New canine heated-related illness study published

A newly published study has identified the early warning signs of heatstroke in dogs.

Heat-related illness is a potentially fatal condition in dogs. Recognising the signs and taking immediate action is key to maximising dogs' chances of recovery.


The study published in Nature Scientific Reports is part of the VetCompass initiative. Scientists from Nottingham Trent University and The Royal Veterinary College explored the veterinary records of dogs from 856 heat-related illness events occurring between 2016 and 2018.


They classified the symptoms of affected dogs as mild, moderate or severe based upon the associated risk of death.



Study highlights


  • The most common clinical signs (symptoms) were:

  • Breathing changes (68.73%)

  • Lethargy (47.79%)

  • Collapse (31.5%)

  • Based on the risk of death associated with each clinical sign, they were classified as mild, moderate and severe (see image, right).

  • All dogs require immediate action; cool and seek veterinary advice.

  • For dogs with mild symptoms, management might be possible on the scene.

  • Dogs with moderate symptoms require immediate veterinary treatment to prevent worsening.

  • Less than half of dogs with severe symptoms, survive.

  • Dogs with mild or moderate symptoms have a >94% chance of survival.

  • 14% of all dogs in this study were severely affected.



More detail


Veterinary records collected in 2016-2018 from >900,000 dogs were scrutinised. 856 events of heat-related illness were identified in 828 dogs (28 dogs had 2 events that required veterinary treatment during this period).


The most commonly recorded clinical sign (symptom) was altered respiration, being reported in more than two thirds (68.73%) of all cases. Affected dogs were panting excessively and/or having breathing difficulties (called dyspnoea). Other common clinical signs were lethargy (47.79% of dogs) and intermittent collapse (31.5%). More than 70% of dogs showed more than one clinical sign.

Dogs with abnormal mentation (e.g. dogs which are unresponsive, in a coma or are having seizures), gastrointestinal haemorrhage, petechiae/purpura (small haemorrhages on their gums) or ataxia (wobbliness) had at least three times the relative risk of death compared to dogs presenting without those clinical signs.


Dogs presenting with a body temperature ≥ 43 °C had a higher relative risk of death and unassisted death compared to dogs with a temperature ≥ 41 °C. Dogs presenting with hypothermia (< 37.2 °C) did not have a significantly increased relative risk of death.


What do the findings mean?


For owners:


Early recognition of mild signs of heat related illness allows owners to take earlier action and to prevent worsening of their dog's condition. Owners of those dogs more prone to heatstroke (e.g. brachycephalic dogs) should be especially vigilant.


This study shows owners should be on the lookout for the following early signs:

  • Continuous panting or breathing changes that persist despite stopping the dog from exercising or removing them from the hot environment

  • Lethargy, drowsiness

  • Stiffness

  • Unwillingness to move


These cases require prompt action (active cooling and oral rehydration), and might be managed on the scene.


Dogs with moderate signs must also be actively cooled but will require veterinary treatment +/- hospitalisation. These include:

  • Failure to respond to cooling

  • Drooling

  • Vomiting and diarrhoea (no blood)

  • A single seizure (fit)

  • Collapse


Dogs which show the following signs are severely affected, and are most at risk of death.

  • Loss of consciousness

  • Loss of coordination

  • Confusion

  • Vomit or diarrhoea (with blood)

  • Multiple seizures (fits)


For vets:


The study identified those symptoms most likely to be associated with death. This allows vets to offer owners with a prognosis, advising on the likelihood of survival:

  • Mild signs: 97.8% survived

  • Moderate signs: 94.5% survived

  • Severe signs: 43.2% survived

  • Dogs which were unresponsive were 37x more likely to die than those which were responsive.


Body temperature on presentation is less indicative of outcome than symptoms. Any dog with a temperature approaching 41 °C should be actively cooled as a matter of urgency, but clinical signs rather than body temperature should be used to then determine the severity of HRI present.


The authors of the study make suggestion about the most appropriate veterinary care of dogs which are mildly, moderately and severely affected.



To find out more about heatstroke in dogs and to stay on top of the latest research in this area, check out the Hot Dogs facebook page.


Full paper reference:

Hall, E.J., Carter, A.J., Bradbury, J. et al. Proposing the VetCompass clinical grading tool for heat-related illness in dogs. Sci Rep 11, 6828 (2021). https://doi.org/10.1038/s41598-021-86235-w

Link to paper




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