Preoperative cognitive and frailty screening in the geriatric surgical patient: A narrative review

Abstract

Purpose

The identification of older patients who may have deficits in cognitive or functional domains will become more pressing as increasing numbers of these patients present for preoperative evaluations. The number of older adults with deficiencies in these areas is projected to grow and more of these patients will present for assessment in preoperative clinics with the expectation that surgeries will be performed.

Methods

We review current outcomes data for preoperative cognitive impairment and frailty.

Findings

We point to a number of directions research is taking as systems for the prevention of postoperative cognitive and functional decline are being developed. We also discuss the current status of screening and examine potential instruments that can be used in the setting of the preanesthesia clinic.

Implications

Clinicians may anticipate that geriatric screening tools focused on cognitive and functional domains will play a direct role in the ongoing evolution of pre-surgical assessment and triage.

Introduction

As the population of the United States continues to age, a greater proportion of surgical and anesthetic services are devoted to geriatric patients. In addition to a standard history and physical, optimal preoperative screening for specific geriatric syndromes includes cognitive and functional testing, frailty score calculation, fall risk documentation, nutritional assessment, and depression screening.(1) In this review, we will focus on two important but frequently overlooked components of the preoperative assessment of the geriatric patient: cognitive and frailty screening. Our review is intended to highlight methods and outcomes that are useful in the busy, time-compressed and highly structured setting of a preanesthetic clinic, where evaluation of patients may be performed by advanced practice providers in addition to physicians. This is not intended to be a systematic review of the literature, but rather a review of the current state of practice and a map of potentially useful techniques in this setting.

Evidence suggests that the aged are most at risk for postoperative deleterious neurocognitive outcomes.(2) In fact, 30–80% of older adults become delirious after major surgery, 30–40% experience early postoperative cognitive dysfunction (POCD), and 10–15% develop late POCD.(3) Postoperative delirium and POCD are associated with increased cost, length of hospital stay, and 1-year mortality. Though it has been well-established that preoperative cognitive impairment is the leading risk factor for postoperative delirium and POCD, preoperative cognitive function is not routinely or formally assessed. Therefore, one of the main arguments for routine preoperative cognitive screening in older adults is for purposes of risk stratification.

In addition to cognitive screening, recent research has begun to evaluate the role of scoring patients based on frailty. Those who are defined as frail, by various metrics, have been shown to have increased short-term and long-term mortality as well as increased susceptibility to specific outcomes such as myocardial infarction and stroke.(4)

The concepts of cognitive dysfunction and frailty both point to dimensions of measurable preoperative function that directly correlate with postoperative outcomes. These include well-investigated associations with morbidity, mortality, postoperative complications, post-discharge institutionalization, and postoperative delirium.(5, 6)

A number of frailty and cognitive scoring systems are available and have been validated for use by clinicians.(7, 8) The institution of a scoring system may assist clinicians in both triage of patients as they prepare for surgery and also the anticipation and provision of necessary postoperative care, whether in the inpatient or outpatient setting.

Preoperative screening of cognitive status

The geriatric patient’s preoperative cognitive status should be evaluated and carefully documented for several reasons. First, it is difficult to determine whether a change has occurred postoperatively without a thorough understanding of the preoperative state. It is likely that preoperative cognitive impairment is frequently unrecognized due to lack of formal screening. One study found that cognitive impairment was present in 35% of patients presenting for elective coronary artery bypass graft surgery.(9) Another investigation found cognitive impairment or dementia in 68% of patients over the age of 60 presenting for vascular surgery and the impairment was previously unrecognized in 88.3% of patients.(10)

Second, recent evidence suggests that the presence of preoperative impaired cognition is associated with postoperative morbidity and mortality. Postoperative delirium is one of the most commonly cited postoperative complications associated with preoperative impaired cognition.(11–13) Additionally, preoperative cognitive impairment is associated with postoperative cognitive dysfunction and cognitive decline.(14)

The presence of impaired cognition preoperatively has implications that extend beyond neurocognitive complications. A recent retrospective cohort study of 3530 participants found that participants with preoperative impaired sensorium were significantly more likely to experience postoperative pneumonia, ventilator dependence, progressive renal insufficiency, urinary tract infection, stroke, venous thromboembolism, and postoperative death.(5) Several other studies have similarly concluded that preoperative impaired cognition is associated with an increased mortality rate.(11, 15)

Current Status of Preoperative Cognitive Screening

Very few institutions in the United States systematically screen patients for preoperative cognitive impairment partly because many tests require specialized training to administer and score and are time and labor intensive. Oftentimes, the only patients that are identified as having preexisting cognitive dysfunction are those that either carry a diagnosis of dementia or those that report subjective memory complaints. An important barrier preventing more widespread screening is the identification of a screening tool that is well-suited for busy preanesthesia clinics. The ideal screening tool would be self-administered, brief, automatically scored, and communicate with the electronic health record. Other considerations include finding a validated test that is reliable across multiple languages, cultures, and education levels. In a review of practical preoperative cognitive screening tools, Long and colleagues identified 6 screening tools that could be administered in 2.5 minutes or less.(8)

To date, the majority of preoperative cognitive screening has occurred in the context of outcomes research. One group found that patients with lower scores on the animal fluency test were at higher risk for developing postoperative delirium.(16) The animal fluency test requires patients to name as many animals as possible within 60 seconds. Other studies have used the Mini-Cog,(17) a test that combines a clock drawing task with a 3-item recall, as a preoperative cognitive screening tool. Poor preoperative performance on the Mini-Cog was associated with an increased incidence of postoperative delirium(18) and an increase in 6-month mortality.(15)

Similarly, poor performance on the rapid screening test Cognitive Disorder Examination (CODEX), was associated with postoperative delirium in older people undergoing hip fracture surgery.(19) Following cardiac surgery, better preoperative performance on the Clock-in-the-Box test, a screening tool that takes less than 2 minutes to deliver, was associated with a reduced risk of being discharged to a facility.(20)

Another screening tool that has been used in the preoperative arena is the Montreal Cognitive Assessment (MoCA), a 10-minute, 30-point screening test.(21) Using the MoCA, cognitive impairment or dementia was found in 68% of patients over the age of 60 presenting for vascular surgery and was previously unrecognized in 88.3% of patients. Another group using the MoCA as a preoperative screening tool found that mild cognitive dysfunction was associated with pulmonary complications after coronary artery bypass graft surgery.(22)

The 2012 American College of Surgeons (ACS) and American Geriatric Society (AGS) guidelines regarding the optimal preoperative assessment of the geriatric surgical patient recommended that a preoperative cognitive assessment be performed for any patient without a known history of cognitive impairment or dementia.(1) These guidelines suggest the use of the Mini-Cog for preoperative cognitive screening.(1) More recently, the AGS published a best practice statement regarding postoperative delirium. This statement includes a recommendation to “assess and clearly document preoperative cognitive function in older adults at risk of postoperative delirium.”(23)

Preoperative assessment of functional status/Frailty

In an attempt to better define risk factors among older adults that go beyond comorbidity to include assessment of strength, functional status, and cognitive capability, researchers and clinicians have developed the concept of frailty. As a measure of a given patient’s risk to experience postoperative complications, frailty scoring may offer advantages over traditional risk scoring.(24)

Understanding that the recognition and potential treatment of the syndrome may confer substantial benefits as patients move through their operative course, the preoperative clinic offers an excellent setting for the screening and triage of older adults with regard to frailty. The institution of frailty screening also offers broad new opportunities to educate patients and families as well as health care providers about potential risks for these vulnerable patient populations.

The determination of frailty, a medical syndrome, depends predominantly on the assessment of a patient’s ability to maintain certain markers of robust physiologic status. A concise definition of frailty would encompass both the clinical presentation of the syndrome as seen by physicians in the clinic as well as clearly defined terms that can be consistently utilized in research. This, to date, has been difficult to achieve. Clearly, there is substantial overlap between the concept of frailty and the common depredations of aging, including sarcopenia, cachexia, disability, and comorbidities. Even so, frailty can be broadly understood as a decrease in physiologic reserve across a number of organ systems and a lack of resistance to stressors.(25, 26) Frailty is associated with degraded activities of daily living and mobility, increased length of hospitalization and institutionalization, increased rate of post-surgical complications, and mortality.(27, 28)

A number of models describing frailty have been put forward. Two of the most common and well-validated are: 1) the frailty phenotype; and 2) the frailty index, or a model describing the incremental, additive effect of deficits or risk factors. Both of these models are derived from large scale, community-based studies.(26, 29)

In practical terms the markers of frailty, as currently established, can be physical, cognitive or comorbidity-based and in many cases they correlate with postoperative morbidity and mortality. For example, surveys currently assess factors such as weight loss, fatigue, ability to ambulate, comorbid illnesses, grip strength or weakness, and a history of falls.(30)

Frailty in the community is common, approaching 10% for those with a complete frailty syndrome and 45% for those with some signs of frailty. It is more common in women and in the oldest old, as well as among older adults facing surgical intervention.(25) Frailty may operate independently of comorbidity and disability. It may also operate independently of age.(31)

Frailty is common in patients preparing to undergo surgery, with some studies suggesting an incidence approaching 50%.(24) There is substantial variation, however, depending on the frailty model used in the study. At minimum, approximately 10% of geriatric pre-surgical patients will display this vulnerable phenotype, and exposure of frail patients to surgery results in deleterious outcomes. These include increased mortality, length of hospitalization, readmission rates, postoperative complication rates, postoperative delirium, and postoperative institutionalization.(25, 32)

In a recent study, Robinson et al found that a scoring system assessing frailty across a number of domains (frailty, disability, and co-morbidity) could help predict 6-month postoperative mortality and post-discharge institutionalization. The study used age, Mini-Cog test, nutritional status (weight loss, BMI and albumin), falls in the past 6 months, depression, hematocrit, Katz score (an index assigning points to each of the six common activities of daily living), Charlson Index (an index of 19 comorbidities weighted for risk of one-year mortality), American Society of Anesthesiologists score, and a measure of polypharmacy. The presence of four or more of these surrogate markers in any one patient predicted six-month mortality with a sensitivity of 81% and a specificity of 86%.(15)

Focusing on institutionalization, a similar analysis found that the rate of institutionalization of frail patients after surgery was markedly elevated. The criteria added assessments of ‘timed get up and go’ as well as extrinsic frailty to the criteria used in the prior study. Extrinsic frailty recognizes social factors that increase mortality in nursing home patients. Timed get up and go, any functional dependence, Charlson score of 3 or higher, and hematocrit less than 35% were the factors most closely associated with discharge to an institution. Three or more frailty markers predicted institutionalization on discharge with a sensitivity of 82% and a specificity of 84%.(33)

Finally, using an analysis simplified to include age, Katz score, timed get up-and-go, Charlson Index, anemia, Mini-Cog score, albumin, and falls, one study found that preoperative frailty was a predictor of postoperative complications, independent of surgical specialty. Non-frail patients undergoing colorectal surgery had a complication rate of 21%, versus frail patients’ complication rate of 58%; Non-frail cardiac surgery patients had complication rates of 17% versus frail patients’ complication rates of 56%.(32)

Some of these assessments have been used as stand alone markers for functional status. They are themselves strong tests for the ability to withstand the operative environment. These include grip strength, walking ability, and a history of falls.(34–36) At the same time, single measures of frailty may be less predictive of postoperative outcomes than multi-dimensional measures.(37) Table 1 describes some common single item frailty markers.

Table 1.

Single Item Frailty Markers

Grip Strength: The Harpenden and Jamar dynamometers are both validated clinical instruments for measurement of grip strength.

Leong et al: Grip strength was inversely associated with all-cause mortality (hazard ratio per 5 kg reduction in grip strength 1·16, 95% CI 1·13–1·20; p<0·0001), cardiovascular mortality (1·17, 1·11–1·24; p<0·0001), non-cardiovascular mortality (1·17, 1·12–1·21; p<0·0001), myocardial infarction (1·07, 1·02–1·11; p=0·002), and stroke (1·09, 1·05–1·15; p<0·0001). Grip strength was a stronger predictor of all-cause and cardiovascular mortality than systolic blood pressure.(4)

Syddall et al: In men, lower grip strength correlated with ten ageing markers compared to chronological age which was significantly associated with seven. In women, there were six significant relationships for grip compared to three for age. The conclusion is grip strength was associated with more markers of frailty than chronological age.(34)

Timed Up-and-Go: Robinson et al: This timed test starts with the subject standing from a chair, walking ten feet, returning to the chair, and ends after the subject sits. Timed up-and-go results are grouped: Fast≤10 sec, Intermediate=11–14 sec, Slow≥15 sec.

272 subjects (mean age of 74±6 years). Slower timed up-and-go was associated with an increased postoperative complications following colorectal (fast-13%, intermediate-29% and slow-77%; p<0.001) and cardiac (fast-11%, intermediate-26% and slow-52%; p<0.001) operations. Slower timed up-and-go was associated with increased one-year mortality following both colorectal (fast-3%, intermediate-10% and slow-31%; p=0.006) and cardiac (fast-2%, intermediate-3% and slow-12%;p=0.039) operations.(35)

Falls: Jones et al: A fall was defined as unintentionally coming to rest on the ground, floor or other lower level. Patients were considered to have had a fall if they had a history of one or more falls in the six-months preceding surgery.

There were 235 subjects with a mean age of 74±6 years. Pre-operative falls occurred in 33%. One or more postoperative complications occurred more frequently in the group with prior falls compared to the non-fallers following both colorectal (59% vs. 25%; p=0.004) and cardiac (39% vs. 15%; p=0.002) operations. These findings were independent of advancing chronologic age. Need for discharge to an institutional care facility occurred more frequently in the group that had fallen in comparison to the non-fallers in both the colorectal (52% vs. 6%; p<0.001) and cardiac (62% vs. 32%; p=0.001) groups. Similarly, 30-day readmission was higher in the group with prior falls following both colorectal (p=0.043) and cardiac (p=0.016) operations.(36)

A recent review of perioperative surgical outcomes and frailty identified 19 studies focusing on the combined topics. All of the studies found an association between frailty and perioperative outcomes. These studies encompassed a variety of surgical arenas, including cardiac, gastrointestinal, vascular, thoracic, and oncologic. Common outcomes included mortality, postoperative complications (including myocardial infarction and arrhythmia), postoperative delirium, increased length of stay, and institutionalization.(38)

A review of studies relating geriatric conditions including frailty to postoperative mortality and complications found broad linkage between preoperative conditions and postoperative outcomes. Preoperative conditions included functional and cognitive impairment, malnutrition, facility residence, and frailty, and the risk of death associated with these syndromes was as high as 40% in the case of cognitive impairment.(39)

Current Status of Frailty Screening

At present, there are a number of commonly used and accepted measurement tools for frailty. For research, the extensive Frailty Index covers a substantial number of risk factors that correspond to an increase in mortality and institutionalization.(28, 40) For the assessment of patients in the preoperative clinic, measures that can be completed quickly are useful. These include the frailty phenotype by Fried et al, the FRAIL screening tool or the Edmonton Frail Scale.(26, 41–43) The Modified Frailty Index uses common comorbid variables that could be identified in a typical preoperative exam.(44) Revenig et al also demonstrated recently that shrinking and grip strength alone hold the same prognostic value as the five-item Fried phenotype for short-term (30-day) morbidity and mortality.(7) Table 2 contains some of the common clinical Frailty assessments and study outcomes.

Table 2.

Common Clinical Frailty Scores

Frailty phenotype(26)

Shrinking, weakness, exhaustion, low activity and slowed walking speed. Shrinking: weight loss, unintentional, of 10 pounds in prior year or, at follow-up, of 5% of body weight in prior year (by direct measurement of weight). Weakness: grip strength in the lowest 20% at baseline, adjusted for gender and body mass index. Poor endurance and energy as indicated by self-report of exhaustion. Slowness: based on time to walk 15 feet, adjusting for gender and standing height. Low physical activity level: A weighted score of kilocalories expended per week is calculated at baseline based on each participant’s report.

Three or more characteristics need to be present for an individual to be considered frail. Those with no characteristics are considered robust, those with one or two characteristics are hypothesized to be in an intermediate, possibly pre-frail, stage.

FRAIL screening tool(41)

Fatigue: “How much of the time during the past 4 weeks did you feel tired?”

Resistance: “By yourself and not using aids, do you have any difficulty walking up 10 steps without resting?”

Ambulation: “By yourself and not using aids, do you have any difficulty walking several hundred yards?”

Illness: For 11 illnesses, participants are asked, “Did a doctor ever tell you that you have [illness The illnesses include hypertension, diabetes, cancer (other than a minor skin cancer), chronic lung disease, heart attack, congestive heart failure, angina, asthma, arthritis, stroke, and kidney disease

Loss of weight: “How much do you weigh with your clothes on but without shoes?” “One year ago, how much did you weigh without your shoes and with your clothes on?”

Edmonton Frail Scale(42)

Cognition: “Please imagine that this pre-drawn circle is a clock. I would like you to place the numbers in the correct positions then place the hands to indicate a time of ten after eleven.”

General health status: “In the past year, how many times have you been admitted to a hospital?” “In general, how would you describe your health?”

Functional independence: “With how many of the following activities do you require help? (meal preparation, shopping, transportation, telephone, housekeeping, laundry, managing money, taking medications).

Social support: “When you need help, can you count on someone who is willing and able to meet your needs?”

Medication use: “Do you use five or more different prescription medications on a regular basis?” “At times, do you forget to take your prescription medications?”

Nutrition: “Have you recently lost weight such that your clothing has become looser?”

Mood: “Do you often feel sad or depressed?”

Continence: “Do you have a problem with losing control of urine when you don’t want to?”

Functional performance: “I would like you to sit in this chair with your back and arms resting. Then, when I say ‘GO’, please stand up and walk at a safe and comfortable pace to the mark on the floor (approximately 3 meters away), return to the chair and sit down.”

Modified Frailty Index(44)

History of diabetes; COPD or pneumonia; congestive heart failure; myocardial infarction; angina/PCI; hypertension requiring medication; peripheral vascular disease; dementia; TIA or CVA; CVA with neurological deficit; ADLs.

A retrospective review of the American College of Surgeons National Surgery Quality Improvement Program Participant Use Data files found that an approach using parameters that can autopopulate from an electronic medical record (age, sex, race, albumin, creatinine, hematocrit, and American Society of Anesthesiologists Score) possessed predictive power comparable to established tests.(45)

It is worth noting that a 2012 review of major frailty scores found that large scale screening for frailty was likely to have benefit in excluding individuals from the syndrome but would have a false-positive rate that was too high for routine diagnostic purposes. Clinical judgement, the authors noted, is still the best instrument for assessing the needs of the individual patient.(46)

Cognitive Dysfunction and Frailty Together Increase Vulnerability

Screening for cognitive dysfunction and frailty in the preoperative clinic potentially allows the clinician to identify and track two important and independent domains for predicting perioperative outcomes.

The combination of cognitive dysfunction and frailty may expose a patient to particularly negative consequences. For example, one prospective study found that frail hospitalized patients were more likely to become delirious, and that patients who became delirious subsequently had a markedly reduced survival time.(47) The combined assessment of frailty and cognition is also predictive of adverse postoperative outcomes and longer length of stay.(10)

One study assessed adults living in the community for frailty. Those who were determined to be frail by a phenotype were more likely to have a lower adjusted Mini-Mental State Exam score four years later. Of note, the single measures of frailty predicting cognitive decline were different between men and women, with women displaying a less robust linkage.(48)

A prospective study looked at more than 700 community-dwelling older people who did not have cognitive decline at baseline. In these people, physical frailty based on a phenotype exam was associated with a substantially elevated risk of incident mild cognitive impairment. Higher levels of frailty were associated with a greater risk.(49)

These findings were echoed by a cross-sectional study of 654 people older than 75, who were assessed for frailty and cognitive function. Frailty was associated with an almost eight-fold risk of cognitive impairment or dementia. “It is possible,” noted the authors, “that cognitive impairment is a clinical feature of frailty and therefore should be included in the frailty definition.”(50) Other studies have also found dementia and frailty to be widely associated, independent of other factors.(51, 52)

Optimizing Patients in the Perioperative Setting

It is important that patients and their caregivers are aware of the potential postoperative complications associated with preexisting cognitive impairment and frailty in order to inform decision-making and to assist with discharge planning.

The 2012 ACS/AGS guidelines recommend that if the patient has known preexisting cognitive impairment or based on results of the Mini-Cog, that the patient be referred to a primary care physician, geriatrician, or mental health specialist.(1) These providers can assist with reviewing medication lists and counseling patients regarding co-existing conditions such as substance abuse. To decrease the risk of postoperative delirium, patients should be instructed to bring any assistive devices such as hearing aids and glasses so that these are immediately available in the postoperative period.

To date, the clinical literature regarding preoperative optimization of cognitive status is scarce. There is, however, a growing body of literature examining the basic science of cognitive dysfunction as well as an increasing interest in animal models. For example, in a rat model, preoperative environmental enrichment attenuated surgery-induced cognitive impairment.(53) One recent clinical trial found that older adults randomized to preoperative cognitive training had a decreased incidence of postoperative cognitive dysfunction following gastrointestinal surgery than participants who did not undergo preoperative training.(54)

In terms of frailty, persons experiencing the syndrome tend to progress along a spectrum, commonly toward a state of increasing frailty. It is possible, however, for patients to become less frail, even without intervention.(25) Because of this observation, it has been suggested that it may be possible to drive individuals toward a more robust state. The frail, both in the community and in the preoperative setting, could benefit from treatment focused on intervening in the progressive nature of the syndrome. There are, as yet, few studies focused specifically on pre-surgical populations.

Ongoing exercise training has shown some benefit in older adults in long-term care, improving a variety of functional measures. Exercise training has not been tested extensively in pre-surgical populations with regard to post-operative outcomes, nor have specific types of exercise having benefit been well-delineated.(55) In line with exercise training, prehabilitation (preoperative exercise training) for surgery has shown some promise and continues to be actively investigated.(56) As this research matures, it may prove productive to expand on these therapies in the setting of the pre-operative clinic.

Nutritional deficiencies play a role in the development of the frailty syndrome and correction likely plays a role in treatment. For example, treatment of anemia in geriatric patients undergoing orthopedic surgery is supported by available evidence—many of these patients are also frail.(57)

Other methods of correcting deficient nutritional status have come under scrutiny. For example, a meta-analysis found that Vitamin D supplementation had a beneficial effect on strength and balance.(58) Vitamin D and protein supplementation may benefit geriatric populations with sarcopenia. Investigation into these areas is actively underway.(59)

Multi-modal approaches to frailty treatment have shown some promise. One study of colorectal surgery patients examined the effects of enrolling participants in a prehabilitation program consisting of protein supplementation, anxiety reduction, and exercise. Over eight weeks, those who were in the prehabilitation program returned to baseline function at a rate almost twice as fast as those who were not enrolled (80% vs 40%).(60)

Conclusion

Preoperative cognitive and frailty screening may help clinicians identify older patients who are particularly vulnerable to experiencing deleterious postoperative outcomes. In the setting of the preoperative clinic, stratifying patients according to their individual risks based on these vulnerabilities offers the opportunity to properly educate patients and their families about the possible harms and benefits of surgery. It also may allow physicians to better anticipate potential outcomes once patients have left the surgical suite.

Screening tests for cognition and frailty that can be rapidly performed in the outpatient clinic are available. These range from multi-domain scores to single item tests that have been validated in a number of settings, for a variety of outcome measures. In the preoperative clinic, current forms of risk stratification primarily address cardiopulmonary factors. For anesthesiologists and other perioperative professionals, implementing some combination of these tests for cognitive dysfunction and frailty in the preoperative setting should ultimately prove a fruitful and powerful adjunct to other forms of risk assessment.

Interventions for cognitive impairment and frailty are now in their infancy, but the volume of research directed at these pressing issues can be expected to grow rapidly.(61, 62) As this occurs, a subset of patients for whom surgery presents an unacceptable risk may emerge. Identification of patients most susceptible to injury will allow resources to be properly allocated to the non-surgical management of their multi-domain health issues. For others, delineation of specific preoperative geriatric profiles may allow specialists to optimize perioperative strategies to prioritize cognitive and functional recovery.