hyperthermia/fever Flashcards

1
Q

where is the thermoregulatory center located?

A

central nervous system in preoptic area of anterior hypothalamus

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2
Q

what is responsible for sensing the changes in ambient and core body temperatures (hint: these things relay information to the anterior hypothalamus via the CNS)

A

peripheral and central thermoreceptors

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3
Q

when ambient temperatures are normal, what is responsible for the body’s main source of heat?

A

muscles

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4
Q

definition of hyperthermia?

A

any elevation in core body temperature above accepted normal range

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5
Q

definition of fever?

A

hyperthermic animals in whom the set point in the AH has been reset to higher temperature

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6
Q

t/f: true fever is a normal response of the body to invasion or injury and is part of the acute phase response?

A

true

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7
Q

list other parts of the acute phase response besides fever

A

increased neutrophil numbers and phagocytosis
enhanced T and B lymphocyte activity
increased acute phase protein production by liver
increased fibroblast activity
increased sleep

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8
Q

what is responsible for initiating the acute phase response in fever? list some examples

A

exogenous pyrogens- infectious agents or their products, immune complex formation, tissue inflammation or necrosis, pharmacologic agents

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9
Q

what are the 4 different classifications of hyperthermia and give at least 1 example of each?

A

true fever- production of endogenous or exogenous pyrogens
inadequate heat dissipation- heat stroke, hyperpyrexic syndromes
exercise-induced hyperthermia- normal exercise, hypocalcemic tetany, seizures
pathologic or pharmacologic origin- lesions around anterior hypothalamus, maligant hyperthermia, hypermetabolic disorders, monoamine metabolism disturbances

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10
Q

what are the primary immune cells involved in endogenous pyrogen production?

A

macrophages

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11
Q

List the 11 endogenous pyrogens and their principal source

A

TNF-a (cachectin)-macrophages
TNF-b (lymphotoxin)- lymphocytes (T and B)
IL-1a- macrophages etc
IL-1b - macrophages, etc
IFNa- leukocytes, espec macrophages
IFNb- fibroblasts
IFNy- T lymphocytes
IL6- many cell types
macrophages inflammatory protein 1a- macrophages
macrophage inflammatory protein 1b- macrophages
IL8- macrophages

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12
Q

list examples of bacterial exogenous pyrogens

A

gram positive and gram negative bacteria

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13
Q

list examples of bacterial products that cause exogenous pyrogen production

A

LPS, streptococcal exotoxin, staph enterotoxin, staph proteins

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14
Q

fungi that cause pyrogen production?

A

fungal products, crypto polysaccharide, crypto proteins

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15
Q

nonmicrobial agents that can cause exogenous pyrogen release

A

soluble Ag-Ab complexes
bile acids
pharmacologic agents
tissue inflammation and necrosis

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16
Q

list the mechanisms for heat loss

A

radiation
conduction
convection
evaporation

17
Q

describe radiation as a mechanism for heat loss

A

electromagnetic or heat exchange between objects in the environment

18
Q

describe conduction as a mechanism for heat loss

A

between the body and environmental objects that are in direct contact with the skin, as determined by the relative temperatures and gradients

19
Q

describe convection as a mechanism of heat loss

A

the movement of fluid, air, or water over the surface of the body

20
Q

describe evaporation as a mechanism of heat loss

A

disruption of heat by the energy required to convert the material from a liquid to a gas, as with panting

21
Q
Which of the following is not recommended for total body cooling of the heat stroke patient (in this chapter) ;) ?
A- IVF therapy
B- tepid water baths
C- ice water bath
D- placing fan near animals
A

C

22
Q

Cooling should be discontinued in a heat stroke patient at what temp?

A

103 F

23
Q

heat stroke is a result of what?

A

inadequate heat dissipation

24
Q

hyperpyrexic syndrome is associated with what?

A

moderate to severe exercise and a hot/humid climate

25
Q

list the cooling options for a hyperthermic patient

A

oxygen and IV fluid therapy
surface cooling techniques
internal cooling techniques
extracorporeal techniques (antipyretic drugs)

26
Q

examples of surface cooling techniques?

A

clip fur
tepid water applied to skin/body
fan
ice packs over areas with large vessels (neck, axilla, inguinal)

27
Q

examples of internal cooling techniques?

A

rectal admin of cool isotonic fluids
gastric lavage
open body cavity
peritoneal dialysis

28
Q

examples of antipyretic drugs?

A

antiprostaglandins, dantrolene, dipyrone, aminoyrine, cox2 inhibitors, glucocorticoids, other NSAIDs

29
Q

name 2 endocrine disorders that can cause increased metabolic rate, vasoconstriction resulting in excessive heat production, decreased ability to dissipate heat?

A

hyperthyroidism and pheochromocytoma

30
Q

what is the mechanism of malignant hyperthermia?

A

disturbed calcium metabolism initiated by pharmacologic agents such as inhalation anesthetics (halothane) and muscle relaxants (succinylcholine) can cause myopathy and subsequent metabolic heat production

31
Q

how may phenothiazines be effective in alleviating true fever?

A

depressing normal thermoregulation and causing peripheral vasodilation

32
Q

list common causes of noninfectious fever in ICU patients

A

phlebitis, thrombophlebitis, post-operative inflammation, transfusion reactions, pancreatitis, hepatitis, cholecystitis, aspiration pneumonitis, ARDS, neoplasia

33
Q

what is the suspected incidence of nosocomial infections in critically ill human patients?

A

3-31%

34
Q

common sites for nosocomial infections in critically ill?

A

lungs (aspiration, VAP), bloodstream, catheters, incisions, urinary tract

35
Q

what are the benefits of a fever?

A

decreases ability of bacteria to use iron, decreases ability of viruses to replicate, increased leukocyte function

36
Q

detriments to having a fever?

A

increases tissue metabolism and O2 consumption; raises caloric and water requirements, supression in appetite center; may lead to DIC, arrhythmias, liver complications, GI signs

37
Q

exertional heat stroke and malignant hyperthermia may lead to….

A

rhabdomyolysis, hyperK, hypoCa, myoglobinemia, myoglobinuria, increased CK

38
Q

body temp >107 F may lead to what specific GI complications

A

epithelial desquamation, endotoxin absorption, bleeding