title: Physiologic responses and plasma endothelin-1 concentrations associated with abrupt cessation of nitric oxide inhalation in isoflurane-anesthetized horses.
abstract: OBJECTIVE
  To assess physiologic responses and plasma endothelin (ET)-1 concentrations associated with abrupt cessation of nitric oxide (NO) inhalation in isoflurane-anesthetized horses.
  
  
  METHODS
  6 healthy adult Standardbreds.
  
  
  METHODS
  Horses were anesthetized with isoflurane in oxygen and placed in dorsal recumbency. Nitric oxide was pulsed into the respiratory tract for 2.5 hours, and then administration was abruptly discontinued. Just prior to commencement and at cessation of NO administration, and at intervals during a 30-minute period following cessation of NO inhalation, several variables including PaO(2), mean pulmonary artery pressure, venous admixture or pulmonary shunt fraction (Qs/Qt), and plasma ET-1 concentration were recorded or calculated.
  
  
  RESULTS
  After cessation of NO inhalation, PaO(2) decreased slowly but significantly (172.7 +/- 29.8 mm Hg to 84.6 +/- 10.9 mm Hg) and Qs/Qt increased slowly but significantly (25 +/- 2% to 40 +/- 3%) over a 30-minute period. Mean pulmonary artery pressure increased slightly (14.0 +/- 1.3 mm Hg to 16.8 +/- 1 mm Hg) over the same time period. No change in serum ET-1 concentration was detected, and other variables did not change or underwent minor changes.
  
  
  CONCLUSIONS
  The improvement in arterial oxygenation during pulsed inhalation of NO to healthy isoflurane-anesthetized horses decreased only gradually during a 30-minute period following cessation of NO inhalation, and serum ET-1 concentration was not affected. Because a rapid rebound response did not develop, inhalation of NO might be clinically useful in the treatment of hypoxemia in healthy isoflurane-anesthetized horses.
authors.affiliation: Riverview Animal Clinic, Uniontown, WA 99179, USA.
authors.forename: Tamara L
authors.initials: TL
authors.lastname: Grubb
authors.forename: Marieann
authors.initials: M
authors.lastname: Högman
authors.forename: Anna
authors.initials: A
authors.lastname: Edner
authors.forename: Jan H M
authors.initials: JH
authors.lastname: Frendin
authors.forename: Erkki
authors.initials: E
authors.lastname: Heinonen
authors.forename: Laís M
authors.initials: LM
authors.lastname: Malavasi
authors.forename: Claes G
authors.initials: CG
authors.lastname: Frostell
authors.forename: Anneli
authors.initials: A
authors.lastname: Ryden
authors.forename: Kjell
authors.initials: K
authors.lastname: Alving
authors.forename: Görel C
authors.initials: GC
authors.lastname: Nyman
mesh_terms: D000280:Administration, Inhalation; D000769:Anesthesia, Inhalation / Q000662:veterinary*; D000818:Animals; D001784:Blood Gas Analysis / Q000662:veterinary; D001794:Blood Pressure / Q000187:drug effects; D001993:Bronchodilator Agents / Q000008:administration & dosage*; D019332:Endothelin-1 / Q000097:blood*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000097:blood / Q000502:physiology*; D008297:Male; D009569:Nitric Oxide / Q000008:administration & dosage*; D012119:Respiration / Q000187:drug effects
chemical_list: D001993:Bronchodilator Agents; D019332:Endothelin-1; D009569:Nitric Oxide