How Should We Identify Patients at Risk for Postoperative Neurocognitive Disorder?

INTRODUCTION

Postoperative neurocognitive disorder (PND) is a term recently proposed to describe a number of situations that occur up to 1 year after surgery and anesthesia; it aligns with other descriptions of neurocognitive disorders in the Diagnostic and Statistical Manual for Mental Disorders fifth edition (DMS-5) diagnostic criteria. These include emergence excitation or delirium, postoperative delirium (POD), delayed neurocognitive recovery, and postoperative mild or major neurocognitive disorder (formerly recognized as postoperative cognitive dysfunction). Up to this point, postoperative cognitive dysfunction has been used as a research term to refer to changes in neuropsychological test scores (compared with the patient baseline and referenced to controls or norms) rather than as a formal diagnosis using a wide range of diagnostic criteria. Few studies have been conducted using the new nomenclature. Thus, although we use the new terminology (postoperative mild or major neurocognitive disorder) throughout this chapter, most of the published work to date has referred to it as postoperative cognitive dysfunction.

Many of the PNDs share common risk factors, and older age is among the most prominent. This is important because worldwide the population is aging. In the United States, nearly 50% of surgical procedures are expected to be performed in patients over the age of 65. It is important to identify patients at risk for PND because the incidence of these complications are high. Although there is variability based on the type of surgical procedure, up to 45% of older patients may develop delirium in the post-anesthesia care unit (PACU) with somewhere between 4% and 58% of patients developing POD. Approximately 10% of patients are at risk for developing minor/major PNDs up to 3 months after surgery, which are associated with other adverse outcomes such as postoperative complications, longer hospital stay, institutionalization at discharge, prolonged functional recovery, cognitive decline, and increased medical costs. ^, It is important to identify patients who are at increased risk for PND before or early in their perioperative course to implement preventable strategies that could help mitigate adverse consequences. Namely, POD may be preventable in up to 40% of cases, and comprehensive geriatric assessment and bundle programs have been shown to improve outcomes and decrease delirium incidence.

Although patients of all ages may be at risk for some type of a PND (e.g., pediatric patients may experience emergence excitation or delirium ), this chapter will focus primarily on how to preoperatively identify older patients at risk for neurocognitive disorders after surgery and anesthesia. To do so, we will include a literature review, some options and evidence for preoperative screening, debatable controversies, and areas of uncertainty around this topic, and finish by providing recommendations and guidelines from experts in the field.

OPTIONS/THERAPIES

Guidelines and consensus statements recommend preoperative evaluation of risk factors for PND. Baseline cognitive impairment and frailty are often associated with worse outcomes and should be formally assessed during the preoperative period. This is because there are things that can be done to prevent the development of POD, such as the use of postoperative geriatric-specific wards like the hospital elder life program (HELP) for medical patients and preoperative geriatric consultations, both of which have been shown to decrease the development of POD, although less is known about their feasibility with regards to longer-term PNDs.