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Cool, Icy, Cold or Tepid? What's Best for Heat Stroke?

Updated: Jul 8

Let us investigate the myth behind cooling animals with heat stroke with tepid water.

Although it is generally agreed that rapid, effective cooling increases survival in heat stroke, there continues to be debate on the optimal cooling method.

As with many things, we often find ourselves with lots of conflicting information when dealing with first aid in humans and animals, but ultimately, we need to try our best to keep up with the every changing evidence base.

A myth that seems to not go is that if your pet has heat stroke, you should only douse in tepid water, in case they cool too quickly and go into shock.

The best advice is always to PREVENT heat stroke, but if you find yourself in the unlucky situation that you have a pet or are helping a pet, outside the veterinary clinic, that has heat stroke here are a few tips (these are not in order, we would prefer them to be simultaneous or prioritized if there is not enough people to help):

  • Get someone to call the local veterinary practice and tell them you're going to travel down with a heat stroke patient

  • Pour, hose or if possible immerse the pet in very cold water (this should obviously be done under constant supervision, ensuring the head is fully above water and immersion should not be attempted if the animal is too large, or you are unable to do so without hurting yourself)

  • NB: If using a hose pipe, make sure it has run through until cold, as they can often contain water that is extremely hot in the tubing initially

  • Do not drape in towels and leave them in situ

  • Move to a cool, shaded area

  • Prepare to transport to vets in a cold, air conditioned car

Remember, heat stroke may present with symptoms like drooling, pacing, panting all the way to unconsciousness and seizures. This is why it is SO important to start actively cooling your pet or the pet/animal you have found whilst getting in contact with your veterinary team. Providing first aid to a pet having a seizure, or an unconscious pet is very different to a pet who is displaying milder (although still potentially life threatening) signs and still conscious. 'Get them wet, straight to the vet!'

Cold water immersion - will it cause problems?

As with many things in veterinary medicine, we have to occasionally draw on human data to assess what we could do in veterinary, although this is not always applicable. When it comes to treatment of heat stroke we can look at how human medical professionals and first aiders are taught to treat heat stroke, most notably in athletes and military personnel as well as in hospital and outdoor settings.

Study: Cooling Methods in Heat Stroke

Ice-water immersion has been shown to be highly effective in exertional heat stroke, with a zero fatality rate in large case series of younger, fit patients.

Study: Outcomes of UK military personnel treated with ice cold water immersion for exertional heat stroke

International consensus from sports medicine organisations supports treating EHS with early rapid cooling by immersing the casualty in cold water. Following changes to enable on-site ice cold water immersion (ICWI) at the Royal Marines Commando Training Centre, Lympstone, UK, we prospectively gathered data on 35 patients treated with ICWI over a 3-year period. These data included the incidence of adverse events. Despite being a cohort of patients in whom we might expect significant morbidity and mortality based on the severity of EHS at presentation, none experienced a serious adverse event.

Study: Optimizing Cold-Water Immersion for Exercise-Induced Hyperthermia: An Evidence-Based Paper

Hyperthermic individuals were cooled twice as fast by CWI as by passive recovery. Therefore, the former method is the preferred choice when treating patients with exertional heat stroke. Water temperature should be <10°C, with the torso and limbs immersed.

Case Study, Geriatric Patients: Safety and efficacy of cold‐water immersion in the treatment of older patients with heat stroke: a case series

Three older patients with severe heat stroke were treated with cold‐water immersion. Core body temperatures decreased rapidly, and no complications occurred during the treatment. Cold‐water immersion can achieve rapid cooling and is effective in treating heat stroke. With special precautions, it can be performed safely for older patients.

Review: Cold water immersion: the gold standard for exertional heatstroke treatment

The key to maximize the chances of surviving exertional heatstroke is rapidly decreasing the elevated core body temperature. Many methods exist to cool the body, but current evidence strongly supports the use of cold water. Preferably, the athlete should be immersed in cold water.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Heat Illness: 2024 Update:

Cold water immersion (CWI) therapy is the optimal field treatment to achieve rapid temperature reduction below critical levels in heat stroke.

Military standard operating procedures translated into civilian best practice: delivery of cold water immersion to treat exertional heat stroke at Brighton marathon 2023

'Cold water immersion (CWI) is the preferred cooling modality in EHS guidelines and the optimal method applicable to UK Service Personnel.'

Study: Ice-Water Immersion and Cold-Water Immersion Provide Similar Cooling Rates in Runners With Exercise-Induced Hyperthermia

Based on this study, we suggest using either ice-water or cold-water immersion when treating hyperthermic athletes. In the only previous study comparing ice-water immersion and cold-water immersion cooling rates, researchers found no difference between ice-water immersion (1 to 3°C) and cold-water immersion (15°C to 16°C) in dogs. Potential side effects of ice-water immersion and cold-water immersion, such as hypothermic overshoot, peripheral vasoconstriction hindering a cooling response, and cardiogenic shock, did not occur during our study.


New research from the Royal Veterinary College (RVC) which investigated heatstroke in UK dogs has found a strong correlation between the occurrence of these episodes in dogs and heatwaves in the UK. Researchers therefore suggest that heat-health alerts designed for humans should also be used as a tool for owners to protect their dogs from heat-related illnesses.


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