Introduction
As the American population ages, the number of patients over the age of 65 undergoing surgical procedures is also rising. Such patients are at increased risk of developing cognitive complications following surgery compared to younger patients and major surgery can also accelerate functional decline in older adults [1–3]. As such, older surgical patients are more likely to be discharged to an institutional care facility (i.e., rehabilitation centers, skilled nursing facilities, and nursing homes) and may have difficulty recovering from some forms of postoperative cognitive impairment [4,5]. Accordingly, it is important to identify patients at risk for poor cognitive outcomes preoperatively so they can be factored into the planning and execution of surgical, anesthetic, and postoperative care.
Currently, patients scheduled to undergo an elective surgical procedure undergo a preoperative assessment with the goals of reducing perioperative complications and unnecessary cancellations [6]. This assessment typically includes a consultation by a medical provider and a detailed review of the patient’s medical history, physical examination, and identification of areas requiring additional testing or evaluation. The traditional preoperative appointment, however, is not designed to address the subtle risk factors for postoperative cognitive disturbances in the geriatric patient [7]. Because more than 40% of surgical procedures are performed on patients over 65 years of age, it makes sense to adapt the preoperative visit to focus on geriatric conditions that might predispose elderly patients to life-altering postsurgical complications [8]. In this chapter, we will focus on mild cognitive impairment (MCI) [9–12], depression [13–16], frailty [10,17–21], and social vulnerability [19,22,23].
Preoperative Cognitive Impairment and Postoperative Cognitive Complications
Mild cognitive impairment (MCI) is a widely accepted neurological syndrome defined as cognitive decline greater than expected for an individual’s age and education [24]. Impairments include decreased performance on cognitive tests without interference with activities of daily living (ADLs). Studies indicate that the prevalence of MCI in adults > 65 years of age is 3%–19%, about half of whom will go on to develop dementia within 5 years whereas the others will remain stable or even improve [24]. A subtype of MCI is amnestic MCI (aMCI), which is more specifically defined by memory impairments [25,26]. This subtype is characterized by memory complaints by the patient or caregiver that are confirmed by medical staff, objective evidence of memory deficits on cognitive testing, normal ADLs, and absence of dementia [11]. Amnestic MCI is associated with a higher rate of progression to dementia of the Alzheimer type [24]. Because of the mild symptoms and intact ADLs, MCI is often missed by health care professionals [11]. Physicians in primary care often forgo formal cognitive screening due to lack of time, lack of patient insight, and concern about stigmatizing the patient [27]. In addition, formal dementia screening and neuropsychological testing is costly and requires a substantial amount of advanced practitioner time [28]. Accordingly, seldom is the cognitive status of patients known preoperatively. It is thus interesting that cognition is not formally screened for prior to a surgical procedure when cognitive complications including postoperative cognitive dysfunction and delirium are the most common postoperative complications in older surgical patients despite a growing body of evidence that doing so can help identify patients at risk for such adverse cognitive outcomes [29].
Preoperative Screening for Cognitive Impairment
There is reason to believe that baseline cognitive impairment is prevalent in patients undergoing a surgical procedure and that it may be a predictor for adverse cognitive outcomes. Cognitive impairment is common among community dwelling seniors and although federally mandated, there is a lack of cognitive testing in primary care. Thus it is not surprising that many older adults scheduled for elective surgery have cognitive impairment that that remains undetected [25,30]. Using a formal neuropsychometric testing battery, Silbert and Evered et al., noted that 32%–33% of patients presenting for surgical procedures have some degree of cognitive impairment at baseline and that patients with preoperative cognitive dysfunction had an increased incidence of POCD at 7 days and 3 months after surgery, and frank cognitive dementia at 12 months [25,30].
Given the rapid pace of most preoperative evaluation clinics, structured screening for cognition must rely on short cognitive tests with high sensitivity and specificity that, ideally, can be administered by nonphysician staff (e.g., medical assistants). In theory, there are many options (Table 14.1), including some that can be administered over the telephone [31–33]. Most can be completed in less than 10 min, some in as few as 1–2 min (Table 14.1). The Mini-Mental State Examination (MMSE), a measure of global cognitive ability, is one of the most popular brief cognitive screening tools used in medical settings but, at 7–10 min to administer, may disrupt workflow in many preoperative evaluation environments [34,35]. A recent study using the MMSE found that the global MMSE score was not a predictor of postoperative delirium but that the memory and working memory components of the MMSE were [36]. This is important because the available data suggest that tests of executive function, which are cognitive processes that deal with complex working memory and mental flexibility, are better for identifying individuals with mild cognitive deficits [35]. Furthermore, a decline in executive function is strongly related to postoperative delirium and a deterioration of functional status [34,35]. Importantly, there are other short cognitive tests that incorporate higher-order cognitive tasks that assess executive function [35]. Unfortunately, all screening tests have limitations. Many of the briefer screening tests lack the sensitivity and specificity of the MMSE, many are biased in terms of education, age, and language, and many do not have normative data available [37]. Some are easy to administer but difficult to score reliably. For example, in a feasibility study, we compared two short tests (Mini-Cog and Clock-in-a-Box) and found ease of administration was comparable but that it took longer to score the Clock-in-a-Box due to a complex scoring algorithm.[38] Importantly, none of these screening tests are adequate to formally diagnose cognitive impairment (e.g., MCI; dementia); for that, lengthy, formal neurocognitive testing is required. Moreover, while some research suggests that incorporating a simple, brief cognitive screen does not disrupt the workflow of a primary care setting and can be administered successfully by nonphysician staff, few studies have directly assessed the feasibility of incorporating these cognitive screens into the preoperative setting [4,31,32,39,40]. We have done so using the Mini-Cog as the screening test, and found that it is possible to implement such screening on a routine basis. In fact, the testing was well received and has since been incorporated into the routine visit for elective surgical patients 70 years of age and older in our institution.
| Cognitive Screens | Sensitivity | Specificity | Time to Administer | Setting |
|---|---|---|---|---|
| Adams Telephone Interview for Cognitive Status (TICS) [30,31,45] | 94% | 100% | 8-item | Phone/in person |
| TICS-M [46,47] | 71.4% | 78.3% | 5.4 min | Phone/in person |
| MMSE [31,36,46] | 91% | 92% | 7–10 min (30 items) | In person |
| Animal Fluency Test [32,42] | 84% | 75% | 1 min | Phone/in person |
| 8-Item Screener (8-IS) [31] | 85.9% | 78.2 | 2 min (8 items) | Phone/in person |
| 6-Item Cognitive Test (6-CIT) [31] | 92.1% | 95.6% | 1–2 min (6 items) | In person |
| The Sweet 16 (S-16) [31] | 99% | 70% | 2 min (16 items) | Phone/in person |
| (5-IRF) [31] | 79% | 98% | 2 min | Phone/in person |
| Mini-Cog [4,31,38,39] | 99% | 93% | 2–4 min | In person |
| 6-Item Screener (6-IS) [31] | 74.2% | 80.2% | 1 min | Phone/in person |
| Informant Questionnaire on Cognitive Decline in the Elderly Short Form (IQCODE-SF) [31,48] | 75% | 68% | 16-item | Phone; health care proxy required |
| Trail-Making Test (Part B) [31,42] | 59.6% | 69.7% | 2 min | In person |
| EXIT25 [31,49] | 93% | 83% | 15 min (25 items) | Phone/in person |
They key question though is whether preoperative cognitive screening can help identify patients at risk of an adverse postoperative outcome. Here the data are limited but suggestive. A number of studies have found that low Mini-Cog scores are predictive of delirium, longer hospital length of stay, discharge to place other than home, and long-term mortality [4,39]. Similarly, others have found that the MMSE, animal fluency, Informant Questionnaire on Cognitive Decline in the Elderly Short Form, and the Trail-Making Test have all been shown to predict various forms of PND [3,32,36,41–44]. Accordingly, it remains surprising that baseline cognitive performance is typically not assessed during the preoperative evaluation as there are many short cognitive screening tools with high sensitivity and specificity that could be used to do so (Table 14.1) [4,31,32,38,39].
Mild Cognitive Impairment and Postsurgical Cognitive Complications
Identification of preoperative cognitive impairment is important because as described above it is associated with an increased risk of both short- and long-term medical complications in geriatric surgical patients [4,9,12,36,39]. For example, patients with MCI have more postoperative complications, longer hospital stay, higher rate of discharge to an institutional care facility, higher 30 day readmission rate, and a higher 6 month mortality [4,9,12,36,39]. In addition, preoperative cognitive impairment is a predictor of postoperative delirium and may also play a role in all forms of PND [30,39].
Geriatric Depression and Surgical Outcomes
Depression is one of the most common psychiatric disorders in older adults, affecting about 13% of cognitively normal seniors, or nearly 5 million persons over age 65 [50]. This mood disorder includes both cases that are diagnosed earlier but progress or recur in later life and those with the initial onset in late-life. Symptoms in geriatric patients include withdrawal, apathy, and lack of vigor. Curiously, depression often co-occurs with mild cognitive impairment [15]. There are a number of theories about why this is so, including notions that they share a common underlying pathogenesis and the possibility that depression is a response to awareness of one’s declining cognition. Regardless, depression is associated with executive dysfunction, including deficits in processing speed and complex sequencing and reasoning, and is common in vascular dementia (31%) and dementia of the Alzheimer’s type (20%) [13,51].
Much like cognitive impairment, geriatric depression is associated with adverse health outcomes [15]. These include a loss of function, diminished quality of life, greater reliance on services and care providers, and higher mortality [15]. Geriatric depression is also a predictor of postoperative complications including hospital readmission, mortality, delirium, long-term cognitive dysfunction, and decline in physical and mental health 1 year after surgery [52–56]. As such, preoperative depression is likely to be a crucial element that determines whether the functional outcome of surgery will be positive.
However, geriatric depression is under diagnosed in general health care facilities and preoperative evaluation clinics are no exception [57]. During the preoperative evaluation, psychological well-being is often overlooked in order to focus on more disease-specific concepts of risk prevention [16]. On the other hand, depression may be easier to detect preoperatively because it is stressful to face surgery and depressive symptoms can fluctuate with stress and anxiety.
Preoperative screening for geriatric depression. There are a number of brief depression scales that are reliable and objective and can be utilized by medical staff with no background in psychiatric diagnosis [58]. Several are created specifically for the older patient (Table 14.2). Self-report scales with simple response sets, such as “yes/no,” are commonly used. Those that can be administered verbally and are easy to understand are ideal for screening older adults who may also have cognitive impairment. Because most geriatric patients undergoing a surgical procedure have some underlying disease, it is also important to choose a depression screen that does not focus on somatic symptoms of depression (i.e., lack of sleep, lack of appetite) so as to avoid the potential bias of the underlying disease processes.
| Depression Scales | Items/Time | Sensitivity | Specificity | Score Range |
|---|---|---|---|---|
| Beck Depression Inventory–II (BDI-II) [13,60] | 21-item (5 min) | 79% | 54% | 0–63 (score >19a) |
| Geriatric Depression Scale Short Form (GDS) [55] | 15-item (2–3 min) | 79% | 71% | 0–15 (score > 5a) |
| Geriatric Depression Scale (GDS) [59] | 30-item (5–7 min) | 77% | 65% | 0–30 (score > 11a) |
| Zung Self-Rating Depression Scale [62] | 20-item (5–10 min) | X | X | 20–80 (score > 50a) |
| Hamilton Rating Scale for Depression (HAM-D) [64] | 17-item | 88% | 89% | 0–53 (score > 20a) |
| Depression in Old Age Scale (DIA-S) [61] | 10-item | 82% | 79% | 0–10 (score > 3/4a) |
| EURO-D [63] | 12-item | 86% | 84% | 0–12 (score > 4a) |
a Indicates probable depression.
The first depression scale developed specifically for the older person was the Geriatric Depression Scale (GDS) [59]. A shorter, 15-item version was adapted from the GDS and is now the test used most frequently in clinical settings (GDS-Short Form) [55]. Other screens, such as the Beck Depression Inventory–II (BDI),[13,60] Depression in Old Age Scale (DIA-S) [61], Zung Self-Rating Depression Scale [62], EURO-D [63], and the Hamilton Depression Rating Scale [64] have been validated for use specifically in older adults but some take longer to administer and might not be suitable for use in a preoperative evaluation clinic. However, all of the screening tests have limited sensitivity and specificity and no studies have directly compared scores obtained with these screening tests in a preoperative evaluation clinic with “gold standard” assessments of clinical depression performed in a less stressful setting. Therefore, preoperative depression screening cannot diagnose clinical depression but rather may screen for the probability of depression.
Frailty and Postoperative Outcomes
Frailty, defined as age-related decline in functional status, is another geriatric syndrome that may affect surgical outcome [17,18]. In nonhospitalized seniors, frailty is associated with falls, disability, morbidity, and mortality as well as increased health care costs, hospitalizations, and institutionalization. Frail older adults often suffer loss of independence and decreased quality of life and psychological well-being that makes them more reliant on caregivers and health care services. Frail persons also recover poorly from stress, especially the stress imposed on the body by a surgical procedure [19] Specifically, frailty is associated with increased risk of postoperative delirium, longer hospital length of stay, a decreased likelihood of discharge to home, higher 30 day readmission, and higher 6 month mortality rates [10,19,60,65,66]. This suggests the preoperative evaluation of seniors should include some measure of frailty. The problem is that there is no standard measure of frailty [18,67]. Although there is agreement that measures should address both biological symptoms and psychosocial factors. As such, a few scales might be useful preoperatively.
Preoperative screening for frailty. Frailty indexes across studies incorporate self-report questionnaires, cognitive tests, functional tests, and other assessments. In general, these indexes sum a list of deficits in an individual patient (Table 14.3). A valid and easy-to-use frailty index can help medical staff in a preoperative setting summarize and quantify a large amount of geriatric symptoms and comorbidities. One caveat is that although many indexes incorporate measures of disability and comorbidity, research suggests that frailty is a distinct and separate vulnerability [17].
Related posts:
Chapter 1 – Emergence Delirium
Chapter 2 – Postoperative Delirium
Chapter 4 – Postoperative Cognitive Improvement
Chapter 10 – Comorbidities and Postoperative Neurocognitive Disorder
Chapter 12 – Biomarkers of Postoperative Cognitive Dysfunction: Finding the Signal amid the Noise
Chapter 11 – Cognitive Testing for Perioperative Neurocognitive Disorder
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