients that evaluated adults and children with non-exertional or exertional heat stroke or exertional hyperthermia, and any cooling technique applicable to first aid and prehospital settings. Outcomes included: cooling rate, mortality, neurological dysfunction, adverse effects and hospital length of stay.

RESULTS

We included 63 studies, of which 37 were controlled studies, two were cohort studies and 24 were case series of heat stroke patients. Water immersion of adults with exertional hyperthermia [cold water (14-17 °C/57.2-62.6 °F), colder water (8-12 °C/48.2-53.6 °F) and ice water (1-5 °C/33.8-41 °F)] resulted in faster cooling rates when compared to passive cooling. No single water temperature range was found to be associated with a quicker core temperature reduction than another (cold, colder or ice).

CONCLUSION

Water immersion techniques (using 1-17 °C water) more effectively lowered core body temperatures when compared with passive cooling, in hyperthermic adults. The available evidence suggests water immersion can rapidly reduce core body temperature in settings where it is feasible.

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.

Effects of Intravenous Cold Saline on Hyperthermic Athletes Representative of Large Football Players and Small Endurance Runners

OBJECTIVE

To evaluate the cooling effects of intravenous (IV) cold normal (0.9%) saline on hyperthermic athletes.

DESIGN

Randomized crossover study design.

SETTING

Controlled research laboratory.

PARTICIPANTS

Twelve male participants who were representative of a collegiate cross-country (6) and American football (6) population.

INTERVENTIONS

Participants underwent body composition analysis using a BodPod. They were placed in an environmentally controlled chamber and brought to a Tc of 39.5°C with dynamic exercise. When temperatures were reached, they were treated with either 2 L of cold saline (CS) (4°C) or intravenous room temperature (22°C) saline (RS) over a ∼30-minute period. Tre was measured with a rectal temperature probe every minute during the treatment period.

MAIN OUTCOME MEASURES

Total ΔTre (ending Tre - starting Tre) and cooling rate (total change in Tre/time) were measured for each condition, and body composition variables calculated included body surface area (BSA), BSA-to-mass ratio (BSA/mass), lean body mass, and body fat percentage (%BF) (P < 0.05).

RESULTS

Statistically significant differences were found in the total ΔTre and cooling rate between the CS and RS trials. The cooling rate for the CS trials was significantly correlated to mass, BSA, BSA/mass, and %BF.

CONCLUSIONS

In hyperthermic athletes, core temperature was reduced more effectively using chilled saline during IV infusion. Body composition had a significant impact on overall cooling revealing that the smaller and leaner participants cooled at a greater rate. When indicated, CS infusion could be considered for cooling hyperthermic individuals when other methods are not available.

Consensus Statement- Prehospital Care of Exertional Heat Stroke

Exertional heat stroke (EHS) is one of the most common causes of sudden death in athletes. It also represents a unique medical challenge to the prehospital healthcare provider due to the time sensitive nature of treatment. In cases of EHS, when cooling is delayed, there is a significant increase in organ damage, morbidity, and mortality after 30 minutes, faster than the average EMS transport and ED evaluation window. The purpose of this document is to present a paradigm for prehospital healthcare systems to minimize the risk of morbidity and mortality for EHS patients. With proper planning, EHS can be managed successfully by the prehospital healthcare provider.

Round Table on Malignant Hyperthermia in Physically Active Populations: Meeting Proceedings

CONTEXT

  Recent case reports on malignant hyperthermia (MH)-like syndrome in physically active populations indicate potential associations among MH, exertional heat stroke (EHS), and exertional rhabdomyolysis (ER). However, an expert consensus for clinicians working with these populations is lacking.

OBJECTIVE

  To provide current expert consensus on the (1) definition of MH; (2) history, etiology, and pathophysiology of MH; (3) epidemiology of MH; (4) association of MH with EHS and ER; (5) identification of an MH-like syndrome; (6) recommendations for acute management of an MH-like syndrome; (7) special considerations for physically active populations; and (8) future directions for research.

SETTING

  An interassociation task force was formed by experts in athletic training, exercise science, anesthesiology, and emergency medicine. The "Round Table on Malignant Hyperthermia in Physically Active Populations" was convened at the University of Connecticut, Storrs, September 17-18, 2015.

CONCLUSIONS

  Clinicians should consider an MH-like syndrome when a diagnosis of EHS or ER cannot be fully explained by clinical signs and symptoms presented by a patient or when recurrent episodes of EHS or ER (or both) are unexplained. Further research is required to elucidate the genetic and pathophysiological links among MH, EHS, and ER.

Evaluation of 2 Heat-Mitigation Methods in Army Trainees

CONTEXT

 Heat injury is a significant threat to military trainees. Different methods of heat mitigation are in use across military units. Mist fans are 1 of several methods used in the hot and humid climate of Fort Benning, Georgia.

OBJECTIVES

 To determine if (1) the mist fan or the cooling towel effectively lowered participant core temperature in the humid environment found at Fort Benning and (2) the mist fan or the cooling towel presented additional physiologic or safety benefits or detriments when used in this environment.

DESIGN

 Randomized controlled clinical trial.

SETTING

 Laboratory environmental chamber.

PATIENTS OR OTHER PARTICIPANTS

 Thirty-five physically active men aged 19 to 35 years.

INTERVENTION(S)

 (1) Mist fan, (2) commercial cooling towel, (3) passive-cooling (no intervention) control. All treatments lasted 20 minutes. Participants ran on a treadmill at 60% V̇o₂max.

MAIN OUTCOME MEASURE(S)

 Rectal core temperature, heart rate, thermal comfort, perceived temperature, perceived wetness, and blood pressure.

RESULTS

 Average core temperature increased during 20 minutes of cooling (F_1,28 = 64.76, P < .001, η_p² = 0.70), regardless of group (F_1,28 = 3.41, P = .08, η_p² = 0.11) or condition (F_1,28 < 1.0). Core temperature, heart rate, and blood pressure did not differ among the 3 conditions. Perceived temperature during 20 minutes of cooling decreased (F_1,30 = 141.19, P < .001, η_p² = 0.83) regardless of group or condition. Perceived temperature was lower with the mist-fan treatment than with the control treatment (F_1,15 = 7.38, P = .02, η_p² = 0.32). The mist-fan group perceived themselves to be cooler even at elevated core temperatures.

CONCLUSIONS

 The mist fan and cooling towel were both ineffective at lowering core temperature. Core temperature continued to increase after exercise in all groups. The mist fan produced feelings of coolness while the core temperature remained elevated, possibly increasing the risk of heat illness.

Research: Testing of a Novel Portable Body Temperature Conditioner Using a Thermal Manikin

A battery-operated active cooling/heating device was developed to maintain thermoregulation of trauma victims in austere environments while awaiting evacuation to a hospital for further treatment. The use of a thermal manikin was adopted for this study in order to simulate load testing and evaluate the performance of this novel portable active cooling/heating device for both continuous (external power source) and battery power. The performance of the portable body temperature conditioner (PBTC) was evaluated through cooling/heating fraction tests to analyze the heat transfer between a thermal manikin and circulating water blanket to show consistent performance while operating under battery power. For the cooling/heating fraction tests, the ambient temperature was set to 15°C ± 1°C (heating) and 30°C ± 1°C (cooling). The PBTC water temperature was set to 37°C for the heating mode tests and 15°C for the cooling mode tests. The results showed consistent performance of the PBTC in terms of cooling/heating capacity while operating under both continuous and battery power. The PBTC functioned as intended and shows promise as a portable warming/cooling device for operation in the field.

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.

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.

Preventing hyperthermia: a cross-over study comparing two negative pressure devices during continuous passive heat stress

Heat-related illness and mortality increase significantly during heatwaves. Out-of-hospital treatment to avoid elevation of body core temperature (hyperthermia) could be beneficial for selected patients. Negative pressure devices have been proposed as an effective treatment method. This study compared the effects of two devices on healthy volunteers under continuous passive heat stress in a climatic chamber. Nine subjects were studied in a prospective cross-over study on two separate days. Subjects were randomized to treatment with either CoreControl® (CC) or ThermoTube (TT) on the first day. They were exposed to an ambient temperature above skin temperature and high air humidity throughout the experiment. Treatment intended to prevent the development of hyperthermia started after 60 min of passive warming. Core temperature continued to rise during treatment with CC, whereas it dropped slightly and then stabilized during treatment with TT.

Wearing long pants while working outdoors in the tropics does not yield higher body temperatures

OBJECTIVE

To compare the thermoregulatory demands of outdoor workers wearing long or knee-length pants while working in situ in a tropical environment.

METHODS

Fifteen male (35.8 ± 10.5 yr) outdoor Council workers completed their daily occupational duties (construction or gardening) in trials conducted six days apart: once wearing knee-length shorts (SHORTS) and once wearing full-length pants (PANTS). Body mass and hydration were assessed prior to and following each trial with core body (T(C) ) and mean skin temperature (MST; weighted from sites: chest, arm, thigh and calf) assessed at 30-minute intervals throughout each trial.

RESULTS

No significant differences between SHORTS and PANTS for T(C) , maximum T(C) , heart rate, MST or body mass changes. Skin temperature at the calf was greater for PANTS (33.8 ± 0.4°C) compared to SHORTS (32.9 ± 0.4°C; p<0.05). Hydration assessments identified 36.7% of participants commenced work hypohydrated while the average body mass lost throughout the workday was 2.5 ± 1.5%. Main effects of time were observed for heart rate and MST but no other assessed variable.

CONCLUSION

The additional exposed surface area available for heat exchange when wearing shorts is insufficient to elicit differences in thermoregulatory demands of outdoor employees under the assessed conditions.

IMPLICATIONS

These results suggest the use of SHORTS or PANTS can be determined by occupational duty requirements rather than risk of heat-related illness during very-light to moderate workloads completed under warm and humid environmental conditions.

Exertional heat stroke

The increasing popularity of mass participation endurance events necessitates that on-site medical teams be well versed in the management of both common and life-threatening conditions. Exertional heat stroke is one such condition, which if left untreated can be fatal.

Palm cooling does not reduce heat strain during exercise in a hot, dry environment

To compare the effectiveness of the rapid thermal exchange device (RTX) in slowing the development of hyperthermia and associated symptoms among hand immersed in water bath (WB), water-perfused vest (WPV), and no cooling condition (NC). Ten subjects performed 4 heat stress trials. The protocol consisted of 2 bouts of treadmill walking, separated by a cooling-rehydration period. The times to reach the predetermined rectal temperature in the first (38.5 degrees C) and second bouts (39 degrees C) were not different among RTX, NC, and WB, but was longer for the WPV in both bouts (p<0.05). Heat storage was significantly lower for WPV only in the first bout vs. the other conditions (p<0.05). Heart rate (HR) was not different at 10, 20, and 30 min during the first bout among RTX, NC, and WB, but was lower for WPV (p<0.05). HR was not different among conditions during the second bout. The RTX was not effective in slowing the development of hyperthermia.