Clinical implementation of Pulsed inhaled Nitric Oxide in equine anaesthesia

Abstract: Hypoxaemia is a common complication during horse anaesthesia that is a challengeto treat. The primary cause of hypoxaemia is the development of a large intrapulmonaryshunt that leads to significant ventilation-perfusion mismatch. Openingand ventilating atelectasis during anaesthesia requires high airway pressures andrepeated manoeuvres. Another approach to improve gas exchange in the lung is toredistribute blood flow from atelectatic to well-ventilated lung regions. Inexperimental studies, it has been shown possible to target the vasodilating gas nitricoxide 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 NitricOxide (PiNO) was evaluated during different modes of ventilation in combinationwith normal or low cardiac output and blood pressure. In the following clinicalstudies, PiNO was evaluated in colic horses undergoing abdominal surgery and inhealthy horses undergoing arthroscopy. In the last study, it was investigated if PiNOinducedimproved arterial oxygenation had an impact on the quality of recovery afteranaesthesia compared to controls. The results showed that PiNO was effectiveduring mechanical ventilation only if cardiac output blood pressure were adequate,while PiNO was effective under both hypotensive and normotensive conditionsduring spontaneous breathing. In the clinical studies, PiNO effectively improvedarterial oxygenation in both healthy and colic horses, ventilated spontaneously ormechanically. In the last study, horses that received PiNO during anaesthesia hadbetter recovery quality compared to controls. In addition, a positive correlationbetween arterial oxygenation during anaesthesia and recovery quality was seen.In summary, PiNO offers a simple and effective option to treat hypoxaemia inanaesthetised horses. In the future, the effect of oxygenation on the quality ofrecovery needs to be further investigated as well as the long-term effects, such aswound healing in the postoperative period.