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.
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Abstract |
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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 (SVCRA junction) via intraoperative transoesophageal echocardiography, and by taking postoperative anteriorposterior chest radiographs, we measured the longitudinal distance from the carina to the SVCRA junction, using the Picture Archiving and Communicating System.
Results. The average distance between the carina and the SVCRA junction was 1.5 cm (95% CI 1.31.8 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 SVCRA 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
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Introduction |
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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 4998), 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 SVCRA 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 SVCRA junction. We attempted to determine whether or not the carina constitutes an effective landmark for the identification of the SVCRA junction in infants and children.
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Methods |
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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 SVCRA 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 SVCRA 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 SVCRA 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 SVCRA junction and the CVC tip (Fig. 1).
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Results |
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Discussion |
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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 SVCRA junction. They also reported that the right tracheobronchial angle is usually located 1.13.8 cm cephalad from the proximal border of the SVCRA 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 SVCRA 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 anteriorposterior 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 SVCRA 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 anteriorposterior chest radiograph films, due to the shorter beamfilm distance compared to that of the posterioranterior chest radiograph. Third and above all, the carina can be identified easily, even on poor quality anteriorposterior chest radiographs.
In this study, the average observed longitudinal distance between the SVCRACA and the carina was 1.5 cm with the 95% CI 1.31.8 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.
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Acknowledgments |
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Footnotes |
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References |
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