Usefulness of the carina as a radiographic landmark for central venous catheter placement in paediatric patients{dagger}

S. Z. Yoon, J. H. Shin, S. Hahn1, A. Y. Oh, H. S. Kim, S. D. Kim and C. S. Kim*

Department of Anaesthesiology, College of Medicine, Seoul National University, Seoul, Korea. 1 Medical Research Collaborating Centre, College of Medicine, Seoul National University, Seoul, Korea

* Corresponding author. E-mail: monday1031{at}yahoo.co.kr

Accepted for publication June 16, 2005.


    Abstract
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 Footnotes
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Background. Several reports have proposed radiographic landmarks for the proper positioning of central venous catheters (CVC). The carina is one of the proposed landmarks in adults. Here, we evaluate the possibility of using the carina as a radiographic landmark for the identification of proper positioning of the CVC tip in paediatric patients.

Methods. We studied 57 right internal jugular vein catheterizations in infants and children undergoing surgery for the treatment of congenital heart disease. After placing the CVC tip at the junction of the superior vena cava and the right atrium (SVC–RA junction) via intraoperative transoesophageal echocardiography, and by taking postoperative anterior–posterior chest radiographs, we measured the longitudinal distance from the carina to the SVC–RA junction, using the Picture Archiving and Communicating System.

Results. The average distance between the carina and the SVC–RA junction was 1.5 cm (95% CI 1.3–1.8 cm). No catheter tip was above the carina. Although there was no particular relationship between this distance and the patient's age, height, or weight, the distance between the carina and the SVC–RA junction tended to be more variable in younger and smaller children.

Conclusions. The carina can be used as a radiographic landmark for the proper CVC tip placement in paediatric patients. If the tip of the CVC is not distal to the carina the chances are minute that it is in the right atrium.

Keywords: heart, central venous catheterization ; measurement techniques, transoesophageal echocardiography, carina


    Introduction
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 Footnotes
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
The tip of a central venous catheter (CVC) has been classically positioned within the superior vena cava–right atrial (SVC–RA) junction, in order to prevent serious complications such as cardiac perforation at the right atrium. Standard anterior–posterior chest radiography has been traditionally used to ensure that the catheter tip is properly positioned in the SVC. However, it is difficult to exactly identify the SVC–RA junction by simple observation of the chest radiography. Moreover, determination of the positioning of the catheter tip may vary according to the reader of the radiograph, because standard radiographic data are not available for reference.

Out of a variety of possible radiographic landmarks,17 the right tracheobronchial angle has been established as the most reliable landmark for the identification of the SVC.14 However, this is rarely the method used in clinical practice, as the right tracheobronchial angle is difficult to identify on a standard chest radiograph.

In a recent study, Schuster and colleagues4 stated that the carina of an adult would be positioned 0.4 cm above the pericardial sac. The carina is not only a reliable, simple anatomical landmark for correct CVC placement, but also constitutes an effective radiographic landmark, which is readable even in portable chest radiographs, which may be of limited quality. As the study of Schuster and colleagues involved only adults with an average age of 78 yr (range 49–98), these findings are not directly applicable to infants and children with anatomically different cardiovascular structures.

Transoesophageal echocardiography (TOE) has become an essential monitoring modality for most patients undergoing surgery for the treatment of congenital heart disease. In addition, TOE is used to assess preoperative and postoperative anatomy, ventricular volume and function, as well as the presence of intracardiac air.6 Finally, TOE has been demonstrated to accurately monitor the placement of catheter tip at the SVC–RA junction,7 and it provides a more sensitive assessment than chest radiography.8

In this study, we reviewed the chest radiographs of 60 paediatric patients who had undergone congenital heart surgery requiring CVC catheterization, in which TOE was used to confirm the positioning of the catheter tip at the SVC–RA junction. We attempted to determine whether or not the carina constitutes an effective landmark for the identification of the SVC–RA junction in infants and children.


    Methods
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
This study was performed over a 6-month period, with approval from the Institutional Ethics Committee of the Seoul National University Hospital. The informed consent was received from the parents of the participating patients, who had been informed of the study purpose and methods in advance. Paediatric patients undergoing congenital heart surgery requiring CVC catheterization were enrolled in the study. Patients with any extra-cardiac vascular or rotational abnormalities were excluded.

After the administration of general anaesthesia, the patient was placed in the Trendelenberg position, with the head rotated 45° to the left. Central venous catheterization was conducted on the right internal jugular vein. If the CVC failed to reach the SVC–RA junction, catheterization was achieved through the right subclavian vein instead. All such cases were excluded from our study. After CVC placement, an anaesthesiologist with at least 3 yr of TOE experience positioned the TOE probe to obtain a bicaval view of the right atrium in order to visualize the SVC–RA junction. The tip of the CVC was identified by the detection of hyperechogenic microbubbles from a transient saline flush. The tip of the CVC was considered to be at the SVC–RA junction when located at the superior border of the crista terminalis.

The position of the tip of the CVC was again verified by TOE, right before the patient was transferred to the paediatric intensive care unit. There, the patient was placed in the supine position with the neck straightened, in order to take the chest radiograph with a portable device. Thereby, the patient's neck was positioned at the centre of the radiographic cassette and the both shoulders were firmly attached to the cassette.

On these radiographic images, a diagnostic radiology specialist determined the distance from the carina level to the CVC tip level in the following manner, using the Picture Archiving and Communicating System (PACS, Maroview ver.5.3, MAROTECH, Inc.); horizontal lines were drawn at the carina level and at the level of the CVC tip. The distance between the two lines was then considered to be the longitudinal distance between the SVC–RA junction and the CVC tip (Fig. 1).



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Fig 1 The method to measure the distance from the level of carina to the level of catheter tip by using the Picture Archiving and Communicating System (PACS).

 
All measurements were expressed as average values (SD). In order to determine the manner in which the distance between the SVC–RA junction and the CVC tip and the patient's age, weight, and height were related, a simple linear regression analysis was used and the scatter diagrams were presented. P value <0.05 was regarded as statistically significant. All statistical analyses were performed with the SPSS 10.0 software (SPSS, Chicago, IL).


    Results
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 Introduction
 Methods
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During the study period, central venous cannulation was performed on 57 paediatric patients, out of which seven patients, in whom the CVC was inserted through the right subclavian vein were excluded. Another three patients in whom the radiographic images were of insufficient quality were also excluded. Diagnoses of the 47 patients analysed are shown in Table 1. The patients were 29 (36) months of age, weighed 12.1 (7.4) kg and were 84 (22) cm tall (Table 2). The longitudinal distance between the SVC–RA junction and the CVC tip was 1.5 (0.7) cm (95% CI 1.3–1.8 cm, range 0.3–2.8 cm), and no catheter tip was found above to the carina (Table 3).


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Table 1 Diagnoses of the enrolled patients. VSD, ventricular septal defect; ASD, atrial septal defect; TOF, tetralogy of Fallot; PDA, patent ductus arteriosus; AR, aortic regurgitation; PVR, pulmonary valve regurgitation; LVOT, left ventricle outlet tract obstruction; DORV, double outlet of right ventricle; CoA, coarctation of the aorta

 

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Table 2 Patients characteristics

 

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Table 3 The longitudinal distance from SVC–RA junction to the carina. SVC–RA junction, the junction of the SVC with the RA

 
There was no particular relationship found between the distance between the SVC–RA junction and the CVC tip and the patient's age, weight, and height (Fig. 2). However, the distance between the SVC–RA junction and the CVC tip was more variable in younger and smaller children.



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Fig 2 Scatter diagrams of the longitudinal distance from the level of carina to the level of SVC–RA junction and age (A), weight (B), and height (C).

 

    Discussion
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 Footnotes
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Central venous catheterization is often performed in children in order to administer i.v. fluids and inotropic agents, and also to measure central venous pressure. Central venous catheterization is sometimes associated with serious complications, including cardiac tamponade, arrhythmia, or cardiac perforation. While the CVC tip should ideally be located cephalad rather than exactly at the SVC–RA junction in order to reduce the risk of perforation, it should still be located as close to the RA as possible, in order to correctly measure central venous pressure.

Several studies regarding the radiographic landmarks relevant to CVC positioning have been done in adults.17 Aslamy and colleagues reported that the heart's right upper cardiac silhouette, as seen on the chest radiography of 38% of patients, did not originate from the right atrium, but rather from the left atrium. This implies that the contact of the SVC and heart silhouette in radiographic images does not always occur at the SVC–RA junction. They also reported that the right tracheobronchial angle is usually located 1.1–3.8 cm cephalad from the proximal border of the SVC–RA junction, and that if the CVC is positioned at the level of the right tracheobronchial angle, the CVC should be located 2.9 cm cephalad from the SVC–RA junction. Thus, they suggested that the right tracheobronchial angle level constitutes the most reliable radiographic landmark for the proper CVC placement.1 However, the right tracheobronchial angle is probably not applicable to actual clinical practice, because even radiologists find it difficult to identify particularly on limited quality anterior–posterior chest radiographs taken in paediatric intensive care units.

The carina has several advantages as a radiographic landmark. First, the carina does not move when pathologic changes occur in the lungs and thus the carina is always slightly cephalad rather than SVC–RA junction.46 Secondly, it is positioned in the centre of the body, the short sagittal distance to the RA, which attenuates the parallax effect.6 The parallax effect occurs when structures in the anterior chest look bigger in anterior–posterior chest radiograph films, due to the shorter beam–film distance compared to that of the posterior–anterior chest radiograph. Third and above all, the carina can be identified easily, even on poor quality anterior–posterior chest radiographs.

In this study, the average observed longitudinal distance between the SVCRA–CA and the carina was 1.5 cm with the 95% CI 1.3–1.8 cm. The distance does not appear to be related to the patient's age, weight, or height. However, because the spectrum of the distance is relatively wide for small children, and using the overall mean may not be appropriate in this group of children. In the older children, especially older than 50 months, the measured distances are more stable around the mean value.

In conclusion, we consider the carina a helpful radiographic landmark for proper CVC placement. If the tip of the CVC is not distal to the carina the chances are minute that it is in the right atrium and thus a right atrial perforation is highly unlikely.


    Acknowledgments
 
Supported solely from departmental sources and performed in the Seoul National University Hospital.


    Footnotes
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
{dagger} Presented, in part, at the 2005 Annual Meeting of European Society of Anaesthesiologists, Vienna, Austria. Back


    References
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 Methods
 Results
 Discussion
 References
 
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2 Defalque RJ, Campbell C. Cardiac tamponade from central venous catheters. Anesthesiology 1979; 50: 249–52[ISI][Medline]

3 Rutherford JS, Merry AF, Occleshaw CJ. Depth of central venous catheterization: an audit of practice in cardiac surgical unit. Anesth Intensive Care 1994; 22: 267–71[ISI][Medline]

4 Schuster M, Nave H, Piepenbrock S, Pabst R, Panning B. The carina as a landmark in central venous catheter placement. Br J Anesth 2000; 85: 192–4[Abstract/Free Full Text]

5 Albrecht K, Nave H, Breitmeier D, Panning B, Tröger D. Applied anatomy of the superior vena cava—the carina as a landmark to guide central venous catheter placement. Br J Anaesth 2004; 92: 75–7[Abstract/Free Full Text]

6 Caruso LJ, Gravenstein N, Layon AJ, Peters K, Gabrielli A. A better landmark for positioning a central venous catheter. J Clin Monit 2002; 17: 331–4[CrossRef]

7 Cobb LM, Vinocur CD, Wagner CW, Weintraub WH. The central venous anatomy in infants. Surg Gynecol Obstet 1987; 165: 230–4[ISI][Medline]

8 Russell IA, Miller-Hance WA, Silverman NH. Intraoperative transesophageal echocardiography for pediatric patients with congenital heart disease. Anesth Anlg 1998; 87: 1058–87

9 Reeves ST, Bevis LA, Biley BN. Positioning a right atrial air aspiration catheter using transesophageal echocardiography. J Neurosurg Anesthesiol 1996; 8:123–5[ISI][Medline]

10 Andropoulos DB, Stayer SA, Bent ST, et al. A controlled study of transesophageal echocardiography to guide central venous catheter placement in congenital heart surgery patients. Anesth Analg 1999; 89: 65–70[Abstract/Free Full Text]

11 Litt IF, Vaughan VC. Assessment of growth and development. In: Behrman RE, Vaughan VC, Nelson WE, eds. Nelson Textbook of Pediatrics. Philadelphia: W.B. Saunders Company, 1987; 31