Evolution of acute lung injury/acute respiratory distress syndrome mortality in an ICU in Southern Brazil

Introduction

Acute lung injury (ALI), including acute respiratory distress syndrome (ARDS), mortality rates are high despite advances in the management of patients with this condition. Our objectives were to compare the ALI/ARDS mortality rates and the ALI mortality risk factors between two cohort studies of the same ICU in different periods of time: 1999/2000 (2000 cohort [1]) and 2004/2007 (2007 cohort).

Methods

A prospective cohort that included 1,115 patients admitted to the ICU between April 2004 and April 2007 who needed mechanical ventilation for at least 24 hours. These results were compared with a previous cohort of 1,301 patients admitted to the same ICU between April 1999 and April 2000 [1]. In both studies all patients were evaluated regarding the presence/development of ALI/ARDS according to the 1994 American–European Consensus Conference. Data were compared between the two cohorts using Student's t or chi square tests. Multivariate analysis by conditional logistic regression was used to identify ALI mortality risk factors.

Results

In ALI patients (n = 50, 2000 cohort; n = 347, 2007 cohort) we observed: (i) an increase in both hospital mortality (from 50 to 67%, P = 0.02) and ICU mortality (from 44 to 63%, P = 0.01); (ii) a higher mean (± SD) APACHE II score (from 17.7 ± 6.5 to 23.7 ± 8.2, P < 0.001), and (iii) an increased percentage of patients with three or more organ failures (from 30 to 42%, P < 0.001). Regarding ARDS patients (n = 30, 2000 cohort; n = 307, 2007 cohort), there were an increase in hospital mortality (from 47% to 68%, P = 0.03), in the mean (± SD) APACHE II score (from 17.6 ± 6.9 to 23.6 ± 8.3, P < 0.001) and in medical patients (from 46 to 73%, P = 0.01). The factors independently associated with increased hospital mortality in ALI patients were renal (P = 0.002) and hematological (P = 0.02) failures in the 2000 cohort. In the 2007 cohort, renal (P = 0.01) and hematological (P = 0.02) failures, use of vasoactive drugs (P < 0.001) and ICU length of stay (P < 0.001) were independently associated with mortality.

Conclusion

We observed an increase in the mortality rates of patients with ALI/ARDS, which are more severely ill. Renal and hematological failures remained independently associated with mortality in these patients. The results suggest that ALI/ARDS patients in our ICU have more severe illness, what could explain the increase in the mortality rates, highlighting the relevance of a better understanding of such findings.