Abstract
Introduction:
The correlation of central venous pressure (CVP) with inferior vena cava (IVC) sonographic diameter has been reported in several studies. However, few studies have attempted to find the best anatomic location of measurement. Therefore, the purpose of this study was determining the best anatomic location to find precise correlation between CVP and IVC diameter using transesophageal echocardiography (TEE).
Methods:
In the present diagnostic accuracy study, patients in need of central venous catheterization and TEE were enrolled. Maximum diameter of IVC were measured during expiratory phase of respiratory cycle at the level of diaphragm, 2cm above the diaphragm and at the point of entry into the right atrium using SonoSite TEE device. CVP was measured using an electronic transducer connected to the central venous line. The best location for sonography was determined via calculating and comparing area under the receiver operating characteristics (ROC) curve (AUC).
Results:
39 patients were enrolled (53.8% female). Mean CVP was 6.8 ± 1.4 mmHg and 25 (64.1%) patients had normal CVP, while 14 (35.9%) showed elevated CVP (> 6 mmHg). Evaluating AUC showed that IVC diameter (p = 0.01), aorta diameter (p = 0.01) and IVC / aorta ratio (p = 0.004) had acceptable correlation with CVP. Point of entry of IVC into the right atrium with AUC of 0.98 (95% CI: 0.95 – 1.00) was the location of highest correlation with CVP.
Conclusion:
Based on the present findings, the IVC sonographic diameter and IVC / aorta ratio had acceptable correlation with CVP at the level of IVC entry into the right atrium.
Key Words: Central venous pressure, vena cava, inferior, aorta, thoracic, echocardiography, transesophageal
Introduction:
Dehydration is the main cause of morbidity and mortality in critically ill patients and assessment of intravascular volume status (IVS) is essential for their management (1, 2). However, diagnosis of dehydration and intravascular volume loss is sometimes difficult (3). Some clinical signs and symptoms are assessed for determining IVS but they have low sensitivity and specificity (4). It could be determined by measuring peripheral blood pressure, but in many conditions, it does not reflect accurate intravascular volume status. Hypotension is detected in late stage of shock, especially when compensatory mechanisms fail (5). Central venous pressure (CVP) is one of the indices of IVS and early goals of goal-directed therapy approach (6, 7). A common and conventional procedure for measuring CVP is inserting a catheter in a central vein such as internal jugular, subclavian, and femoral veins. However, the major problem with this procedure is the probability of some dangerous and sometimes lethal complications such as arterial puncture, pneumothorax, hemothorax, misplacement in carotid artery, infection, and other rare complications such as cardiac tamponade etc. In addition, central venous catheter insertion is a time consuming and invasive procedure (8-12). Recently, researchers and physicians have attempted to measure CVP with non-invasive procedures such as ultrasonography, transthoracic echocardiography, and transesophageal echocardiography (TEE). They have reported a correlation between sonographic inferior vena cava (IVC) diameter and CVP (1, 9, 13-16). Donahue et al. found a direct correlation between internal jugular vein sonographic diameter and CVP (17). However, few studies have attempted to find the best anatomic location and cut points. Therefore, the purpose of this study was determining the best anatomic location to find precise correlation between CVP and IVC diameter using TEE.
Methods:
Study design and setting
In the present prospective cross-sectional study, the correlation of sonographic IVC diameter, aorta diameter, and IVC / aorta ratio with CVP were evaluated. Patients in need of catheterization and TEE who were referred to a teaching hospital in Tabriz, Iran, from 2013 to 2015 were enrolled. This study was approved by the Ethics Committee of Tabriz University of Medical Sciences. The patients or their relatives had signed the informed written consent form before initiation of the study and the researchers adhered to the principles of Helsinki declaration.
Participants:
Over the course of the study, all patients over 18 years old who needed central venous catheterization and TEE were included. Consecutive sampling was used and the patients’ need for catheterization and TEE was determined by an independent cardiologist. Those who were prohibited from assuming a supine position (severe orthopnea, intracerebral pressure rising), patients who had moderate-to-severe tricuspid regurgitation, congestive heart failure, broncho-pulmonary dysplasia, body mass index > 30, and renal and liver diseases were excluded.
Measurements:
Central venous catheterization and TEE were done in the operating room. After central catheterization using Seldinger technique, CVP was measured using electronic transducer connected to the CV line inserted in the right internal jugular vein by central approach while the patient was placed in a 15-degree Trendelenburg position (18). IVC and aorta diameter were measured using TEE (SONOS 5500; Philips Medical Systems, Andover, MA) and a 3.5 MHz probe. All the ultrasonographies were done by a trained cardiology fellow who was blind to the patients’ CVP. IVC and aorta diameter were measured at end-expiration and end-diastole in 2-dimensional long-axis mid-esophageal bicaval view. Measurements were done in the level of diaphragm, 2 centimeters above the diaphragm and at the point of entry into the right atrium and recorded in millimeter. All evaluations were done in the supine position.
Statistical analysis
Sample size was determined to be about 45 patients considering minimum correlation coefficient of IVC diameter and CVP to be 0.48 with 95% confidence interval (CI) (α = 0.05) and 90% power (β = 0.1). Analyzes were done with SPSS 20. Spearman’s rank correlation test was used to determine the relationship between sonographic IVC diameter and CVP. Best index (IVC diameter, aorta diameter, or IVC / aorta ratio) and best measurement location (the level of diaphragm, 2cm above the diaphragm and at the point of entry into the right atrium) were determined via calculating and comparing area under the receiver operating characteristics (ROC) curve (AUC). Normal CVP was considered 2-6 mmHg for this purpose (19). In all analyses, p < 0.05 was considered as significance level.
Results:
Over the course of the study, 39 patients were included (53.8% male; mean age 62.1 ± 5.8 years). Baseline characteristics of the patients are summarized in table 1. Mean CVP was 6.8 ± 1.4 mmHg and 25 (64.1%) patients had normal CVP, while 14 (35.9%) showed elevated CVP (> 6 mmHg).
Table 1.
Baseline characteristics of the patients
| Variable | Mean (SD) | Median | Minimum | Maximum |
|---|---|---|---|---|
| Age (year) | 62.1 (5.8) | 61 | 54 | 83 |
| Weight (kg) | 69.5 (11.0) | 68 | 53 | 94 |
| Height (cm) | 161.3 (7.3) | 160 | 145 | 178 |
| SBP (mmHg) | 110 (9.6) | 110 | 95 | 130 |
| DBP (mmHg) | 63.8 (6.9) | 63 | 45 | 80 |
| HR (beat/min) | 71.3 (12.4) | 73 | 45 | 90 |
| CVP (mmHg) | 6.8 (1.04) | 7 | 4 | 9 |
| IVC diameter (mm) | ||||
| Point of entry into the right atrium | 23.2 (3.6) | 22 | 18 | 31 |
| 2cm above the diaphragm | 18.6 (2.6) | 19 | 12 | 23 |
| Level of diaphragm | 17.1 (3.4) | 17 | 10 | 25 |
| Aorta diameter (mm) | ||||
| Point of entry into the right atrium | 24.6 (2.1) | 25 | 21 | 29 |
| 2cm above the diaphragm | 22.4 (1.6) | 23 | 19 | 27 |
| Level of diaphragm | 21.3 (1.6) | 21 | 19 | 27 |
| IVC/Aorta ratio | ||||
| Point of entry into the right atrium | 0.94 (0.09) | 0.96 | 0.78 | 1.12 |
| 2cm above the diaphragm | 0.83 (0.13) | 0.86 | 0.52 | 1.05 |
| Level of diaphragm | 0.81 (0.16) | 0.81 | 0.48 | 1.09 |
SBP: systolic blood pressure, DBP: diastolic blood pressure, HR: heart rate, CVP: central venous pressure, IVC: inferior vena cava.
The relationship of CVP with IVC and aorta diameter
Table 2 shows the relationship of CVP with sonographic IVC diameter, aorta diameter, and IVC / aorta. As can be seen, CVP had a significant correlation with IVC diameter at the point of entry into the right atrium (r = 0.85; p < 0.001), 2cm above the diaphragm (r = 0.48; p = 0.002), and in the level of diaphragm (r = 0.85; p < 0.001). At the same time, aorta diameter showed a significant correlation with CVP at the point of entry into the right atrium (r = 0.68; p < 0.001) and 2cm above the diaphragm (r = 0.44; p = 0.005). IVC / aorta ratio also had a significant correlation with CVP at all 3 points.
Table 2.
Correlation of CVP with IVC and aorta diameters, and IVC/Aorta ratio
| Index | R | 95 % CI | P |
|---|---|---|---|
| IVC | |||
| Point of entry into the right atrium | 0.85 | 0.73-0.92 | <0.001 |
| 2cm above the diaphragm | 0.48 | 0.19-0.69 | 0.002 |
| Level of diaphragm | 0.68 | 0.47-0.82 | <0.001 |
| Aorta | |||
| Point of IVC entry into the right atrium | 0.68 | 0.45-0.81 | <0.001 |
| 2cm above the diaphragm | 0.44 | 0.15-0.66 | 0.005 |
| Level of diaphragm | 0.15 | -0.17-0.44 | 0.37 |
| IVC/Aorta ratio | |||
| Point of IVC entry into the right atrium | 0.69 | 0.48-0.83 | 0.001 |
| 2cm above the diaphragm | 0.43 | 0.16-0.68 | 0.007 |
| Level of diaphragm | 0.53 | 0.26-0.72 | 0.001 |
IVC: Inferior vena cava; CI: Confidence interval.
Comparing diagnostic values of IVC and aorta diameter
Evaluation of area under the ROC curve showed that the best point for determining CVP was at the point of entry into the right atrium for IVC diameter (p = 0.01), aorta diameter (p = 0.01), and IVC / aorta ratio (p = 0.004) (figure 1A-C). Therefore, to identify the best index among the 3, their area under the ROC curve was compared at this point (table 3 and figure 1-D). Based on the findings, IVC diameter (AUC = 0.98; 95% CI: 0.95-1.0) and IVC / aorta ratio (AUC = 0.96; 95% CI: 0.92-1.0) had higher diagnostic values compared to aorta diameter (AUC = 0.89; 95% CI: 0.79-0.98) at this point (p = 0.01).
Figure 1.
Comparison of area under the curve of inferior vena cava (IVC) diameter (A), aorta diameter (B), and IVC / aorta ratio (C) in different points in estimation of central venous pressure and comparison between the three indices (D
Table 3.
area under ROC curve of IVC and aorta diameters, and IVC/Aorta ratio in estimation of CVP
| Index | AUC | 95 % CI | P |
|---|---|---|---|
| IVC | |||
| Point of entry into the right atrium | 0.98 | 0.95-1.0 | 0.01 |
| 2cm above the diaphragm | 0.78 | 0.62-0.93 | |
| Level of diaphragm | 0.81 | 0.66-0.96 | |
| Aorta | |||
| Point of IVC entry into the right atrium | 0.89 | 0.79-0.98 | 0.01 |
| 2cm above the diaphragm | 0.64 | 0.45-0.84 | |
| Level of diaphragm | 0.53 | 0.45-0.84 | |
| IVC/Aorta ratio | |||
| Point of IVC entry into the right atrium | 0.96 | 0.92-1.0 | 0.004 |
| 2cm above the diaphragm | 0.67 | 0.48-0.85 | |
| Level of diaphragm | 0.80 | 0.66-0.94 |
IVC: Inferior vena cava; AUC: Area under curve; CI: Confidence interval.
Discussion:
This study was conducted to find the precise anatomic location with the best correlation between CVP and IVC diameter, aorta diameter, or IVC/aorta ratio. Based on the present findings, the IVC diameters and IVC / aorta ratio had acceptable correlation with CVP. In addition, the point of IVC entry into the right atrium was the best anatomic location to estimate CVP. Ultrasound is a non-invasive, easy, available, and useful tool for assessment of volume status (20). Wiwatworapan et al. showed that when end-expiratory IVC diameter was lower than 10 mm, the CVP would be 10 cmH2O, (sensitivity 77% and specificity 91%) and when end-expiratory IVC diameter was 15 mm, CVP would be 15 cmH2O (sensitivity 90% and specificity 89%) (21). Baumann et al. measured CVP using ultrasound and concluded that although estimation of CVP by ultrasound is easy, but absolute values differ from invasive measurements of CVP and IVC indices alone can’t be used to accurately estimate intravascular volume status (22). In line with our study, Arthur et al. reported a statistically significant correlation between IVC diameter and CVP (16). In addition, De Lorenzo et al. compared different anatomic locations such as subxiphoid, mid-abdomen and suprailiac to find best anatomic location for calculating the correlation between CVP and IVC diameter. They reported that suprailiac view had better correlation with CVP compared to other anatomic locations but measurement of CVP using ultrasound had low yield (23). Yet, some studies demonstrate that an increase or decrease in the collapsibility of IVC can be helpful in management of patients in poor condition. Based on the findings of those studies, the combination of absolute IVC diameter and collapsibility level, which is known as Caval index, is a better estimation of CVP compared to absolute IVC diameter and can be a good replacement for invasive tests (24-26). The mechanism of this method is based on the fact that the negative pressure generated while inhalation leads to an increase in venous return to heart and IVC collapse. While exhaling, venous return decreases and IVC diameter goes back to the basic state (25, 27, 28). In the present study, Caval index could not be assessed, as the ultrasonography film could not be recorded in the device used. Therefore, it is recommended to take this into account in future studies. Another limitation of this study was the little sample size, yet the minimum power calculated for this study was 85%; so it seems that little sample size has not affected the results of this study.
Conclusion:
Based on the present findings, the IVC sonographic diameter and IVC / aorta ratio had acceptable correlation with CVP at the level of IVC entry into the right atrium.
Acknowledgments:
Authors would like to thank all the staff of operating room in Shahid Madani Hospital.
Conflict of interest:
None
Funding support:
None
Authors’ contributions:
All authors passed four criteria for authorship contribution based on recommendations of the International Committee of Medical Journal Editors.
References
- 1.Thanakitcharu P, Charoenwut M, Siriwiwatanakul N. Inferior vena cava diameter and collapsibility index: a practical non-invasive evaluation of intravascular fluid volume in critically-ill patients. J Med Assoc Thai. 2013;96:S14–22. [PubMed] [Google Scholar]
- 2.Control CfD, Prevention Managing acute gastroenteritis among children: oral rehydration, maintenance, and nutritional therapy. Pediatrics. 2004;114(2):507. [PubMed] [Google Scholar]
- 3.Riccardi A, Chiarbonello B, Minuto P, Guiddo G, Corti L, Lerza R. Identification of the hydration state in emergency patients: correlation between caval index and BUN/creatinine ratio. Eur Rev Med Pharmacol Sci. 2013;17(13):1800–3. [PubMed] [Google Scholar]
- 4.Gorelick MH, Shaw KN, Murphy KO. Validity and reliability of clinical signs in the diagnosis of dehydration in children. Pediatrics. 1997;99(5):E6. doi: 10.1542/peds.99.5.e6. [DOI] [PubMed] [Google Scholar]
- 5.Pershad J, Myers S, Plouman C, et al. Bedside limited echocardiography by the emergency physician is accurate during evaluation of the critically ill patient. Pediatrics. 2004;114(6):e667–71. doi: 10.1542/peds.2004-0881. [DOI] [PubMed] [Google Scholar]
- 6.Marcelino P, Fernandes A, Marum S, Ribeiro J. Non-invasive evaluation of central venous pressure by echocardiography. Rev Port Cardiol. 2002;21(2):125–33. [PubMed] [Google Scholar]
- 7.Rivers E, Nguyen B, Havstad S, et al. Early goal-directed therapy in the treatment of severe sepsis and septic shock. N Engl J Med. 2001;345(19):1368–77. doi: 10.1056/NEJMoa010307. [DOI] [PubMed] [Google Scholar]
- 8.Gong P, Huang X-E, Chen C-Y, Liu J-H, Meng A-F, Feng J-F. Comparison of complications of peripherally inserted central catheters with ultrasound guidance or conventional methods in cancer patients. Asian Pac J Cancer Prev. 2012;13(5):1873–5. doi: 10.7314/apjcp.2012.13.5.1873. [DOI] [PubMed] [Google Scholar]
- 9.Jardim JM, Lacerda RA, Soares NdJD, Nunes BK. Evaluation of practices for the prevention and control of bloodstream infections in a government hospital. Rev Esc Enferm USP. 2013;47(1):38–45. doi: 10.1590/s0080-62342013000100005. [DOI] [PubMed] [Google Scholar]
- 10.Kaye C, Smith D. Complications of central venous cannulation. BMJ. 1988;297(6648):572–3. doi: 10.1136/bmj.297.6648.572. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.McGee DC, Gould MK. Preventing complications of central venous catheterization. N Engl J Med. 2003;348(12):1123–33. doi: 10.1056/NEJMra011883. [DOI] [PubMed] [Google Scholar]
- 12.Pivalizza EG, Gumbert SD, Marasigan B, Guzman-Reyes S. 'Evidence'for practice guidelines for central venous access? Anesthesiology. 2012;117(4):916–7. doi: 10.1097/ALN.0b013e318268ffb7. [DOI] [PubMed] [Google Scholar]
- 13.Chen L, Kim Y, Santucci KA. Use of ultrasound measurement of the inferior vena cava diameter as an objective tool in the assessment of children with clinical dehydration. Acad Emerg Med. 2007;14(10):841–5. doi: 10.1197/j.aem.2007.06.040. [DOI] [PubMed] [Google Scholar]
- 14.Chen L, Hsiao A, Langhan M, Riera A, Santucci KA. Use of bedside ultrasound to assess degree of dehydration in children with gastroenteritis. Acad Emerg Med. 2010;17(10):1042–7. doi: 10.1111/j.1553-2712.2010.00873.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Bailey JK, McCall J, Smith S, Kagan RJ. Correlation of internal jugular vein/common carotid artery ratio to central venous pressure: a pilot study in pediatric burn patients. J Burn Care Res. 2012;33(1):89–92. doi: 10.1097/BCR.0b013e318234d965. [DOI] [PubMed] [Google Scholar]
- 16.Arthur ME, Landolfo C, Wade M, Castresana MR. Inferior vena cava diameter (IVCD) measured with transesophageal echocardiography (TEE) can be used to derive the central venous pressure (CVP) in anesthetized mechanically ventilated patients. Echocardiography. 2009;26(2):140–9. doi: 10.1111/j.1540-8175.2008.00772.x. [DOI] [PubMed] [Google Scholar]
- 17.Donahue SP, Wood JP, Patel BM, Quinn JV. Correlation of sonographic measurements of the internal jugular vein with central venous pressure. Am J Emerg Med. 2009;27(7):851–5. doi: 10.1016/j.ajem.2008.06.005. [DOI] [PubMed] [Google Scholar]
- 18.Ely EW, Smith AC, Chiles C, et al. Radiologic determination of intravascular volume status using portable, digital chest radiography: a prospective investigation in 100 patients. Crit Care Med. 2001;29(8):1502–12. doi: 10.1097/00003246-200108000-00002. [DOI] [PubMed] [Google Scholar]
- 19.Jeremias A, Brown D. Cardiac Intensive Care. 2 ed. Philadelphia: Elsevier Health Sciences; 2010. 384 pp. [Google Scholar]
- 20.Zengin S, Al B, Genc S, et al. Role of inferior vena cava and right ventricular diameter in assessment of volume status: a comparative study: ultrasound and hypovolemia. Am J Emerg Med. 2013;31(5):763–7. doi: 10.1016/j.ajem.2012.10.013. [DOI] [PubMed] [Google Scholar]
- 21.Wiwatworapan W, Ratanajaratroj N, Sookananchai B. Correlation between inferior vena cava diameter and central venous pressure in critically ill patients. J Med Assoc Thai. 2012;95(3):320–4. [PubMed] [Google Scholar]
- 22.Baumann UA, Marquis C, Stoupis C, Willenberg TA, Takala J, Jakob SM. Estimation of central venous pressure by ultrasound. Resuscitation. 2005;64(2):193–9. doi: 10.1016/j.resuscitation.2004.08.015. [DOI] [PubMed] [Google Scholar]
- 23.De Lorenzo RA, Morris MJ, Williams JB, et al. Does a simple bedside sonographic measurement of the inferior vena cava correlate to central venous pressure? J Emerg Med. 2012;42(4):429–36. doi: 10.1016/j.jemermed.2011.05.082. [DOI] [PubMed] [Google Scholar]
- 24.Goldflam K, Saul T, Lewiss R. Focus On: Inferior Vena Cava Ultrasound. Vol. 6. ACEP News; 2011. pp. 24–5. [Google Scholar]
- 25.Nagdev AD, Merchant RC, Tirado-Gonzalez A, Sisson CA, Murphy MC. Emergency department bedside ultrasonographic measurement of the caval index for noninvasive determination of low central venous pressure. Ann Emerg Med. 2010;55(3):290–5. doi: 10.1016/j.annemergmed.2009.04.021. [DOI] [PubMed] [Google Scholar]
- 26.Sridhar H, Mangalore P, Chandrasekaran V, Manikam R. Caval Aorta Index and Central Venous Pressure Correlation in Assessing Fluid Status!“Ultrasound Bridging the Gap”. ISRN Emerg Med. 2012;2012:1–5. [Google Scholar]
- 27.Tayal V, Blaivas M. American College of Emergency Physicians: ACEP emergency ultrasound guidelines-2001. Ann Emerg Med. 2009;53:470–81. [PubMed] [Google Scholar]
- 28.Blehar DJ, Dickman E, Gaspari R. Identification of congestive heart failure via respiratory variation of inferior vena cava diameter. Am J Emerg Med. 2009;27(1):71–5. doi: 10.1016/j.ajem.2008.01.002. [DOI] [PubMed] [Google Scholar]