b. Post-anesthetic shivering can be treated with a variety of drugs.
Specifically how many of these agents prevent shivering remains
unknown. Both clonidine and dexmedetomidine reduce the vasocon-
striction and shivering thresholds, making modulation of the central
thermoregulatory center likely. Studies on meperidine suggest its effect
on shivering is modulated by non-opioid receptors as well as central
adrenoreceptors. Compared to other opioids, meperidine appears to
have the best efficacy for treating shivering.
12. Forced hot-air warming is most effective __________ .
a. pre-operatively
b. intra-operatively
c. post-operatively
d. it is not an effective means of warming
a. Most heat is lost in the first 30 minutes following induction when
warm core blood is redistributed to the colder periphery due to vasodi-
lation. Once core temperature drops, compensatory vasoconstriction of
AV shunts will begin. This constriction is limited, however, by potent
vasodilating anesthetics. Post-operatively, in hypothermic patients, the
ability to vasoconstrict in response to cold returns. The sequence of the
physiologic changes has a striking influence on the efficacy of hot-air
warmers. Forced hot-air warming devices are most effective at prevent-
ing hypothermia when applied in the pre-operative period. Normally
dilated skin vessels enable peripheral blood to gain heat in as little as 30
minutes during the pre-op period. This can significantly attenuate the
drop in core temperature during the initial redistribution of blood.
Forced hot-air devices are also somewhat helpful during the intra-oper-
ative period when anesthetically induced vasodilation allows for better
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