Preventing & treating heatstroke with Dr. Kelly
by Kelly Dunham, DVM
Sure, it’s been hot outside, but a lot of people don’t realize that even when the temperature isn’t particularly high the humidity can play a huge factor in heatstroke as well. And boy, has it been humid!
When talking to clients about the risks of heat stroke it’s important to educate owners on the normal physiology of their furry friends. Since cats and dogs can’t sweat like we do they are more prone to overheating and can not cool off as quickly. If their dog or cat is anything like my dog, they won’t stop running around to take a break to cool down, or drink some water and will just keep going until they drop.
Even if it’s not hot or humid outside, just a few minutes in a car can prove fatal. Last summer there was a news story about a golden retriever who died from heat stroke after being left in the car while the owners stopped in for lunch even though the AC was running. It can happen to anyone, and it can happen fast.
Signs of heatstroke
Initial signs of overheating can be difficult for our clients to notice right away. Things like excessive panting and excessive drooling can sometimes be missed. The more advanced signs of difficulty breathing, vomiting, diarrhea, weakness, incoordination, collapse and seizure tend to be what get’s their attention, and what we’re seeing in hospital.
On the way into the hospital the owners can start cooling their pet by applying rubbing alcohol to the paw pads, providing cool (but NOT cold!) water and covering their pet with cool to lukewarm soaked towels. Many owners will want to use cold water or ice, but this can this cause hypothermia, sudden blood pressure changes, and can actually decrease cooling due to vasoconstriction.
So… What are we going to see?
For pets experiencing heat stroke rectal temperatures usually exceed 105F. However, if the owner instituted cooling at home, sometimes the pet will come in normothermic or worse, hypothermic. If the pet was overcooled and presented hypothermic this is a poor prognostic indicator as extreme temperature swings and sudden blood pressure fluctuations can contribute to additional damage.
Once a critical temperate of 109F is reached normal cellular enzyme activity and cell membrane stability is altered. These pets will typically present obtunded or comatose, and unfortunately, they do not usually survive.
Treating heatstroke in the clinic
When presenting with heatstroke, a physical exam will typically reveal tachypnea, tachycardia +/- cardiac arrhythmias, +/- shock and spontaneous bleeding. In some cases, patients can experience seizure activity and present obtunded or comatose. Mucus membranes will often be muddy or pale with an extended CRT. If the patient presents with cold extremities and poorly palpable peripheral pulses this indicates severe shock.
Diagnosis CBC, Chem and Coag panels should be run. Nucleated RBCs are seen in 90% of dogs with heatstroke. Anemia, thrombocytopenia, elevated CK, ALKP, and ALT are also commonly seen in 80-97% of affected pets. Cellular death and rhabdomyolysis can also contribute to hyperkalemia.
Hypoxia can contribute to a metabolic acidosis with a compensatory respiratory alkalosis which will need to be corrected. Pets with elevated renal values and/or coagulation disorders (elevated coag panel) related to heatstroke have an increased mortality up to 24 hours after the heatstroke event.
Pending the level of heatstroke and shock, you should also consider thoracic radiographs to evaluate for ARDS/ pulmonary edema, BP levels, ECG to evaluate tachycardia and arrhythmias +/- Ultrasound.
We know the pet has heat stroke, we know to what degree, now what?
Cooling as heatstroke treatment
Alcohol should be applied to the paw pads, pinna and other thinly haired areas, cool water soaked towels can be applied and frequently changed out and fans can be used to improve heat dissipation through evaporation.
In pets with thick hair coats, shaving is required to prevent the wet coat from acting as an insulator, trapping heat in. Ice baths and packs as well as cold water enemas and gastric lavage should be avoided as this can contribute to vasoconstriction and either reduce heat dissipation or overcool the pet causing hypothermia. Cooling should be stopped once the pet reaches 102-103F to prevent hypothermia.
Depending on the degree of heatstroke and shock additional therapies such as oxygen, fluid, dextrose, mannitol and antibiotic therapy may also be instituted. Due to the GIT involvement bacterial translocation may occur. Antibiotics and gastroprotectants can be used to mitigate this as well as prevent further GI ulceration.
Depending on the degree on heatstroke, once stabilized, you’re not out of the woods yet. Heatstroke patients should be monitored closely for a minimum of 24-48 hours as complications such as DIC, renal failure, hypoglycemia and cardiac arrhythmias may still develop after initial presentation.
How can we prevent it? On hot, humid and sunny days, owners should keep their pets, but especially brachiocephalic, elderly, obese and/or sick pets (as they are most at risk) inside and enjoy the air conditioning. Pets should never be left in a vehicle or on hot and humid days in other confined spaces.
Keeping pet owners educated on the dangers of heatstroke and how to prevent it is key. To learn even more about preventing and treating heatstroke, check out Episode 11 of our podcast, The IndeVets Happy Hour – part of our “Hot Pet Summer” series on common warm weather issues affecting your pets.
Kelly Dunham is IndeVets Area Medical Director for the Greater NYC region.