Exam 4 - Canine Heatstroke Flashcards
what is heat stress?
perceived discomfort & physiological strain associated with exposure in a hot environment
what is heat exhaustion?
mild o moderate illness due to water or salt loss
thirst, weakness, discomfort, anxiety, fainting
core temperature may be normal, low, or slightly elevated
what is heat stroke?
core body temperature > 105.8 F
central neurologic dysfunction
varying degrees of organ dysfunction
what are the 2 types of heat stroke?
environmental (classic) - due to high temperatures
exertional - due to strenuous exercise
or combination of both
what are some examples of causes of heat stroke?
exercise/heat, seizures, pyrexia, eclampsia, amphetamines, metalaldehydes, macademia nuts, organophosphates
what are some risk factors associated with heat stress?
intact male, geriatric, brachycephalic, dense/dark hair coat, CV disease, neuro disease, confinement, humidity, furosemide, b-blockers, & phenothiazines
why is acclimatization important in animals? what are some components?
gradual adaptation to increasing temperatures
increased CO, activation of RAAS, salt conservation, water conservation, increased GFR, & resistance to rhabdomyolysis
how long does the acclimatization process take?
takes 60 days but starts in 10-20 days
what are the effects of increasing heat on the hypothalamus?
temperature increases <2F activates thermoreceptors
renal & splanchnic vessel constriction, cutaneous vasodilation, activation of RAAS, catecholamine release, & activate panting center
why is it important that nearly all cells produce heat shock proteins?
it helps stabilize other proteins & cellular integrity
protects against oxidative stress
decreased production with age & genetics
what is the acute phase response in regards to the effects of heat in cells?
immune & inflammatory response - can be protective or destructive
what is the difference between humans & animals when it comes to adapting to heat?
humans acclimate by increasing the sweat response
animals are more dependent on evaporation - especially when the temp is > 89.6 F - panting increases evaporation from oronasal mucosa
T/F: evaporation stops being useful when humidity is > 80%
true
what are the damages seen when an animals temperature hits 105.8? 109.4? 120.2?
105.8 - possible permanent CNS damage
109.4 - severe tissue injury
120.2 - tissue necrosis
what is the shock organ of the dog?
gi tract
what are some clinical signs seen in a dog with heat stroke?
CNS depression, petechia, panting, dry MM, absent/rapid CRT, vomiting/diarrhea, variable pulse quality
what is the best way to cool a heat stroke animal off?
put a cold t-shirt on them, iv fluid therapy, & put fans on them - stop at 103/104F
what are some less effective ways to cool a heat stroke animal off?
cold IV fluids, ice water bath, ice water lavage, & ice water enema
what is happening inside the body at 106-107F temperatures?
endotoxin translocation from the gi tract
apoptosis in liver, spleen, lymph nodes, & gi mucosa
what is happening inside the body at 109.4F?
uncouples oxidative phosphorylation
proteins denatured
what are the cardiovascular effects of heat stroke?
initially increased cardiac output - renal & splanchnic vasoconstriction
eventual decompensation - splanchnic vasodilation & cutaneous vasodilation, venous pooling, decreased circulation leads to decreased heat removal
arrhythmias are common
what are the coagulation abnormalities seen with heat stroke?
coagulation & fibrinolysis are activated by heat - consumption of coagulant & anticoagulant factors with coagulation factors remaining activated even after cooling
direct platelet activation & endothelial damage
eventual widespread thrombosis & hemorrhage
what are the mechanisms of the gi effects seen in heat stroke?
direct thermal injury & hypoperfusion & microthrombosis
what gi side effects are seen with heat stroke?
translocation of endotoxin, ileus, vomiting/diarrhea, mucosal sloughing, & protein loss
