title: Early protective effect of hypothermia in newborn pigs after hyperoxic, but not after normoxic, reoxygenation.
abstract: Abstract Mild hypothermia can attenuate the development of brain damage after asphyxia. Supplemental oxygen during resuscitation increases generation of reactive oxygen species, compared to room air. It is unknown if supplemental oxygen affects hypothermic neuroprotection. We studied the early effects of hyperoxic reoxygenation and subsequent hypothermia on tissue oxygenation, microcirculation, inflammation and brain damage after global hypoxia. Anesthetized newborn pigs were randomized to control (n=6), or severe global hypoxia (n=46). Three pigs died during hypoxia or reoxygenation. After 20-min reoxygenation with room air (n=22) or 100% oxygen (n=21), pigs were randomized to normothermia (deep rectal temperature 39 degrees C, n=22) or total body cooling (35 degrees C, n=21) for 6.5 h before the experiment was terminated. We demonstrated a differential effect of post-hypoxic hypothermia between animals reoxygenated with 100% oxygen and with room air, with reduced damage only in hypothermic animals reoxygenated with 100% oxygen (P=0.001). Hyperoxic reoxygenation resulted in a significant overshoot in striatal oxygen tension, without affecting microcirculation. Inflammatory response after the insult did not differ between groups. The results indicate an early protective effect of hypothermia which may vary with oxygen level used during reoxygenation.
authors.affiliation: Department of Paediatric Research, University of Oslo and Oslo University Hospital, Rikshospitalet, Oslo, Norway. marit.dalen@rr-research.no
authors.forename: Marit L
authors.initials: ML
authors.lastname: Dalen
authors.forename: Tomas N
authors.initials: TN
authors.lastname: Alme
authors.forename: Berit H
authors.initials: BH
authors.lastname: Munkeby
authors.forename: Else Marit
authors.initials: EM
authors.lastname: Løberg
authors.forename: Are Hugo
authors.initials: AH
authors.lastname: Pripp
authors.forename: Tom Eirik
authors.initials: TE
authors.lastname: Mollnes
authors.forename: Terje
authors.initials: T
authors.lastname: Rootwelt
authors.forename: Ola Didrik
authors.initials: OD
authors.lastname: Saugstad
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001238:Asphyxia Neonatorum / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D001921:Brain / Q000098:blood supply / Q000473:pathology / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004195:Disease Models, Animal; D005260:Female; D015870:Gene Expression; D006801:Humans; D018496:Hyperoxia / Q000473:pathology / Q000503:physiopathology; D007036:Hypothermia, Induced / Q000379:methods*; D007231:Infant, Newborn; D007249:Inflammation / Q000209:etiology; D008297:Male; D010100:Oxygen / Q000378:metabolism; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D016133:Polymerase Chain Reaction; D012151:Resuscitation / Q000009:adverse effects / Q000379:methods; D034421:Sus scrofa
chemical_list: D016207:Cytokines; D017931:DNA Primers; D010100:Oxygen