title: The effect of a low-dose infusion of ritodrine on cardiac output distribution and uteroplacental blood flow in unanaesthetized pregnant guinea pigs.
abstract: Cardiac output and its distribution were measured using the microsphere technique before and at 2 and 6 h during the infusion of ritodrine, 1.5 microgram X min-1 X kg-1 i.v., into near-term pregnant guinea pigs. Average cardiac output increased 16 and 25%, and total peripheral resistance decreased 16 and 19% after 2 and 6 h of ritodrine infusion. The carcass and gastrointestinal tract together received two-thirds of the extra cardiac output. Uteroplacental blood flow and uteroplacental vascular resistance were not significantly different from the preinfusion values after 2 h of ritodrine treatment, but were increased 35% and decreased 31%, respectively (p less than 0.05 and less than 0.01), after 6 h of infusion. The increase in uteroplacental blood flow between the 2- and 6-h measurements was positively, and the decrease in uteroplacental vascular resistance negatively correlated with the increase in cardiac output during the same period.
mesh_terms: D000818:Animals; D002302:Cardiac Output / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D007262:Infusions, Intravenous; D008863:Microspheres; D010920:Placenta / Q000098:blood supply* / Q000187:drug effects; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects*; D012039:Regional Blood Flow / Q000187:drug effects; D012312:Ritodrine / Q000008:administration & dosage*; D013997:Time Factors; D014599:Uterus / Q000098:blood supply* / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D012312:Ritodrine