Venous excess and lung ultrasound during continuous renal replacement therapy in critically ill patients (VExLUS-RRT): a prospective observational study.

Background: No gold standard currently exists to evaluate fluid status during continuous renal replacement therapy (CRRT). We aimed to describe systemic venous congestion by using venous excess ultrasound (VExUS) and pulmonary congestion by lung ultrasound (LUS) in critically ill patients with acute kidney injury (AKI) who received CRRT. Methods: This was a single-centre prospective cohort study. Adult patients with AKI undergoing CRRT underwent serial ultrasound assessments on Day 1 and 3 by two independent operators. VExUS score and its individual components, including an inferior vena cava (IVC) diameter (≥2 cm), hepatic vein, portal vein, as well as intrarenal vein Doppler flow patterns, and 6-zone lung ultrasound (LUS) scores (ranged from 0 to 20 points), were collected. An exploratory modified VExUS (mVExUS) grading was derived by incorporating an IVC distensibility index (<18%) or collapsibility index (<50%). Venous congestion was defined as VExUS or mVExUS Grade ≥2. The primary descriptive outcome was the prevalence of venous congestion and serial LUS score changes. The principal clinical endpoint was the association between ultrasound parameters and 90-day mortality Results: Among 100 enrolled patients (median age 66 years, male 58%), baseline venous congestion was documented in 20% by VExUS score and 35% by mVExUS scores. The median LUS score was 4 (interquartile range 1-9). Baseline VExUS Grade 2-3 (Log rank p = 0.049) and mVExUS Grade 2-3 (Log rank p = 0.01) were associated with lower 90-day survival. In time-updated Cox models after adjustment for baseline Sequential Organ Failure Assessment score, hepatic vein Doppler Grade 2-3 (adjusted hazard ratio (aHR) 1.78; 95% confidence interval (CI) 1.05-3.01, p = 0.01) and higher LUS scores (aHR 1.04; 95% CI 1.001-1.08, p = 0.04) were independently associated with 90-day mortality. Unchanged or worsening LUS scores between Day 1 and Day 3 were associated with a significantly higher cumulative fluid balance compared to improved scores (p = 0.01). Conclusion: Systemic and pulmonary congestion assessed by multiorgan point-of-care ultrasound was associated with increased 90-day mortality in AKI patients receiving CRRT. Future studies should explore the utility of these tools in guiding individualised fluid management during CRRT.