Tuba Şafak , Ahmet Burak Erdem
Abstract
Accurate assessment of intravascular volume status in hypernatremic patients presenting to the emergency department is often challenging due to advanced age, altered mental status, and unreliable physical examination. Bedside ultrasonography may provide rapid, noninvasive support for early volume evaluation. This study aimed to assess the clinical utility of inferior vena cava (IVC) diameter and the IVC-to-aorta (IVC/Ao) ratio in relation to early sodium response in patients with hypernatremia.
Introduction
Hypernatremia is a common electrolyte disorder defined by a serum sodium concentration exceeding 145 mmol/L and is observed in approximately 1–3% of hospitalized patients [1]. It is associated with particularly high mortality rates—reaching up to 40–60%—among vulnerable populations, including patients of advanced age, those with a high burden of comorbidities, and individuals managed in intensive care units. From a pathophysiological perspective, hypernatremia most commonly results from a relative reduction in total body water compared with electrolyte content and is frequently accompanied by intravascular volume depletion [2,3].
Materials and methods
2.1. Study design
This prospective, observational study was conducted in a tertiary care emergency department (ED). Adult patients presenting to the ED with hypernatremia were consecutively enrolled. Patient recruitment began on February 1, 2024, and continued until the predetermined sample size was reached over an approximate one-year period. As this was an observational, non-interventional study without randomization or experimental treatment assignment, prospective clinical trial registration was not required.
Results
3.1. Characteristics of study subjects
The study population consisted of 60 patients with a median age of 84.5 years (IQR: 80.0–91.0), of whom 56.7% were female. The cohort had a high burden of comorbidities, with hypertension being the most prevalent condition, followed by coronary artery disease and cerebrovascular disease. Baseline vital signs and laboratory findings, including a median corrected serum sodium level of 159 mmol/L (IQR: 153–169), are presented in Table 1.
Discussion
This study provides an early comparative assessment of ultrasonographic parameters measured during the initial phase of treatment (third hour) in patients presenting to the emergency department with hypernatremia, a condition associated with substantial morbidity and mortality. The findings suggest that baseline and early follow-up measurements of non-invasive ultrasonographic indices, particularly the inferior vena cava–to–aorta (IVC/Ao) ratio, are associated with early sodium response patterns as defined by short-term sodium correction
Conclusion
In patients presenting to the emergency department with hypernatremia, early ultrasound-based assessment of intravascular volume—particularly using the IVC/Ao ratio—was associated with early sodium response patterns and short-term prognostic outcomes. Higher baseline IVC/Ao ratios were observed in patients with less pronounced early sodium reduction, a pattern that showed an association with increased 30-day mortality.
Citation: Şafak T, Erdem AB (2026) Clinical value of the caval–aortic index and inferior vena cava diameter for volume assessment in hypernatremic patients. PLoS One 21(8): e0356486. https://doi.org/10.1371/journal.pone.0356486
Editor: Yusuke Hoshino, Ibaraki Children’s Hospital: Ibaraki Kenritsu Kodomo Byoin, JAPAN
Received: February 13, 2026; Accepted: August 4, 2026; Published: August 27, 2026
Copyright: © 2026 Şafak, Erdem. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: The data collected and analyzed in this study are not publicly available due to confidentiality obligations outlined in the Good Clinical Practice (GCP) guidelines. However, access to these data can be granted upon justified request and subject to the necessary ethical and institutional approvals. Data requests may be directed to the corresponding author or to the Ethics Committee of Ankara Etlik City Hospital, Ankara, Türkiye (etliksh.etikkurul@saglik.gov.tr).
Funding: The author(s) received no specific funding for this work.
Competing interests: The authors have declared that no competing interests exist.
