Pathophysiology of heatstroke in dogs – revisited 2017 Flashcards
What temperature cut off is considered as heatstroke?
> 41°C
Which breeds are overrepresented
Golden, lab, brachycephalic, Belgian and Dutch shepherds (military dogs)
Why are brachycephalic dogs overrepresented?
ineffective evaporative ability due to stenotic nares, elongated soft palate and hypoplastic trachea and laryngeal edema
What is Hereditary exercise-induced collapse (EIC)?
Episodic limb weakness, ataxia and collapse,
has been described in Labrador retriever dogs,
and might thus account for some heatstroke cases
in this breed.
Which breed is affected by induced malignant hyperthermia?
English Springlers Spaniels
What happens?
Moderate exercise results in collapse, dyspnea,
hyperthermia and hyperlactatemia
Patophys of it
Calcium homeostasis
defect, due to ryanodine receptor (RYR) calcium
release dysfunction
What environmental factor affects evaporation in dogs?
Humidity:
>35% -> less effective
>80% -> neglected
What are the main causes of death in dogs with heatstroke?
systemic hemodynamic deterioration and pulmonary lesions (postmortem)
What is seen in brain histopathology followed by heatstroke?
cerebral
edema, hemorrhage, hyperemia, and neuronal necrosis.
Brain damage is caused secondary to…
shock, MODS, bleeding, micro thrombi more than direct brain tissue thermal injury as dogs have intrinsic thermal
resistance, protecting it from direct thermal injury.
Explain the muscle damage and rnhabdomylosis occurring in the HS
Rhabdomyolysis is a prominent feature of heatstroke
in dogs, occurring during and following the heat
insult, and is exacerbated during the first 24 hrs of
hospitalization due to skeletal and cardiac muscular
hypoperfusion, resulting from hypovolemic, distributive
shock and microthromboses, secondary to developing
DIC.
How can we confirm rhabdomyolysis in human and dogs?
What other parameter can we look at in dogs?
Human: serum and urinary myoglobin concentration.
In dogs, the human-based myoglobin immunoassays are insensitive, and currently no myoglobin immunoassay has been validated for use in dogs.
CK
What is the pathogenesis of AKI in heatstroke?
Multifactorial: direct renal thermal injury, decreased renal perfusion due to hypovolemic, distributive shock and dehydration, endotoxemia, myoglobulinemia secondary
to rhabdomyolysis, release of cytokines and vasoactive
mediators and microthromboses, associated with DIC
How is the blood pressure at presentation in animals with naturally occurring heatstroke and why?
Normotensive. Because they present in the compensatory phase (neurohormonal
compensatory mechanisms to maintain blood pressure
react fast).
List risks factors which ultimately worsen the prognosis (result of dx test on presentation, during hosp etc)
Obesity, prolonged
(>90 min) time-lag from the occurrence of the heat
insult to presentation for veterinary care, hypoglycemia
(glucose <47 mg/dL) at presentation, azotemia
(serum creatinine concentration >1.5 mg/dL) at 24 hours post presentation, and occurrence of DIC,
AKI, ventricular arrhythmia, seizures and abnormal
mental status.
What extra-cardiac mechanisms were proposed as
contributing processes to myocardial damage and
development of cardiac arrhythmias?
myocardial
hypoperfusion and injury, lactic acidosis, hypoxemia,
electrolyte imbalance and possibly, direct thermal
injury
What markers are increased in heatstroke?
Serum cardiac troponins I and T concentrations
What is an excellent prognostic marker for prediction
of secondary complications as well as survival?
Pathologic metarubricytosis (nucleated cells)
What parameters are included in their severity scoring system and predict outcome?
the PT, aPTT and hemoglobin concentration,
occurrence of petechiae,
AKI, shock, DIC and seizures
What was the sensitivity and specificity?
93% 86%
Name some potential novel molecular biomarkers
HSP72, histones
