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

• Objectives Anaesthetized horses commonly become hypoxaemic due to ventilation/perfusion ((V) over dot(A)/(Q) over dot) mismatch and increased pulmonary shunt fraction ((Q) over dots/(Q) over dott). 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 (SaO(2)), calculated ((Q) over dots/(Q) over dott) and ET-1 concentration; and Study 2) assess ((V) over dot(A)/(Q) over dot) matching and measured ((Q) over dots/(Q) over dott) in isoflurane-anaesthetized horses in left lateral recumbency receiving pulse-delivered inhaled nitric oxide (PiNO group) or inhalant gas only (C group). Study design Prospective research trial. Animals 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, SaO(2), ((Q) over dots/(Q) over dott) 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) over dot(A)/(Q) over dot) matching and ((Q) over dots/(Q) over dott) 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 ((Q) over dots/(Q) over dott) 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) over dot(A)/(Q) over dot) matching and measured ((Q) over dots/(Q) over dott) were improved from baseline in all horses but PiNO60% provided no improvement when compared to PiNO30%. Conclusions and Clinical Relevance PiNO delivered in the initial portion of the inspiration effectively relieves hypoxaemia in anaesthetized horses by improving ((V) over dot(A)/(Q) over dot) matching and decreasing ((Q) over dots/(Q) over dott) without affecting ET-1.

Subject headings

LANTBRUKSVETENSKAPER  -- Veterinärmedicin (hsv//swe)

AGRICULTURAL SCIENCES  -- Veterinary Science (hsv//eng)

LANTBRUKSVETENSKAPER  -- Veterinärmedicin -- Klinisk vetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Veterinary Science -- Clinical Science (hsv//eng)

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Jordbruksvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Agricultural Science (hsv//eng)

Keyword

anaesthesia

endothelin-1

gas exchange

horse

hypoxaemia

MIGET

nitric oxide

(Q) over dots/(Q) over dott

shunt

(V) over dot(A)/(Q) over dot

Publication and Content Type

ref (subject category)

art (subject category)