Research Progress Of POCD’s Neuroinflammation Mechanism

Postoperative cognitive dysfunction (POCD) is a common postoperative complication, especially in the elderly. The exact pathogenesis is still unclear<> Recent studies focus on the neuroinflammation mechanism in the POCD induced by operation or anesthesia. Here we summarize and analyze it.POCD refers to continuous decline of patients’cognition after anesthesia or operation. The common assessment tools include Mini-Mental State Examination scale (MMSE), Wechsler Adult Memory Scale (WMS), the Minnesota Multiphasic Personality Inventory (MMPI)and etal. An authoritative testing tool and definition are still unclear.Commonly used animal experiments include space memory tests (such as platform, Morris water maze, and space shuttle box) and perception memory test (such as conditioned taste aversion memory test and conditioned pain aversion memory test). The long-term memory formation is referred as the standard, especially with LTP as measurement basis.The neuroinflammatory mechanism of POCD includes the following several aspects:1.Inflammatory cells. Astrocytes hinder nerve regeneration and release inflammatory factor. Activated microglial cells release neurotoxic substances, damage neurons, and have long-term effect by chronic sustained activation.Peripheral inflammatory cells will infiltrate into CNS by the facilitation of neuroinflammation,mainly lymphocytes and monocytes.They affect cognitive function independently.2. Inflammatory factor. IL-1beta can promote the release of neurotoxic substances, and impaire the formation of hippocampal LTP through ROS/MAPK pathways. TNF-a may promote excitatory neurotoxicity injuries of glutamine, ease the infiltration of peripheral inflammatory factors and promote the cascade of neuroinflammatory reaction; IL-6could inhibit LTP, impaire generation of hippocampal neurons and cause their morphological changes. The actions of inflammatory factors have confirmed in vitro animal experiments. Furthermore, inflammatory factors act together to cause injury of neurons.In central nervous system of aged people, inflammation factors and inflammatory cells themselves are at a higher level.In stress situations,neuroinflammation happen more easily,leading to the impaire of cognitive function.Propofol, minocycline, ulinastatin D and some other drugs can interfere with neuroinflammation, reduce the level of circulating inflammatory cytokines levels, improve postoperative cognitive function, and thus reduce the incidence of POCD.Effects of propofol on cognitive function improvement are mostly compared with inhalation anesthesia of sevoflurane. Influences of minocycline and ulinastatin still need further animal experiments and clinical validation.Finally, with the review and relevant literature as the background, we collect several clinical cases and analyse the pathogenesis and treatment.