Superficial brain is cooler in small piglets: neonatal hypothermia implications.
OBJECTIVE
Hypothermia was not neuroprotective in low body weight (BW) infants on subgroup analysis in a recent clinical trial of selective head cooling (SHC) in neonatal encephalopathy (CoolCap Trial).


METHODS
The BW dependence of regional cerebral temperature was investigated in 14 newborn piglets under normothermia (38.5 degrees C), whole-body cooling (WBC; 36.5, 34.5, 32.5, and 30.5 degrees C), or SHC (20, 15, and 10 degrees C).


RESULTS
Normothermia: Lower BW led to lower superficial brain temperature (p < 0.01). Deep to superficial brain and rectal to superficial brain temperature gradients increased with decreasing BW (both p < 0.05). WBC: Lower BW led to lower superficial brain temperature and higher rectal to superficial brain temperature gradient (p < 0.05 and p < 0.01, respectively). SHC: For lower BW, superficial and deep brain temperatures decreased (p < 0.01 and p < 0.05, respectively), whereas rectal to deep, rectal to superficial, and deep to superficial brain temperature gradients increased (p < 0.05, p < 0.01, and p < 0.05, respectively). Compared with SHC alone, superimposition of WBC (34.5 degrees C) reduced all regional temperatures (all p < 0.001); gradients were unaffected.


CONCLUSIONS
Brain cooling (under normothermia, WBC, or SHC) was more efficient with lower BW due to greater head surface area-to-volume ratios. In the CoolCap Trial, low BW infants might have been excessively cooled. WBC and SHC may require BW adjustment to accomplish consistent regional temperatures and optimal neuroprotection.
Iwata
Sachiko
S
Centre for Perinatal Brain Research, Institute for Women's Health, University College London, The Rayne Institute, London, United Kingdom.
Iwata
Osuke
O
Centre for Perinatal Brain Research, Institute for Women's Health, University College London, The Rayne Institute, London, United Kingdom.
Thornton
John S
JS
Lysholm Department of Neuroradiology, National Hospital for Neurology and Neurosurgery, London, United Kingdom.
Shanmugalingam
Shanthi
S
Centre for Perinatal Brain Research, Institute for Women's Health, University College London, The Rayne Institute, London, United Kingdom.
Bainbridge
Alan
A
Department of Medical Physics and Bio-Engineering, University College London Hospitals NHS Foundation Trust, London, United Kingdom.
Peebles
Donald
D
Centre for Perinatal Brain Research, Institute for Women's Health, University College London, The Rayne Institute, London, United Kingdom.
Wyatt
John S
JS
Centre for Perinatal Brain Research, Institute for Women's Health, University College London, The Rayne Institute, London, United Kingdom.
Cady
Ernest B
EB
Department of Medical Physics and Bio-Engineering, University College London Hospitals NHS Foundation Trust, London, United Kingdom.
Robertson
Nicola J
NJ
Centre for Perinatal Brain Research, Institute for Women's Health, University College London, The Rayne Institute, London, United Kingdom.
D000818:Animals; D000831:Animals, Newborn; D001831:Body Temperature / Q000502:physiology*; D001835:Body Weight; D001921:Brain / Q000378:metabolism*; D001930:Brain Injuries / Q000628:therapy; D007035:Hypothermia; D007036:Hypothermia, Induced; D008297:Male; D013552:Swine