Heatstroke in small animal medicine: a clinical practice review


Address correspondence and reprint requests to:
Dr. Scott I. Johnson, 12034 Research Blvd., #8 Austin, TX 78759.
E-mail: statdvm@theanimaler.com


Objective: To review the pathophysiology, diagnosis, current treatment, and prognosis of heatstroke.

Etiology: Heatstroke can be a life-threatening condition occurring because of an imbalance of heat dissipation and production. Certain factors may predispose some animals to heatstroke. The pathophysiology and sequelae of heatstroke share similarities with that of sepsis; thus, multiple organ dysfunction often ensues. The pathophysiological derangements that occur with heatstroke result from a complex series of events associated with direct cytotoxicity of heat and initiation of the acute-phase response by endotoxin, inflammatory cytokines, and chemokines. Activation of endothelial cells, coagulation factors, and fibrinolysis (with ensuing microvascular thrombosis) leads to hypoxia and organ dysfunction. Heat shock proteins produced secondary to sudden heating act as protein chaperones or molecular guardians to provide protection against future heatstroke and may be implicated as a possible genetic component of heatstroke.

Diagnosis: A history of recent exercise or being confined in a hot and/or humid environment, combined with clinical signs such as body temperature above 40°C (104°F), panting, tachycardia, hyperemia, dry mucous membranes, and depression to prostration is consistent with a diagnosis of heatstroke. A complete blood count performed during the initial examination of dogs with suspected heatstroke often includes nucleated red blood cells.

Therapy: The mainstays for treating heatstroke include rapid evaporative cooling, volume replacement to provide cardiovascular support, and management of secondary complications.

Prognosis: The prognosis is multifactorial. There is a significant negative correlation between comatose mental status, decreased temperature, and hypoglycemia with mortality.