Metabolic and Muscular Determinants of Weaning Failure - The Role of BUN/Creatinine Ratio and Rectus Femoris Thickness

Sep 30, 2026

Weaning failure remains a major challenge in intensive care, often linked to systemic catabolism and skeletal muscle wasting. This retrospective observational study assessed whether the blood urea nitrogen-to-creatinine (BUN/Cr) ratio and ultrasound-based rectus femoris thickness relate to weaning outcomes. Among 42 mechanically ventilated adults, BUN/Cr independently predicted weaning failure, and affected patients showed lower rectus femoris thickness. An exploratory composite metabolic–muscle indicator improved discrimination, suggesting integrated metabolic and morphologic assessment may identify high-risk patients.

LanguageEnglish

CategoryHealthcare

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Pages13

Reading Time33 min

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Abstract

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Article Metabolic and Muscular Determinants of Weaning Failure: The Role of BUN/Creatinine Ratio and Rectus Femoris Thickness Erdem Yalçınkaya 1, *, Muhammet Topçu 1, Umut Sabri Kasapo ˘glu 1, Hüseyin Arıkan 1, Hasan Basri Yapıcı 2, Semiha Emel Eryüksel 1 and Sait Karakurt 1 Academic Editor: Chiara Lazzeri Received: 30 November 2025 Revised: 16 December 2025 Accepted: 24 December 2025 Published: 1 January 2026 Copyright: © 2026 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license. 1 Department of Pulmonary and Critical Care Medicine, Marmara University School of Medicine, 34854 Istanbul, Türkiye; [drmuhammettopcu@gmail.com](drmuhammettopcu@gmail.com) (M.T.); [umutkasapoglu@gmail.com](umutkasapoglu@gmail.com) (U.S.K.); [arikanhuseyin@gmail.com](arikanhuseyin@gmail.com) (H.A.); [dreryuksel@gmail.com](dreryuksel@gmail.com) (S.E.E.); [saitkarakurt@hotmail.com](saitkarakurt@hotmail.com) (S.K.) 2 Department of Internal Medicine, Marmara University School of Medicine, 34854 Istanbul, Türkiye; [hbasriyapici@gmail.com](hbasriyapici@gmail.com) * Correspondence: [drerdemyalcinkaya@gmail.com](drerdemyalcinkaya@gmail.com); Tel.: +90-533-453-7388 Abstract Background: Weaning failure remains a major challenge in intensive care practice, often reflecting the interplay between systemic catabolism and skeletal muscle wasting. The blood urea nitrogen-to-creatinine (BUN/Cr) ratio is a routinely available biochemical index influenced by renal handling, hemodynamic status, protein metabolism, and muscle mass, and has been associated with adverse outcomes in critical illness. This study aimed to evaluate the association between BUN/Cr ratio, weaning outcomes, and ultrasoundbased rectus femoris thickness. Methods: This retrospective observational study included 42 mechanically ventilated adults admitted to the medical ICU of Marmara University between December 2024 and September 2025 . Rectus femoris thickness was measured via bedside ultrasonography at the time of the spontaneous breathing trial (SBT). Weaning success was defined as extubation without reintubation, death, or need for NIV/HFNO due to respiratory distress within 7 days. Laboratory and clinical variables—including BUN/Cr ratio, SOFA, APACHE II, mNUTRIC, and albumin—were recorded. Multivariable logistic regression and receiver operating characteristic (ROC) analyses were performed. Results: Weaning failure occurred in 13 patients (31.0%) . These patients had higher BUN/Cr ratios (58.7 [44.6–76.9] vs. 39.7 [23.8–49.2], p = 0.007) and lower rectus femoris thickness (6.2 [5.4–7.0] vs. 7.8 [6.9–8.6] mm, p = 0.021) . The BUN/Cr ratio independently predicted weaning failure (OR 1.07; 95% CI 1.01–1.14; p = 0.024) . ROC analysis identified a BUN/Cr cut-off of 44.6 (AUC = 0.76) for weaning failure. An exploratory composite metabolic–muscle indicator (MMI), combining BUN/Cr ratio and rectus femoris thickness, demonstrated higher discriminative performance in this cohort (AUC = 0.81) . Conclusions: An elevated BUN/Cr ratio was independently associated with weaning failure and lower rectus femoris thickness in this cohort. Given the observational design and potential confounding, these findings should be interpreted as hypothesis-generating. Combined biochemical and ultrasound-based assessment highlights the potential value of integrating metabolic and morphologic information when characterizing patients at risk for weaning failure. However, whether incorporation of such markers into clinical decision-making improves weaning outcomes requires prospective validation. Keywords: weaning failure; BUN/Creatinine ratio; catabolism; ICU-acquired sarcopenia; muscle ultrasound; mechanical ventilation; rectus femoris 1. Introduction Weaning from mechanical ventilation (MV) represents a pivotal and often challenging stage in the management of cri

FAQs

What was the primary aim of the study?

To evaluate the association between the BUN/Cr ratio, weaning outcomes, and ultrasound-based rectus femoris thickness.

How was weaning success defined in this study?

Success meant extubation without reintubation, death, or need for NIV/HFNO due to respiratory distress within 7 days.

What did the results show about BUN/Cr ratio and weaning failure?

Weaning failure patients had higher BUN/Cr ratios, and the BUN/Cr ratio independently predicted weaning failure.

Sep 30, 2026

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