title: Hemodynamic effects of exogenous nitric oxide in ovine transitional pulmonary circulation.
abstract: To determine the hemodynamic effects of exogenous nitric oxide (NO) on the immature pulmonary circulation, we studied the response to NO inhalation in 19 mechanically ventilated late-gestation ovine fetuses in three separate protocols. In protocol 1, we examined the relative effects of 1) mechanical ventilation while maintaining fetal arterial O2 tension (PaO2) constant [fractional inspired O2 concentration (FIO2) less than 0.10)], 2) NO inhalation [5-20 parts per million (ppm)] at fetal PaO2, and 3) high FIO2 (1.00) (n = 7). NO increased left pulmonary artery blood flow (Qlpa) in a dose-dependent fashion, from 254 +/- 62 (baseline) to 398 +/- 49 ml/min with 20 ppm NO (P less than 0.001). The response of Qlpa to a FIO2 equal to 1.00 was not different from NO alone. Systemic arterial pressure was not affected by NO. In protocol 2 we studied the effects of prolonged NO inhalation (2 h, 20 ppm) during mechanical ventilation with low FIO2 (n = 4). NO increased Qlpa from 267 +/- 92 to 468 +/- 75 ml/min at 10 min of NO inhalation (P less than 0.001). The increase in Qlpa was sustained during the entire 2-h study period. In protocol 3 we measured left ventricular output (LVO), systemic vascular resistance (SVR), and ductus arteriosus shunting using radiolabeled microspheres (n = 8) during baseline mechanical ventilation and 20 ppm NO inhalation. LVO and SVR were not significantly different in the two study periods; however, the percentage of LVO that reached the lungs (predominantly left-to-right shunting across the ductus arteriosus) increased from 18 +/- 5 to 43 +/- 4% during NO inhalation.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pediatrics, Children's Hospital, Denver, Colorado.
authors.forename: J P
authors.initials: JP
authors.lastname: Kinsella
authors.forename: J A
authors.initials: JA
authors.lastname: McQueston
authors.forename: A A
authors.initials: AA
authors.lastname: Rosenberg
authors.forename: S H
authors.initials: SH
authors.lastname: Abman
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005333:Fetus / Q000187:drug effects* / Q000502:physiology; D006439:Hemodynamics / Q000187:drug effects*; D009569:Nitric Oxide / Q000494:pharmacology*; D011652:Pulmonary Circulation / Q000187:drug effects*; D012121:Respiration, Artificial; D012756:Sheep; D014655:Vascular Resistance / Q000187:drug effects; D016277:Ventricular Function, Left / Q000187:drug effects
chemical_list: D009569:Nitric Oxide