Measurement of Exercise Tolerance before Surgery (METS) study: a protocol for an international multicentre prospective cohort study of cardiopulmonary exercise testing prior to major non-cardiac surgery

Abstract

IntroductionPreoperative functional capacity is considered an important risk factor for cardiovascular and other complications of major non-cardiac surgery. Nonetheless, the usual approach for estimating preoperative functional capacity, namely doctors’ subjective assessment, may not accurately predict postoperative morbidity or mortality. 3 possible alternatives are cardiopulmonary exercise testing; the Duke Activity Status Index, a standardised questionnaire for estimating functional capacity; and the serum concentration of N-terminal pro-B-type natriuretic peptide (NT pro-BNP), a biomarker for heart failure and cardiac ischaemia.Methods and analysisThe Measurement of Exercise Tolerance before Surgery (METS) Study is a multicentre prospective cohort study of patients undergoing major elective non-cardiac surgery at 25 participating study sites in Australia, Canada, New Zealand and the UK. We aim to recruit 1723 participants. Prior to surgery, participants undergo symptom-limited cardiopulmonary exercise testing on a cycle ergometer, complete the Duke Activity Status Index questionnaire, undergo blood sampling to measure serum NT pro-BNP concentration and have their functional capacity subjectively assessed by their responsible doctors. Participants are followed for 1 year after surgery to assess vital status, postoperative complications and general health utilities. The primary outcome is all-cause death or non-fatal myocardial infarction within 30 days after surgery, and the secondary outcome is all-cause death within 1 year after surgery. Both receiver-operating-characteristic curve methods and risk reclassification table methods will be used to compare the prognostic accuracy of preoperative subjective assessment, peak oxygen consumption during cardiopulmonary exercise testing, Duke Activity Status Index scores and serum NT pro-BNP concentration.Ethics and disseminationThe METS Study has received research ethics board approval at all sites. Participant recruitment began in March 2013, and 1-year follow-up is expected to finish in 2016. Publication of the results of the METS Study is anticipated to occur in 2017.

Total haemoglobin mass, but not haemoglobin concentration, is associated with preoperative cardiopulmonary exercise testing-derived oxygen-consumption variables

“…Patients were either receiving CPET as part of their routine preoperative assessment or were (approved) co-recruits to the 'METS' study of the relationship between CPET-derived physiological variables and surgical outcome. 16 Age, sex, height, weight, diagnosis, planned surgical procedure, co-morbidities (such as diagnosis of diabetes, respiratory, or cardiovascular disease), and current medications were documented.…”

Inter-observer reliability of preoperative cardiopulmonary exercise test interpretation: a cross-sectional study

“…14 Whilst preoperative exercise capacity has been associated with morbidity and mortality after major surgery, it remains unclear which CPETderived variable is best for predicting outcome after major surgery. 15,16 Two of the most commonly used variables are the anaerobic threshold (AT), an index of sustainable, submaximal exercise capacity, and peak oxygen consumption (VO 2 peak), an index of maximal exercise capacity. 17 The AT is the point during an incremental exercise test above which arterial lactate concentration increases in a sustained manner above resting levels, 18 while VO 2 peak is the highest oxygen uptake attained at end-exercise.…”

Elevated preoperative heart rate is associated with cardiopulmonary and autonomic impairment in high-risk surgical patients

“…10 11 Cardiopulmonary exercise testing (CPET) can identify cardiopulmonary dysfuntion, autonomic dysfunction, or both, and has been used for prognostication in patients with confirmed cardiac failure and for risk assessment before surgery. [12][13][14] In the general population, elevated resting HR is an independent risk factor for the development of heart failure. 4 15 16 Therefore, elevated preoperative HR may indicate underlying subclinical cardiac impairment; thus generating several plausible, and potentially novel, pathophysiological mechanisms that may contribute to perioperative myocardial injury, morbidity, and mortality.…”