48-Hour Fluid Balance Does Not Predict a Successful Spontaneous Breathing Trial

Both premature and delayed liberation from mechanical ventilation are associated with increased morbidity and mortality, and fluid balance could negatively influence extubation outcomes. We sought to determine the impact of fluid balance in the 48 h before a spontaneous breathing trial (SBT) on weaning outcomes in a mixed ICU population.

This was a prospective observational study in 2 adult medical-surgical ICUs. All enrolled subjects met eligibility criteria for weaning from mechanical ventilation. SBT failure was defined as inability to tolerate a T-piece trial for 30-120 min. Data on demographics, physiology, fluid balance in the 48 h preceding SBT (fluid input minus output over the 48-h period), lung ultrasound findings, and outcomes were collected.

Of a total of 250 SBTs, SBT failure eventuated in 51 (20.4%). Twenty-nine subjects (11.6%) had COPD, and 40 subjects (16%) were intubated due to respiratory sepsis. One-hundred eighty-nine subjects (75.6%) were extubated on the first attempt. Compared with subjects with SBT success, SBT failure subjects were younger (median of 66 vs. 75 y, P = .001) and had a higher duration of mechanical ventilation (median of 7 vs. 4 d, P < .001) and a higher prevalence of COPD (19.6 vs. 9.5%, P = .04). There were no statistically significant differences in 48-h fluid balance before SBT between groups (SBT failure, 1,201.65 ± 2,801.68 mL; SBT success, 1,324.39 ± 2,915.95 mL). However, in the COPD subgroup, we found a significant association between positive fluid balance in the 48 h before SBT and SBT failure (odds ratio of 1.77 [1.24-2.53], P = .04).

Fluid balance should not delay SBT indication because it does not predict greater probability of SBT failure in the medical-surgical critically ill population. Notwithstanding, avoiding positive fluid balance in patients with COPD might improve weaning outcomes. (ClinicalTrials.gov registration NCT02022839.).