Severity of illness assessment with application of the APACHE IV predicted mortality and outcome trends analysis in an academic cardiac intensive care unit

Purpose: To assess trends in life support interventions and performance of the automated Acute Physiology and Chronic Health Evaluation (APACHE) IV model at mortality prediction compared with Oxford Acute Severity of Illness Score (OASIS) in a contemporary cardiac intensive care unit (CICU). Methods and materials: Retrospective analysis of adults (age ≥ 18 years) admitted to CICU from January 1, 2007, through December 31, 2015. Temporal trends were assessed with linear regression. Discrimination of each risk score for hospital mortality was assessed with use of area under the receiver operating characteristic curve (AUROC) values. Calibration was assessed with Hosmer-Lemeshow goodness-of-fit test. Results: The study analyzed 10,004 patients. CICU and hospital mortality rates were 5.7% and 9.1%. APACHE IV predicted death had an AUROC of 0.82 (0.81–0.84) for hospital death, compared with 0.79 for OASIS (P <.05). Calibration was better for OASIS than APACHE IV. Increases were observed in CICU and hospital lengths of stay (both P <.001), APACHE IV predicted mortality (P =.007), Charlson Comorbidity Index (P <.001), noninvasive ventilation use (P <.001), and noninvasive ventilation days (P =.02). Conclusions: Contemporary CICU patients are increasingly ill, observed in upward trends in comorbid conditions and life support interventions. APACHE IV predicted death and OASIS showed good discrimination in predicting death in this population. APACHE IV and OASIS may be useful for benchmarking and quality improvement initiatives in the CICU, the former having better discrimination.