Systemic effects of whole-body cooling to 35 °C, 33.5 °C, and 30 °C in a piglet model of perinatal asphyxia: implications for therapeutic hypothermia.
BACKGROUND
The precise temperature for optimal neuroprotection in infants with neonatal encephalopathy is unclear. Our aim was to assess systemic effects of whole-body cooling to 35 °C, 33.5 °C, and 30 °C in a piglet model of perinatal asphyxia.


METHODS
Twenty-eight anesthetized male piglets aged <24 h underwent hypoxia-ischemia (HI) and were randomized to normothermia or cooling to rectal temperature (Trec) 35 °C, 33.5 °C, or 30 °C during 2-26 h after insult (n = 7 in each group). HR, MABP, and Trec were recorded continuously.


RESULTS
Five animals cooled to 30 °C had fatal cardiac arrests. During 30 °C cooling, heart rate (HR) was lower vs. normothermia (P < 0.001). Although mean arterial blood pressure (MABP) did not vary between groups, more fluid boluses were needed at 30 °C than at normothermia (P < 0.02); dopamine use was higher at 30 °C than at normothermia or 35 °C (P = 0.005 and P = 0.02, respectively). Base deficit was increased at 30 °C at 12, 24, and 36 h vs. all other groups (P < 0.05), pH was acidotic at 36 h vs. normothermia (P = 0.04), and blood glucose was higher for the 30 °C group at 12 h vs. the normothermia and 35 °C groups (P < 0.05). Potassium was lower at 12 h in the 30 °C group vs. the 33.5 °C and 35 °C groups. There was no difference in cortisol level between groups.


CONCLUSIONS
Cooling to 30 °C led to metabolic derangement and more cardiac arrests and deaths than cooling to 33.5 °C or 35 °C. Inadvertent overcooling should be avoided.
Institute for Women's Health, University College London, London, UK.
Aron
A
Kerenyi
Dorottya
D
Kelen
Stuart D
SD
Faulkner
Alan
A
Bainbridge
Manigandan
M
Chandrasekaran
Ernest B
EB
Cady
Xavier
X
Golay
Nicola J
NJ
Robertson
D000818:Animals; D001237:Asphyxia / Q000628:therapy*; D004195:Disease Models, Animal; D006854:Hydrocortisone / Q000097:blood; D007036:Hypothermia, Induced; D008279:Magnetic Resonance Imaging; D008297:Male; D013552:Swine; D014336:Troponin / Q000097:blood
D014336:Troponin; D006854:Hydrocortisone