title: Effects of hypoxia and reoxygenation with 21% and 100%-oxygen on cerebral nitric oxide concentration and microcirculation in newborn piglets.
abstract: Bioelectric sensors for continuous registration of nitric oxide (NO) concentrations in tissues provide a new tool for invasive measurement of this gaseous molecule. This study sought to validate cerebral NO measurements using an amperiometric sensor. A series of experiments in 1- to 3-day-old piglets was carried out to study the response of NO and microcirculation during hypoxia (F(i)O(2) 0.06) and reoxygenation with 100% and 21% oxygen. Two-channel laser Doppler flowmetry was performed in the forebrain cortex. Significant decreases of NO levels were observed immediately after induction of hypoxemia (p < 0.05). During reoxygenation with 21 or 100% O(2) for 30 min, NO increased significantly compared to the values at the end of hypoxia (p < 0.05). The increase of NO levels in the 100% oxygen group was greater than the increase in the 21% oxygen group (p < 0. 05). There were no significant differences between the two groups during the following 3.5 h of observation. A significant increase in CBF was found in the first 2 min of hypoxia (p < 0.05), it then continued to fall to values significantly lower than baseline values at the end of hypoxemia (p < 0.05). During reoxygenation CBF normalised and there were consistent but no significant differences between the two reoxygenation groups. We conclude that NO concentration decreased during the course of hypoxia. Hypoxia-induced cerebral hyperaemia occurred in spite of significantly lower NO concentrations. Reoxygenation with 21 or 100% O(2) restored CBF in both groups similarly, although values were higher after reoxygenation with 100% O(2) compared to air. In fact, reoxygenation with 100% O(2) led to supranormal levels of NO by contrast to 21% O(2).
authors.affiliation: Department of Pediatric Research, Institute for Surgical Research, National Hospital, Department of Neurosurgery, Ullevaal Hospital, and Department of Anesthesiology, Aker Hospital, University of Oslo, Norway. stefan.kutzsche@klinmed.uio.no
authors.forename: S
authors.initials: S
authors.lastname: Kutzsche
authors.forename: O J
authors.initials: OJ
authors.lastname: Kirkeby
authors.forename: I R
authors.initials: IR
authors.lastname: Rise
authors.forename: O D
authors.initials: OD
authors.lastname: Saugstad
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D001921:Brain / Q000098:blood supply* / Q000378:metabolism*; D002245:Carbon Dioxide / Q000097:blood; D000860:Hypoxia / Q000378:metabolism*; D017078:Laser-Doppler Flowmetry; D008833:Microcirculation; D009569:Nitric Oxide / Q000378:metabolism*; D010100:Oxygen / Q000008:administration & dosage* / Q000097:blood; D013552:Swine
chemical_list: D002245:Carbon Dioxide; D009569:Nitric Oxide; D010100:Oxygen