Fluid balance and weaning outcomes

To examine the relationship of fluid balance and weaning outcomes.

We prospectively collected demographic, physiological, daily fluid balance (measured inputs minus outputs), and weaning data from 87 mechanically ventilated patients.

We examined 87 patients, a median age of 66 years, APACHE II of 22, and performed 205 breathing trials (BT); 38 patients (44%) were successfully extubated after their first BT with minimal or no pressure support.

Positive fluid balance (inputs>outputs) in the 24, 48, and 72 h and cumulatively (from hospital admission) prior to weaning were significantly greater in weaning failures than successes. Both univariate and multivariate analyses, adjusted for duration of mechanical ventilation and presence of chronic obstructive pulmonary disease, showed negative cumulative fluid balance 24 h prior to BTs (OR=2.9) and cumulative fluid balance (OR=3.4) to be independently associated with first-day weaning success. Similar relationships were demonstrated when all weaning attempts were analyzed. Negative fluid balance was as predictive of weaning outcomes as f/V_t (likelihood of success was 1.7 for patients with negative fluid balance 24 h prior to weaning and 1.2 for those with f/V_t<100 min⁻¹ l⁻¹). Although administration of diuretics was associated with more negative fluid balance, it was not independently associated with weaning outcomes.

These data suggest that fluid balance, a potentially modifiable factor, is associated with weaning outcomes. A randomized study is required to determine whether diuresis to treat positive fluid balance expedites liberation from mechanical ventilation.