Clinical implementation of Pulsed inhaled Nitric Oxide in equine anaesthesia

Abstract

Hypoxaemia is a common complication during horse anaesthesia that is a challenge to treat. The primary cause of hypoxaemia is the development of a large intrapulmonary shunt that leads to significant ventilation-perfusion mismatch. Opening and ventilating atelectasis during anaesthesia requires high airway pressures and repeated manoeuvres. Another approach to improve gas exchange in the lung is to redistribute blood flow from atelectatic to well-ventilated lung regions. In experimental studies, it has been shown possible to target the vasodilating gas nitric oxide to open ventilated lung parts by pulsing the gas at the beginning of inspiration. In the first experimental study of the present thesis, the effect of Pulsed inhaled Nitric Oxide (PiNO) was evaluated during different modes of ventilation in combination with normal or low cardiac output and blood pressure. In the following clinical studies, PiNO was evaluated in colic horses undergoing abdominal surgery and in healthy horses undergoing arthroscopy. In the last study, it was investigated if PiNOinduced improved arterial oxygenation had an impact on the quality of recovery after anaesthesia compared to controls. The results showed that PiNO was effective during mechanical ventilation only if cardiac output blood pressure were adequate, while PiNO was effective under both hypotensive and normotensive conditions during spontaneous breathing. In the clinical studies, PiNO effectively improved arterial oxygenation in both healthy and colic horses, ventilated spontaneously or mechanically. In the last study, horses that received PiNO during anaesthesia had better recovery quality compared to controls. In addition, a positive correlation between arterial oxygenation during anaesthesia and recovery quality was seen. In summary, PiNO offers a simple and effective option to treat hypoxaemia in anaesthetised horses. In the future, the effect of oxygenation on the quality of recovery needs to be further investigated as well as the long-term effects, such as wound healing in the postoperative period.