Abstract and Introduction
Abstract
Introduction: There is limited information on whether the incidence of acute kidney injury (AKI) in critically ill patients has changed over time and there is controversy on whether its outcome has improved.
Methods: We interrogated the Australian New Zealand Intensive Care Society Adult Patient Database to obtain data on all adult admissions to 20 Australian intensive care units (ICUs) for ≥ 24 hours from 1 January 1996 to 31 December 2005. Trends in incidence and mortality for ICU admissions associated with early AKI were assessed.
Results: There were 91,254 patient admissions to the 20 study ICUs, with 4,754 cases of AKI, for an estimated crude cumulative incidence of 5.2% (95% confidence interval, 5.1 to 5.4). The incidence of AKI increased during the study period, with an estimated annual increment of 2.8% (95% confidence interval, 1.0 to 5.6, P = 0.04). The crude hospital mortality was significantly higher for patients with AKI than those without (42.7% versus 13.4%; odds ratio, 4.8; 95% confidence interval, 4.5 to 5.1; P < 0.0001). There was also a decrease in AKI crude mortality (annual percentage change, -3.4%; 95% confidence interval, -4.7 to -2.12; P < 0.001), however, which was not seen in patients without AKI. After covariate adjustment, AKI remained associated with a higher mortality (odds ratio, 1.23; 95% confidence interval, 1.14 to 1.32; P < 0.001) and there was a declining trend in the odds ratio for hospital mortality.
Conclusion: Over the past decade, in a large cohort of critically ill patients admitted to 20 Australian ICUs, there has been a significant rise in the incidence of early AKI while the mortality associated with AKI has declined.
Introduction
Acute kidney injury (AKI) is a common clinical problem in critically ill patients and typically portends an increase in morbidity and mortality. Multiple epidemiologic investigations have provided a broad range of estimates of the incidence of AKI in critically ill patients. Likewise, numerous studies have shown that AKI in the intensive care unit (ICU) is associated with high short-term and long-term case fatality rates, with dialysis dependence, with reduced quality of life and with excess utilization of health resources.
Regrettably, many of these studies suffer from limited generalizability as a result of disparities in the study methodology, the study population and the definitions of AKI. Moreover, no study has purposely evaluated or been capable of assessing trends in the incidence and outcome of AKI in critically ill patients over time, once changes in illness severity have been taken into account. Accordingly, there is limited information on whether the incidence of AKI in the ICU has changed significantly over time and there is considerable controversy on whether its outcome has improved. On the other hand, the Australian New Zealand Intensive Care Society (ANZICS) Adult Patient Database (APD) is a high-quality clinical database containing data from > 600,000 individual adult admissions to 135 ICUs from 1987 to the present that now captures approximately > 80% of all admissions to ICUs in Australia and New Zealand. Twenty of these units have contributed data for a decade, making it possible to assess changes in incidence and outcome over a significant timespan.
We therefore interrogated the ANZICS APD to obtain information on the incidence and outcome of AKI in a cohort of critically ill patients from 20 Australian hospitals over a decade. We sought to describe the 10-year trend in the incidence of AKI at the time of or within 24 hours of admission to ICU, and the 10-year trend in the crude and adjusted hospital mortality rates associated with AKI.