Early and delayed onset of acute respiratory failure: different patterns?

Introduction

Multiple organ dysfunction has been recognized as a major factor associated with mortality in patients with acute respiratory failure (ARF). To investigate whether early and late onset ARF can present different patterns of nonpulmonary associated organ dysfunction (OD), a prospective data bank was created with physiological variables and organ function scores.

Methods

For the purpose of this study, 313 patients who stayed in the ICU for more than 48 h were prospectively evaluated from April to July 1999. ARF was defined as a PaO₂/FiO₂ ratio less than 200 mmHg and the need for any form of respiratory support. The group of early ARF included the patients who met the criteria for ARF at the time of ICU admission (123/313, 39%) and late ARF those who met 48 h after ICU admission (50/313, 16%). Organ failure was defined as a SOFA score of ≥ 3 points in each system.

Results

The most frequently associated nonpulmonary OD was cardiovascular dysfunction (25%) for early-onset ARF, and neurologic dysfunction (36%) for late-onset ARF (Figure). Nonsurvivors and survivors of early ARF had similar respiratory scores on admission (3.2 ± 0.5 versus 3.1 ± 0.5; NS), but nonsurvivors had higher cardiovascular (1.8 ± 1.7 versus 1.2 ± 1.3; P = 0.012) and neurologic (1.8 ± 1.7 versus 0.9 ± 1.4; P = 0.000) scores. Nonsurvivors of late ARF had significantly higher coagulation (0.8 ± 1.0 versus 0.4 ± 0.8; P = 0.0006) scores than survivors.

Conclusion

The process of evolution of early ARF is related to cardiovascular dysfunction. The recognized pathogenic sequence of nosocomial pneumonia is oropharyngeal colonization and the aspiration of gastric contents could be related to the neurologic dysfunction in late ARF. The degree of initial respiratory dysfunction was not a reliable prognostic indicator. Trends in oxygenation and nonpulmonary compromise at 48 h are more useful.