title: The effect of continuous or pulsatile administration of oxytocin to ewes at 126 to 136 days' gestation on myometrial activity and fetal oxygenation.
abstract: Oxytocin was infused either continuously or in pulses to pregnant ewes to compare the responses of myometrial activity (contractures) and changes in fetal arterial PO2. Group 1 (n = 5) was infused with saline solution throughout the experiment. In group 2 (n = 5) oxytocin was infused continuously (160 microU.kg-1.min-1) for 7 days whereas group 3 (n = 5) ewes received 960 microU.kg-1.min-1 for 5 minutes every 30 minutes for 7 days. Contracture frequency increased in both oxytocin-infused groups. With continuous infusion contracture frequency returned to preinfusion levels during the last 4 days of infusion, whereas the pulsatile infusion contracture frequency remained increased throughout the infusion period. Fetal arterial PO2 was decreased throughout the 7 days of infusion in both oxytocin-infused groups. Pulsatile group fetal arterial PO2 levels remained decreased after the oxytocin infusion was stopped. These findings show: (1) Myometrial response to oxytocin in late pregnant ewes is influenced by the mode of administration; (2) administration of oxytocin to pregnant ewes resulted in a decrease in fetal PO2, and thus fetal hypoxemia cannot be attributed exclusively to increased contracture frequency.
authors.affiliation: Department of Physiology, New York State College of Veterinary Medicine, Cornell University, Ithaca 14853.
authors.forename: G
authors.initials: G
authors.lastname: Pimentel
authors.forename: E R
authors.initials: ER
authors.lastname: Poore
authors.forename: P W
authors.initials: PW
authors.lastname: Nathanielsz
mesh_terms: D000818:Animals; D001784:Blood Gas Analysis / Q000662:veterinary; D002245:Carbon Dioxide / Q000097:blood; D005260:Female; D005312:Fetal Blood / Q000378:metabolism*; D006454:Hemoglobins / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007262:Infusions, Intravenous / Q000662:veterinary; D010100:Oxygen / Q000097:blood*; D010121:Oxytocin / Q000008:administration & dosage / Q000494:pharmacology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects*; D012756:Sheep; D014590:Uterine Contraction / Q000187:drug effects*
chemical_list: D006454:Hemoglobins; D002245:Carbon Dioxide; D010121:Oxytocin; D010100:Oxygen