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Central venous catheter malposition in the azygos arch

Schummer, W.; Schummer, C.

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European Journal of Anaesthesiology (EJA): November 2002 - Volume 19 - Issue 11 - p 832-834
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Azygos arch cannulation is a rare but hazardous central venous catheter (CVC) malposition that carries a substantial risk of perforation, thrombosis and vascular stenosis. Intra-atrial electrocardiography (ECG) and routine chest radiographs help to verify the correct position.

Catheters are inserted into the venous system of patients on a routine basis. According to definition and the academic literature [1-3], the incidence rate of complications during central venous cannulation is as high as 12%. Most of the complications of central venous access occur early during attempts to search for the vein, or because of advancement of the catheter into the vein. Although malposition of catheters within the central venous system frequently occurs, positioning of a catheter within a tributary of the superior vena cava (SVC) is rarely described.

We report on a 73-yr-old patient with right-sided malignant infarction of the medial cerebral artery territory of the brain. Because of thrombosis of the right internal jugular vein, a CVC was placed in the left subclavian vein. No problems of catheter placement were reported. Venous blood could be aspirated easily, the transduced venous pressure measurements showed a typical waveform and the clinical function tests were normal. However, despite sinus rhythm, the right atrial electrocardiogram could not be derived. A frontal chest radiograph demonstrated the catheter tip as a ring structure in projection of the SVC; contrast medium enhanced the lateral view confirming the suspicion of a malposition in the azygos arch. The catheter was removed immediately and another CVC was placed without complication via the right subclavian vein. Ten days later, this catheter had to be removed owing to catheter-related sepsis. Because the patient was now receiving vasopressors, a new CVC had to be placed. The left subclavian vein was cannulated by the Seldinger technique and some slight resistance advancing the guide-wire was met. The catheter was placed and the clinical function tests were normal, and again a right atrial electrocardiogram could not be derived. Therefore, a repeated malposition in the azygos arch was suspected and a second central venous cannulation performed via the left brachiocephalic vein. Again minimal resistance was felt. This time the guide-wire was retracted 1 cm and the catheter was advanced by 8 cm into the vein; the guide-wire was then pushed further into the vein. This time no resistance was felt. Intra-atrial ECG confirmed a correct catheter position in the SVC. A frontal radiograph taken afterwards demonstrated the tip of the first catheter curling up in the azygos arch (Fig. 1). The second catheter was correctly positioned. After performing radiography, the malpositioned catheter was removed. The patient was discharged to a rehabilitation institution 1 week later.

Figure 1
Figure 1:
Frontal chest radiograph demonstrating two central venous catheters. The first catheter is in the left subclavian vein: the tip is curling up in the azygos arch (white upper arrow). The second catheter is in the left brachiocephalic vein: the correct position of catheter tip is in superior vena cava (black lower arrow).

Today, percutaneous catheterization of central veins is a routine technique in hospitals. Most catheterizations are performed blindly. The optimal position for the tip of the CVC is within the SVC: intra-atrial ECG during insertion can tell the operator only whether the tip is in the atrium, but not where it is within the venous system. Plain frontal chest radiographs help to verify the correct position but do not exclude a catheter position in smaller vessels (e.g. azygos vein) or an extravascular site adjacent to the correct site. The site and frequency of catheter misplacement depend on the site of insertion, the technique used and the individual anatomical variations. Malposition in the azygos arch occurs in 1.2% of central venous cannulations [4].

The azygos and hemiazygos system are thoracic continuations of the ascending lumbar veins within the posterior aspect of the thorax. Usually, the azygos arch drains into the posterior aspect of the SVC approximately 1 cm below the junction of the left and right innominate (brachiocephalic) veins. The hemiazygos system drains into the left innominate vein via the left superior intercostal vein [5]. The risk of azygos arch cannulation is substantially increased if catheters are inserted via left-sided veins [4]. Anatomically, when compared with the right innominate vein, the left innominate vein is more horizontal and its junction with the SVC is almost a right angle. Guide-wires inserted from the left side will always contact the lateral wall of the SVC before turning round into the correct position. This seems the mechanism for misplacement of catheters into the azygos arch. The tips of catheters that are inserted via the left approach are also more likely to impinge on the right caval wall; this is particularly true when the length of the inserted catheter is insufficient. Unfavourable angulation of the catheter against the SVC wall, hyperosmolar irritation produced by the infused solution and mechanical forces from catheter migration promote vascular performation. Erosion may occur even when the proper position of the catheter tip in the SVC has been confirmed radiographically. It is well documented that flexion and extension of the neck can cause a CVC to migrate several centimetres, and this migration can unfavourably reposition the catheter tip [6,7].

In our patient, the azygos arch drained close to the junction of the brachiocephalic veins (Fig. 2). We blame this anatomical variation for causing the repeated difficulties in advancing the guide-wire into the SVC: the guide-wire and the catheter got caught in the azygos arch. We succeeded in releasing the tip of the guide-wire from the azygos arch by changing the angle between the guide-wire and the vein. Retracting the guide-wire by 1 cm from the resistance and advancement of the catheter by several centimetres over the guide-wire into the vein achieved this.

Figure 2
Figure 2:
Schematic lateral view of the superior vena cava and tributaries.

Malposition, whether aberrant into another vein or poorly positioned, may have disastrous consequences [6]. Perforation, thrombosis, vascular stenosis and even complete vascular occlusion in children have been reported from malposition in the azygos arch [7]. In one series, 19% of misplacements of a CVC into the azygos arch caused a perforation [4].

Without a pressure wave or ECG monitoring at the bedside, it is difficult to ensure the correct placement of a CVC in the SVC. Any difficulty in advancing a guide-wire or catheter is the vital clue that should alert the operator that misplacement may be occurring. Also, catheter dysfunction and/or in the conscious patient persistent, intermitted or exacerbating chest or back pain after central venous infusion always require immediate good chest radiography (frontal and lateral), eventually with contrast material. A catheter tip in the azygos arch must be repositioned immediately.

W. Schummer

Klinik für Anästhesiologie und Intensivtherapie; Friedrich-Schiller Universität Jena; Jena, Germany

C. Schummer

Klinik für Anästhesiologie und Intensivtherapie; Friedrich-Schiller Universität Jena; Jena, Germany


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© 2002 European Academy of Anaesthesiology