First Aid Cooling Techniques for Heat Stroke and Exertional Hyperthermia

Conflict of Interest Declaration

The ILCOR Continuous Evidence Evaluation process is guided by a rigorous ILCOR Conflict of Interest policy. The following Task Force members and other authors were recused from the discussion as they declared a conflict of interest: none applicable

The following Task Force members and other authors declared an intellectual conflict of interest and this was acknowledged and managed by the Task Force Chairs and Conflict of Interest committees: none applicable

CoSTR Citation

Lin S, Douma M, Aves T, Allan K, Bendall J, Berry D, Chang WT, Hood NA, Singletary EM, Zideman D, Epstein J

Collaborators:

Borra V, Carlson JN, Cassan P, Charlton NP, Meyran D, Woodin JA, Sakamoto T, Swain J.

First Aid Cooling Techniques for Heat Stroke and Exertional Hyperthermia Consensus on Science with Treatment Recommendations [Internet] Brussels, Belgium: International Liaison Committee on Resuscitation (ILCOR) First Aid Task Force, 2019 November 2. Available from http://ilcor.org

Methodological Preamble and Link to Published Systematic Review

The continuous evidence evaluation process for the production of Consensus on Science with Treatment Recommendations (CoSTR) started with a systematic review of first aid cooling techniques for heat stroke and exertional hyperthermia (Lin S 2019 – PROSPERO 2019 CRD42019128445) conducted by a systematic review team led by Dr. Steve Lin, St. Michael’s Hospital, Toronto, Ontario, Canada with involvement of clinical content experts from the ILCOR First Aid Task Force.

Heat stroke is an emergent condition characterized by severe hyperthermia and organ dysfunction, typically manifested by central nervous system dysregulation. The majority of studies comparing cooling techniques used in this systematic review were small experimental trials undertaken in healthy adults with exertional hyperthermia (i.e. no organ dysfunction) providing indirect evidence to determine the effectiveness of individual cooling techniques for classic and exertional heat stroke. The direct evidence for heat stroke patients were primarily from case series, which are classified as lower quality of evidence in determining the effectiveness of individual cooling techniques.

The included studies used core temperature measurements (e.g. rectal and esophageal). These types of measurements may not be available to all first aid providers. Peripheral temperature measurements (e.g. tympanic, oral or axillary) may be more readily available, but must be considered as an unreliable indication of core temperature cooling.

The use of intravenous (IV) fluids was included in this systematic review. We recognize that this cooling technique may not be available to all first aid providers; however, there are potentially advanced level first aid providers who are able to administer IV fluids.

Systematic Review

Douma MJ, Aves T, Allan K, Bendall JC, Berry D, Chang WT, Epstein J, Hood N, Singletary EM, Zideman D, Lin S; First Aid Task Force of the International Liaison Committee on Resuscitation. First aid cooling techniques for heat stroke and exertional hyperthermia: a systematic review and meta-analysis. Resuscitation. 2020 Jan 22. pii: S0300-9572(20)30028-9. doi: 10.1016/j.resuscitation.2020.01.007. [Epub ahead of print] Review. PMID: 31981710

PICOST

The PICOST (Population, Intervention, Comparator, Outcome, Study Designs and Timeframe):

Population: Adults and children (all ages) with heat stroke or exertional hyperthermia.

Intervention: Any cooling technique (or combination of techniques) appropriate for first aid (conduction, evaporation, convection, or radiation).

Comparators: Another cooling technique (or combination of techniques) appropriate for first aid. For case series, there will be no comparator or control group. Studies without a comparison group will be described narratively.

Outcomes: Mortality and rate of body temperature reduction (°C/min or °C/hour) were ranked as critical outcomes. Clinically important organ dysfunction, adverse effects (e.g. overcooling, hypothermia, injury) and hospital length of stay were ranked as important outcomes.

Study Designs: Randomized controlled trials (RCTs) and non-randomized studies (non-randomized controlled trials, interrupted time series, controlled before-and-after studies, cohort studies), case series of 5 or more are eligible for inclusion. It is recognized that case series are limited in providing high level evidence, particularly without a comparator group; however, they provide direct evidence in hyperthermic patients compared to indirect evidence when using healthy volunteers. Unpublished studies (e.g., conference abstracts, trial protocols) were excluded.

Timeframe: All years and all languages were included; unpublished studies (e.g., conference abstracts, trial protocols) were excluded. Literature search updated to July 11, 2019.

PROSPERO: CRD42019128445

NOTE FOR RISK OF BIAS:

In most cases bias was assessed per comparison rather than per outcome, since there were no meaningful differences in bias across outcomes. In cases where differences in risk of bias existed between outcomes this was noted.

Consensus on Science

Cold Water Immersion (14-15°C; 57.2-59°F)

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of inconsistency and indirectness) from seven controlled trials (Clements 2002 146, DeMartini 2011 2065; Peiffer 2009 987, Peiffer 2010 461, Taylor 2008 1962, Walker 2014 1159, Weiner 1980 507) recruiting 143 adult subjects with exertional hyperthermia which showed a faster rate of body temperature reduction with cold water immersion (14-15°C; 57.2-59°F) of the torso compared with passive cooling (mean difference range from 0.01 to 0.10°C/min). Due to high heterogeneity between studies, a pooled estimate of the mean difference in rate of body temperature reduction was not performed.

For the critical outcome of rate of core body temperature reduction, we identified very low certainty evidence (downgraded for risk inconsistency, indirectness and imprecision) from three controlled trials (Caldwell 2018 512, Proulx 2003 1317, Taylor 2008 1962) recruiting 23 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with cold water immersion (14°C; 57.2°F) of the torso compared with temperate water immersion (20-26°C; 68-78.8°F) of the torso (mean difference range from -0.04 to 0.21°C/min). Due to high heterogeneity between studies, a pooled estimate of the mean difference in rate of body temperature reduction was not performed.

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Proulx 2003 1317) recruiting 7 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of body temperature reduction with the use of cold water immersion (14°C; 57.2°F) of the torso compared with the use of “colder” water immersion (8°C; 46.4°F) (mean difference -0.04°C/min; 95% CI -0.11-0.03).

For the critical outcome of rate of core body temperature reduction, we identified very low certainty evidence (downgraded for risk of inconsistency, indirectness and imprecision) from two controlled trials (Clements 2002 146, Proulx 2003 1317) recruiting 24 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with the use of cold water immersion (14°C; 57.2°F) of the torso compared with ice water immersion (2-5°C;35.6-41°F) of the torso (mean difference range from -0.20 to 0.00°C/min). Due to high heterogeneity between studies, pooled estimate of the mean difference in rate of core body temperature reduction was not performed.

Cold Water Immersion (10-17°C; 50.0-62.6°F) of Hands and Feet

For the critical outcome of rate of core body temperature reduction, we identified moderate certainty evidence (downgraded for risk of indirectness) from six controlled trials (Barwood 2009 385, Carter 2007 109, Clapp 2001 160, DeMartini 2011 2065, Selkirk 2004 521, Zhang 2014 17) recruiting 62 adult subjects with exertional hyperthermia which showed a faster rate of core body temperature reduction with the use of cold water immersion (10-17°C; 50.0-62.6°F) of the hands and/or feet compared with passive cooling (mean difference 0.01°C/min; 95% CI 0.01-0.01).

Colder Water Immersion (9-12°C; 48.2-52.6°F)

For the critical outcome of rate of core body temperature reduction, we identified moderate certainty evidence (downgraded for risk of indirectness) from three controlled trials (Clapp 2001 160, Halson 2008 331, Hosokawa 2016 347) recruiting 30 adult subjects with exertional hyperthermia which showed a faster rate of core body temperature reduction with the use of “colder” water immersion (9-12°C; 48.2-52.6°F) of the torso compared with passive cooling (mean difference 0.11°C/min; 95% CI 0.07-0.15).

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Pointon 2012 2483) recruiting 10 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with the use of colder water immersion (9°C; 48.2°F) up to the iliac crest compared with passive cooling (mean difference 0.02°C/min; 95% CI -0.00-0.04).

For the critical outcome of rate of core body temperature reduction, we identified moderate certainty evidence (downgraded for risk of indirectness) from one controlled trial (Lee 2012 655) recruiting 4 adult subjects with exertional hyperthermia which showed a faster rate of core body temperature reduction with the use of colder water immersion (11.7°C; 53.0°F) of the torso compared with temperate water (23.5°C; 74.3°F) immersion (MD 0.08°C/min, 95% CI 0.02-0.14).

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Clapp 2001 160) recruiting 5 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with the use of colder water immersion (10-12°C; 50.0-52.6°F) of the hands/feet compared with the use of colder water immersion of the torso (mean difference -0.09°C/min; 95% CI -0.19-0.01).

Ice Water Immersion (1-5°C; 33.8-41.0°F)

For the critical outcome of mortality, we identified very low certainty evidence (downgraded for risk of imprecision) from one small observational cohort study (Hostler 2013 456) of 23 adult exertional heat stroke patients evaluating the use of ice water immersion (5-10°C; 33.8-41.0°F) of the torso and the administration of intravenous (IV) 0.9% normal saline at ambient temperature together compared with the use of ice bags applied to the axilla which showed no deaths in either group.

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of inconsistency and indirectness) from four controlled trials (Clements 2002 146, Flouris 2014 2551, Gagnon 2010 157, Luhring 2016 946) recruiting 54 adult subjects with exertional hyperthermia and low certainty evidence from one observational cohort study (Armstrong 1996 355) enrolling 21 exertional heat stroke patients, which showed a faster rate of core body temperature reduction with the use of ice water immersion (1-5°C; 33.8-41.0°F) of the torso compared with passive cooling (MD range from 0.06 to 0.23°C/min). Due to high heterogeneity between studies, a pooled estimate of the difference in mean rates of body temperature reduction was not performed.

For the critical outcome of rate of core body temperature reduction, we identified moderate certainty evidence (downgraded for risk of indirectness) from two controlled trials (Friesen 2014 1727, Proulx 2003 1317) recruiting 27 adult subjects with exertional hyperthermia which showed a faster rate of core body temperature reduction with the use of ice water immersion (2°C; 35.6°F) of the torso compared with temperate water immersion (20-26°C; 68.0-78.8°F) of the torso (MD 0.14°C/min; 95% CI 0.09-0.18).

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence from one small observational cohort study (Hostler 2013 456) of 23 adult patients with exertional heat stroke which showed a faster rate of core body temperature reduction with the use of ice water immersion (5-10°C; 33.8-41.0°F) of the torso combined with the administration of IV 0.9% normal saline compared with the use of ice packs to the axilla (mean difference 0.06°C/min; 95% CI 0.01-0.11).

Evaporative Cooling (Mist and fan)

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness) from two controlled trials (Kielblock 1986 378, Sefton 2016 936) recruiting 23 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with evaporative cooling compared with passive cooling (mean difference 0.01°C/min; 95% CI 0.00-0.01).

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Sinclair 2009 1984) recruiting 11 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of body temperature reduction with evaporative cooling compared with use of ice packs applied to the neck, axilla and groin (mean difference 0.00°C/min; 95% CI -0.01-0.01).

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Kielblock 1986 378) recruiting 5 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of body temperature reduction with evaporative cooling compared with the use of commercial ice packs applied to the neck, axilla and groin (MD 0.00°C/min; 95% CI -0.00-0.00).

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Kielblock 1986 378) recruiting 5 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with evaporative cooling compared with the use of commercial ice packs applied to the whole body (mean difference 0.00°C/min; 95% CI -0.00-0.00).

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Kielblock 1986 378) recruiting 5 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with evaporative cooling combined with the use of commercial ice packs to the neck, axilla and groin compared with passive cooling (mean difference 0.00°C/min; 95% CI -0.00-0.00).

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Kielblock 1986 378) recruiting 5 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with the use of evaporative cooling and commercial ice packs to the neck, axilla compared with evaporative cooling alone (mean difference 0.00°C/min; 95% CI -0.00-0.00).

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Sinclair 2009 1984) recruiting 11 adult subjects with exertional hyperthermia showed no significant mean difference in the rate of core body temperature reduction using evaporative cooling compared with the administration of IV 0.9% normal saline at 20°C (68.0°F) (MD 0.00°C/min; 95% CI -0.01-0.01).

Ice Sheets

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from two controlled trials (Butts 2017 e1951, DeMartini 2011 2065) recruiting 29 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with the use of ice sheet application (bed sheets soaked in ice water kept at 3°C(37.4°F) and towels soaked in ice water kept at 14°C(57.2.0°F), respectively, to the body compared with passive cooling (mean difference 0.01°C/min; 95% CI -0.00-0.02).

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Nye 2017 294) recruiting 18 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with the use of ice sheet application (sheets soaked in ice and water at 5-10°C; 33.8-41.0°F) to the body compared with colder water (5-10°C; 33.8-41.0°F) immersion (mean difference 0.02°C/min; 95% CI -0.01-0.05).

Commercial Ice Packs

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from two controlled trials (Kielblock 1986 378, Lissoway 2015 173) recruiting 15 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with the use of commercial ice packs to the neck, groin and axilla compared with passive cooling (mean difference 0.02°C/min; 95% CI -0.03-0.07).

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Kielblock 1986 378) recruiting 5 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with the use of commercial ice packs to the whole body compared with passive cooling (mean difference 0.00°C/min; 95% CI -0.00-0.00).

For the critical outcome of rate of core body temperature reduction, we identified moderate certainty evidence (downgraded for risk of indirectness) from one controlled trial (Lissoway 2015 173) recruiting 10 adult subjects with exertional hyperthermia which showed a faster rate of core body temperature reduction with the use of commercial ice packs to the facial cheeks, palms and soles compared with passive cooling (mean difference 0.18°C/min; 95% CI 0.12-0.24).

For the critical outcome of rate of core body temperature reduction, we identified moderate certainty evidence (downgraded for risk of indirectness) from one controlled trial (Lissoway 2015 173) recruiting 10 adult subjects with exertional hyperthermia which showed a faster rate of core body temperature reduction with the use of commercial ice packs to the facial cheeks, palms and soles compared with the use of commercial ice packs applied to the neck, groin and axilla (mean difference 0.13 °C/min; 95% CI 0.09-0.17).

Fan Alone

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from two controlled trials (Barwood 2009 385, DeMartini 2011 2065) recruiting 25 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with the use of fanning alone compared with passive cooling (mean difference D 0.02°C/min; 95% CI 0.00-0.04).

Cold Shower

For the critical outcome of rate of core body temperature reduction, we identified moderate certainty evidence (downgraded for risk of indirectness) from one controlled trial (Butts 2016 252) recruiting 17 adult subjects with exertional hyperthermia which showed a faster rate of core body temperature reduction with the use of cold showers (20.8°C; 69.4°F) compared with passive cooling (mean difference 0.03 °C/min; 95% CI 0.01-0.05).

Hand Cooling Devices

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from three controlled trials (Adams 2016 936, Maroni 2018 441, Zhang 2009 283) recruiting 29 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with the use of hand cooling devices compared with passive cooling (mean difference 0.02°C/min; 95% CI -0.00-0.04).

Cooling Vests and Jackets

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from two controlled trials (Brade 2010 164, Maroni 2008 441) recruiting 24 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with the use of the Arctic Heat cooling jacket (Arctic Heat Products Pty Ltd, Queensland, Australia) compared with passive cooling (MD 0.01°C/min; 95% CI -0.01-0.03).

For the critical outcome of rate of body temperature reduction, we identified very low certainty evidence (downgraded for risk of inconsistency, indirectness and imprecision) from five controlled trials (Barwood 2009 385, Brade 2010 164, DeMartini 2011 2065; Lopez 2008 55, Smith 2018 413) recruiting 73 adult subjects with exertional hyperthermia that compared the use of various cooling vests with passive cooling, of which none evaluated showed no significant mean difference in the rate of core body temperature reduction when compared with passive cooling. Due to the high heterogeneity of commercial vests used between studies, pooled estimates were not performed.

Reflective Blankets

For the critical outcome of rate of body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Reynolds 2015 97) recruiting 20 adult subjects with exertional hyperthermia which no significant mean difference in rate of core body temperature reduction with the use of reflective blankets compared with passive cooling (mean difference -0.01°C/min; 95% CI -0.02 to -0.00).

Intravenous Fluids

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Sinclair 2009 1984) recruiting 11 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of core body temperature reduction with administration of 2 liters of IV 0.9% normal saline at 20°C(68°F) over 20 minutes compared with the use of ice packs to the neck, axilla and groin (mean difference 0.00°C/min; 95% CI -0.01-0.01).

For the critical outcome of rate of core body temperature reduction, we identified low certainty evidence (downgraded for risk of indirectness and imprecision) from one controlled trial (Morrison 2018 493) recruiting 12 adult subjects with exertional hyperthermia which showed no significant mean difference in the rate of body temperature reduction with administration of 2 liters of cold (4°C;39.2°F)) IV 0.9% normal saline over 30 minutes compared with 2 liters of IV NS at 22°C(71.6°F) (mean difference 0.01°C/min; 95% CI -0.00-0.02).

For the critical outcome of mortality (with the exception of ice water immersion) and the important outcomes of clinically important organ dysfunction, adverse events and hospital length of stay, there were no comparator studies evaluating any of the above cooling techniques.

Treatment Recommendations

For adults with exertional hyperthermia or exertional heat stroke:

• We recommend immediate active cooling using whole body (neck down) water immersion techniques (1-26°C; 33.8-78.8°F) until a core body temperature of less than 39°C (102.2°F) is reached (weak recommendation, very low certainty evidence).
• We recommend that where water immersion is not available, any other active cooling technique be initiated (weak recommendation, very low certainty of evidence).
• We recommend immediate cooling using any active or passive technique available to care providers that provides the most rapid rate of cooling (weak recommendation, very low certainty of evidence)

For adults with classic heat stroke, we cannot make a recommendation for or against any specific cooling technique compared with an alternative cooling technique (no recommendation, very low certainty evidence)

For children with exertional or classic heat stroke, we cannot make a recommendation for or against any specific cooling technique compared with an alternative cooling technique (no recommendation, very low certainty evidence).

Technical remarks

1. The most rapid cooling was achieved using whole-body (from the neck down) water immersion techniques between 1-26°C (33.8-78.8°F). While there was heterogeneity in cooling rates between different water temperatures, colder water temperatures were associated with faster cooling rates.
2. Cooling rates achieved with water immersion techniques were faster than other active cooling modalities such as commercial ice packs, cold showers, evaporative cooling, ice sheets and towels, fanning, evaporative cooling, cooling vests and jackets. However, because confidence intervals cross for most of the mean weighted cooling rates for cooling techniques studied, we are unable to provide a rank order list. Graphically displayed trends in mean weighted cooling rates for cooling techniques are available in Figure 1 of the accompanying Evidence to Decision document.
3. The evidence summary consistently reports core body temperature as measured rectally. The absence of core rectal temperature measurement availability should not preclude initiation of whole-body cold-water immersion if available.

Justification and Evidence to Decision Framework Highlights

This PICO was prioritized for review by the First Aid Task Force based on a) the importance of the problem; b) increases in the number of extreme heat events (heatwaves); c) major sporting events being held in hot climates; and d) survival and morbidity associated with heat stroke could be improved with rapid cooling.

In making these recommendations, the First Aid Task Force considered the following:

• With the exception of case series, there were no studies that evaluated cooling techniques for exertional heat stroke. This is likely due to ethical restraints related to the morbidity associated with heat stroke. In addition, none of the included studies evaluated cooling techniques in children.
• We noted that there is a wide variation of cooling methods employed across different regions and in different settings.
• It was considered feasible to provide whole-body (from the neck down) cold water immersion using relatively inexpensive “fit for purpose” equipment or improvised materials in most settings.
• Passive cooling (e.g. moving to cooler environment) is an essential part of the initial management of exertional hyperthermia and heat stroke based on consensus expert opinion. However, it is a slower cooling method compared with most other studied cooling modalities.
• Given the clinical consequences of delayed cooling for heat stroke, the Task Force considered that core temperature measurement should be available in first aid settings where there is a high risk of encountering heat stroke, such as sports events, particularly when high ambient or wet bulb temperatures were anticipated.
• The Task Force recognizes that the optimal immersion time to reduce core temperature to below 39^oC is unknown. We considered that even in the absence of core temperature measurement, the use of water immersion, if available, should be continued until there has been resolution of symptoms or for a reasonable amount of time, such as 15 minutes, as benefit is more plausible than harm. To arrive at this time the Task Force created scenarios with different initial temperatures and different rates of cooling in an attempt to strike a balance between benefits and harms. Included studies did not report significant hypothermia or thermal injuries during cold-water immersion across the recommended temperature ranges.
• Combinations of less effective techniques may result in an overall faster cooling rate than if any technique is used alone, although this has not been studied.
• The Task Force recognizes that times required to cool a person with heat stroke or exertional hyperthermia will vary with their body size, age and multiple additional factors. The Task Force does not feel that a treatment recommendation that included specific time limits for cooling could be made in the absence of further clinical evidence.

Knowledge Gaps

Current knowledge gaps include but are not limited to:

• There are no prospective comparative studies of cooling techniques for individuals with exertional or classic (nonexertional) heat stroke, and only a few cohort studies were identified for cooling of exertional stroke. Recommendations in this review are based on indirect evidence from exertional hyperthermia.
• There is an urgent need for studies investigating the optimal duration of cooling by cold water immersion techniques when core temperature measurement is unavailable
• Specific pediatric intervention studies for heat-related illness are lacking.
• There are no comparative studies of combined active with passive cooling techniques on rate of cooling and on clinical outcomes, for example, the use of ice packs with evaporative and passive cooling.
• There are no studies of the optimal method of cooling for heat related illness in children or based on body mass index
• Research is lacking into the ability of a first aid provider to recognize heat stroke without a core temperature measurement and the educational requirement to bridge this gap
• Research is required into the optimal approach of the management of extreme heat events involving multiple victims with heat related illness, including evaluation of the health economic impact and the impact of active cooling techniques.

Evidence-to-Decision Table

EtD: Heat Stroke Cooling

Acknowledgements

We acknowledge the assistance of Eddy Lang, MD, in the task force discussions for this CoSTR and the Evidence to Decision table.

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