Recommendations for the Nomenclature of Cognitive Change Associated With Anaesthesia and Surgery–2018

L. Evered; B. Silbert; D. S. Knopman; D. A. Scott; S. T. DeKosky; L. S. Rasmussen; E. S. Oh; G. Crosby; M. Berger, R. G. Eckenhoff; The Nomenclature Consensus Working Group

Disclosures

Anesthesiology. 2018;129(5):872-879. 

In This Article

Abstract and Introduction

Abstract

Cognitive change affecting patients after anaesthesia and surgery has been recognised for more than 100 yr. Research into cognitive change after anaesthesia and surgery accelerated in the 1980s when multiple studies utilised detailed neuropsychological testing for assessment of cognitive change after cardiac surgery. This body of work consistently documented decline in cognitive function in elderly patients after anaesthesia and surgery, and cognitive changes have been identified up to 7.5 yr afterwards. Importantly, other studies have identified that the incidence of cognitive change is similar after non-cardiac surgery. Other than the inclusion of non-surgical control groups to calculate postoperative cognitive dysfunction, research into these cognitive changes in the perioperative period has been undertaken in isolation from cognitive studies in the general population. The aim of this work is to develop similar terminology to that used in cognitive classifications of the general population for use in investigations of cognitive changes after anaesthesia and surgery. A multispecialty working group followed a modified Delphi procedure with no prespecified number of rounds comprised of three face-to-face meetings followed by online editing of draft versions.

Two major classification guidelines (Diagnostic and Statistical Manual for Mental Disorders, fifth edition [DSM-5] and National Institute for Aging and the Alzheimer Association [NIA-AA]) are used outside of anaesthesia and surgery, and may be useful for inclusion of biomarkers in research. For clinical purposes, it is recommended to use the DSM-5 nomenclature. The working group recommends that 'perioperative neurocognitive disorders' be used as an overarching term for cognitive impairment identified in the preoperative or postoperative period. This includes cognitive decline diagnosed before operation (described as neurocognitive disorder); any form of acute event (postoperative delirium) and cognitive decline diagnosed up to 30 days after the procedure (delayed neurocognitive recovery) and up to 12 months (postoperative neurocognitive disorder).

Introduction

COGNITIVE change affecting patients after anaesthesia and surgery, particularly in the elderly, has been recognised in one form or another for more than 100 yr. Many clinicians are familiar with the clinical syndrome of delirium, a set of fluctuating changes in attention, mental status, and level of consciousness, which is often seen after anaesthesia and surgery. Aside from delirium, a large body of research has examined postoperative cognitive dysfunction (POCD) or decline after full recovery of consciousness, and persisting well beyond the expected pharmacological and physiological effects of anaesthetic drugs. Anaesthesia almost always accompanies surgery and its associated stresses, including healing and inflammation, and therefore the two will be considered together in this document.

Clinical complaints prompted research into cognitive change after anaesthesia and surgery, which accelerated in the 1980s when multiple studies used detailed neuropsychological testing for assessment after cardiac surgery. This body of work consistently documented decline in cognitive function in elderly patients in the short (7 days) and medium (1 to 3 months)[1–3] term after anaesthesia and surgery, even in the absence of symptoms. The natural history of these changes still requires further investigation, and although cognitive changes have been identified as long as 7.5 yr afterwards,[4] causal associations remain unclear at least in part because of lack of well-defined baseline status, lack of control groups in most studies, and other methodological limitations of previous work. Consistently, studies have confirmed that cognitive decline is associated with increasing age, lower premorbid intelligence quotient, fewer years of education, or a combination of these.[5] Further understanding has been complicated by significant heterogeneity in the type and number of tests administered, the criteria or definition for change, and the timing of administration of the tests.[6] Details of these studies and the associated issues are provided in Supplement 1.

Interestingly, research into perioperative cognitive change has occurred in isolation from cognitive studies in the general population, and in other medical disciplines. In fact, perioperative cognition has become largely a research area rather than a clinical state; subjective complaints are rarely sought or reported and capacity for activities of daily living (ADLs) is overlooked. Elderly individuals are a large subset of the general population, and, when normalised to population, are the major consumers of operative care; yet for those with spontaneous postoperative cognitive complaints, there exists no nomenclature, diagnostic framework, or referral recommendations within the specialties of anaesthesiology and surgery.

We consider a formal classification to be critical at this time for the following reasons:

  1. The number of patients aged >60 yr undergoing anaesthesia and surgery has increased significantly and is projected to increase further. In Australia, individuals >60 yr receive nearly one-third of all anaesthetics, although they represent <14% of the population. By 2050, they will comprise 25% of the population and receive 50% of all anaesthetics.[7] In the USA, more than 19 million anaesthetics are administered to those aged >65 yr every year, and a similar increase in exposure is expected.[8]

  2. The diagnostic criteria for the cognitive changes associated with anaesthesia and surgery detected by psychometric testing should not be differentiated from neurocognitive disorders (NCD) in the general population, and should therefore be aligned with the clinical diagnostic criteria of neurocognitive disorders such as those already used in the Diagnostic and Statistical Manual for Mental Disorders, fifth edition (DSM-5).[9]

  3. The terminology of cognitive change associated with anaesthesia and surgery should be aligned with other NCD to promote cross-specialty communication, aid clinical management of patients, and further high-quality research.

  4. Neurocognitive disorders occur frequently in the community with 14 to 48% aged >70 yr suffering mild cognitive impairment (MCI)[10] and an additional 10% suffering dementia.[11] Therefore many individuals will have these disorders, even if preclinical, before they undergo anaesthesia and surgery. Switching to a different terminology to classify these individuals when they are having an operation is confusing, counterintuitive, and counterproductive.

This work aims: 1) to develop and encourage the use of nomenclature and diagnostic criteria that are consistent with the terminology used in the wider clinical community when assessing and reporting cognitive impairment, but that retains the temporal association with anaesthesia and surgery; and 2) to align perioperative cognitive disorders with terms used in the community, namely the DSM-5 and National Institute for Aging and the Alzheimer Association (NIA-AA) definitions. This clinical nomenclature will offer a framework for understanding the impact of anaesthesia and surgery on outcomes, care, and management for the elderly and thereby enhance consistency of communication and reporting.

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