Body temperature and stabilization in the
NICU
After completing the study to warm infants on transit
from the delivery room to the NICU, I moved forward
to examine body temperature in ELBW infants
during their first 12 hours of life. Even though we
reduced the incidence of hypothermia on admission
to the NICU, we found their temperatures decreased
during stabilization.
In my next study, I examined body temperature in
ten ELBW infants during their first 12 hours of life,
from admission in the NICU (Knobel et al., 2009).
Abdominal (central) and foot (peripheral) temperatures
were measured every minute. This exploratory
study aimed to describe maturation of thermoregulation
in ELBW infants and the ability of a newborn
ELBW infant to exhibit peripheral vasoconstriction.
In this study, none of the ten infants displayed peripheral
vasoconstriction consistently in their first 12
hours of life. Peripheral vasoconstriction is defined
as foot temperature below abdominal temperature
by 2°C. Only one infant showed peripheral vasoconstriction
for 9% of his measurements. Another
interesting and main finding of this study was that
seven of the ten infants kept their foot temperature
higher than their abdominal temperature for about
8 of their 12 hours on average. Other researchers
have seen this phenomenon but it is not widely documented
(Lyon, Pikaar, Badger, & McIntosh, 1997).
This unusual temperature pattern with the related
perfusion is concerning because the infant’s core is
not protected during episodes of hypothermia. It is
not clear from published studies if this temperature
pattern is related to immaturity or instability.
In addition to body temperature, I measured each infant’s
heart rate every minute to examine the relationship
between heart rate and body temperature during
the stabilization period. These data helped to define
the body temperature that was associated with heart
rate measures in each infant’s normal range; normal
heart rate was defined as the 25th to 75th percentile or
inner 50% of heart rate measures from all heart rate
measures observed over each infants’ 12 hour study
period. Results indicated that these infants had more
normal heart rates when their abdominal temperature
was in the 36.8-36.9 range (Knobel, Holditch-Davis,
& Schwartz, 2010). This finding provides evidence
that ELBW infants’ temperatures should be kept
slightly higher than the WHO’s recommended minimal body temperature for infants, most likely due
to their inefficient thermoregulation and capacity to
lose heat easily.