Background: An elevated urea–creatinine ratio (UCR) is used as a surrogate for catabolism and elevated protein metabolism in critically ill patients. This study investigated the effect of continuous renal replacement therapy (CRRT) on UCR. Methods: In this retrospective single-centre study, ICU patients from 2011 to 2022 with an ICU stay >2 days before CRRT and a CRRT duration of ≥4 days were included. Patients were grouped by UCR at CRRT initiation into high (UCR ≥ 75 mg/dL:mg/dL) and low groups and compared to matched controls not requiring CRRT. Propensity score matching considered age, sex, bodyweight, SAPS3, SOFA score, and UCR values on baseline and pre-baseline days. Results: In the high UCR group, UCR significantly decreased after CRRT initiation, reaching a significant difference from controls on day 2 (85.0 [IQR: 69.5–96.4] vs. 94.4 [IQR: 83.0–115.2]; p = 0.036) and falling below the threshold of 75 by day 3. In the low group, UCR increased post-CRRT initiation, but was less pronounced than in controls, with significant differences on day 1 (44.0 [IQR: 34.2–59.8] vs. 40.6 [IQR: 32.1–52.5]; p = 0.024). Conclusions: CRRT significantly affects UCR in critically ill patients, showing a marked decrease when compared to matched controls.

Background/Objectives: The urea-to-creatinine ratio (UCR) serves as a biochemical marker for catabolism in the intensive care unit (ICU). UCR increases mainly due to an elevated urea generation from increased protein metabolism. This study aimed to evaluate the impact of protein intake on UCR progression in ICU patients. Methods: The inclusion criteria of this retrospective, single-center analysis required an ICU stay of at least 14 days without requirement of renal replacement therapy (n = 346 patients). Patients were grouped based on daily mean protein intake per kilogram between days 5 and 14: low (≤0.8 g/kg/d, n = 120), medium (0.9–1.2 g/kg/d, n = 132), and high (≥1.3 g/kg/d, n = 94). Data on daily protein and calorie intake, calorie deficit, urea generation rate, serum creatinine, urea, UCR and creatinine clearances were analysed. Risk factors for developing a high UCR were determined via logistic regression analysis adjusted for sex, age, bodyweight, disease severity (SAPS III admission score) as well as mean protein intake and calorie deficit during day 5 and 14 on ICU. Results: Higher protein intake was associated with increased calorie intake, lower calorie deficit, and led to an elevated urea generation rate and higher UCR. Renal function and serum urea trends were comparable between all groups, while creatinine was significantly lower in the high-protein group. Risk factors for developing an elevated UCR included older age, female sex and higher protein intake. Conclusions: An elevated UCR in the early ICU phase may indicate an increased protein metabolism, not only deriving from catabolism but also from a high protein feed.

Purpose of review: Fluid management in hemorrhagic shock is a controversial topic, and there are evolving clinical guidelines and evidence-based practice. This review aims to highlight the physiological aspects in the light of current evidence on which volume replacement solution to use. Recent findings: Current evidence and international guidelines are shifting from a liberal to a restrictive volume resuscitation strategy, emphasizing the potential risks associated with aggressive fluid therapy. The ‘lethal triad of trauma’ (hypoperfusion, acidosis, and coagulopathy) plays a crucial role in the pathophysiology of hemorrhagic shock. While crystalloids are less effective at restoring intravascular volume, colloids (especially hydroxyethyl starch) have raised concerns about potential adverse effects on renal function and coagulation. Albumin remains controversial, as studies have shown no clear benefit and an increased mortality in traumatic brain injury patients. Fresh frozen plasma may be useful in massive transfusion situations but is not recommended for volume resuscitation. Summary: The management of volume resuscitation evolves, with a trend toward more restrictive strategies. Crystalloids, although less effective for severe volume depletion, remain a cornerstone of initial resuscitation. Among the colloids, gelatin-based solutions and albumin can be used when crystalloids are inadequate, while hydroxyethyl starch is no longer recommended.

Background: The urea-to-creatinine ratio (UCR) is used as a biomarker of protein catabolism in critical illness. However, the impact of acute kidney injury (AKI) severity on UCR dynamics remains poorly understood.Methods: This retrospective study analyzed 1567 consecutive ICU (intensive care unit) patients at two different ICUs at the university hospital of Innsbruck. Patients were categorized by AKI stage (KDIGO criteria). Temporal trajectories of UCR, urea generation rate and creatinine clearance were modeled using generalized additive models. Risk factors for an elevated UCR (>75 mg/dl:mg/dl) were identified via multivariate logistic regression.Results: Peak urea levels occurred consistently around days 6–7 across all groups. In contrast, creatinine peaked earlier (day 2 in stage 0; days 4–5 in stages I–III). The delay between urea and creatinine in achieving peak levels led to a decrease in UCR in dependence of AKI severity. Urea generation rate remained fairly comparable between groups. Multivariate analysis revealed that higher urea generation rate, protein intake, SAPS III, and older age independently predicted elevated UCR on day 4. However, the presence of AKI and male sex significantly reduced the risk of an elevated UCR.Conclusions: UCR dynamics are strongly influenced by asynchronous trajectories of creatinine and urea across different stages of acute kidney injury. In severe AKI, the earlier peak in creatinine relative to urea transiently lowers the UCR, potentially masking catabolic signals and limiting its reliability as a standalone marker of catabolism.

The urea-to-creatinine ratio (UCR) is used as a biomarker of protein catabolism in critical illness. However, the impact of acute kidney injury (AKI) severity on UCR dynamics remains poorly understood. This retrospective study analyzed 1567 consecutive ICU (intensive care unit) patients at two different ICUs at the university hospital of Innsbruck. Patients were categorized by AKI stage (KDIGO criteria). Temporal trajectories of UCR, urea generation rate and creatinine clearance were modeled using generalized additive models. Risk factors for an elevated UCR (>75 mg/dl per mg/dl) were identified via multivariate logistic regression. Peak urea levels occurred consistently around days 6-7 across all groups. In contrast, creatinine peaked earlier (day 2 in stage 0; days 4-5 in stages I-III). The relationship between evolving AKI and UCR was time-dependent and non-monotonic. While AKI was associated with a significantly lower UCR during the early ICU course, this was followed by a reversal later during the ICU stay. Urea generation rate remained fairly comparable between groups. Multivariate analysis revealed that higher urea generation rate, protein intake, SAPS III, corticosteroid administration and older age independently predicted elevated UCR on day 4. However, the presence of AKI and male sex significantly reduced the risk of an elevated UCR. UCR dynamics are strongly influenced by asynchronous trajectories of creatinine and urea plasma levels across different stages of acute kidney injury. Evolving AKI was associated with a lower UCR during the early ICU course, limiting its reliability as a standalone marker of catabolism.