Prolonged mild hypoxia alters fetal sheep electrocorticogram activity.
OBJECTIVE
To assess the effects of prolonged mild hypoxemia on fetal brain electrocorticogram (ECoG) in late gestation.


METHODS
Fetal and maternal catheters were placed under general anesthesia and animals allocated at random to receive intratracheal maternal administration of either nitrogen (n = 8) or compressed air (n = 8). Five days after surgery (125 days' gestational age), nitrogen infusion was adjusted to reduce fetal brachial artery PO2 by 25%. The targeted decrease in fetal oxygenation was maintained for 5 days while fetal ECoG activity and fetal and maternal cardiovascular variables were continuously recorded. Data are presented as mean +/- SEM and were analyzed by two-way analysis of variance (ANOVA) or two-sample t test.


RESULTS
Nitrogen infusion decreased fetal Po2 by 26% (20.5 +/- 1.7 versus 14.3 +/- 0.8) without changing fetal PCO2 or pH. Mild fetal hypoxemia was associated with fetal tachycardia and increased fetal blood pressure (P < .05). Fetal ECoG in hypoxic fetuses showed a significant decrease in the time spent in high voltage (HV) (P < .05) and an increase in the time spent in low voltage (LV) and in the number of low voltage events (P < .05). Also, a significant decrease in the proportion of 1-4 Hz and an increase in the proportion of 13-20 Hz frequencies was observed in LV events without a significant change in the frequency profile of HV events (P < .05).


CONCLUSIONS
Prolonged mild hypoxemia significantly altered fetal homeostasis as reflected by the sustained tachycardia and increased blood pressure. Fetal ECoG activity was affected significantly in a qualitatively and quantitative manner by mild prolonged hypoxemia.
Pulgar
Victor M
VM
Perinatal Research Laboratory, Department of Obstetrics and Gynecology, Center for Research in Obstetrics and Gynecology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
Zhang
Jie
J
Massmann
G Angela
GA
Figueroa
Jorge P
JP
D000818:Animals; D001794:Blood Pressure; D002245:Carbon Dioxide / Q000097:blood; D002540:Cerebral Cortex / Q000196:embryology* / Q000503:physiopathology; D004569:Electroencephalography; D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D005311:Fetal Hypoxia / Q000209:etiology / Q000503:physiopathology*; D005865:Gestational Age; D006340:Heart Rate, Fetal; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000008:administration & dosage; D010100:Oxygen / Q000097:blood; D011247:Pregnancy; D012756:Sheep
D002245:Carbon Dioxide; D009584:Nitrogen; D010100:Oxygen