title: Oxygen concentration and pulmonary hemodynamics in newborn lambs with pulmonary hypertension.
abstract: The effect of oxygen concentration on lowering pulmonary vascular resistance (PVR) during resuscitation in a model of persistent pulmonary hypertension of the newborn (PPHN) is not known. PPHN was induced in fetal lambs by ductal ligation 9 d before delivery. After delivery by cesarean section, resuscitation of PPHN lambs with 21%, 50%, or 100% O2 (n = 6 each) for 30 min produced similar decreases in PVR. Lambs were then ventilated with 50% O2 for 60 min and exposed to inhaled nitric oxide (iNO, 20 ppm). Initial resuscitation with 100% O2 significantly impaired the subsequent response to iNO compared with 21% O2 (42 +/- 9% vs 22 +/- 4% decrease from baseline PVR). Finally, each lamb was randomly and sequentially ventilated with 10%, 21%, 50%, or 100% O2. PVR decreased with increased concentrations of inhaled O2 up to 50%, there being no additional decrease in PVR with 100% O2. When PVR was correlated with Pao2, the maximal change in PVR was achieved at Pao2 values <60 mm Hg. We conclude that resuscitation with 100% O2 does not enhance pulmonary vasodilation compared with 21% and 50% O2, but impairs the subsequent response to iNO in PPHN lambs. Hypoxia increases PVR but hyperoxia does not confer significant additional pulmonary vasodilation in lambs with PPHN.
authors.affiliation: Department of Pediatrics, State University of New York, Buffalo, New York 14214, USA. slakshmi@buffalo.edu
authors.forename: Satyan
authors.initials: S
authors.lastname: Lakshminrusimha
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Swartz
authors.forename: Sylvia F
authors.initials: SF
authors.lastname: Gugino
authors.forename: Chang-Xing
authors.initials: CX
authors.lastname: Ma
authors.forename: Karen A
authors.initials: KA
authors.lastname: Wynn
authors.forename: Rita M
authors.initials: RM
authors.lastname: Ryan
authors.forename: James A
authors.initials: JA
authors.lastname: Russell
authors.forename: Robin H
authors.initials: RH
authors.lastname: Steinhorn
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001794:Blood Pressure; D004195:Disease Models, Animal; D006439:Hemodynamics; D006976:Hypertension, Pulmonary / Q000503:physiopathology*; D008168:Lung / Q000378:metabolism* / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism*; D012151:Resuscitation; D012756:Sheep; D013997:Time Factors
chemical_list: D009569:Nitric Oxide; D010100:Oxygen
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