(221) Correlation Analysis of Trends in Capillary Leak Index and Fluid Balance in Critically Ill Patients

Introduction: Although fluid administration is a prevalent therapeutic intervention in critical care, fluid overload is related to increased morbidity and mortality. Despite the availability of data referencing fluid administration timings, significant knowledge gaps exist regarding the optimal timing for fluid reduction or withdrawal. The capillary leak index (CLI), calculated as serum C-reactive protein divided by serum albumin, has physiological implications suggesting its usefulness as an indicator for the diuretic phase. Despite these physiological possibilities, the lacking evidence regarding its clinical efficacy presents a significant challenge. Therefore, we aimed to investigate the potential correlation between CLI and daily fluid balance (DFB) in mechanically ventilated patients admitted to the intensive care unit (ICU).

Methods: We conducted a single-center retrospective study on consecutive adult patients admitted to the ICU of a tertiary hospital in Japan from October 2018 to December 2022. The inclusion criteria were intubation within the first 24 hours of admission and an ICU stay >5 days. The primary outcome was the correlation between CLI and DFB analyzed using Pearson's correlation coefficient. In-hospital mortality was assessed as the secondary outcome using binary logistic regression.

Results: This study included 901 patients (median age, 71.0 (58.0–78.0) years; 570 (63.3%) men). APACHE II scores, and max CLI scores were 22.0 (18.0–28.0), and 74.8 (38.8–127.0), respectively. The median CLI was 15.0 (2.2–52.0) on Day 1, reaching a peak median of 58.2 (28.4–99.5) on Day 3. The median DFB was 499.2 (−48.3 to 2968.9) on Day 1, reaching a peak of 896.6 (254.0–3075.4) on Day 2, followed by a decreasing trend from Day 3. A weak negative non-significant correlation was observed between CLI and DFB (r = 0.06, p < 0.001). Additionally, multivariate analysis revealed no statistically significant association between max CLI and mortality (odds ratio = 1.00, 95% CI: −0.0011 to 0.0031; p = 0.34).

Conclusions: The correlation between CLI and DFB was weak in mechanically ventilated patients admitted to the ICU. Considering the potential indicators for the diuretic phase and our findings, relying solely on the CLI may not be adequate to determine the diuretic phase in clinical settings.