Pulsed inhaled nitric oxide during mechanical ventilation in horses undergoing abdominal surgery : the effect on arterial oxygenation

Abstract: The aim of this study was to evaluate the effect of pulsed inhaled nitric oxide (PiNO) during intermittent positive pressure ventilation (IPPV) on arterial oxygenation and right to left vascular shunt in colic horses undergoing abdominal surgery. Hypoxemia is a serious complication commonly occurring during general equine anaesthesia. Several different methods to improve oxygenation have been studied, where use of PiNO has introduced novel thinking. Previous studies have shown that PiNO is an effective method to treat low arterial oxygenation during general anaesthesia in both healthy horses and in spontaneously breathing colic horses. The combination of mechanical ventilation and PiNO has however not before been studied. This is a crucial step before the method can be adapted to clinical practise, as many horses require mechanical ventilation during general anaesthesia to avoid hypoventilation and respiratory acidosis. The results from the present study showed that the alveolar-artieral oxygen partial pressure difference (P(A-a)O2) decreased in horses receiving PiNO during IPPV. A significant increase in partial pressure of oxygen (PaO2), oxygen saturation of arterial blood (SaO2) and oxygen content (CaO2) was measured. Furthermore, the right to left vascular shunt decreased during PiNO. In conclusion, the present study showed that PiNO during IPPV results in an improved arterial oxygenation in colic horses undergoing abdominal surgery.