Pulsed delivery of nitric oxide counteracts hypoxaemia in the anaesthetized horse.

This research investigated how the pulsed delivery of nitric oxide (NO) can improve oxygen exchange in anaesthetized horses, showing that such delivery can effectively counteract the negative effects of anesthesia on lung function. The beneficial effects, however, disappear shortly after cessation, suggesting the need for continuous delivery during the anesthesia period.

Research Methodology

• The study was a prospective, controlled randomized study involving five healthy Standardbred trotters, two mares and three geldings.
• The horses were anaesthetized using thiopentone and isoflurane and placed in a dorsal recumbency position.
• Nitric oxide was pulsed into the horses’ inhaled gas during the first half of each breath.
• Three of the horses were also tested for the impact of nitric oxide on ventilation-perfusion distribution using the multiple inert gas elimination technique.
• The data collected were analyzed using repeated measures ANOVA.

Research Findings

• The study showed an increase in arterial oxygen tension during spontaneous breathing from 14 ± 2 to 29 ± 3 kPa with NO inhalation.
• Arterial oxygen tension also increased from 17 ± 3 to 31 ± 5 kPa during intermittent positive pressure ventilation.
• The increased oxygen tension was primarily a result of a reduced right-to-left vascular shunt, a condition that often hampers the supply of oxygenated blood in the body. Additionally, ventilation and perfusion matching improved.
•  However, the beneficial effects of nitric oxide inhalation were lost within 5 minutes of its discontinuation, indicating the importance of continuous administration during anesthesia.

Conclusion of the Research

• The findings confirmed that the timely administration of nitric oxide during inhalation is a potent method to manage the compromised gas exchange in horses that occurs under anesthesia.
• Because the beneficial effects of NO inhalation are short-lived, administration must be continuous to be effective.
• This research contributes to veterinary anesthesiology practices, suggesting an effective solution for horses with impaired pulmonary gas exchange during anesthesia through the pulsed inhalation of NO.