Hyperthermia

Hyperthermia



Basic Information image



Definition


An increase in body temperature without an alteration in the body temperature set point



Epidemiology


Caused by an increase in heat production, impaired heat loss, or absorption of heat beyond the ability of the body to compensate



Genetics and Breed Predisposition




• Quarter Horses are genetically prone to malignant hyperthermia (MH).


• Draft horses are predisposed to anhydrosis, which can induce hyperthermia.



Geography and Seasonality


Hot, humid weather may predispose to heat stroke as well as anhydrosis.



Clinical Presentation



Disease Forms/Subtypes




• Heat stroke (Figure 1)


• Exercise- or seizure-related hyperthermia


• Anhydrosis


• MH


• Drug or toxin reaction


• Central nervous system (CNS) disorders


image image image

FIGURE 1 The consequences of heat stroke after becoming tangled in a fence in right lateral recumbency. A shows the acute edema of the neck (arrow) and localized swelling in the throatlatch. B (right mandible) and C (right flank) were taken 10 days later, where extensive tissue necrosis has occurred. Coagulation abnormalities were noted by increased bleeding times and right jugular thrombosis. Acute laminitis without rotation also developed.



History, Chief Complaint




• Depression


• Excessive sweating or unusual lack thereof


• Increased respiratory rate


• Seizures


• Weakness or collapse



Physical Exam Findings




• Elevated rectal temperature (>106° F)


• Altered mentation


• Hyperemic mucous membranes ± a toxic line


• Tachycardia


• Tachypnea


• Petechiation


• Myopathy


• Synchronous diaphragmatic flutter



Etiology and Pathophysiology


Depends on the initiating cause of hyperthermia:



• Heat stroke occurs when environmental factors elevate the body temperature above 107° F (41.5° C).


image Sweating and dehydration may increase the risk because of electrolyte imbalances.

image Vasoconstriction, reduced cardiac output, and decreased blood pressure initiate circulatory shock and may lead to disseminated intravascular coagulation (DIC), multiorgan failure, and death.

• Anhydrosis is caused by the loss of the ability to sweat.


image Unknown etiology

image Draft foals may be susceptible

image Hot, humid climates predispose
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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Hyperthermia

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