a. Most anesthetics are potent inhibitors of the compensatory responses
to even mild hypothermia: shivering and vasoconstriction, in addition to
their ability to lower the hypothalamic threshold for cold response by as
much as 3 to 5°C. Versed, tested at doses exceeding those used for pre-
medication, only lowers the point at which thermogenic controls
respond to cold by 0.2° to 0.7°C. It also has less of an effect on the ability
to respond to cold. Nitrous oxide similarly has less effect on thermoregu-
lation when compared to other more potent volatile anesthetics.
4. Which anesthetic technique will safely avoid the risk of hypothermia?
a. total intravenous anesthesia
b. spinal/epidural anesthesia
c. local infiltration anesthesia
d. none of the above
d. None of the above. Propofol, fentanyl and remifentanyl, frequently
used in TIVA techniques, produce significant changes in thermoregu-
lation and place the patient at risk of developing hypothermia.
Regional anesthesia impairs both central and peripheral thermoregu-
lation. Regional techniques produce vasodilation and impair ther-
moregulation by blocking autonomic signaling. This results in core
hypothermia similar to that seen with general anesthetics. Because
peripheral skin sensation is altered by regional anesthesia, this
hypothermia is often not perceived by patients and can cause a poten-
tially dangerous clinical paradox: a hypothermic patient who denies
feeling cold. Patients under regional anesthesia can shiver in non-
blocked areas even though they do not feel cold. All thermoregulatory
responses are neurally mediated; anything that blocks accurate neural
input and output will affect thermoregulation and place the patient at
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