Pre-operative subjective functional capacity and postoperative outcomes in adult non-cardiac surgery: a systematic review and meta-analysis

Introduction Assessment of functional capacity is an essential part of peri-operative risk stratification. Subjective functional capacity is easier to examine than objective tests of patient fitness. However, the association between subjective functional capacity and postoperative outcomes has not been established. Methods Four databases were searched for studies describing the associations between subjective functional capacity and postoperative outcomes in adults undergoing non-cardiac surgery. Meta-analysis was conducted among studies where functional capacity was expressed in metabolic equivalents. The primary outcome was postoperative major adverse cardiovascular events. Secondary outcomes were mortality and postoperative overall complications. We estimated the ORs of the outcomes in patients with poor functional capacity (< 4 metabolic equivalents) as compared with those with good functional capacity (>= 4 metabolic equivalents). Random-effects models were used for the meta-analysis. Results We identified 7835 abstracts. After screening and a full-text review, 23 studies were selected. Evaluation methods of functional capacity included: questionnaires (n = 7); specific questions (n = 6); and subjective assessment by anaesthetists (n = 5). The probability of major postoperative adverse cardiovascular events was significantly higher in patients with poor functional capacity (OR 1.84, 95%CI 1.62-2.08) than in those with good functional capacity. Patients with poor functional capacity also had higher odds of mortality (OR 2.48, 95%CI 1.45-4.25) and postoperative complications (OR 1.85, 95%CI 1.34-2.55). Discussion Subjective functional capacity of < 4 metabolic equivalents was associated with postoperative complications including cardiovascular events and other serious outcomes. The results need to be interpreted with caution due to the diverse measures used to assess functional capacity.