The "Pinch-Off Sign":A Warning of Impending Problems with Permanent Subclavian Catheters

The "Pinch-Off Sign": A Warning of Impeding Problems with Permanent Subclavian Catheters

From the Department of Surgery, the Ohio State University College of Medicine, Columbus, Ohio. This work was supported in part by Public Health Service Grant CCA 18016, awarded by the National Cancer Institute, Department of Health and Human Services, Bethesda, Maryland.

Central venous Hickman and Broviac catheters are now frequently used when long-term venous access is needed for home parenteral nutrition, frequent blood sampling, or delivery of medication such as chemotherapy for cancer. Use of the peel-away sheath has been advocated to facilitate rapid insertion of these Silastic catheters.1, 2, 3, Complications related to this method of catheter insertion have not been reported previously, but recently we have seen four instances of complications resulting from the passage of the catheter between the clavicle and the first rib.

All observations were made in 48 cancer patients who underwent placement of Hickman catheters for the administration of chemotherapy. A retrospective review showed that four of the patients had partial catheter obstruction owing to a pincher action of the clavicle and first rib.

In each instance, the catheter was inserted with the peel-away sheath under fluoroscopic surveillance 1. Two separate 1 cm incisions were made, one over the medial chest wall at the sternal edge at nipple level and the second, 2 cm below the midclavicle. The catheter was brought through a subcutaneous tunnel that connected the two incisions. Through the infraclavicular incision, a 20 gauge needle was used to locate the subclavian vein as it enters the thoracic outlet near the junction of the clavicle and first rib. A J-guide wire was threaded through the needle into the subclavian vein and on into the superior vena cava The needle was removed, and the peel-away introducer sheath and dilator were inserted over the guide wire. The guide wire and dilator were removed, and the catheter was threaded through the sheath, positioning the tip in the right atrium. The sheath was removed by peeling it apart, leaving the silastic catheter in position. The upper incision was closed with intracutaneous 0-0 DexonŽ suture, and the catheter was sutured to the skin at the lower incision exit site with 0-0 monofilment suture.

The four instances of complications involved postural-related difficulty during injection of medication, catheter leak, and catheter transection with distal embolication. Resistance to the injection of chemotherapeutic agents and heparin flushes were encountered in two patients. The postural-related difficulty was alleviated by having the patients perform the injection while lying supine or with the arm and shoulder slightly raised. A chest roentgenogram showed a narrowing of the catheter, termed the "pinch-off sign," as it passed over the first rib and beneath the clavicle (Figure 1). One patient had infraclavicular discomfort and swelling at the time of medication injection. The catheter was removed, showing a split in the tubing that corresponded to the portion of the catheter that passed beneath the clavicle. A pinch-off sign was present on the postinsertion roentgenogram of another patient (Figure 2). Three weeks later, she noticed infraclavicular swelling with cathter injection. A repeat chest roentgenogram showed catheter transection at the clavicle, with the distal catheter segment coied in the mediastinum (Figure 3). After removal of the catheter, the embolizrd segment located in the right pulmonary artery was successfully removed transcutaneously with a foreign body retrieval snare wire under fluoroscopic observation. A new Hickman catheter was placed at a more peripheral position. Review of the chest roentgenograms in each patient revealed a narrowing of catheter as it passed between the first rib and clavicle.

The anatomy of the axillary-subclavian vein as it enters the thoracic outlet and the complexity of the sternoclavicular and first costosternal articulations explain the cause of these catheter-associated complications. The axillary vein passes behind the costocoracoid ligament and the pectoralis monor tendon before crossing the edge of the first rib to become the subclavian vein, which then joins the internal jugular vein to form the innominate vein. As the axillary vein becomes the subclavian vein, it is confined in a narrow space bounded by the first rib and the anterior scalene muscle posteriorly and the costocoracoid ligament, subclavian muscle, and the clavicle anteriorly. Medially, the clavicle and the first rib are joined by the tough membraneous costoclavicular ligament fibers 4, 5,.

Movement in the sternoclavicular joint and the first costosternal articulation is varied and complex. The sternoclavicular and artculation is the only joint between the shoulder-arm complex and the truncal skeleton, and it takes part in all movements of the pectoral girdle. This saddle joint provides three degrees of free motion in the frontal, sagittal, and perpendicular axis. Rotational excusion of the clavicle in the frontal axis is 30 to 50 degrees. In addition, there is circumferential movement along the longitundinal axis of the clavicle. Isolated movements are not possible and are always accompanied by movements in other planes 6.

The costoclavicular ligament is strong, dense band of membraneous fibers 1.5 to 2 cm wide that connects the first costal cartilage and rib to the inferior surface of the medial clavicle. During respiration, the first rib moves up and down in an axis almost at a right angle with the sagittal plane 7.

Central venous catheters inserted by the way of the sabclavian approach pierce the medial vein wall to enter the lumen as the vein passes between the clavicle and the first rib (Figure 4). Various tricks to facilitate entry into the subclavian vein include maneuvers to open the angle between the clavicle and rib (placing a pillow or cloth roll between the scapulas or repositioning the head, shoulder, or arm) and to increase the vein diameter (Trendelenburg position).

Catheter-associated problems are due to insertion of the catheter in a medial location, where the clavicular first rib window forms the widest possible angle. When the patient is upright, the weight of the shoulder narrows the window and pinches off the medially positioned catheter (figure 5). Various maneuvers that change the shoulder position will temporarily relieve the obstruction of the catheter so that medications can be easily injected. However, the pinching action and friction on the catheter by the clavicle and first rib movements can eventually wear through and transect the catheter tubing.

The axillary-subclavian vein is the most medial of the major structures passing through outlet (brachial plexus, artery, and vein). We believe catheter compression problems occur when the catheter enters the vein in the subclavian segment rather than passing through the thoracic outlet inside the axillary vein lumen. A small, empty space composed of this areolar tissue exists between the vein and the angle formed by the clavicle and first rib. When the catheter enters the thoracic outlet through this empty space medial to the vein, it is confined to a narrow area immediately adjacent to the clavicle, first rib, and costoclavicular ligament. A catheter in this unfavorable location is likely to be subjected to constant wear and tear from the pincher action associated with normal arm and shoulder use. A catheter entering more proximal to the axillary vein enters the thoracic outlet inside the venous lumen, and the position is more lateral, the space is larger, and there is less chance of catheter obstruction and wear (Figure 6).

We still use the peel-away sheath, but now enter the axillary vein at the midclavicular location to avoid problems associated with more medial venous insertion. A final fluoroscopic confirmation of catheter placement should include checking for the pinch-off sign, as well as taking an upright chest roentgenogram after catheter insertion. If there is evidence of catheter obstruction, the catheter should be removed and replaced by way of a more lateral entry into the subclavian vein or another route, such as through the cephalic or inter jugular vein.

Figure 4. Catheter entering the lumen of the subclavian vein. The extraluminal portion of the catheter passes through the areolar tissue filling the space between the clavicle and first rib.

Figure 5. At the time of catheter insertion, the clavicular-first rib angle is wide, and the catheter can pass through it medial tot he vein before entering the subclavian vein (left). In the upright position, the angle and pinches the medially positioned catheter (right).

Figure 6. When the catheter enters the axillary vein lateral to the thoracic outlet, it passes between the clavicle and first rib in a more lateral position where the angle is wider, and it is less likely to be affected by pincher action.

The roentgenographic presence of the pinch-off sign indicates potential serious problems with central venous Silastic catheters and is an indication for immediate catheter removal and replacement at another site or position.