#2058 IVC diameter and collapsibility via point-of-care ultrasound among clinically euvolemic Filipinos in Victoriano Luna Medical Center, Philippines
Authors: Vidal Arielle , Montepio Rafael 
Published: May 2024

Abstract

Background and Aims
History, physical findings, and laboratory tests have limited sensitivity and specificity to assess relative intravascular volume or volume responsiveness. Inferior vena cava (IVC) ultrasound provides a direct assessment of relative intravascular volume status. The Journal of the American Society of Echocardiography (2010), recommended that an IVC diameter of &lt;2.1 cm and collapsibility of &gt;50% with a sniff indicates normal right atrial pressure of 3 mmHg (0-5 mmHg), while an IVC diameter of &gt;2.1 cm with &lt;50% inspiratory collapse indicates high right atrial pressure of 15 mmHg (10-20 mmHg). However, there have been occasions in the hospital setting wherein clinically hypervolemic Filipino patients were observed to have inferior vena cava diameters of less than 2.0 cm. This study aims to determine the average IVC diameter among clinically euvolemic Filipinos and to evaluate the applicability of standardized ultrasonographic IVC measurements in the Filipino population.

Method
This is a prospective observational study that included 45 clinically euvolemic patients and staff of Victoriano Luna Medical Center from 01 September 2023 to 01 November 2023. The demographic profile and anthropometric measurements of the volunteers were obtained. Ultrasound assessment was performed bedside and the IVC diameter was measured during passive respiration without sniff test 1 to 2 cm distal to the hepatic vein or 3 to 4 cm distal to the junction of the right atrium and inferior vena cava. The maximum and minimum diameters of the inferior vena cava was also measured using M-mode, and its collapsibility index was computed using the following formula: collapsibility index (CI) = (IVC max – IVC min) / IVC max. Categorical variables such as sex and comorbidities will be presented as frequencies and percentages while continuous variables such as age, body mass index, and inferior vena cava diameter and collapsibility will be presented as mean and standard deviation or median and interquartile range.

Results
The study group mainly consisted of males aged 65 years and below with normal body mass index for Asians. Cut-off values for the maximum inferior vena cava diameter were based on the venous excess ultrasound grading system, or VEXUS score, by Beaubien-Souligny et al. (2020) wherein congestion was considered at IVC diameters more than or equal to 2.0 cm. Of the 45 participants, 33 had maximum inferior vena cava diameter of less than 2.0 cm. Twenty-eight (28) out of 45 participants had a collapsibility index of more than 50%, which is indicative of normal right atrial pressure. Of the 33 with a maximum inferior vena cava diameter of less than 2.0 cm, 11 of which had a collapsibility index between 20 and 50%, and 22 with more than 50%. The remaining 12 participants had a maximum IVC diameter of more than or equal to 2.0 cm, with five having a collapsibility index between 20 and 50% and six with more than 50%. The mean maximum IVC diameter in the 45 volunteers on quiet respiration was 1.79 cm (+0.47), with an average computed collapsibility index of 54.43% (+19.78).

Conclusion
Thirty-three participants (73.33%) had a maximum inferior vena cava diameter of less than 2.0 cm, 22 of which have a collapsibility index of more than 50%. Among the 45 volunteers, the mean IVC maximum diameter on quiet respiration was 1.79 cm (+0.47), with an average computed collapsibility index of 54.43% (+19.78). Based on the results, standardized ultrasonographic IVC measurements can be applied on the Filipino population. Considering the Filipinos’ petite stature, the average IVC diameter among Filipinos is smaller and further investigation is warranted to establish clear cut-off values to identify plethoric IVCs in the Filipino setting.