Systemic organ and core temperatures during deep hypothermia:
Comparison of whole-body and selective head cooling for perinatal
hypoxic-ischemic encephalopathy
Abstract: Objectives: Mild hypothermia has been shown to be neuroprotective
for newborn infants with hypoxic ischemic encephalopathy (HIE). In this study,
we examined the effects of deep hypothermia on systemic and brain temperature
changes during whole-body or selective head cooling in an animal model of
perinatal HIE. Methods: Twelve piglets were studied under anesthesia and artificial
ventilation. Five ultra-sensitive, flexible, titanium, thermocouple probes were
used for continuous temperature recording from five brain regions, two kidney
regions; the thoracic aorta, the wall of the small intestine, and the rectal
lumen using single sensor probes for each. Changes in temperatures from the 10
sites were recorded continuously during baseline, 20 minutes of
hypoxic-ischemic injury; 60 minutes whole-body cooling (n=6) or selectively the
head cooling (n=6); and 60 minutes of re-warming. Results: Deep hypothermia with whole-body cooling led to uniform
drops in temperature in the five brain regions, maintaining a constant gradient
across the superficial and deep brain regions. Deep hypothermia with selective
head cooling led to larger drops in superficial than in the deep brain
temperatures. Deep whole-body hypothermia led to sharp drops in core body,
kidney and small intestinal temperatures; the latter dropping to
−11.27°C ± 3.72°C below baseline compared to
−3.32°C ± 1.52°C below the baseline with deep hypothermia
for selective head cooling (P<0.001). Conclusions: Deep hypothermia with whole-body cooling can lead to
severe core hypothermia especially of the kidney and small intestines, which
get cooled far in excess of the aortic blood. Reduced kidney and small
intestinal blood flow, and a direct cooling effect from lying on the cooling
mattress may be responsible for rapid cooling of the kidney and the intestines.
These findings underscore the need to target the core temperatures to strict
ranges, as specified in the published hypothermia trials, especially during the
transportation of infants to centers providing therapeutic hypothermia.
