Timing of Fluid Overload and Association with Patient Outcome

Objectives: To determine if the timing of excess fluid accumulation (fluid overload) is associated with adverse patient outcomes. Design: Secondary analysis of a prospectively collected dataset. Setting: PICU of a tertiary care hospital. Patients: Children 3 months to 25 years old admitted to the PICU with expected length of stay greater than or equal to 48 hours. Interventions: Patients were dichotomized by time of peak overload: peak fluid overload from ICU admission (Day₀) to 48 hours (Day_3-7) and peak fluid overload value after 48 hours of ICU admission, as well as time of first-time negative daily fluid balance: net fluid out greater than net fluid in for that 24-hour period. Measurements and Main Results: There were 177 patients who met inclusion criteria, 92 (52%) male, with an overall mortality rate of 7% (n = 12). There were no differences in severity of illness scores or fluid overload on Day₀between peak fluid overload from ICU admission (Day₀) to 48 hours (Day_3-7) (n = 97; 55%) and peak fluid overload value after 48 hours of ICU admission (n = 80; 45%) groups. Peak fluid overload value after 48 hours of ICU admission was associated with a longer median ICU course (8 [4-15] vs 4 d [3-8 d]; p ≤ 0.001], hospital length of stay (18 [10-38) vs 12 [8-24]; p = 0.01], and increased risk of mortality (n = 10 [13%] vs 2 [2%]; χ²= 7.6; p = 0.006]. ICU length of stay was also longer in the peak fluid overload value after 48 hours of ICU admission group when only patients with at least 7 days of ICU stay were analyzed (p = 0.02). Timing of negative fluid balance was also correlated with outcome. Compared with Day_0-2, a negative daily fluid balance on Day_3-7was associated with increased length of mechanical ventilation (3 [1-7] vs 1 d [2-10 d]; p ≤ 0.001) and increased hospital (17 [10-35] vs 11 d [7-26 d]; p = 0.006) and ICU (7 [4-13] vs 4 d [3-7 d]; p ≤ 0.001) length of stay compared with a negative fluid balance between Day_0-2. Conclusions: Our results show timing of fluid accumulation not just peak percentage accumulated is associated with patient outcome. Further exploration of the association between time and fluid accumulation is warranted.