Cooling of patients with Classic Heat Stroke
Date First Published:
December 12, 2013
Last Updated:
June 5, 2014
Report by:
Adam Waller, Emergency Nurse Practitioner / Clincal Lead (Berkshire Lowland Search & Rescue)
Three-Part Question:
In [patients presenting with classic heat stroke at mass gathering events] is [fine mist water spraying and evaporation more effective than ice packs] at [reducing core body temperature and decreasing ongoing cerebral dysfunction]
Clinical Scenario:
39 year old male presents to the medical facility at an international air show having spent the day on grass and concrete watching the air show. Clinically he presents with significant confusion, disorientation, tachycardia, tachypnoea, and absence of sweating. On initial assessment he is found to have a rectal temperature of 41.2 degrees and HR of 118.
Following rapid assessment he is taken to the decontamination shelter where he is taken through the tent which is spraying cool water - he is passed along the tent twice and following this his rectal temperature is 39.3 degrees. He returns to the P1 (resuscitation) area and cooling and treatment continues with fine mist water spraying (plant sprayers), blow by air and IV fluids. After 1 hour of treatment his core body temperature has returned to normal and he is alert and orientated.
Following rapid assessment he is taken to the decontamination shelter where he is taken through the tent which is spraying cool water - he is passed along the tent twice and following this his rectal temperature is 39.3 degrees. He returns to the P1 (resuscitation) area and cooling and treatment continues with fine mist water spraying (plant sprayers), blow by air and IV fluids. After 1 hour of treatment his core body temperature has returned to normal and he is alert and orientated.
Search Strategy:
Medline (Ovid)
Exp Heat stress disorders/ OR exp heat exhaustion/ OR exp heat stroke/ or heat illness.mp
AND
Exp body temperature/ OR body temperature regulation/ OR cooling.mp
AND
Evaporation.mp
Limit to humans and English language
Ovid Nursing Database
Heat stroke.mp OR heat stroke/
AND
Exp Body temperature/ OR cooling.mp
CINAHL (EBSCOHOST)
(MH “heat stroke”) OR “heat stroke” OR (MH “heat stress disorders”) OR (MH “Heat Exhaustion”)
AND
(MH "Heat Stroke") OR (MH "Heat Exhaustion") OR "cooling"
AND
“Evaporation”
Exp Heat stress disorders/ OR exp heat exhaustion/ OR exp heat stroke/ or heat illness.mp
AND
Exp body temperature/ OR body temperature regulation/ OR cooling.mp
AND
Evaporation.mp
Limit to humans and English language
Ovid Nursing Database
Heat stroke.mp OR heat stroke/
AND
Exp Body temperature/ OR cooling.mp
CINAHL (EBSCOHOST)
(MH “heat stroke”) OR “heat stroke” OR (MH “heat stress disorders”) OR (MH “Heat Exhaustion”)
AND
(MH "Heat Stroke") OR (MH "Heat Exhaustion") OR "cooling"
AND
“Evaporation”
Search Details:
Medline – 24 results of which 2 were useful
OVID Nursing Database – 47 results of which 4 were useful
CINAHL – 4 results of which 2 were useful
Out of all the useful results 5 were deemed of good enough quality for inclusion. Any duplicate articles that were found during the searching were removed.
OVID Nursing Database – 47 results of which 4 were useful
CINAHL – 4 results of which 2 were useful
Out of all the useful results 5 were deemed of good enough quality for inclusion. Any duplicate articles that were found during the searching were removed.
Outcome:
Medline – 24 results of which 2 were useful
OVID Nursing Database – 47 results of which 4 were useful
CINAHL – 4 results of which 2 were useful
Out of all the useful results 5 were deemed of good enough quality for inclusion. Any duplicate articles that were found during the searching were removed.
OVID Nursing Database – 47 results of which 4 were useful
CINAHL – 4 results of which 2 were useful
Out of all the useful results 5 were deemed of good enough quality for inclusion. Any duplicate articles that were found during the searching were removed.
Relevant Paper(s):
| Study Title | Patient Group | Study type (level of evidence) | Outcomes | Key results | Study Weaknesses |
|---|---|---|---|---|---|
| 'Heat stroke: a comprehensive review.' Yeo, T.P 2004 USA | Classic Heat stroke Exertional heat stroke |
Review | Normothermia | Evaporative cooling methods are safest – best tolerated by all patient groups | Doesn’t clearly show type of studies reviewed nor does it show populations’ sizes. Lacks rigour in assessment of outcomes. Non therapy driven paper. |
| Reduction in CNS dysfunction | Treatment should include fluid resuscitation preferably with isotonic sodium chloride | ||||
| Reduction in organ damage | The use of benzodiazepines to sedate and reduce shivering or chlorpromazine to reduce shivering may help reduce time to normothermia by preventing increased heat production. | ||||
| 'Heat-stroke: a review of rapid cooling techniques.' Harker, J. and Gibson, P. 1995 UK | Patients suffering from heat stroke | Comparative review | Preferential cooling modality | Evaporative cooling outperforms cold water immersion. Key feature of evaporative cooling is to maintain skin warmth, aiming to avoid vasoconstriction and shivering | No definition of type of study reviewed or total populations. Highlights lack of direct comparative evidence between cooling modalities. |
| 'Cooling and haemodynamic management in heatstroke: practical recommendations.' Bouchama, A. et al 2007 Saudi Arabia | 556 total patients in 19 studies subdivided as below: Classic Heat stroke - 386 Exertional heat stroke - 170 |
Level 1 Systematic Review of RCT’s and case series. | Classic Heat stroke (CHS) | No clear best method for cooling. Although Iced water immersion suggest increased morbidity and mortality. Both evaporative and conductive non-invasive techniques comparable in efficacy | Failed to effectively compare conduction and evaporation methods in EHS. Lack of high level studies included – may lead to lack of reliability |
| Exertional Heat stroke (EHS) | Conduction (iced-water immersion) is only method reviewed for EHS. Shown to be effective. | ||||
| Temperature for stopping cooling | No clear end point temperature for cessation of cooling identified | ||||
| 'Management of heatstroke and heat exhaustion.' Glazer, J. L. 2005 USA | Heat-related illness in humans | Review | Pre-hospital management of heat-related illness | Cooling by evaporation is most effective method in pre-hospital environment with cooling rates of up to 0.31 degrees C/minute compared to 0.15 degrees C/minute in conduction methods. | Review of literature fails to demonstrate strength of literature included. Key recommendations come from less rigorous data than may be hoped. |
| Patients are more accessible when being cooled by evaporation | |||||
| Immersion may trigger mammalian diving reflex | |||||
| 'Heat stroke : a review of cooling methods.' Hadad, E. et al 2004 Israel | 11 studies reviewed Cold water immersion – 3 Evaporation – 3 Dantrolene - 5 |
Level 2 review | Overall best modality for rapid and safe cooling | Evaporative cooling was better in 2 out of 3 controlled trials reviewed | Small cohorts in studies reviewed. Participant numbers not included and no mention to statistical significance |
| There is no clear preferential modality for cooling however, evaporation techniques are more tolerable and available pre-hospitally | |||||
| In patients who may not be fit and healthy evaporative techniques are preferred |
Author Commentary:
Heat stroke is a heat related illness defined by a core body temperature in excess of 40.6°C due to environmental heat exposure (McGugan, 2001). It is characterised by a failure of the body’s thermoregulatory system in the presence of high core body temperature.
Heat stroke may be divided into exertional (may not need high environmental temperatures) and non-exertional (classic) heat stroke. Classic heat stroke occurs during extreme heat waves, the elderly and young being particularly vulnerable.
The methods of cooling patients with heat stroke is still highly contentious. The number and quality of available studies is significantly lacking. Much research has been published in the assessment and management of exertional heat stroke but little in comparison has been done for classic heat stroke with those studies that have been done being rather old.
The pre-hospital environment poses many challenges to clinicians and even more challenges can be seen at mass gathering events like air shows. In this environment it is imperative that patients are rapidly cooled in a safe and effective manner especially given that a large number of heat related casualties may present in a very short period of time. Further consideration needs to be given to the siting of onsite facilities to give best access to required resources in order to provide optimal care to patients.
Heat stroke may be divided into exertional (may not need high environmental temperatures) and non-exertional (classic) heat stroke. Classic heat stroke occurs during extreme heat waves, the elderly and young being particularly vulnerable.
The methods of cooling patients with heat stroke is still highly contentious. The number and quality of available studies is significantly lacking. Much research has been published in the assessment and management of exertional heat stroke but little in comparison has been done for classic heat stroke with those studies that have been done being rather old.
The pre-hospital environment poses many challenges to clinicians and even more challenges can be seen at mass gathering events like air shows. In this environment it is imperative that patients are rapidly cooled in a safe and effective manner especially given that a large number of heat related casualties may present in a very short period of time. Further consideration needs to be given to the siting of onsite facilities to give best access to required resources in order to provide optimal care to patients.
Bottom Line:
There is as yet not enough evidence to fully support either method for cooling patients. More good quality controlled trials need to be done comparing evaporation with convection techniques as at present both techniques appear equally efficacious.
In the clinical setting detailed above it is preferable that the use of evaporation techniques in conjunction with cardiovascular support in the form of cooled IV fluids is used to rapidly cool the patient with heat stroke in order to minimise ongoing cerebral dysfunction and further organ damage.
In the clinical setting detailed above it is preferable that the use of evaporation techniques in conjunction with cardiovascular support in the form of cooled IV fluids is used to rapidly cool the patient with heat stroke in order to minimise ongoing cerebral dysfunction and further organ damage.
Level of Evidence:
Level 2: Studies considered were neither 1 or 3
References:
- Yeo, T.P. 'Heat stroke: a comprehensive review.'
- Harker, J. and Gibson, P.. 'Heat-stroke: a review of rapid cooling techniques.'
- Bouchama, A. et al. 'Cooling and haemodynamic management in heatstroke: practical recommendations.'
- Glazer, J. L.. 'Management of heatstroke and heat exhaustion.'
- Hadad, E. et al. 'Heat stroke : a review of cooling methods.'