Perioperative medicine training resources: U1M11 Functional capacity assessment

Abstract
Cardiopulmonary exercise testing (CPET) has become an important clinical tool to evaluate exercise capacity and predict outcome in patients with heart failure and other cardiac conditions. It provides assessment of the integrative exercise responses involving the pulmonary, cardiovascular and skeletal muscle systems, which are not adequately reflected through the measurement of individual organ system function. CPET is being used increasingly in a wide spectrum of clinical applications for evaluation of undiagnosed exercise intolerance and for objective determination of functional capacity and impairment. This review focuses on the exercise physiology and physiological basis for functional exercise testing and discusses the methodology, indications, contraindications and interpretation of CPET in normal people and in patients with heart failure.

Full citation:
Arena R, Myers J, Williams MA, et al. Assessment of functional capacity in clinical and research settings: a scientific statement from the American Heart Association Committee on Exercise, Rehabilitation, and Prevention of the Council on Clinical Cardiology and the Council on Cardiovascular Nursing. Circulation. 2007;116(3):329-343.

Abstract
Objective: There is a significant cardiac morbidity and mortality after endovascular aneurysm repair (EVAR). However, information about long-term risk of cardiac events after EVAR and potential predictors is lacking. Therefore, the aim of this study was to determine incidence and predictors of major adverse cardiac events (MACE) at 1 and 5 years after elective EVAR for infrarenal abdominal aortic aneurysms.

Methods: Baseline, perioperative, and postoperative information of 320 patients was evaluated. The primary outcome was the incidence of MACE after EVAR, which was defined as acute coronary syndrome, unstable angina pectoris, de novo atrial fibrillation, hospitalization for heart failure, mitral valve insufficiency, revascularization (including percutaneous coronary intervention and coronary artery bypass grafting), as well as cardiovascular and noncardiovascular death. Kaplan-Meier analyses were performed to determine incidences of MACE, MACE excluding noncardiovascular death and cardiac events by excluding noncardiovascular and vascular death from MACE. Predictors of MACE were identified using univariate and multivariate binary regression analysis.

Abstract
Exercise stress testing is a validated diagnostic test for coronary artery disease in symptomatic patients, and is used in the evaluation of patients with known cardiac disease. Testing of asymptomatic patients is generally not indicated. It may be performed in select deconditioned adults before starting a vigorous exercise program, but no studies have compared outcomes from preexercise testing vs. encouraging light exercise with gradual increases in exertion. Preoperative exercise stress testing is helpful for risk stratification in patients undergoing vascular surgery or who have active cardiac symptoms before undergoing nonemergent noncardiac surgery. Exercise stress testing without imaging is the preferred initial choice for risk stratification in most women. Sensitivity and specificity increase with the use of adjunctive imaging such as echocardiography or myocardial perfusion imaging with single-photon emission computed tomography. Exercise stress testing is rarely an appropriate option to evaluate persons with known coronary artery disease who have no new symptoms less than two years after percutaneous intervention or less than five years after coronary artery bypass grafting. The Duke treadmill score has excellent prognostic value for exercise stress testing. Imaging is not necessary if patients are able to achieve more than 10 metabolic equivalents on exercise stress testing. Exercise stress testing is not indicated before noncardiac surgeries in patients who can achieve 4 metabolic equivalents without symptoms.

Abstract
Purpose of review: This review examines how functional capacity informs preoperative risk stratification, as well as strengths and limitations of options for estimating functional capacity.

Recent findings: Functional capacity (or cardiopulmonary fitness) overlaps with other important characteristics, including muscular strength, balance, and frailty. Poor functional capacity is associated with postoperative morbidity, especially noncardiovascular complications. Both patient interviews and exercise tests are used to assess functional capacity. The usual approach of an unstructured patient interview does not predict outcomes. Structured interviews that incorporate validated questionnaires (Duke Activity Status Index) or standardized questions about physical activity (ability to climb stairs) do predict moderate-or-severe complications and cardiovascular complications. Among exercise tests, cardiopulmonary exercise testing (CPET) has shown the most consistent association with risks of complications. Other tests (6-min walk test, incremental shuttle walk test, stair climbing) might predict complications, but still require further high-quality evaluation.

Summary: A straightforward way to better assess functional capacity is a structured interview with validated questionnaires or standardized questions about physical activities. Functional capacity can also be assessed by exercise tests, with the strongest evidence supporting CPET. Although some simpler exercise tests have shown promise, more research remains needed to better define their role in preoperative evaluation.

Abstract
Background: Perioperative cardiovascular guidelines endorse functional capacity estimation, based on 'cut-off' daily activities for risk assessment and climbing two flights of stairs to approximate 4 metabolic equivalents. We assessed the association between self-reported functional capacity and postoperative cardiac events.

Methods: Consecutive patients at elevated cardiovascular risk undergoing in-patient noncardiac surgery were included in this predefined secondary analysis. Self-reported ability to walk up two flights of stairs was extracted from electronic charts. The primary endpoint was a composite of cardiac death and cardiac events at 30 days. Secondary endpoints included the same composite at 1 yr, all-cause mortality, and myocardial injury.\

Full citation:
Lurati Buse GAL, Puelacher C, Gualandro DM, et al. Association between self-reported functional capacity and major adverse cardiac events in patients at elevated risk undergoing noncardiac surgery: a prospective diagnostic cohort study. Br J Anaesth. 2021;126(1):102-110.

Abstract
We aimed to assess the reliability of patients as historians in terms of the self assessment of functional capacity and also examined the usefulness of a simple ward exercise tolerance test. One hundred consecutive elective vascular surgery patients were interviewed preoperatively using a modified Duke Activity Status Index (DASI) questionnaire. To test reliability in reference to an independent observer, the questionnaire concerning the patient was also applied to each patient's closest relative who was blinded to the patient's responses. Patients were then asked to walk up two flights of stairs and the time taken to complete the task or the reason for failing to complete the task was recorded.

Abstract
Purpose: The six-minute walk test (6MWT) is a simple and valid test for assessing cardiopulmonary fitness. Nevertheless, the relationship between preoperative 6MWT distance and postoperative complications is uncertain. We conducted a secondary analysis of the 6MWT nested cohort substudy of the Measurement of Exercise Tolerance before Surgery study to determine if 6MWT distance predicts postoperative complications or death.

Methods: This analysis included 545 adults (≥ 40 yr) who were at elevated cardiac risk and had elective inpatient non-cardiac surgery at 15 hospitals in Canada, Australia, and New Zealand. Each participant performed a preoperative 6MWT and was followed for 30 days after surgery. The primary outcome was moderate or severe in-hospital complications. The secondary outcome was 30-day death or myocardial injury. Multivariable logistic regression modelling was used to characterize the adjusted association of 6MWT distance with these outcomes.

Abstract
Background: Accurate assessment of functional capacity, a predictor of postoperative morbidity and mortality, is essential to improving surgical planning and outcomes. We assessed if all 12 items of the Duke Activity Status Index (DASI) were equally important in reflecting exercise capacity.

Methods: In this secondary cross-sectional analysis of the international, multicentre Measurement of Exercise Tolerance before Surgery (METS) study, we assessed cardiopulmonary exercise testing and DASI data from 1455 participants. Multivariable regression analyses were used to revise the DASI model in predicting an anaerobic threshold (AT) >11 ml kg-1 min-1 and peak oxygen consumption (VO2 peak) >16 ml kg-1 min-1, cut-points that represent a reduced risk of postoperative complications.

Abstract
Background: For perioperative risk stratification, a robust, practical test could be used where cardiopulmonary exercise testing (CPET) is unavailable. The aim of this study was to assess the utility of the 6 min walk test (6MWT) distance to discriminate between low and high anaerobic threshold (AT) in patients awaiting major non-cardiac surgery.

Methods: In 110 participants, we obtained oxygen consumption at the AT from CPET and recorded the distance walked (in m) during a 6MWT. Receiver operating characteristic (ROC) curve analysis was used to derive two different cut-points for 6MWT distance in predicting an AT of <11 ml O(2) kg(-1) min(-1); one using the highest sum of sensitivity and specificity (conventional method) and the other adopting a 2:1 weighting in favour of sensitivity. In addition, using a novel linear regression-based technique, we obtained lower and upper cut-points for 6MWT distance that are predictive of an AT that is likely to be (P≥0.75) <11 or >11 ml O(2) kg(-1) min(-1).

Abstract
Importance: Perioperative cardiovascular complications occur in 3% of hospitalizations for noncardiac surgery in the US. This review summarizes evidence regarding cardiovascular risk assessment prior to noncardiac surgery.

Observations: Preoperative cardiovascular risk assessment requires a focused history and physical examination to identify signs and symptoms of ischemic heart disease, heart failure, and severe valvular disease. Risk calculators, such as the Revised Cardiac Risk Index, identify individuals with low risk (<1%) and higher risk (≥1%) for perioperative major adverse cardiovascular events during the surgical hospital admission or within 30 days of surgery. Cardiovascular testing is rarely indicated in patients at low risk for major adverse cardiovascular events. Stress testing may be considered in patients at higher risk (determined by the inability to climb ≥2 flights of stairs, which is <4 metabolic equivalent tasks) if the results from the testing would change the perioperative medical, anesthesia, or surgical approaches. Routine coronary revascularization does not reduce perioperative risk and should not be performed without specific indications independent of planned surgery. Routine perioperative use of low-dose aspirin (100 mg/d) does not decrease cardiovascular events but does increase surgical bleeding. Statins are associated with fewer postoperative cardiovascular complications and lower mortality (1.8% vs 2.3% without statin use; P < .001) in observational studies, and should be considered preoperatively in patients with atherosclerotic cardiovascular disease undergoing vascular surgery. High-dose β-blockers (eg, 100 mg of metoprolol succinate) administered 2 to 4 hours prior to surgery are associated with a higher risk of stroke (1.0% vs 0.5% without β-blocker use; P = .005) and mortality (3.1% vs 2.3% without β-blocker use; P = .03) and should not be routinely used. There is a greater risk of perioperative myocardial infarction and major adverse cardiovascular events in adults aged 75 years or older (9.5% vs 4.8% for younger adults; P < .001) and in patients with coronary stents (8.9% vs 1.5% for those without stents; P < .001) and these patients warrant careful preoperative consideration.

Abstract
Background: The Duke Activity Status Index (DASI) questionnaire might help incorporate self-reported functional capacity into preoperative risk assessment. Nonetheless, prognostically important thresholds in DASI scores remain unclear. We conducted a nested cohort analysis of the Measurement of Exercise Tolerance before Surgery (METS) study to characterise the association of preoperative DASI scores with postoperative death or complications.

Methods: The analysis included 1546 participants (≥40 yr of age) at an elevated cardiac risk who had inpatient noncardiac surgery. The primary outcome was 30-day death or myocardial injury. The secondary outcomes were 30-day death or myocardial infarction, in-hospital moderate-to-severe complications, and 1 yr death or new disability. Multivariable logistic regression modelling was used to characterise the adjusted association of preoperative DASI scores with outcomes.

Abstract
Background: Functional capacity is an important component of risk assessment for major surgery. Doctors' clinical subjective assessment of patients' functional capacity has uncertain accuracy. We did a study to compare preoperative subjective assessment with alternative markers of fitness (cardiopulmonary exercise testing [CPET], scores on the Duke Activity Status Index [DASI] questionnaire, and serum N-terminal pro-B-type natriuretic peptide [NT pro-BNP] concentrations) for predicting death or complications after major elective non-cardiac surgery.

Methods: We did a multicentre, international, prospective cohort study at 25 hospitals: five in Canada, seven in the UK, ten in Australia, and three in New Zealand. We recruited adults aged at least 40 years who were scheduled for major non-cardiac surgery and deemed to have one or more risk factors for cardiac complications (eg, a history of heart failure, stroke, or diabetes) or coronary artery disease. Functional capacity was subjectively assessed in units of metabolic equivalents of tasks by the responsible anaesthesiologists in the preoperative assessment clinic, graded as poor (<4), moderate (4-10), or good (>10). All participants also completed the DASI questionnaire, underwent CPET to measure peak oxygen consumption, and had blood tests for measurement of NT pro-BNP concentrations. After surgery, patients had daily electrocardiograms and blood tests to measure troponin and creatinine concentrations until the third postoperative day or hospital discharge. The primary outcome was death or myocardial infarction within 30 days after surgery, assessed in all participants who underwent both CPET and surgery. Prognostic accuracy was assessed using logistic regression, receiver-operating-characteristic curves, and net risk reclassification.

Abstract
Background: Algorithms for preoperative cardiac evaluation prior to noncardiac surgery use indices of the metabolic equivalent of activities of daily living (METs). We evaluated METs as a predictor of cardiac complications following elective, noncardiac surgery.

Methods: A study was performed in an outpatient university preadmission center METs were estimated prospectively for 5,939 inpatients admitted for elective, noncardiac surgery who underwent a preanesthetic assessment within two months prior to surgery. Cardiac outcomes were retrieved retrospectively from relational databases. Outcomes included death, myocardial infarction, acute congestive failure, arrhythmias, cardiac arrest, acute ischemia, acute renalfailure, stroke, respiratory failure, severe hypertension, peripheral vascular occlusion, and pericardial effusion. Adverse outcomes were correlated with age, gender, surgical procedure, activities, and the American Society of Anesthesiologist's Physical Status (ASA-PS) using receiver operator characteristic curve analysis.

Function is a major focus of physical therapist assessment and intervention. Traditionally, therapists have assessed function through observation of the individual’s performance, making a subjective assessment of the quantity, quality, and outcome of the functional movement or task. The use of performance measures has been driven by evidence-based practice and globalization, in particular the universal perspective of health, known as the World Health Organization’s International Classification of Functioning, Disability, and Health (ICF). Measuring health and disability through the framework of the ICF model requires valid and reliable measures of both function and quality of life.

Abstract
One metabolic equivalent (MET) is defined as the amount of oxygen consumed while sitting at rest and is equal to 3.5 ml O2 per kg body weight x min. The MET concept represents a simple, practical, and easily understood procedure for expressing the energy cost of physical activities as a multiple of the resting metabolic rate. The energy cost of an activity can be determined by dividing the relative oxygen cost of the activity (ml O2/kg/min) x by 3.5. This article summarizes and presents energy expenditure values for numerous household and recreational activities in both METS and watts units. Also, the intensity levels (in METS) for selected exercise protocols are compared stage by stage. In spite of its limitations, the MET concept provides a convenient method to describe the functional capacity or exercise tolerance of an individual as determined from progressive exercise testing and to define a repertoire of physical activities in which a person may participate safely, without exceeding a prescribed intensity level.