Chapter 10 - hyperthermia & fever

Question 1

where is the ‘thermoregulatory set point’ located

Answer 1

preoptic region in the anterior hypothalamus

Question 2

rectal temperature that is considered elevated

Answer 2

> 102.5 (>39.2)

Question 3

in one retrospective study of 50 dogs with fever, what percentage had a noninfectious cause?

Answer 3

almost 50% (included 14/25 with no diagnosis found)

Question 4

with normal ambient temperature, what mechanism produces the most body heat?

Answer 4

muscular activity, even while at rest

Question 5

what besides infectious agents can act as exogenous pyrogens

Answer 5

soluble Ag-Ab complexes, bile acids, bleomycin, colchicine, tetracycline, levamisole (cats), tissue inflammation/necrosis

Question 6

how do inflammatory cytokines cause fever?

Answer 6

directly bid to the vascular endothelial cells within the anterior hypothalamus and stimulate release of prostaglandins, esp PGE2 and PGF2a –> increased set point

Question 7

briefly describe the four mechanism of heat loss from the body

Answer 7

radiation: electromagnetic or heat exchange between objects in the environment
conduction: between the body and environmental objects in direct contact with the skin along temperature gradients
convection: movement of fluid, air or water over the surface of the body
evaporation: disruption of heat by the energy required to covert the material from a liquid to a gas, as with panting

Question 8

pathophysiology of malignant hyperthermia

Answer 8

drug induced (esp halothane, succinylcholine) disturbance in calcium metabolism leads to myopathy & metabolic heat production

Question 9

treatment for malignant hyperthermia and MOA

Answer 9

dantrolene sodium (muscle relaxant) - binds to ryanodine receptor, depresses excitation-contraction coupling in skeletal muscle