Some areas of the country, especially Central Otago are forecast to have some particularly high temperatures again this summer.
This will increase the incidence of heat stress related illness and heatstroke emergency cases in our veterinary patients.
- Heatstroke is the severe illness that can occur when the animal’s body temperature goes above 40 degrees C, causing neurological and cardiac depression. This may rapidly progress to multi-organ failure and death.
- Be especially careful not to leave a pet unattended in the car. In less than 40 minutes the temperature inside a vehicle can reach over 60 degrees Celsius, even in a light coloured vehicle with the windows partly opened.
- Mild heat stress illness cases may have a normal to only slightly increased body temperature but have clinical signs of discomfort, muscle cramps (lameness or reluctance to run) due to water and sodium depletion, weakness, anxiety and fainting.
- Exertional heatstroke is associated with strenuous exercise and is more commonly seen in working dogs, particularly in the summer.
Dogs lose 70% of their excess heat through conduction (contact with a cooler surface),
radiation (releasing heat off the body) and convection (transfer to surrounding cooler air as it passes over the animal).
The other 30% they lose by panting to increase the evaporation of body water into water vapour.
All of these mechanisms become less efficient as the environmental temperature and humidity increase.
Predisposing factors for Heatstroke:
- Cardiovascular disorders
- Neurologic or muscular disease
- Thick hair coat, dark hair coat. (Consider clipping the dog in the summer) .
- Upper airway disorders (short nose, long soft palate, laryngeal paralysis ) that reduce the dogs ability to pant effectively
- Lack of acclimatization to heat and exertion
- Confinement with limited ventilation or shade
- Water deprivation
- Medications (diuretics, heart medications, sedatives)
There are physiological protection mechanisms that help protect the heart, muscles and kidneys of acclimatized individuals ( fit working dogs , human marathon runners etc) , but this acclimatization process takes several weeks and their organs may still be overwhelmed in cases of severe hyperthermia with subsequent damage to the gastro-intestinal tract and the blood coagulation, renal, cardiac , pulmonary and central nervous systems.
Emergency veterinary treatment is centred on active cooling, restoration of the patient’s circulation status and measures to try and prevent multi-organ failure.
Actions the owner can take to improve the chance of recovery.
- Don’t submerge the patient in deep water due to the risk of drowning if neurologically impaired.
- Actively cool the patient while on the way to the clinic. Apply cool water to the coat or place wet towels over it in conjunction with open car windows or air conditioning. This assists in heat dissipation through evaporation and convection.
- Do not submerge the patient in iced water or use ice packs because this may cause constriction of surface blood vessels and impair the heat loss process.
- Hugh Hasselman