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Summary 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 ( 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. Findings Between March 1, 2013, and March 25, 2016, we included 1401 patients in the study. 28 (2%) of 1401 patients died or had a myocardial infarction within 30 days of surgery. Subjective assessment had 19·2% sensitivity (95% CI 14·2–25) and 94·7% specificity (93·2–95·9) for identifying the inability to attain four metabolic equivalents during CPET. Only DASI scores were associated with predicting the primary outcome (adjusted odds ratio 0·96, 95% CI 0·83–0·99; p=0·03). Interpretation Subjectively assessed functional capacity should not be used for preoperative risk evaluation. Clinicians could instead consider a measure such as DASI for cardiac risk assessment. Funding Canadian Institutes of Health Research, Heart and Stroke Foundation of Canada, Ontario Ministry of Health and Long-Term Care, Ontario Ministry of Research, Innovation and Science, UK National Institute of Academic Anaesthesia, UK Clinical Research Collaboration, Australian and New Zealand College of Anaesthetists, and Monash University.

According to a former US politician ‘‘There are known knowns . . .There are known unknowns . . .But there are also unknown unknowns . . . ’’ This phrase is also apt in the respiratory function laboratory. One particular ‘‘known unknown’’ is the safety of respiratory function testing (RFT) in patients with abdominal aortic aneurysms (AAAs). Abdominal aortic aneurysm affects approximately 4% to 7% of men and 1% to 2% of women older than 65 years of age. Aneurysms >5.5 cm diameter in men and >5.0 cm in women are at significant risk of rupture and are considered for elective repair unless major contraindications exist. Respiratory function testings are recommended in the preoperative assessment of patients with AAA to reduce the morbidity and mortality associated with elective AAA repair. However, performing RFTs in patients with large (>6 cm) aneurysms is a potential contraindication because of concern of AAA rupture. An important reason for the persistence of this concern is a lack of data on the safety of performing RFTs in patients with AAA. We conducted a retrospective observational study of patients who had undergone preoperative RFTs for infrarenal nonruptured AAA between October 2008 and March 2014 in our institution. Patients’ hard copy medical records and electronic discharge summaries were reviewed. The study was approved by the Gold Coast Hospital and Health Service Human Research Ethics Committee (HREC/13/QGC/129). We identified 56 patients who had undergone RFTs during their AAA preoperative assessment. Median age was 73 years (range: 55-83), and 14% were women. The median size of the AAA was 6 cm (range 5-13 cm). Spirometry was performed in all 56 patients, diffusion capacity was performed in 29 (52%) patients, and lung volumes were measured in 26 (46%) patients. Chronic obstructive pulmonary disease was found in 43 (77%) patients, among whom 20 (36%) patients had mild (forced expiratory volume in 1 second [FEV1] 80% predicted), 15 (27%) patients had moderate (FEV1 50%-79% predicted), and 8 (14%) patients had severe (FEV1 30%-49% predicted) disease. Importantly, there were no reported early or late complications following RFTs. Three patients declined to perform lung volume testing because of concern about their AAA size (size of the AAA was 7 cm in 2 patients and 5.5 cm in 1 patient). In all, 45 (80%) patients underwent operative intervention for the AAA (open AAA repair in 29 patients and endovascular aneurysm repair in 16 patients). The median time between a patient performing RFT and undergoing operative intervention for the AAA was 41 days (range 3-353 days). At the end of the study, 7 (13%) had died, and the median time of the death since performing RFT was 138 days (range 60-1286 days). Among the 7 patients who died, 3 patients had surgical intervention for the AAA and died within 30 days of surgery due to postoperative complications. Our study demonstrates the safety of performing RFTs even in patients with large AAAs. Additionally in a recent study, 188 patients with large AAAs (>5.5 cm) underwent preoperative spirometry and cardiopulmonary exercise testing, implying that spirometry can be safely performed in patients with large AAAs. Although our contribution to global geopolitics has been negligible, we think the results of our study contribute to the burden of proof that RFTs are safe even in patients with large AAAs and make it one of the ‘‘known knowns.’’