Background: Ultrasound-based assessment of the inferior vena cava (IVC) is a widely used, non-invasive tool for estimating volume status and central venous pressure (CVP) in critically ill patients. However, elevated intra-abdominal pressure (IAP) may distort IVC measurements, reducing the accuracy of CVP estimation. This study aimed to quantify the effect of varying IAP on IVC diameters and evaluate the accuracy of ultrasound-based CVP predictions under such conditions. Methods: A prospective study was conducted including two groups of adult critically ill patients: one with spontaneously elevated IAP due to ascites (n = 36), undergoing stepwise pressure reduction via paracentesis, and one with normal baseline IAP (n = 30), undergoing stepwise pressure elevation using an abdominal belt with an inflatable balloon. End-inspiratory and end-expiratory IVC diameters and CVP were repeatedly measured at different IAP levels. Agreement between predicted and measured CVP was assessed using Gwet’s agreement coefficient, and a correction model for IVC diameters was developed based on IAP categories. Results: Increasing IAP led to a progressive reduction in both inspiratory and expiratory IVC diameters, while CVP showed no consistent trend. Predictive accuracy declined with rising IAP, with Gwet’s agreement coefficient decreasing from 0.851 (95 percent confidence interval: 0.750–0.952) at normal pressure to 0.392 (95 percent confidence interval: 0.141–0.642) at IAP above 25 mmHg. Applying the correction model improved prediction accuracy, with Gwet’s agreement coefficient increasing to 0.749 (95 percent confidence interval: 0.589–0.908) at the highest IAP category. Conclusions: Elevated IAP significantly alters IVC diameters and reduces the reliability of ultrasound-based CVP estimation. A correction model based on IAP improves predictive accuracy and may enhance volume assessment in critically ill patients. Further validation is warranted.

Background and Objectives: Sepsis still represents a syndrome with a high mortality. A timely sepsis diagnosis and an early intervention are crucial for the disease outcomes. Sepsis-associated acute kidney injury (SA-AKI) is highly prevalent but often diagnosed late. We aimed to investigate whether serum interleukin-6 (IL-6) and leukocyte cell population data (CPD) could be adequate biomarkers for the prediction of survival and SA-AKI development. Materials and Methods: We conducted a prospective observational study in a medical intensive care unit of a tertiary hospital centre in Zagreb, Croatia from June 2020 to October 2023. Adult patients with newly diagnosed sepsis were included and classified as immunocompetent or immunocompromised. Blood samples were collected upon admission. Results: A total of 150 patients were included in the study. Ninety-six (64%) patients were immunocompetent and fifty-four (36%) were immunocompromised. The median SOFA score was 8 (6–11). SA-AKI was diagnosed in 108 (72%) patients. ICU and hospital mortality was 27.3% and 37.3%, with no significant difference between groups. Significantly higher serum IL-6 levels were noted in the immunocompromised group, while neutrophil granularity intensity was higher in the immunocompetent group. According to logistic regression analyses, elevated IL-6 levels predicted a lethal ICU outcome, while elevated IL-6 levels and neutrophil reactivity intensity were predictors of SA-AKI development. A cluster analysis revealed two patient groups with different IL-6 concentrations, and further studies indicated that the group with higher IL-6 values had significantly higher SA-AKI occurrence and increased lethal outcomes. Conclusions: An early serum IL-6 measurement regardless of the patients’ immune status indicates disease severity. Its measurement in the early phase of disease presentation, potentially in the emergency department, might facilitate ICU admission. Further research is warranted in the field of leukocyte CDP application.