Characteristics and outcomes of nonagenarians admitted to the intensive care unit: A single-centre observational study

There is limited data regarding the mortality risk factors for Australian nonagenarians requiring intensive care unit admission. The objectives of the study were to determine the mortality rates, length of stay, and indicators of poor outcomes in nonagenarian patients admitted to the intensive care unit. Data were retrospectively collected from a single-centre university hospital in Australia over a 10-year period. Cox regression survival analysis, hazard ratios (HRs) and receiver operating characteristic curves were used to assess characteristics and associated survival. A total of 25,766 adult patients were admitted to the intensive care unit during the study period, of whom 89 (0.35%) were nonagenarians. The intensive care unit and hospital mortality rates of nonagenarians were 10.1% and 22.5%, respectively. The Australian and New Zealand risk of death model was the most significant predictor of mortality among the risk scoring systems. Nonagenarians who experienced a cardiac arrest had the highest hazard of death in the intensive care unit (HR 7.60, 95% confidence interval (CI) 1.49 to 38.66, P = 0.015) and throughout their hospital admission (HR 6.77, 95% CI 1.52 to 30.28, P = 0.012). Acute renal failure and invasive ventilation had a significantly increased hazard of death in the intensive care unit and hospital admission. Lactate levels also demonstrated a significant increase in the hazard of death per 1 mmol/l increase (HR 1.64, 95% CI 1.3 to 2.08, P < 0.001). Over the study follow-up period of a minimum of 3.5 years, 50 of 89 patients (56.2%) died. Intensive care unit and hospital mortality among nonagenarians admitted to the intensive care unit was relatively low. These findings support early identification of mortality risk factors, allowing for the timely implementation or withdrawal of interventions.