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Dogs and Heatstroke

Oh the joys of a San Diego summer! The puppies are in bloom, daylight is abundant & the weather gets us outdoors with our best 4-legged pals. A few simple considerations help protect our pets in summertime: minimize sunburn
in light thin-coated pets or those with actinic dermatosis (skin disease from sun exposure). White pets, especially cats prone to squamous cell carcinoma or bull breeds prone to hemangiomas, sometimes small or numerous
purple-red tumors frequently seen on undersides while bull breeds should be coaxed to shade or slathered with sunscreen. We protect dogs walking on blacktop pavement with booties & choose shaded paths. We buy doggie goggles
for cataract-prone breeds. We can do a lot.

0446379001525973803.jpgThen there’s this: Heatstroke, a nagging fear for all informed dog owners as temperatures rise. It’s of greater concern for dogs with a health quirk or two. Under the wrong conditions, any pet is at risk but is a watchword forbrachycephalic (short-faced) breeds such as Bulldogs, Bostons, Pugs & Chows prone to Brachycephalic Airway Syndrome (anatomic differences compromising respiratory cooling). Dogs with laryngeal paralysis, bronchitis, heart disease or anemia similarly suffer a functional challenge to cooling. Sitting in car “with the windows cracked just for a minute” is illegal for a reason and is easily avoided by responsible pet owners. We can choose not to exercise them during mid-day since loyal relatively healthy dogs, like kids, don’t limit themselves; instead they strive to please us. We don’t leave a dog with water & shade that looked to be enough in the morning but really isn’t enough at 2pm. Those would have all become unfortunate ways to get too familiar with this deadly summertime curse.

Heatstroke is more unpredictable than anyone would like since two pets in the same environment may not have the same risk for developing it & one who once tolerated certain conditions without problems may not avoid heatstroke the next time. Heatstroke’s more likely in dogs with heart or vascular issues (diagnosed or not), older or overweight dogs. Sadly, it’s much more likely in pet’s with previous injury to the brain’s thermoregulatory center during a previous heatstroke. Frustrated vets & owners see how an exposure lasting mere minutes can cause it, and struggle with how rapidly & aggressively we are required to intervene medically to preserve the chances of survival (which are only 40-65%). Even if the dog appears to stabilize quickly or apparently “recover” it can take days for some life-threatening damage to appear. Diagnostics and emergency care for heatstroke are extensive & time consuming. So, summer is never as long as many of us like, but neither is the time you have to get your dog evaluated by a doctor if you have any suspicions of possible heatstroke. Some pet medical conditions can be contemplated at home or evaluated over time with a watch & wait stance. First aid can be helpful for some animal health conditions. This isn’t one of them.

0019079001525973861.jpgIf the thermometer isn’t at hand, I advise you just find the car keys & put windows down & A/C on (yes, do it) as you drive to your vet. A maximum rectal temperature reading before any cooling is attempted can be helpful for your vet to know, but delays of just minutes can drop your dog’s chances of survival significantly. I recommend placing wet towels on theback of the neck, in the armpits & groin as long as they do not hamper the dog’s ability to breathe deep. Do not under any circumstances try to force a possible heatstroke dog to drink or immerse her to cool water or ice. Overcooling below 103 degrees Farenheit or stressing the gut can be fatal.

Heatstroke is a constellation of damage & malfunction resulting from a body temperature (usually over 105F) which first overwhelms the brain’s thermoregulartory center & its ability to correct to the body’s metabolically-required set point. When the body’s overwhelmed, triggering heat-dissipating mechanisms like dilating the surface vessels & panting
fails. Outside the range of normal body temperature, a catastrophic cascade of organ-system malfunction & damage snowballs until nearly every function is crippled by heat or the failure of upstream systems. The elegant web of physiology is what draws me to medicine, but it’s the Achilles Heel in heatstroke when virtually no system is spared.

0624922001525973905.jpgWhen overwhelmed by heatstroke, the brain can suffer damage which lessens the pet’s ability to protect themselves from heat. The heart & lungs then labor under ever-increasing demands to cool & circulate oxygenated blood which protects tissues. While at work, the heart & lungs sustain heat damage & further injury from other tissues which are not receiving the blood they need. The body dilates the vessels to cool itself then asks the heart to pump harder & faster, despite dehydration and possible arrhythmias. The heart may hemorrhage & its cells can die. That’s a recipe for “cardiogenic shock” in addition to the hypovolemic (low blood volume) shock but toxic shock (from bacteria crossing damaged gut) then joins the mix. When the liver can’t make enough clotting factors, coagulation is over-activated & the kidneys lose function it’s a recipe for a poor prognosis. Shock is a condition of dangerously low circulation to vital tissues resulting in cellular injury, inadequate tissue function and death. Vets are taught “the gut is the shock organ in the dog” (the respiratory system is the cat’s) meaning any shock tends to first & most severely affect that organ. Heatstroke is very “shocky.” The frequent bloody stools caused by gut lining cell death which these pets usually suffer not only consumes clotting factors, it also then compromises coagulation. It also allows gut bacteria & their toxins get right into the bloodstream. Overall, heatstroke's a recipe for disaster which quickly & reliably threatens lives.

Veterinarians evaluate heatstroke dogs for injuries such as coagulation & vascular issues, heart and lung dysfunction, organ failure, acid-base & electrolyte abnormalities, GI & neurologic damage. The extent of the disease can take at least 3 days to develop and early treatment is critical and can be rewarding. In addition to controlled active cooling, treatments
include hydration and those to replace lost blood from the GI tract, impaired coagulation ability and to support healthy circulation. We attempt to minimize gut injury and promote healing while controlling and preventing infection from the gut. We support breathing, manage heart and lung injury and supplement oxygen if necessary while protecting and
improving airway function. Some dogs develop cerebral edema or hemorrhage and require intense management for those conditions. Any metabolic abnormalities such as electryolyte disturbances, blood sugar drops, liver or kidney damage or failure must be intensely monitored and supported. If you think your dog has been diagnosed with heatstroke and you will be taking him home "all better" that night, think again. If you think that sentence is suggesting you should just "keep an eye on him" & not go to the vet NOW, then I need you to go to the top of this post and start reading again and repeat as needed. As you can see, this is one preventable disease that you want to prevent at all costs.

Though I ABSOLUTELY do not feel the pet owner should attempt to evaluate whether their dog is having heatstroke since any whiff of a maybe should put you and your dog on the road to the vet (and who is going to bet their dog's life on Dr Google?), I will give you a brief list of some of the basic signs and information we would see with the pet just to come full

  • evidence of underlying disease or event/condition precipitating heatstroke or previous heatstroke
  • muddy gums/slow capillary refill time/rapid heart rate/weak pulses/abnormal heart rhythms
  • frantic panting/respiratory distress/hypersalivation
  • high temperature (though we may have missed it when the dog overheated hours ago and now is suffering after effects only)
  • decreased mentation/glassy eyes/seizures/coma
  • bruising on belly or ears/small bruises on gums
  • cold extremities
  • swollen painful distended abdomen
  • low urine production
  • fluid-filled bowels/bloody diarrhea

Gee, Jayme, you're just a hoot today!!!! Yeah, I am just trying to keep all the pets in the funzone, you know? Also, if you leave your pet in the car around here, I doubt the police will have time to come and rescue her, though they will, as some of my neighbors are known to rescue first and ask questions later ;-) Everyone please take the time to check on your pet
during summer daytime fun, don’t let them overdo it just to be part of the games with you and the other dog park pets. Please be sure you can both go home just a little sleepy and able to do it again tomorrow.

Thanks to Barbara and D.O.G.S. Dog Owners of Grape Street Park. This volunteer organization publishes the newsletter I contributed a brief version of this article for, who suggested such a timely and important topic and who keeps our dog park safe and fun for everyone!

Have a Happy and Safe Pet-Lovin' Summer!

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