Impact of frailty on outcomes after cardiac surgery

Abstract Purpose: To evaluate whether increasing frailty, as measured by the Clinical Frailty Scale (CFS), was associated with increased risk of hospital mortality for patients undergoing cardiac surgery. Methods: A retrospective binational cohort study of 46,928 patients who underwent cardiac surgery in Australia and New Zealand was conducted. The primary exposure, frailty, was measured using the CFS. Associations between frailty and the primary outcome, hospital mortality, were evaluated using multivariable, mixed effects logistic regression models. Secondary outcomes including hospital and ICU length of stay, invasive ventilation hours, need for renal replacement therapy and tracheostomy, and non-home discharge were also evaluated. Results: 6.7% (3122/46928) patients were classified as frail (CFS 5-8) and 93.3% (43,806/46,928) were non-frail (CFS 1-4). Raw mortality was 4.2% (132/3122) in the frail group and 1.05% (461/43,806) in the non-frail group. After multivariable adjustment for illness severity, age, elective status, type of surgery, hospital type and country, frailty was significantly associated with increased hospital mortality (OR=2.879, 95% CI 2.284-3.629, p<0.001). Increasing frailty was also significantly associated with higher risk of secondary outcomes including length of stay in hospital and ICU, receipt of renal replacement, tracheostomy and duration of mechanical ventilation. Conclusion: This study demonstrated that increasing frailty was strongly associated with increased hospital mortality, hospital and ICU length of stay, invasive ventilation, need for renal replacement therapy and tracheostomy insertion among patients undergoing cardiac surgery in Australia and New Zealand.