Exploring the lung-brain axis in perioperative neurocognitive disorders: a potential therapeutic target

Perioperative neurocognitive disorders (PND), primarily including postoperative delirium (POD) and postoperative cognitive dysfunction (POCD), are common and serious complications in elderly surgical patients. However, the exact mechanisms underlying PND are not fully understood. The lung-brain axis has recently been recognized as an important pathway in neurodegenerative diseases such as Alzheimer's disease (AD). Given that PND shares pathological features with AD, such as amyloid-β (Aβ) accumulation, the lung-brain axis may also represent a plausible mechanistic contributor to PND. Furthermore, elderly surgical patients often receive inhalation anesthetics and undergo mechanical ventilation during general anesthesia, which directly affect the lungs and may alter the pulmonary microenvironment. Therefore, we hypothesize that the lung-brain axis plays a role in the development of PND. In this article, we discuss potential mechanisms by which surgery and anesthesia-especially inhalation anesthetics and mechanical ventilation-may influence cognitive function via the lung-brain axis. Potential mechanisms include changes in the pulmonary microbiota, secretion of brain-derived neurotrophic factor, and lung-derived inflammatory responses. These pathways may disrupt the blood-brain barrier, promote neuroinflammation, and exacerbate Aβ deposition, ultimately leading to cognitive impairment. Exploring the role of the lung-brain axis could provide new insights into PND pathophysiology and reveal potential targets for prevention and treatment of PND by targeting pulmonary-mediated cascades.