Revisiting the pathophysiology of heatstroke

Heat stroke is an extremely lethal syndrome, caused by high core body temperature. It is characterized by the inability to dissipate heat during exposure to hot environments, or during intense physical exercise under heat stress.

It has been described innumerous times, and in 2017 Bruchim, Horowitz and Aroch wrote an article revisiting the pathophysiology of this syndrome.

Here is a sum up of some important considerations mentioned in the article.

Predisposing factors:

• Global climate and weather patterns (e.g., heat waves)
• High body weight or obesity
• Breed predisposition (e.g., brachycephalic breeds)
• Lack of fitness
• Lack of acclimation to heat stress
• Hot and humid environments

Systemic assessment:

• Heatstroke in dogs is described by core temperatures above 41^oC, with central nervous system dysfunction.
• Heat stress results in several alterations in the dog’s physiology having severe consequences in its cardiac output, blood flow distribution and metabolic processes.
• Hyperthermia and dehydration happen and result in hypotension and consequently shock.
• Shock can lead to major organs ischemia and hypoxia of tissues. Intestinal ischemia and hypoxia lead to hyperpermeability.
• Hyperthermia causes inflammatory and hemostatic processes that end up causing systemic inflammatory response syndrome (SIRS), which can progress to multiple organ dysfunction syndrome (MODS).
• Combination of heat stress, severe hypovolemic, distributive shock, metabolic acidosis, neurologic dysfunction, endotoxemia and disseminated intravascular coagulation (DIC) result in serious complications such as rhabdomyolysis, neurological damage and dysfunction, acute kidney injury (AKI), cardiac arrhythmia, acute respiratory distress syndrome (ARDS), hepatobiliary damage, sepsis, acute pancreatitis and DIC.

Diagnostic: Should be based on the combination of anamneses, clinical signs, and laboratory results, and not exclusively on presence of hyperthermia or neurological abnormalities upon admission.

Treatment: Should be intensive and prolonged, since a lot of the complications have delayed beginnings and most of them can be major risk factors for death.

In conclusion, heatstroke in dogs is a very serious condition that can threaten life or result in severe secondary complications, having a high mortality rate.

Bruchim, Y, Horowitz, M, Aroch, I, Pathophysiology of heatstroke in dogs – revisited, 2017, Temperature, VOL. 4, NO. 4, 356–370. DOI: 10.1080/23328940.2017.1367457