The study objective was to evaluate whether increasing frailty, as measured by the Clinical Frailty Scale, was associated with an increased risk of hospital mortality for patients undergoing cardiac surgery.

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 Clinical Frailty Scale. Associations between frailty and the primary outcome, hospital mortality, were evaluated using multivariable, mixed effects logistic regression models. Secondary outcomes including hospital and intensive care unit length of stay, invasive ventilation hours, need for renal replacement therapy and tracheostomy, and nonhome discharge were also evaluated.

A total of 3122 of 46,928 patients (6.7%) were classified as frail (Clinical Frailty Scale 5-8), and 93.3% (43,806/46,928) were nonfrail (Clinical Frailty Scale 1-4). Raw mortality was 4.2% (132/3122) in the frail group and 1.05% (461/43,806) in the nonfrail 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 (odds ratio, 2.879, 95% CI, 2.284-3.629, P < .001). Increasing Clinical Frailty Scale was also significantly associated with a higher risk of secondary outcomes, including length of stay in the hospital and intensive care unit, receipt of renal replacement therapy and tracheostomy, and increased duration of mechanical ventilation.

This study demonstrated that increasing Clinical Frailty Scale was strongly associated with increased hospital mortality, hospital and intensive care unit length of stay, invasive ventilation hours, renal replacement therapy, and tracheostomy insertion among patients undergoing cardiac surgery in Australia and New Zealand.