Physiologic responses and plasma endothelin-1 concentrations associated with abrupt cessation of nitric oxide inhalation in isoflurane-anesthetized horses.
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.
Grubb
Tamara L
TL
Riverview Animal Clinic, Uniontown, WA 99179, USA.
Högman
Marieann
M
Edner
Anna
A
Frendin
Jan H M
JH
Heinonen
Erkki
E
Malavasi
Laís M
LM
Frostell
Claes G
CG
Ryden
Anneli
A
Alving
Kjell
K
Nyman
Görel C
GC
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
D001993:Bronchodilator Agents; D019332:Endothelin-1; D009569:Nitric Oxide