QUARTERLY BEAT / OCTOBER 2023 ///
/// QUARTERLY BEAT / OCTOBER 2023
Heatstroke in Dogs
effective in hot, humid environments. Conduction is the transfer of heat from one object to another. This is why you will often find dogs seeking a cool place to lay down, as contact with their lightly-haired abdomens on a cool surface will cause a transfer of heat. (Likewise, how patients become hypothermic lying on a cold, stainless steel gurney or surgical table in the hospital!) Convection is when the movement of air over the body allows the dissipation of heat into the environment. This is most often seen with wind or a fan. Radiation is when the body dissipates heat into the environment naturally. This is less effective as the environmental temperature reaches that of a patient’s body temperature.
to increase heat loss through the integument. The cardiovascular system aids in this by first increasing heart rate. This, along with the decreased systemic vascular resistance, will ensure maximum blood flow and subsequently maximum heat loss through the periphery. If these initial compensatory methods are not effective, the body will continue to try and cool itself; however, deleterious side effects may be seen at this stage. Patients will start to exhibit splanchnic vascular dilation which can cause venous pooling and decreased circulating volume. The lack of forward blood flow significantly decreases heat dissipation through the integument and the venous pooling from splanchnic vasodilation leads to hypotension and inevitably circulatory shock.
Under normal conditions, greater than half of a patient’s total body heat is dissipated through convection and radiation. Heatstroke can occur when the body is unable to dissipate the accumulated heat.
LEXI HANSEN, BS, LVT, RVT, VTS(ECC)
ECC Veterinary Technician Manager, BluePearl Pet Hospital Cary, NC
Beat Heat THE
In veterinary medicine, as temperatures increase during the summer, we’re often presented with the dog with heatstroke! What is Heatstroke? • Injected mucous membranes
• • • • • •
Vomiting
Diarrhea
Heatstroke is defined as a non-pyrogenic elevation in core body temperature greater than 105.8 0 F/41 0 C along with central nervous system (CNS) dysfunction. In veterinary medicine, heatstroke can be broken into two categories: exertional and environmental. Exertional heatstroke is exercise-induced or can be seen in dogs who are not acclimated to their environment. Environmental heatstroke is due to an increase in environmental temperatures and can be exacerbated by an absence of adequate cooling means such as water or shade. When a patient suspected of heatstroke shows up at your veterinary clinic, it is vital to obtain a thorough history and diagnostics. This will inevitably help direct the treatment plan, as treatment needs to be quick and aggressive for success. Patients will commonly present with a history of collapse, tachypnea, and ataxia or disorientation.
Hematemesis
Hematochezia
Melena
Temperature > 105 0 F/40.5 0 C *
• Signs of coagulopathy (e.g., petechia, bruising, erythema) • Cardiovascular collapse/shock (e.g., tachycardia, poor perfusion, weak pulses) • CNS signs (e.g., dull mentation, coma, tremors, seizures). Often, we may not have an accurate peak patient temperature, as owners often try to actively cool their pet prior to presentation (e.g., cold water, fan, air conditioning, etc.). Normal Thermoregulation The body has normal cooling methods to help maintain homeostasis, including evaporation, conduction, convection, and radiation. Evaporation is one of the most important ways that a dog can cool themselves. This occurs through panting and subsequently evaporation of water. This method of cooling is less
As the body continues to decompensate secondary to global hypoperfusion, massive cellular destruction, thermal injury, and damage or failure of vital organs can occur. Multi-organ dysfunction syndrome (MODS), where body systems become affected secondary to heatstroke, can occur; it is important to recognize how to monitor and support each system to create an effective treatment plan and monitor for decline. Body System Complications from Heatstroke Patients often present with some level of CNS dysfunction. They may present with mild CNS signs such as ataxia or dulled mentation, all the way up to seizures, coma, and even death. This can be due to the hypoperfusion of the brain, thrombi, cerebral edema, cerebral hemorrhage,
The body has a thermoregulatory center located in the anterior hypothalamus that maintains core body temperature within a very narrow set point. This thermoregulatory center in the brain is so sensitive that it can sense a non-pyrogenic change in core body temperature as little as 1 0 C. When an elevation in body temperature outside the normal set point occurs, it triggers a cascade of changes within the body to maintain hemostasis. Pathophysiology of Heatstroke Once a patient starts accumulating more heat than they can dissipate utilizing normal methods, the body will trigger compensatory pathways to aid in more aggressive cooling. The first step is to peripherally vasodilate
With heat stroke, we can see the following clinical signs: • Tachycardia • Tachypnea
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VETGIRL BEAT EMAGAZINE | VETGIRLONTHERUN.COM
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