1Department of Anaesthesiology and 2Department of Anatomy, Medical School Hannover, D-30623 Hannover, Germany
This article is accompanied by Editorial II.
Accepted for publication: February 7, 2000
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Abstract |
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Br J Anaesth 2000; 85: 1924
Keywords: catheters, venous; complications, cardiac tamponade; heart, pericardium
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Introduction |
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We are unaware of any anatomical studies to verify the exact location of the pericardial sac in relation to other radiographically visible anatomical structures. Some clinicians use the carina as a landmark for the correct location of CVC tips, but this has not been investigated systematically. The aim of our study was to determine whether the carina can be used as a landmark below which no catheter tip should be located.
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Material and methods |
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In this university hospital with 1400 beds, several thousand CVCs are inserted each year. To assess whether the carina is visible in CXRs taken in the intensive care units, we studied 100 consecutive newly placed CVCs in seven intensive care units (cardiac surgery, abdominal surgery, transplantation surgery, trauma, anaesthesiology, cardiology and respiratory). All CXRs were taken as portable antero-posterior CXRs with the patient lying supine.
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Results |
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Discussion |
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To prevent cardiac tamponade, various safe location criteria have been suggested, but all have major drawbacks. Greenall and colleagues suggested that the catheter tip should be no more than 2 cm inferior to a line drawn between the lower borders of the clavicles on an erect posterior-anterior CXR.2 However, in the portable antero-posterior CXR used in intensive care units with the patient lying supine, the film is located much closer to the beam source than in posterior-anterior CXRs taken with the patient standing upright. As a consequence, anatomical structures located anteriorly and more peripherally, such as the clavicles, can be augmented on the film by more than 20%. This parallax effect makes the criteria suggested by Greenall less reliable. To circumvent the parallax problem, Rutherford and colleagues suggested that the angle formed between the right main bronchus and the trachea, which is located closer to the SVC, is a more appropriate landmark.3 However, their work was not based on anatomical studies and it remained unclear whether it really guarantees an extrapericardial location of the CVC tip. Collier and colleagues suggested avoiding any location of the CVC tip which can be seen inside the cardiac silhouette on CXR,4 but the border between the SVC and the right atrium is often indeterminable on CXRs. Moreover, the cardiac silhouette does not match the anatomical location of the pericardial sac, as our data show that the intrapericardial part of the SVC is 3.0 (0.2) cm (range 1.05.0 cm). A correctly placed catheter according to the criterion suggested by Collier and colleagues could still cause a cardiac tamponade by vascular erosion of the intrapericardial SVC, which has been reported previously.8 12
Our study shows that the carina is a reliable landmark for the placement of CVCs. In all cases, the pericardial sac ends below the level of the carina. The longitudinal distance between the level of the carina and the level of the upper end of the pericardial sac has a relatively small variability and does not correlate with the length of the patient. Our study also explains why CVC tips abutting the lateral wall of the SVC are especially dangerous:13 the lateral side of the SVC is much weaker than the medial side, where the pericardial sac fortifies the vessel wall.
The carina as an anatomical landmark has several advantages; due to its fixation with connective tissue, its location is preserved even in pulmonary pathology. The central location and the small sagittal distance between it and the SVC (range 1.54.1 cm in our study) limit any parallax effect. Most importantly, the carina is easily visible even in a poor quality portable antero-posterior CXR.
In conclusion, cardiac tamponade is a potentially life-threatening complication of CVC placement which can be avoided if all catheter tips are located above the carina on CXR.
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Footnotes |
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References |
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