Comparison of postasphyxial resuscitation with 100% and 21% oxygen on cortical oxygen pressure and striatal dopamine metabolism in newborn piglets.
The present study tests the hypothesis that ventilation with 100% O2 during recovery from asphyxia leads to greater disturbance in brain function, as measured by dopamine metabolism, than does ventilation with 21% oxygen. This hypothesis was tested using mechanically ventilated, anesthetized newborn piglets as an animal model. Cortical oxygen pressure was measured by the oxygen-dependent quenching of phosphorescence, striatal blood flow by laser Doppler, and the extra-cellular levels of dopamine and its metabolites by in vivo microdialysis. After establishment of a baseline, both the fraction of inspired oxygen (FiO2) and the ventilator rate were reduced in a stepwise fashion every 20 min over a 1-h period. For the subsequent 2-h recovery, the animals were randomized to breathing 21 or 100% oxygen. It was observed that during asphyxia cortical oxygen pressure decreased from 36 to 7 torr, extracellular dopamine increased 8,300%, and dihydroxyphenylacetic acid and homovanillic acid decreased by 65 and 60%, respectively, compared with controls. During reoxygenation after asphyxia, cortical oxygen pressure was significantly higher in the piglets ventilated with 100% oxygen than in those ventilated with 21% oxygen (19 vs. 11 torr). During the first hour of reoxygenation, extracellular dopamine levels decreased to approximately 200% of control in the 21% oxygen group, whereas these levels were still much higher in the 100% oxygen group (approximately 500% of control). After approximately 2 h of reoxygenation, there was a secondary increase in extracellular dopamine to approximately 750 and approximately 3,000% of baseline for the animals ventilated with 21 and 100%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Huang
C C
CC
Department of Biochemistry and Biophysics, Medical School, University of Pennsylvania, Philadelphia 19104.
Yonetani
M
M
Lajevardi
N
N
Delivoria-Papadopoulos
M
M
Wilson
D F
DF
Pastuszko
A
A
D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D001237:Asphyxia / Q000378:metabolism / Q000628:therapy*; D003342:Corpus Striatum / Q000098:blood supply / Q000166:cytology / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D010100:Oxygen / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*; D012039:Regional Blood Flow / Q000502:physiology; D012151:Resuscitation / Q000379:methods*; D013552:Swine / Q000378:metabolism*; D013997:Time Factors
D010100:Oxygen; D004298:Dopamine