Functional Capacity Before Major Noncardiac Surgery
How does the clinician’s subjective preoperative assessment of a patient’s functional capacity compare with alternative quantitative measures (peak oxygen consumption [VO2 max] during cardiopulmonary exercise testing [CPET], Duke Activity Status Index [DASI] score, and N-terminal pro–B-type natriuretic peptide [NT-proBNP] concentration) in predicting 30-day postoperative death or nonfatal myocardial infarction (MI) after major noncardiac surgery (NCS)?
A total of 1,401 patients aged ≥40 years, with ≥1 risk factor for a postoperative major adverse cardiovascular event, scheduled for major NCS between March 2013-March 2016 at 25 hospitals across Canada, United Kingdom, Australia, and New Zealand, were enrolled. All underwent preoperative assessment including subjective functional assessment, CPET, DASI questionnaire, and NT-proBNP measurement. Subjective judgment was categorized based on estimates of exercise capacity (in metabolic equivalents, <4 or unknown = poor, 4-10 = moderate, >10 = very good). The primary outcome was death or nonfatal MI within 30 days of surgery. The secondary outcome was death within 1 year of surgery. Additional outcomes were death or myocardial injury (MINS) within 30 days, and moderate-severe complications during hospitalization.
Of the 1,401 total patients, 28 (2%) died or suffered an MI within 30 days, and 38 (3%) died within 1 year of surgery; 176 (13%) died or had myocardial injury within 30 days, and 194 (14%) suffered moderate-severe complications during hospitalization. Among assessment measures, only DASI score provided a statistically significant correlation to both primary and secondary outcomes. NT-proBNP was predictive of both secondary outcome and combined endpoint of 30-day death or MINS. VO2max was associated with respiratory and infectious complications, but not with MI or MINS. Subjective assessment of functional capacity showed no correlation to any of the study outcomes, and was insensitive in predicting CPET performance.
For patients undergoing major NCS, standardized assessment of functional capacity by the DASI questionnaire was significantly predictive of 30-day mortality, MI, and MINS. Elevated BNP provided predictive value for 30-day mortality, MI, and MINS, and 1-year mortality, whereas decreased VO2 max was associated only with noncardiovascular complications. Subjective assessment of functional status showed no significant association with any adverse outcome in this study.
These findings underscore the limitations of subjective assessment and should discourage its use in isolation. Standardized, scaled assessments produced better risk discrimination all around. Consistent with previous findings, reduced VO2max indicates greater risk of complications, but may not reflect MI/MINS risk per se. Future investigation must address rational use of scaled measures to optimize prediction of mortality, adverse cardiovascular outcomes, and noncardiovascular complications.
Keywords: Exercise Test, Functional Residual Capacity, Metabolic Equivalent, Myocardial Infarction, Myocardial Reperfusion Injury, Natriuretic Peptide, Brain, Outcome Assessment (Health Care), Peptide Fragments, Preoperative Period, Postoperative Period, Risk Assessment, Secondary Prevention, Surgical Procedures, Operative
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