title: Pulsed delivery of nitric oxide counteracts hypoxaemia in the anaesthetized horse.
abstract: OBJECTIVE
  To study the effect of the pulsed delivery of nitric oxide (NO) on pulmonary gas exchange in the anaesthetized horses. Design  Prospective, controlled randomized.
  
  
  METHODS
  Five healthy Standardbred trotters, three geldings and two mares.
  
  
  METHODS
  The horses were anaesthetized with thiopentone and isoflurane and positioned in dorsal recumbency. Nitric oxide was added as a pulse to the inspired gas during the first half of each inspiration. In three horses the effect of NO on the ventilation-perfusion distribution was also investigated using the multiple inert gas elimination technique. Data were analysed with repeated measures ANOVA.
  
  
  RESULTS
  During spontaneous breathing, arterial oxygen tension (PaO2) increased with NO inhalation, from 14 ± 2 to 29 ± 3 kPa (105 ± 15 to 218 ± 23 mm Hg) (p < 0.001). Arterial oxygen tension also increased, from 17 ± 3 to 31 ± 5 kPa (128 ± 23 to 233 ± 38 mm Hg) (p < 0.05) during intermittent positive pressure ventilation. The increase in PaO2was mainly due to a reduced right to left vascular shunt, but ventilation and perfusion matching also improved. The beneficial effect of NO inhalation was lost within 5 minutes of its discontinuation.
  
  
  CONCLUSIONS
  Delivery of NO as a pulse during inspiration is an effective method for counteracting impaired gas exchange caused by anaesthesia in horses. Pulsation has to be continuous because of the transience of NO's therapeutic effect.
  
  
  CONCLUSIONS
  Horses with impaired pulmonary gas exchange during anaesthesia can be treated with pulsed NO inhalation.
authors.affiliation: Department of Medical Sciences; Clinical Physiology, Uppsala University, Uppsala, Sweden.
authors.forename: Erkki
authors.initials: E
authors.lastname: Heinonen
authors.affiliation: Department of Medical Sciences; Clinical Physiology, Uppsala University, Uppsala, Sweden.
authors.forename: Göran
authors.initials: G
authors.lastname: Hedenstierna
authors.affiliation: Department of Medical Sciences; Clinical Physiology, Uppsala University, Uppsala, Sweden.
authors.forename: Pekka
authors.initials: P
authors.lastname: Meriläinen
authors.affiliation: Department of Medical Sciences; Clinical Physiology, Uppsala University, Uppsala, Sweden. Electronic address: marieann.hogman@medsci.uu.se.
authors.forename: Marieann
authors.initials: M
authors.lastname: Högman
authors.affiliation: Department of Large Animal Clinical Sciences, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Görel
authors.initials: G
authors.lastname: Nyman
keywords: Anaesthesia; gas exchange; horse; hypoxia; nitric oxide