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ORIGINAL ARTICLE
Year : 2022  |  Volume : 25  |  Issue : 6  |  Page : 825-832

Sonographic measurements of Inferior Vena Cava, Aorta, anda IVC/aorta ratio in healthy children


1 Department of Pediatric Intensive Care, Çukurova University, Faculty of Medicine, Adana, Turkey
2 Department of Pediatrics, Çukurova University, Faculty of Medicine, Adana, Turkey
3 Department of Biostatistics, Çukurova University, Faculty of Medicine, Adana, Turkey
4 Department of Pediatric Infectious Diseases, Çukurova University, Faculty of Medicine, Adana, Turkey
5 Department of Radiology, Çukurova University, Faculty of Medicine, Adana, Turkey

Date of Submission08-Sep-2021
Date of Acceptance16-Mar-2022
Date of Web Publication16-Jun-2022

Correspondence Address:
Dr. O Ozgur Horoz
Department of Pediatric Intensive Care, Çukurova University Faculty of Medicine, Adana
Turkey
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njcp.njcp_1801_21

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   Abstract 


Background: Assessment of intravascular volume status is important in pediatric patients admitted to the emergency departments and pediatric intensive care units. Inferior vena cava (IVC) diameter and collapsibility index are used to evaluate the intravascular volume status in adults. The normal range of IVC diameter is available for adults and the normal range considered for adults is between 1.7 to 2.1 cm, but such normative data is limited for children of all ages. Aims: Our aim in this study was to obtain the IVC and the aorta diameter reference values and the mean vena cava collapsibility index in healthy and normovolemic children. Subjects and Methods: Vena cava inferior and aorta images in B mode were obtained. IVC diameter in the inspiratory and the largest IVC diameter in the expiratory were recorded, and the vena cava collapsibility index was calculated. Results: Ultrasonographic measurements were performed in total on 1938 children. A significant positive correlation was found between IVC and aorta diameters with age. The collapsibility index was found as 37.2% (SD 11.8) in the overall study population. In addition, the reference values for the IVC and aorta diameters obtained from the measurements were also acquired. Conclusions: We believe that our IVC and aorta diameter measurements obtained from a large number of participants may be used as reference values in emergency departments and intensive care units.

Keywords: Aorta, children, collapsibility index, inferior vena cava, percentile


How to cite this article:
Horoz O O, Yildizdas D, Aslan N, Coban Y, Misirlioglu M, Haytoglu Z, Sertdemir Y, Gundeslioglu O O, Soyupak S. Sonographic measurements of Inferior Vena Cava, Aorta, anda IVC/aorta ratio in healthy children. Niger J Clin Pract 2022;25:825-32

How to cite this URL:
Horoz O O, Yildizdas D, Aslan N, Coban Y, Misirlioglu M, Haytoglu Z, Sertdemir Y, Gundeslioglu O O, Soyupak S. Sonographic measurements of Inferior Vena Cava, Aorta, anda IVC/aorta ratio in healthy children. Niger J Clin Pract [serial online] 2022 [cited 2022 Jul 5];25:825-32. Available from: https://www.njcponline.com/text.asp?2022/25/6/825/347609




   Introduction Top


Particularly in children who are admitted to the emergency department, and critically ill pediatric patients in intensive care units, it is important to evaluate the intravascular volume status. To evaluate the volume status of the patients; historical findings, vital signs, physical examination findings, laboratory tests, and other more invasive methods are used. Evaluation of volume status also brings interobserver variability. Patients who are in shock must receive a fluid replacement on time. The American College of Critical Care Medicine Guideline on hemodynamic support of pediatric and neonatal shock in 2002 stressed early and aggressive fluid resuscitation.[1] However, it is beneficial to be careful in terms of excessive fluid resuscitation in children who undergo volume replacement because various complications, including intra-abdominal hypertension, might occur.[2] Therefore, researchers continue to evaluate the intravenous volume status more accurately.

In recent years, the use of ultrasonography has become increasingly widespread both in emergency departments and intensive care units.[3] Bedside ultrasound is a non-invasive, painless, economical, and objective method used more in adult patients. Its use in children is also increasing. One of the usage areas of ultrasonography in the evaluation of the volume status of patients with the help of vena cava inferior, diameter, and vena cava collapsibility index (the percentage decrease in inferior vena cava [IVC] diameter with inspiration) measurements.[4],[5] In spontaneous respiration, during inspirium decrease in intrathoracic pressure occurs due to negative pressure which receives blood from the vena cava inferior (that collects all the blood from below the diaphragm) causing the vessel to collapse. In the case of low intravascular volume, this collapse becomes more distinctive. Furthermore, since there is no valve between the vena cava inferior and the right atrium, the increased right atrial pressure is reflected as vena cava distension. Normal vena cava inferior diameter range for adults has been reported to range between 1.7 and 2.1 cm.[6],[7] Unfortunately, it is not possible to give a substantive number for the IVC diameter in children. However, in children, the IVC diameter varies in correlation with age and anthropometric measurements. This correlation has been reported in previous pediatric studies.[8],[9] We aimed to create normative data and percentile curves for IVC and aorta in healthy, spontaneously breathing, and normovolemic children. In adults, IVC collapses by 50% during quiet respiration, however, knowledge on this in children is unfortunately limited.[6],[10] With broad case series, we also planned to give threshold values for the IVC collapsibility index. It was reported in previous studies that the descending aorta diameter did not change with the volume status, and the IVC/aorta ratio decreased during dehydration and increased with volume replacements.[5],[11] Thus, we aimed to add reference values for the IVC/aorta ratio to the literature by also measuring the diameter of the aorta in healthy and normovolemic children.


   Material-Method Top


This cross-sectional study was performed between April 2018-September 2019. The study was carried out at primary and secondary schools in Adana province, three kindergarten and nursery level schools, a family health center and Cukurova University General Pediatric Outpatient Clinic. We conducted sonographic measurements in the area shown to us by the school administration office in the schools. Patients with clinical history, physical examination, and objective findings of hypovolemia, vomiting, diarrhea, fever, abdominal pain, malnutrition, and chronic disease (renal insufficiency, diabetes, cardiac disease, liver disease) were excluded from the study. A total of 1914 children who met the criteria were included in the study.

Approval for the study was obtained from Cukurova University Faculty of Medicine Clinical Research Ethics Committee (Date: 13.04.2018, number: 76), Adana Provincial Directorate of National Education, and Adana Provincial Directorate of Health. Written consent (from their guardians) was obtained for all children.

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Data collection was performed by the two investigators, who were coordinated by a pediatric intensive care specialist, and who also underwent an 8-h training course consisting both of theoretical and practical experience and completed more than 300 supervised scans in a variety of pediatric intensive care unit applications before the initiation of the study. These researchers were also approved by the faculty member of the radiology department. Before the enrolment of the overall population, a sample of 30 subjects was evaluated over three to four normal cycles during quiet respirations by raters in order to assess the intra and inter-operator reliability; Lin's concordance coefficient resulted to be excellent, with values over 0.90.

After each participant had rested for at least 5 minutes, the clinical and demographic characteristics age (months), body weight (kg), height (cm), body mass index (BMI) (kg/m2), and body surface area (BSA) (m2) (Haycock formula) were recorded.

The standardized sonographic measurements were initiated while all participants were in the supine position and performing quiet respiration. Ultrasound examinations of the IVC and aorta were performed with Mindray Ultrasound System (China), using a 2.1-5.1 MHz phased array transducer. A transducer was placed just below the level of the xiphoid bone. Vena cava inferior and aorta images in B mode were obtained in the transverse plane. Just after the point where the left renal vein is poured into the IVC, the maximum systolic diameter in M mode of the aorta from the inner wall to the inner wall and the maximum anterior-posterior diameters of the IVC were recorded [Figure 1]. IVC images were taken in the sagittal and transverse planes. To obtain the sagittal image, the probe was placed in the subxiphoid area and the liver was used as an acoustic window. The IVC entry into the atrium was identified. In the M-mode, the smallest IVC diameter in the inspiratory and the largest IVC diameter in the expiratory [Figure 2] was measured upstream (caudal) of the hepatic veins. Vena cava collapsibility index was calculated with the following formula: CI = (Expiratory maximum IVC diameter-inspiratory minimum IVC diameter)/Expiratory maximum IVC diameter.
Figure 1: Transverse view of the aorta and IVC in the subxiphoid region just distal to the insertion of the left renal vein into the IVC

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Figure 2: Sagittal view of the IVC in the subxiphoid region. Maximum expiratory and minimum inspiratory diameters were measured just distal to the junction of the hepatic veins (1–2 cm from distal the hepatic vein)

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Statistical analysis

All analyses were performed using IBM SPSS Statistics Version 20.0 statistical software package. Categorical variables were expressed as numbers and percentages, whereas continuous variables were summarized as mean ± standard deviation and as median (minimum-maximum) where appropriate. The normality of distribution for continuous variables was confirmed with the Kolmogorov-Smirnov test. To evaluate the correlations between measurements, Pearson Correlation Coefficient was used. The upper and lower limits of the 95% CI for the vena cava collapsibility index were assessed with the nonparametric Bootstrap method. The statistical level of significance for all tests was considered to be 0.05.[12]


   Results Top


In a period of 18 months, measurements were carried out on 1938 children in total, of which 1914 (51.5% female) met the criteria and were included in the study. The children were divided into 18 age groups as: 1 m <age ≤12 m, 13 m <age ≤24 m, 25 m <age ≤36 m, 37 m <age ≤48 m, 49 m <age ≤60 m, 61 m <age ≤72 m, 73 m <age ≤84 m, 85 m <age ≤96 m, 97 m <age ≤108 m, 109 m <age ≤120 m, 121 m <age ≤132 m, 133 m <age ≤144 m, 145 m <age ≤156 m, 157 m <age ≤168 m, 169 m <age ≤180 m, 181 m <age ≤192 m, 193 m <age ≤204 m, 205 m <age ≤216 m. Demographic characteristics of the population are listed in [Table 1]. Descriptive statistics with mean and SD, median, minimum, and maximum for all sonographic measurements are listed in [Table 2]. Pearson r coefficient for the correlation between anthropometric parameters and sonographic measurements are listed in [Table 3]. The percentile distribution for sagittal maximum IVC, sagittal minimum IVC, transverse maximum aorta and transverse IVC/Aorta within each age group are given in [Supplemental Table S1], [Supplemental Table S2], [Supplemental Table S3], [Supplemental Table S4]. IVC sagittal max measurements ranges for all children are presented graphically in [Figure 3] where the main percentiles are plotted versus age. When the males and females were examined in terms of the sagittal maximum IVC measurement difference, it was determined that in the age group of 61 to 72 months the measurements were higher in males, in the age group of 133 to 144 months it was higher in the females' group and in the age group of 193 to 204 months it was higher in the males group (P < 0.05). In the other age groups, the sagittal maximum IVC measurements did not present any difference between males and females (P > 0.05). The sagittal maximum IVC measurements of the males and females are given in [Figure 4].
Table 1: Demographic characteristics of subjects by age classes

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Table 2: Sonographic measurements of subjects by age classes

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Table 3: Correlation coefficients (r) between anthropometric and sonographic measurements

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Figure 3: IVC sagittal max measurements ranges are presented graphically for all children

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Figure 4: Difference between males and females for mean IVC sagittal maximum diameter

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The collapsibility index was found as 37.2% (SD 11.8) in the overall study population.


   Discussion Top


As planned, we were able to perform both IVC and aorta measurements in 1938 healthy and normovolemic children, and we included 1914 children who met the criteria for our study. As we had aimed, this number was higher than the number of children in previous studies. We revealed a significant positive correlation between IVC and aorta diameters with age, whereas the IVC/aorta ratio does not correlate. In addition, the reference values for the IVC, aorta diameters and CI obtained were also acquired from the measurements during quiet respiration. Since we are the largest series in the literature, we believe that the reference values we have obtained are more reliable.

Previous studies carried out by Haines et al.[13] (with 25 healthy children from 4 weeks to 20 years of age), Kathuria et al.[8] (with 63 normovolemic children aged 0 to 22 years of age), Kutty et al.[14] (with 132 normal pediatric subjects from 1 to 18 years of age), Munk et al.[15] (with 176 healthy children aged 1 to 16 years of age), Taneja et al.[16] (with 475 healthy Indian children aged 1 to 12 years of age), and more recently Mannarino et al.[9] (with 516 healthy Caucasian Italian children aged 1 month to 16 years of age) performed IVC and/or aorta measurements. Taneja only measured IVC and Munk measured infrarenal aorta and iliac artery, but others measured both IVC and aorta. Our study is the largest series known to date in which both IVC and aorta diameters are measured in healthy and normovolemic children.

The normal range of IVC diameter is available for adults and the normal range considered for adults is between 1.7 to 2.1 cm, but such normative data is limited for children of all ages.[6],[7] As we have determined in our study, along with the increasing age in children, variability occurs in IVC and aorta diameter. In other words, it is clear that there is a positive correlation between age and anthropometric measurements and sonographic measurements (sagittal maximum IVC, sagittal minimum IVC, transverse maximum IVC, transverse maximum aorta). Mannarino et al.[9] found that IVC and aorta diameters showed a high positive correlation with all the parameters except body mass index (BMI). Kathuria et al.[8] reported that the IVC diameter might be more closely related to the age and weight of the patient than to the BMI. Similar to other studies, we determined that IVC and aorta diameters showed a significant positive correlation with anthropometric measurements other than BMI (weight, height, BSA) and age.

Studies have shown that the descending aorta diameter does not change the volume status.[5] In other words, while IVC collapses in low volume and distends in a volume increase in spontaneously breathing persons, a similar response is not valid for the aorta. In studies on this, Chen et al.[11] have shown in their studies that IVC/aorta ratio was lower in dehydrated children with gastroenteritis and that this rate increased with volume replacement. Yanagawa[17] has shown that the mean abdominal aortic diameter remains stable, unchanged even with excessive blood loss. Due to the above reasons, it has been suggested that it would be more beneficial to use IVC/aorta ratio instead of the aorta diameter to evaluate the volume status. Also, Mannarino[9] reported IVC max/aorta ratio mean value of 1.03 (SD 0.28) in 516 subjects. In our study, the IVC/aorta ratio was found to be 0.98 (SD 0.14) in the overall study population, and it was observed that the transverse IVC/aorta ratio increased in correlation with age, and this is in line with the literature. In the same publication, IVC/aorta is 0.83 (SD 0.20) under the age of 1, 0.92 (SD 0.19) between the ages of 1–4, and 1.22 (SD 0.31) in the age group of 13–16 years, and our measurements are also in line with the literature [Table 2].[9] An increase depending on age in the IVC is more evident. Kwon et al.[18] have shown that the cut-off value of aorta/IVC was 1.81 (sensitivity: 72%, specificity: 89%) in dehydrated children under 10 years, and the authors have claimed that the aorta/IVC ratio for dehydration may have higher diagnostic performance than the maximum IVC and aorta diameter. We think that the reference values in our study will also help to use the aorta/IVC ratio, and more studies will certainly be needed to evaluate and improve the diagnostic benefit of IVC/aorta or aorta/IVC ratio in children.

IVC diameter measurements are made in both clinical and experimental studies in order to evaluate the volume status. A positive correlation has been demonstrated between IVC diameter and central venous pressure.[19],[20],[21] We believe that the reference values we have obtained for every age group can be used as reference values in emergency departments and intensive care units.

Mannarino has reported that the IVC diameters of males and females were not different.[9] However, in our study we have found that sagittal maximum IVC measurements of the 61 to 72 months age group was higher in males, of the 133 to 144 months age group was higher in females and of the 193 to 204 months age group was higher in males, and the sagittal maximum IVC measurements of the other age groups was not different between males and females. The higher IVC diameter in females in the age group of 133 to 144 months can be explained by the earlier onset of puberty in females.

The IVC is a highly compliant vessel and its diameter is influenced by many factors.[22] Especially, as the age groups get younger the sonographic measurements of IVC become more difficult. Younger children are more active and had tendencies to Valsalva against the ultrasound probe. In our study, there were in total 98 participants from the age group of 1 month to 12 months of age and 93 participants from the age group of 13 to 24 months of age. When we were performing the measurements on young children, we had to spend more time. We tried to overcome these problems in a calm environment, by getting support from their mother, using warm USG gel, giving them pacifiers, or feeding them during the measurement. In previous studies, the number of samples in this age group was less and only three children were included in one study.[8] When compared with the studies conducted so far, our study includes most infants and young children.

The collapsibility index has high variability in the sample and was not correlated with age and anthropometric measurements which were in line with the literature.[9],[14]. It was reported that CI was 30% (SD 17%) in children >1 year and 36% (SD 16%) in children <1 year in one recent study.[9] In our study, CI was 39.3% (SD 9.1) for the age group of 1 month to 12 months of age, and CI 37.2% (SD 11.8) for the overall study population. Nagdev et al.[23] reported that in patients with suspected sepsis CI >50% is associated with CVP <8 mmHg, Kircher et al.[24] reported that CI ≥50% is associated with central venous pressure (CVP) <10 mmHg whereas CI <50% is associated with CVP ≥10 mmHg. The number of studies in which the CI is taken as a predictor for the evaluation of responsiveness to fluid in children is small. The Pediatric Research in Emergency Departments International Collaborative (PREDICT) study has demonstrated that there is no significant correlation between CI and fluid responsiveness in spontaneously ventilating septic children.[25] The Bedside Ultrasound to Detect Dehydration in Youth (BUDDY) study has shown that there is little utility to using CI in dehydrated children.[26] It seems that CI is inconclusive in evaluating intravenous volume status in children, and further studies should be conducted in the future to clarify the relationship between CI and IV volume status and right atrial pressure. CI values of healthy, normovolemic, and spontaneously breathing children obtained from our study may lay the groundwork for future studies.

Although validation studies are limited in pediatrics, a recent pediatric study has suggested that IVC parameters can be indexed to BSA for comparison.[14] However, it is impractical to measure the bodyweight of a critical patient in emergency departments, therefore, we can say that IVC parameters may be indexed to age because they correlate with the IVC parameters at least as much as BSA [Table 3] and [Figure 1].


   Conclusion Top


We think that our IVC and aorta diameter measurements obtained from a large number of participants may be used as reference values in emergency departments and intensive care units and, the reference values in our study may also help to use the aorta/IVC ratio. Additionally, we believe that the CI obtained from our measurements will form the basis for future studies.

Limitations of our study

The first limitation: It includes a specific population that does not have different racial and ethnic characteristics. The second limitation: Data were collected from children assumed to be euvolemic based on their clinical history and vital signs, a more detailed clinical evaluation was not applied. The third limitation: In our study, we did not add obesity among the exclusion criteria. In obese children, it may be necessary to evaluate IVC and aorta measurements separately. The fourth limitation: IVC measurements were assessed using the M-mode, inspiratory and expiratory diameters were measured at different locations. The fifth limitation: The standardized sonographic measurements were initiated while all participants were in the supine position and performing quiet respiration. These results could not be applied in semi-recumbent, agitated, or children with respiratory distress.

Informed consent

Written consent (from their guardians) was obtained for all children.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Brierley J, Carcillo JA, Choong K, Cornell T, Decaen A, Deymann A, et al. Clinical practice parameters for hemodynamic support of pediatric and neonatal septic shock: 2007 update from the American College of Critical Care Medicine. Crit Care Med 2009;37:666–88.  Back to cited text no. 1
    
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Mannarino S, Bulzomì P, Codazzi AC, Rispoli GA, Tinelli C, De Silvestri A, et al. Inferior vena cava, abdominal aorta, and IVC-to-aorta ratio in healthy Caucasian children: Ultrasound Z-scores according to BSA and age. J Cardiol 2019;74:388-93.  Back to cited text no. 9
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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