Perioperative neurocognitive dysfunction: thinking from the gut?

Abstract

With the aging of the world population, and improvements in medical and health technologies, there are increasing numbers of elderly patients undergoing anaesthesia and surgery. Perioperative neurocognitive dysfunction has gradually attracted increasing attention from academics. Very recently, 6 well-known journals jointly recommended that the term perioperative neurocognitive dysfunction (defined according to the Diagnostic and Statistical Manual of Mental Disorders, fifth edition) should be adopted to improve the quality and consistency of academic communications. Perioperative neurocognitive dysfunction currently includes preoperatively diagnosed cognitive decline, postoperative delirium, delayed neurocognitive recovery, and postoperative cognitive dysfunction. Increasing evidence shows that the gut microbiota plays a pivotal role in neuropsychiatric diseases, and in central nervous system functions via the microbiota-gut-brain axis. We recently reported that abnormalities in the composition of the gut microbiota might underlie the mechanisms of postoperative cognitive dysfunction and postoperative delirium, suggesting a critical role for the gut microbiota in perioperative neurocognitive dysfunction. This article therefore reviewed recent findings on the linkage between the gut microbiota and the underlying mechanisms of perioperative neurocognitive dysfunction.

Keywords: brain-gut axis; gut microbiota; perioperative neurocognitive dysfunction; postoperative cognitive dysfunction; postoperative delirium.

Figure 1

The mechanisms of microbiota-gut-brain axis. Gut microbiota can influence the cognitive function of brain through neural signalling, endocrine, metabolic and immune pathways. 5-HT: 5-hydroxytryptamine; ACTH: adrenocorticotropic hormone; BBB: blood-brain barrier; CRH: corticotropin releasing hormone; EC: enteroendocrine cell; ENS: enteric nervous system; GABA: gamma amino butyric acid; Glu: glutamic acid; HPA: hypothalamic-pituitary-adrenal; SCFA: short-chain fatty acids.

Figure 2

The pathogenesis of perioperative neurocognitive dysfunction. Postoperative delirium and postoperative cognitive dysfunction are two repensentive symptoms of perioperative neurocognitive dysfunction, and that multiple factors and pathways are probably involved in the pathogenesis of PND. α7 nAChR: α7 nicotinic acetylcholine receptor; AChE: acetylcholin esterase; BDNF: brain-derived neurotrophic factor; CHAT: choline acetylase; DFO: deferoxamine; GR: glucocorticoid receptor; Hcy: homocysteine; MAP: mean arterial pressure; MV: mechanical ventilation; PACU: postanaesthesia care unit; PND: perioperative neurocognitive dysfunction; POCD: postoperative cognitive dysfunction; POD: postoperative delirium; ROS: reactive oxygen species.