title: The effects of pulse-delivered inhaled nitric oxide on arterial oxygenation, ventilation-perfusion distribution and plasma endothelin-1 concentration in laterally recumbent isoflurane-anaesthetized horses.
abstract: OBJECTIVE
  Anaesthetized horses commonly become hypoxaemic due to ventilation/perfusion (V·A/Q·) mismatch and increased pulmonary shunt fraction (Qs·/Qt·). Pulse-delivered inhaled nitric oxide may improve oxygenation but may increase plasma concentration of the potent vasoconstrictor, endothelin-1 (ET-1). Objectives: Study 1) compare arterial oxygen concentration (PaO2) and saturation (SaO2), calculated Qs·/Qt· and ET-1 concentration; and Study 2) assess V·A/Q· matching and measured Qs·/Qt· in isoflurane-anaesthetized horses in left lateral recumbency receiving pulse-delivered inhaled nitric oxide (PiNO group) or inhalant gas only (C group).
  
  
  METHODS
  Prospective research trial.
  
  
  METHODS
  Ten Healthy adult Standardbred horses. Two horses were anaesthestized in both groups in a random cross-over design with >4 weeks between studies.
  
  
  METHODS
  Study 1) Cardiopulmonary data including PaO2, SaO2, Qs·/Qt· and ET-1 concentration were measured or calculated prior to and at various points during PiNO administration in 6PiNO and 6C horses. Two-way repeated measures anova with Bonferroni significant difference test was used for data analysis with p < 0.05 considered significant. Study 2) V·A/Q· matching and Qs·/Qt· were determined using the multiple inert gas elimination technique in 3 horses. Data were collected after 60 minutes of anaesthesia without PiNO (baseline) and 15 minutes after PiNO was pulsed during the first 30%, and then the first 60%, of inspiration. Data were descriptive only.
  
  
  RESULTS
  Study 1) PaO2 and SaO2 were higher and calculated Qs·/Qt· was lower in the PiNO group than the C group at most time points. ET-1 was not different over time or between groups. Study 2) V·A/Q· matching and measured Qs·/Qt· were improved from baseline in all horses but PiNO60% provided no improvement when compared to PiNO30%.
  
  
  CONCLUSIONS
  PiNO delivered in the initial portion of the inspiration effectively relieves hypoxaemia in anaesthetized horses by improving V·A/Q· matching and decreasing Qs·/Qt· without affecting ET-1.
authors.affiliation: Department of Animal Environment and Health, Faculty of Veterinary Medicine and Animal Husbandry, Swedish University of Agricultural Sciences, Skara, Sweden; Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA, USA.
authors.forename: Tamara
authors.initials: T
authors.lastname: Grubb
authors.forename: Jan H M
authors.initials: JH
authors.lastname: Frendin
authors.forename: Anna
authors.initials: A
authors.lastname: Edner
authors.forename: Pia
authors.initials: P
authors.lastname: Funkquist
authors.forename: Göran
authors.initials: G
authors.lastname: Hedenstierna
authors.forename: Görel
authors.initials: G
authors.lastname: Nyman
mesh_terms: D000769:Anesthesia, Inhalation / Q000379:methods / Q000662:veterinary*; D018685:Anesthetics, Inhalation; D000818:Animals; D019332:Endothelin-1 / Q000097:blood*; D005260:Female; D006736:Horses / Q000097:blood* / Q000601:surgery; D007530:Isoflurane; D008297:Male; D009569:Nitric Oxide / Q000008:administration & dosage; D010100:Oxygen / Q000097:blood*; D014692:Ventilation-Perfusion Ratio / Q000187:drug effects
chemical_list: D018685:Anesthetics, Inhalation; D019332:Endothelin-1; D009569:Nitric Oxide; D007530:Isoflurane; D010100:Oxygen
keywords: MIGET; Qs·/Qt·; V·A/Q·; anaesthesia; endothelin‐1; gas exchange; horse; hypoxaemia; nitric oxide; shunt