Review highlights nitric oxide’s potential in equine hypoxaemia: full analysis

A new review in Veterinary Anaesthesia and Analgesia is putting fresh attention on nitric oxide as a possible tool for managing hypoxaemia in anesthetized horses. The article reviews nitric oxide biology, its use in human medicine, and the equine evidence behind pulsed inhaled nitric oxide, or PiNO. Its central takeaway is cautious but notable: PiNO is not yet standard equine practice, but technical redevelopment of the original delivery system may make clinical use more feasible in the near term. (sciencedirect.com)

That matters because hypoxaemia has been a persistent problem in equine anesthesia for decades. Horses are especially prone to impaired gas exchange under general anesthesia, particularly in dorsal recumbency, where compression atelectasis and ventilation-perfusion mismatch can sharply reduce arterial oxygenation. A 2017 review of hypoxaemia in anesthetized horses found the problem is common and difficult to manage, even though direct links to mortality have been harder to prove than many clinicians might expect. Broader outcome reviews of equine anesthesia also continue to identify cardiorespiratory instability, hypotension, body weight, case complexity, and recovery events as important contributors to peri-anesthetic risk. (sciencedirect.com)

The new narrative review synthesizes a line of experimental work, much of it from the same research group, suggesting PiNO can improve oxygenation by redirecting pulmonary blood flow toward better-ventilated lung regions. In a 2019 American Journal of Veterinary Research study of 27 healthy adult horses, investigators found the effect of PiNO depended on ventilation mode and perfusion conditions, with dobutamine used to maintain mean arterial pressure above 70 mm Hg in some groups. In a 2022 AJVR study in dorsally recumbent ponies, PiNO increased perfusion to aerated lung regions, decreased perfusion to atelectatic regions, improved arterial oxygen tension, and reduced venous admixture; those changes were more pronounced during spontaneous breathing than during mechanical ventilation. (pubmed.ncbi.nlm.nih.gov)

The review also points to a practical development beyond the physiology itself: the prototype equine PiNO delivery device, the NOrse system developed by Datex-Ohmeda, has been redeveloped. That’s important because one of the longstanding barriers to clinical uptake has been logistics, not just biology. In other words, the field may now be moving from proof-of-concept studies toward questions of usability, availability, and whether the technique can fit into referral-hospital anesthesia workflows. That is an inference from the review’s emphasis on device redevelopment and “realistic treatment option” language, rather than a formal commercialization announcement. (sciencedirect.com)

Direct outside commentary on this specific review appears limited so far, but the surrounding literature is broadly consistent: PiNO has shown physiologic benefits in experimental equine studies, while the wider equine anesthesia literature keeps highlighting the clinical importance of maintaining oxygenation and hemodynamic stability. The 2022 AJVR paper framed PiNO as a potential treatment option for recumbency-induced impaired oxygenation, and a recent review of equine anesthesia outcomes noted that dobutamine use in some settings was associated with lower mortality risk, reinforcing the likely importance of perfusion support when clinicians are trying to improve oxygen delivery, not just oxygen numbers. (avmajournals.avma.org)

Why it matters: For veterinary professionals, this review is useful because it organizes a scattered evidence base into a clearer clinical narrative. It does not establish PiNO as routine care, and it does not show that improving PaO2 alone will improve survival. But it does sharpen the case for PiNO as a targeted rescue or adjunctive strategy in horses that remain hypoxaemic despite conventional adjustments in positioning, ventilation, inspired oxygen, recruitment approaches, or cardiovascular support. It also underscores that response may depend on the whole anesthetic picture, especially blood pressure, cardiac output, and whether the horse is breathing spontaneously or mechanically ventilated. (sciencedirect.com)

What to watch: The next step is likely clinical translation. Watch for prospective studies in referral-hospital case loads, data on safety and workflow with the redeveloped device, and evidence on harder endpoints such as recovery quality, post-anesthetic complications, and mortality. Until then, PiNO looks promising, but still sits in the category of emerging equine anesthesia support rather than established standard of care. (sciencedirect.com)