Precise assessment of postoperative volume status is important to administrate optimal fluid management. Bioelectrical impedance analysis (BIA) which measures the body composition using electric character. Extracellular water (ECW) ratio by BIA represented as the ratio of ECW to total body water (TBW) and is known to reflect the hydration status. Based on this, we aimed to determine whether aggressive fluid control using ECW ratio could improve clinical outcomes through a single blind, randomized controlled trial. From November 2021 to December 2022, intensive care unit (ICU) patients admitted after surgery were randomly assigned to an intervention group or a control group whether postoperative fluid management was controlled via BIA. Among patients in the intervention group, dehydrated patients received a bolus infusion with crystalloid fluid whereas diuretics were administrated to overhydrated patients until the value of ECW ratio fell within its normal setting range (0.390-0.406). Contrarily, BIA was performed once a day for the control group. Patients in the control group received traditional fluid treatment regardless of BIA results. Primary outcome was in-hospital mortality in two groups. The secondary outcomes were postoperative morbidities, 28-day mortality. 77 patients of the intervention group and 90 patients of the control group were finally analyzed. The in-hospital mortality (0 in intervention, 4.4% in control, p = 0.125) and 28-day mortality (1.3% in intervention, 14.4% in control, p = 0.002) showed lower incidence in the intervention group than in the control group. In multivariate analysis, the overhydrated status whose ECW ratio exceeding 0.406 [odds ratio (OR): 2.731, 95% confidence interval (CI): 1.001-7.663, p = 0.049] and high capillary leak index (CLI) value at ICU admission (OR: 1.024, 95% CI: 1.008-1.039, p = 0.002) were risk factors of postoperative morbidities. Regarding the 28-day mortality, high CLI value (OR: 1.025, 95% CI: 1.002-1.050, p = 0.037) and traditional strategy without BIA monitoring (OR: 9.903, 95% CI: 1.095-89.566, p = 0.041) were the significant predisposing factors. Our results revealed the rigorous fluid treatment with volume control based on ECW ratio by BIA failed to achieve significant improvement in in-hospital mortality, but it could reduce 28-day mortality of ICU patients. Monitoring of ECW ratio may help establish optimal fluid treatment strategies for postoperative ICU patients who are susceptible to fluid imbalances with fluid overload. ClinicalTrials.gov, NCT06097923, retrospectively registered on October 16, 2023, https://clinicaltrials.gov/study/NCT06097923?term=NCT06097923&rank=1.

Background/Objectives: Endotoxin, a component of lipopolysaccharide (LPS) from bacteria, disrupts the immune system, potentially leading to multiorgan failure. Unlike previous studies, we enrolled patients with mild clinical conditions after major abdominal surgery and assessed the predictive value of endotoxin activity (EA) levels for acute complications which occur within 7 days postoperatively. Also, the differential diagnostic value of EA was assessed in a subgroup of patients with abnormal liver function during the immediate postoperative period. Methods: Patients admitted to the surgical ICU of our institution following elective abdominal surgery were enrolled. Participants were classified into low/high postoperative EA groups based on EA cutoff values for predicting complications. Additionally, participants were categorized based on liver function assessed at ICU admission using total bilirubin (TB) levels. Abnormal liver function was defined as a TB level > 1.2 mg/dL. Results: 86 patients were analyzed. The EA cutoff for postoperative complications was 0.485, with 49 patients (57%) categorized in the low EA group (EA levels < 0.485) and 37 patients (43%) in the high EA group (EA levels ≥ 0.485). The high EA group experienced statistically worse outcomes, including longer ICU stays and higher mortality rates. Logistic regression analysis confirmed that EA levels and SOFA scores were significant predictors of postoperative complications. For patients with elevated TB, the EA cutoff value for postoperative complications was 0.515, which is higher than those obtained for the total patient cohort. Conclusions: EA level is a viable surveillance tool for detecting postoperative complications in the acute period among ICU patients undergoing major abdominal surgery, and must be interpreted carefully considering the patient’s liver function.