ICU patients requiring mechanical ventilation: incidence, mortality, characteristics and mortality risk factors

Introduction

Acute respiratory failure (ARF) is a frequent cause of admission to ICUs and usually necessitates mechanical ventilation (MV). Knowledge about the incidence, mortality, and risk factors associated with patients that require MV is essential to improve outcomes.

Objectives

To determine the characteristics, risk factors prior and/or during MV, and general and specific mortality rates in patients under MV in a general university ICU in southern Brazil.

Methods

A prospective cohort of 400 adult patients admitted to the ICU who needed MV for at least 24 hours, between March 2004 and April 2005. Data were collected daily, for up to 28 days. The age, gender, APACHE II score, medical or surgical patients, causes for the requirement of MV, organ dysfunction/failure developed prior to MV and during MV, ventilatory parameters, duration of MV, modes of MV, tracheostomy and duration of weaning were some variables studied. Univariable and multivariable analysis were performed.

Results

The incidence of MV was 18.5%; the overall and specific mortality rates were 9.4% and 57.0%, respectively. The mean (± SD) age was 67.4 ± 8.6 years; 51% were males; the mean APACHE II was 29.1 ± 23.9; the mean duration of MV was 10.4 ± 7.4 days. A multivariable analysis indicated that age (P < 0.001), MV duration (P = 0.02), vasoactive drug use (P = 0.01), acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) (P = 0.002) and renal failure (P = 0.05 – borderline) occurring during the MV period were independently associated with death.

Conclusion

The risk factors associated with mortality in 28 days (age, MV duration, vasoactive drug use, ALI/ARDS, and renal failure during MV) are similar to some literature studies. The overall and specific mortality rates were higher. Final conclusions will require evaluation of the mortality rates of specific pathologies, planned when our sample size will be increased. The identification of these factors may allow early interventions to improve therapeutic strategies.