Postoperative cognitive decline: A current problem with a difficult future

The ageing population is both a marvel of civilisation and a huge challenge for healthcare provision. Coupled with surgical and anaesthetic advances, this shift in population distribution has meant that far greater numbers of elderly patients are undergoing surgery than has ever previously been the case. This is a double edged sword as the elderly population are more prone to develop perioperative complications than younger patients. Postoperative cognitive dysfunction (POCD) is one such complication, and can result in a serious deterioration in quality of life and an increased duration of hospital stay. It may persist for months or even years, and could yet prove to be a harbinger for the development of dementia in later life. The pathogenesis of POCD is still not yet fully understood, though a number of mechanisms have been postulated and there are several clearly identified risk factor. POCD also does not yet have a standardised diagnostic classification, and this has proven problematic in terms of research progress. Unsurprisingly, the complex relationship between POCD and dementia has also yet to be fully elucidated, though there is considerable overlap in risk factors for the two conditions. The common theme that runs through the risk factors for POCD is that they all pertain to either a reduction in functional reserve or a propensity to cerebral injury. Many of these risk factors are non-modifiable such as age, genotype, history of cerebrovascular disease and preoperative cognitive function. One exception to this is the development of postoperative delirium, which may also increase the risk of POCD. Postoperative delirium has myriad potential causes, many of which are treatable, if not preventable. This makes postoperative delirium an interesting prospect for study, as if it does contribute to the development of POCD then its early detection and management could produce real improvements in quality of life for many elderly patients. This review will outline the existing theories as to the pathophysiology underpinning POCD, the problems in defining it and the merits of various methods used in its detection. Risk factors precluding the development of POCD will also be discussed, with a focus placed specifically on age, preoperative cognitive status and the role of postoperative delirium. Common causes of postoperative delirium and their potential as modifiable risk factors will be highlighted and the protective or deleterious roles of common anaesthetic agents, type of surgery and certain individual factors will also be examined. Finally, the authors have offered some general principles of good practice to guide management in lieu of more concrete, targeted recommendations. (c) 2018 Elsevier Ltd. All rights reserved.