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HEAT STRESS (HEAT STROKE)

On Sunday, 1st Jan. 2006, we experienced the hottest day on record in Sydney and Wollongong with temperatures of 45 degrees Celsius (113 Fahrenheit) and a strong westerly wind. We had 3 dogs presented dead on arrival. Two of these were brachycephalic breeds (a British Bulldog and a young Pug) and the other an older Chihuahua with a chest condition. It was a very upsetting experience for the owners.

Should the weather forecast issue a hot day warning, make sure your pets are kept cool, have plenty of fresh water and are not left alone at home. Dogs with thick coats should have them shaved off prior to the hot season. Watch closely for signs of heat stress.

See below for treatment

Body heat regulation

Heat is produced from:

• Normal daily activities e.g. heart beating, kidneys making urine (a body’s metabolism)
  
• Food digestion
  
• Exercise

Heat loss is achieved by a number of means:

• Panting
  
• Increased respiration rate
  
• Loss of appetite
  
• Dilation of skin blood vessels
  
• Inactivity
  
• Seeking cool places
  
• Drinking water

Clinical signs of Heat Stress

• Temperature > 41 degrees
  
• Panting
  
• Dark gum colour
  
• Vomiting
  
• Diarrhoea (often bloody)
  
• Shock
  
• Collapse
  
• Loss of consciousness
  
• Loss of body’s normal control of body temperature regulation

Causes of Heat Stress

Nearly all cases of heat stress have a pre-existing disease present such as:

• Upper airway disease
  
• Cardiovascular disease
  
• Fever from an infection
  
• Dehydration from recent vomiting and/or diarrhoea
  
• Obesity
  
• Previous episode of heat stroke causing permanent damage to the brains control centre for heat regulation

Pre-disposing factors

Heat stroke in a previously healthy animal occurs in the following conditions:

• Over exertion e.g. marathon runners
  
• Locked in cars/poorly ventilated cages
  
• Effects of heat stroke on the body organs
  
• Untreated heat stroke can cause major damage to the internal organs of the body:
  
• Brain damage
  
• Blood clotting problems- either early or some days later
  
• Bloody watery diarrhoea
  
• Liver damage
  
• Kidney damage

Treatment

Immediate reduction in body temperature is critical to survival of heat stroke patients.

Preferred methods include:

• Ice bags over large blood vessels in the upper groin (femoral vein) &/or neck (jugular vein).
• Head cooling.
• Covering the body in a wet towel in the path of a fan.

NB: Remove the wet towel and dry the patient once the temperature reaches 39 degrees to avoid the temperature overshooting and going below normal.

Transfer to a veterinary hospital A.S.A.P. for further treatment involving:

• I.V. drips to correct dehydration and shock.
  
• Blood and urine tests
• Cortisone injections
• Continual intensive care monitoring