Heatstroke in dogs: poor prognostic factors
6-year-old overweight Labrador that collapsed after running alongside a bicycle at midday in July. He arrives 2 hours later; the owners did not cool him. He is stuporous, with congested mucous membranes and a rectal temperature of 41.2 °C.
| Parameter | Result | Reference |
|---|---|---|
| Nucleated red blood cells | 32/100 white cells | 0–1/100 |
| PCV | 58% | 37–55% |
| ALT | 95 U/L | 10–100 |
Which of these admission findings is most clearly associated with a poor prognosis?
chevron_right Show answer and explanation
A. Rectal temperature on admission: the higher it is, the worse the prognosis
Temperature on arrival depends on the elapsed time and whether the dog was cooled, and has not proved a good predictor of survival. A dog that is normothermic on arrival can still have severe organ damage.
B. A high PCV due to haemoconcentration
Haemoconcentration is common because of dehydration and fluid shifts, but it is not a specific prognostic marker.
C. A mild increase in ALT on admission
Heat-induced liver damage becomes evident over the following hours to days; a mildly raised ALT on arrival does not discriminate outcome well.
D. A markedly increased number of nucleated red blood cells on the smear
Correct. Release of nucleated red blood cells reflects thermal damage to the marrow and endothelium, and a marked increase has been associated with mortality in dogs with heatstroke. Hypoglycaemia, coagulopathy and persistent azotaemia also worsen the prognosis.
lightbulb Key takeaway
In heatstroke, delayed cooling and arrival, obesity, coma or seizures, hypoglycaemia, DIC and markedly increased nucleated red blood cells worsen the prognosis. Many deaths occur within the first 24 hours: monitor glucose, coagulation, renal function and neurological status.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.