Thermoregulatory vasoconstriction is comparably impaired in infants,
children, and adults given isoflurane[37]
or halothane
( Fig. 40-4
).[38]
In contrast, the vasoconstriction threshold is about 1°C less in patients aged
60 to 80 years than in those between 30 and 50 years old ( Fig.
40-5
).[39]
[40]
Nonshivering thermogenesis does not occur in anesthetized adults,
[41]
which is unsurprising because this
Figure 40-4
The core thermoregulatory threshold in 23 healthy children
and infants undergoing abdominal surgery with halothane anesthesia. Differences
among the groups are not statistically significant. Results are presented as means
± SD. (Redrawn from Bissonnette B, Sessler DI: Thermoregulatory
thresholds for vasoconstriction in pediatric patients anesthetized with halothane
or halothane and caudal bupivacaine. Anesthesiology 76:387–392, 1992.)
Figure 40-5
The vasoconstriction threshold was significantly less
in the elderly (33.9 ± 0.6°C) than in younger patients
(35.1 ± 0.3°C) during 60% nitrous oxide and isoflurane
(0.75% end-tidal concentration). Filled circles
indicate the vasoconstriction threshold in each patient; open
circles show the mean and standard deviation in each group. (Redrawn
from Kurz A, Plattner O, Sessler DI, et al: The threshold for thermoregulatory vasoconstriction
during nitrous oxide/isoflurane anesthesia is lower in elderly than young patients.
Anesthesiology 79:465–469, 1993.)
response is not particularly important in unanesthetized adults.[14]
In contrast to adult humans, nonshivering thermogenesis is an important thermoregulatory
response in animals and human infants. However, nonshivering thermogenesis in animals
is inhibited by volatile anesthetics,[42]
and it
fails to increase the metabolic rate in infants anesthetized with propofol.[43]
