Acute respiratory distress syndrome: analysis of incidence and mortality in a university hospital critical care unit

Introduction

The aim was to determine the incidence of acute respiratory distress syndrome (ARDS) in patients admitted to a university hospital ICU, analyse the ICU and the in-hospital mortality, and evaluate the associated factors.

Methods

A prospective study in an ICU from October 2008 to January 2011. The ICU comprises 20 beds in a medical-surgical area, 10 in a critical burns area. All patients who underwent mechanical ventilation (MV) during 48 hours or more and who fulfilled ARDS criteria as defined by the 1994 American-European Consensus Conference on ARDS were included. All patients were ventilated following the protective MV strategy recommended.

Results

During this period 1,900 patients were admitted, 697 needed MV for at least 48 hours and 108 fulfilled the ARDS criteria (5.6% of those admitted, 17% of the group on MV); 63% were male. The patients' age was 52 ± 12. The APACHE II score on admission was 23 ± 7, in survivors (S) 20 ± 7 and 24 ± 6 in nonsurvivors (NS) (P = 0.002). ARDS was primary in 70% and secondary in 30%. The most common aetiology was pneumonia (53%) followed by sepsis of intra-abdominal origin (15%). Duration of MV was 32.7 ± 30.2 days in S, 20.79 ± 20.73 in NS (P = 0.019). Survivors' mean length of stay was 35 ± 24 days, 23 ± 20 for NS (P = 0.007). ICU mortality was 49% and in-hospital mortality was 55%. Primary ARDS had an ICU mortality of 47%, an in-hospital mortality of 52%. Secondary ARDS had a 55% ICU mortality, an in-hospital mortality of 64%. Duration of primary ARDS was longer, 15.3 ± 12.2 versus 8.7 ± 79. Globally the main cause of death was multiple organ dysfunction, predominantly respiratory failure (55%). In primary ARDS the main cause of death was chiefly pulmonary (69%), while in secondary ARDS it was mainly multiple organ dysfunction associated with septic shock (71%). Factors associated with increased mortality were APACHE II score >23 and the presence of multiple organ dysfunction.

Conclusion

Certain controversy remains regarding a decrease in ARDS-related mortality. Despite the fact that its incidence is not very high, it is still a clinical entity with a high mortality, and with a prognosis influenced not only by the degree of pulmonary involvement but by the association with multiple organ dysfunction.