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Three Part Question

In [adult patients presenting to the ED with heat-stroke] does [whole body ice-water immersion] provide the [most effective cooling rates]?

Clinical Scenario

A 50 year old male is brought in by ambulance after a collapse. It is a hot day and the patient had been playing 5-aside football when he collapsed. In the Emergency Department he is a assessed, having a rectal temperature of 41.5C and a GCS of 4. The patient is hot and not sweating. A diagnosis of heatstroke is made. You have heard contradictory evidence as to the most effective cooling modality available and wonder if whole body ice-water immersion might be the best option.

Search Strategy

Ovid Medline 1950 to July Week 3 2012

Ovid Embase 1980 to 2 July 2012

Ovid EBM Reviews Cochrane Central Register of Controlled Trials 3rd Quarter 2012

Ovid EBM Reviews Cochrane Database of Systematic Reviews 3rd Quarter 2012

EBSCOHost CINAHL Plus

Ovid Medline and Embase search strategy:
[(heat stress.mp) OR (exp Heat Stress Disorders/) OR (hyperthermia.mp)] AND [(cooling adj3 efficiency).mp OR (ice adj3 water).mp OR (cold adj3 water).mp OR (exp Immersion/) OR (immersion.mp) OR (whole adj3 body adj3 cooling).mp OR (cooling adj1 methods).mp)]

Cochrane search strategy:
[heat stress.mp. or exp Heat Stress Disorders/OR. hyperthermia.mp.] AND [(cooling adj3 efficiency).mp. OR (ice adj3 water).mp. OR (cold adj3 water).mp. OR exp Immersion/or immersion.mp. OR (whole adj3 body adj3 cooling).mp. OR (cooling adj1 methods).mp.]

CINAHL Plus search strategy:
(MH ‘Heat Stroke’) or (MH ‘Heat Exhaustion’) AND (immersion OR ice-water OR cold-water OR cooling efficiency)

Search Outcome

This search returned 22 relevant papers, four of which were deemed to be of suitable quality for inclusion. Evidence relating to hand and forearm immersion was excluded as the data were mainly procured with the involvement of heavy duty clothing/equipment and are not representative of the clinical question posed. Meta-analyses and systematic reviews primarily cross-referencing other studies found in this search were excluded as nothing new would have been added.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Bouchama et al, 2007, Saudi Arabia	556 patients identified through 19 publications	Systematic review	Exertional heatstroke	Conductive cooling, namely ice-water immersion, shown to be effective in young patients with exertional heatstroke such as athletes/military recruits	Systematic review taking evidence from case-series studies. Lack of reliability to the data.
			Classical heatstroke	No cooling method superiority evident
			End-point temperature for cooling cessation	No evidence found for safe cessation temperature
Proulx et al, 2003, Canada	7 healthy volunteers Male N=4 Female N=3	Comparative study	Cooling began once exercising brought Trec >40°C (45.4 +/- 4.1 min at 39°C ambient temperature) & continued until Trec =37.5°C		Small sample size.
			Overall rate using 20°C	0.19°C/min ±0.10°C
			Overall rate using 14°C	0.15°C/min ±0.06°C
			Overall rate using 8°C	0.19°C/min ±0.07°C
			Overall rate using 2°C	0.35°C/min ±0.14°C
Armstrong et al, 1996, USA	21 hyperthermic runners all having completed an 11.5km summer race.	Comparative study	Initial Trec (n=21)	41.2°C ±0.2°C	Small sample size
			Ice-water immersion at 1-3°C modality (n=14)	Trec pre-therapy to post-therapy change -3.0°C ±0.3°C with mean rate 0.2°C ±0.02°C
			Air exposure & wet towel wrap (n=7) in 24.4°C ambient	Trec pre-therapy to post-therapy change -1.4°C ±0.3°C with mean rate 0.11°C ±0.02°C
Clements et al, 2002, U.S.A	17 distance runners, completing ~19km run in wet-bulb ambient temperature of 27°C ±1.0°C followed by immersion variations.	RCT	Length of run, completion time, Trec, % dehydration, wet-bulb globe temperature	No significant differences (P>0.05)	Extrapolation from a milder hyperthermia than that seen in true exertional heatstroke.
			All cooling rates before 8 minutes	No significant differences (P>0.05)
			Ice-water immersion, cold water immersion and mock immersion comparison	Ice-water and cold water significantly different than mock immersion only at 8-12minutes. Trec not significantly different in ice-water or cold water immersion except in ice at 6-10 minutes post-immersion (P<0.05).

Comment(s)

While it is agreed that rapid diagnosis and prompt cooling ensues in all heatstroke patients, the modality with which to go about this has been the subject of much dispute. The evidence highlighted in the enclosed systematic review points towards the superiority of immersion techniques, notably ice-water in exertional heatstroke. The often-held objections on the grounds of vasoconstriction, shivering and hyperthermia recurrence would appear groundless, although the studies highlight that in a conscious patient ice-water immersion may be unpleasant to the point of being intolerable and a producing combativeness. Further randomised controlled trials into the effects of water movement in immersion would be of benefit. This area of heatstroke management is the most likely to diversify as novel ideas, for example, chilled vests for athletes or the seemingly highly successful helicopter downdraft technique in air-evacuation settings.

Editor Comment

RCT, randomised controlled trial.

Clinical Bottom Line

Best evidence points towards immersion in ice-water as the most effective modality of lowering core body temperature in exertional heatstroke patients. Shivering & vasoconstriction concerns are unfounded, although the tendency for continuing cooling post-immersion and hypothermia must be considered seriously.

References

1. Bouchama A. Dehbi M. Chaves-Carballo E. Cooling and hemodynamic management in heatstroke: practical recommendations. Critical Care (London, England) 11(3):R54, 2007.
2. Proulx C.I. Ducharme M.B. Kenny GP. Effect of water temperature on cooling efficiency during hyperthermia in humans. J Appl Physiol 2008;94:1317–23.
3. Armstrong LE. Crago AE. Adams R et al. Whole-body cooling of hyperthermic runners: comparison of two field therapies. Am J Emerg Med 1996;14:355–8.
4. Clements JM, Casa DJ, Knight JC, et al. Ice-water immersion and cold-water immersion provide similar cooling rates in runners with exercise-induced hyperthermia. J Athl Train 2002:37:146–50.