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Venous Thrombosis Associated with VADs
Vijaya M. Dasari, MD, Abdullah Shatnawei, MD, and Ezra Steiger, MD
One of the most common non-infectious complications associated with the use of central venous catheters—more properly known as central vascular access devices (VADs), but often just called “lines”—is catheter occlusion. A line is occluded when it is difficult to infuse into the line or withdraw blood through it. Occlusion can be due to mechanical obstructions, calcium phosphate or drug precipitates, and lipid emulsions. However, most VAD occlusions are caused by a blood clot.
Catheter-related thrombotic occlusions are distinguished as either intraluminal, with clots occurring inside the lumen of the catheter, or extraluminal, with clots outside of the catheter and within the blood vessel. A clot inside the catheter can happen when blood backs up into the catheter, or when blood is drawn and not followed by an adequate flush.
A clot within the vein, but outside the catheter, is called a mural or vein wall thrombosis. If left untreated, such a clot can cause complete occlusion of the blood vessel. It is this type of occlusion, venous thrombosis, that we will focus on here.
Incidence of Venous Thrombosis
The incidence of symptomatic catheter-related thrombosis varies from 0.3 percent to 28.3 percent. In a study of 50,470 patients on home infusion care, it was found that catheter dysfunction like kinking, breakage, falling out, infiltration, and symptomatic thrombosis occurred 0.83 times per 1000 catheter days. Nonthrombotic causes for the dysfunction accounted for 0.6 and thrombotic 0.23 times per 1000 catheter days.
In this group, rates of complications like local or systemic infections and thrombosis were found to be higher for midline catheters, followed by peripherally inserted central catheter (PICC) lines, non-tunneled catheters, tunneled catheters, and chest ports. The time of occurrence of thrombosis from different types of central VADs was also reported to be shorter for midline catheters followed by PICC lines, non-tunneled catheters, tunneled catheters, and chest ports. A report by Verso et al noted that tunneled catheters like Hickman catheters and chest ports have less venous thrombotic complications compared to PICC or midline catheters.
Risk factors for venous thrombosis include catheter tip position, catheter material and type, site of VAD insertion, infusate like chemotherapy and PN, underlying illness like cancer and congestive heart failure, duration of catheter in place, traumatic catheter insertion, malposition, immobility, dehydration, and hypercoagulability. Large-gauge VADs with multiple lumens are also associated with a higher risk of thrombosis. Femoral catheters carry a higher risk of thrombosis than internal jugular or subclavian catheters. Silicone and polyurethane catheters are less likely to form clots compared to those made of stiffer plastics.
In several studies it was noted that optimal tip position to prevent venous thrombosis is in the lower third of the superior vena cava (SVC) and above or within the upper chamber of the heart (right atrium). This position allows for the rapid dilution of the concentrated parenteral nutrition solution. Vein wall trauma can lead to thrombosis, and this position is also less likely to traumatize the wall of the SVC.
The three pathophysiological factors that lead to clot formation are injury to the inner lining (endothelium) of the vein, circulatory stasis (sluggish circulation), and hypercoagulability. Endothelial injury may be due to surgery, trauma, or intravascular devices. Central VADs may damage the lining of the vessel, causing platelet aggregation and clot formation. Damage may occur during catheter placement, especially if the catheter is stiff, or secondary to malposition of the tip of the catheter.
Circulatory stasis is secondary to general immobility, inadequate hydration, or congestive heart failure. Hypercoagulability may lead to clots occurring in patients with malignancies, pregnancies, infections, diabetes, high blood pressure, inherited coagulation disorders, and inflammatory bowel diseases (such as Crohn’s disease).
Steps to avoid venous thrombosis should begin at day one of catheterization. Catheter insertion should be done by an experienced clinician using technical assistance, such as ultrasound, to accurately locate the vein and other imaging support for proper VAD tip positioning. Interventional radiologists usually prefer right-side internal jugular catheters as the catheter can be shorter, and can lie parallel to the vein, and there is a straight line down from the right internal jugular vein to the lower third of the superior vena cava.
Vascular access devices need proper maintenance after insertion. Appropriate flushing regimens and site dressing are some key points to consider in possibly preventing venous thrombosis. Other strategies for thrombosis prevention include early mobilization, limb exercise, and adequate hydration. Use of prophylactic anticoagulation with heparin or coumadin remains controversial. However, patients who have had catheter-associated venous thrombosis in the past should discuss long-term anticoagulation with their physicians (Duerksen).
Signs and Symptoms
Early signs of VAD venous thrombosis include persistent pump alarms, inability to infuse or withdraw, and visible clots in the catheter hub. Symptoms of VAD-related thrombosis can include swelling of the neck, face and arm; appearance of superficial collateral veins on the chest wall (Figure 1); swelling and discoloration of the arm (Figure 2); swelling around the eyes; rapid heart rate; shortness of breath; armpit tenderness; shoulder or jaw pain; headache; tearing of the eyes; runny nose; and sore throat. Symptoms vary based on the location of the thrombus. (See Table 2.)
A good physical examination is very important in the diagnosis of venous thrombosis. Color Doppler (ultrasound) is now the investigation of choice. It has 95 percent accuracy for clots in the internal jugular and subclavian veins. However, it has less than 50 percent accuracy for clots in superior vena cava because you can’t see through the sternum. Ultrasound is non-invasive and can be easily done as an outpatient. Venograms are the gold standard, can be done easily as an outpatient, require very little contrast (less than 50ml), and are quite specific. However, they are expensive and the intravenous contrast may be harmful to the kidneys.
Treatment options are primarily anticoagulation (or thinning of the blood) or thrombolysis (dissolving the clot). Anticoagulation is either with unfractionated heparin, low molecular weight heparin, warfarin, or direct thrombin inhibitors like ximelagatran. In thrombolysis, thrombolytic agents like Alteplase are usually infused through the catheter to dissolve clots that form within the catheter (intraluminal clots). Most of the time, these treatments are all that are necessary. In some cases, a VAD may need to be removed when substantial clot is present and swelling and pain are severe.
Thrombus is a great medium for bacterial growth. Management of a septic central vein thrombosis includes removal of the catheter, intravenous heparin, and antibiotics for four to eight weeks. If central venous access is essential for care of the patient and no other access is available, the catheter may be left in place and anticoagulation with heparin must be initiated with conversion to coumadin for at least three to six months, or for as long as the catheter is needed.
Some patients can develop a stricture or marked narrowing at the site of a previous clot, rendering the vein unsuitable for further catheter insertions. Interventional radiologists can sometimes dilate up these strictures and restore patency of the vein by inserting a stent device.
Pulmonary embolism associated with upper extremity venous thrombosis (clots located only in patients’ upper extremities) is estimated at about 12 percent of patients with symptomatic catheter-related thrombosis, and is likely between 15 and 25 percent in cancer patients with symptomatic catheter-related thrombosis. If the patient experiences signs of venous thrombosis mentioned previously and/or sudden onset of rapid heart rate, shortness of breath, and chest pain, he or she should seek medical help immediately.
Although it is controversial, thrombosis might predispose the patient to catheter-related blood stream infections. Multiple major venous thromboses may limit venous access for continued parenteral nutrition and is a relative indication for considering intestinal transplantation according to Medicare criteria.
Preventing, diagnosing, and treating VAD dysfunction and thrombosis are critical for maintaining consumer health and comfort and can prolong the life of the VAD for consumers in need of home PN. A skilled vascular access clinician should be consulted for VAD placement to correctly position the catheter tip, minimize complications associated with infection, and effectively prevent and treat complications. Consumers must learn how to recognize the signs and symptoms of venous thrombosis, and report any of these signs and symptoms in a timely manner to their clinicians.
Duerksen DR. Central venous thrombosis in patients receiving long-term parenteral nutrition. Appl Physiol Nutr Metab. 2008;33(1):32-38.
Verso M, Agnelli G. Venous thromboembolism associated with long-term use of central venous catheters in cancer patients. J Clin Oncol. 2003;21(19):3665-75.
Table 1. Types of Catheters
*SVC: Superior vena cava, a large vein draining blood into the right atrium (RA) of the heart.
Table 2. Signs and symptoms of venous thrombosis