Peripherally inserted central catheter in leukemia: insertion site determines clotting risk

Central lines are essential tools in the management of patients with hematological disorders. A well-functioning catheter allows the efficient administration of chemotherapy, fluids, antibiotics, transfusions, and other drugs necessary during the treatment of acute leukemia and related disorders. However, central lines are also associated with serious catheter-related morbidity and discomfort. The main risks are catheter-related deep venous thrombosis (DVT) with its risk of pulmonary embolism, and catheter-related sepsis. The choice of appropriate catheter for each patient, and each phase of the disease, as well as rigorous surveillance and management of the catheter lumens and insertion site, are essential to limit complications.

Peripherally inserted central catheters (PICCs) have been routinely used as central catheters for the past 3–4 decades, for hospitalized patients and in ambulatory care [1,2]. PICCs are inserted in the basilic or cephalic vein of the arm, with the tip of the catheter placed in the superior vena cava. PICCs function as central catheters, allowing both drug infusion and blood sampling, but lessen the risk associated with central venous catheter insertion (i.e. carotid puncture, pneumothorax). They may be inserted in patients with coagulopathy or thrombocytopenia. Depending on the center, the catheter is inserted in the angiography suite to allow secure positioning, or at the bedside followed by an X-ray, and is withdrawn easily at the bedside [3]. Different sizes, numbers of lumens, and materials are available, and are chosen depending on the clinical use and institutional preference. PICC-related intravascular infections appear very rarely, probably because the insertion site is distant from the oropharynx area [4]. Concerns have been raised, however, about the risk of developing DVT with a PICC [5]. The incidence of PICC-related DVT has been variable in uncontrolled studies, depending on the definition of DVT (the basilic vein being considered alternatively a superficial or a deep vein) [6], the method of diagnosis (systematic search for asymptomatic DVT vs. only symptomatic DVT), and the design of the study (prospective vs. retrospective). Few data are available on the incidence of PICC-related DVT in patients with hematological malignancies.

In this issue of Leukemia and Lymphoma, Tran and colleagues report their experience with a large number of leukemic patients treated with PICCs over several years, and provide important novel information on the topic [7]. They retrospectively reviewed 899 PICCs placed in 498 patients, between 2001 and 2006, in the Leukemia Unit of Emory University Hospital, Atlanta. Some 7.8% of patients (39 of 498) had a symptomatic PICC-associated DVT diagnosed by ultrasonography. The DVTs were mostly located in the subclavian, axillary, and brachial veins, whereas the internal jugular vein was involved only in two cases. In 2006, the institution changed its protocol of PICC insertion. The same device was inserted in the internal jugular (IJ) vein under sonographic guidance, and tunneled under the skin, with the exit site at the subclavicular region.

What was the result of this very inspired idea? There was a slight increase in procedure time in the angiography suite, and a dramatic decrease in the incidence of PICC-related DVT (0.4% of symptomatic DVTs for the 667 next patients with tunneled IJ catheter). What could explain such a success? Why is the thrombogenicity of the catheter so much reduced by this new insertion method? The PICC consists of a thin and very floppy material, and this probably reduces its thrombogenicity in the central vein by decreasing the mechanical stress to the venous wall. However, peripherally inserted catheters have long portions in the very thin veins of the arm, which have slow blood flow, and high spasticity. Thrombosis may start in these small superficial veins, at their junction with the deep veins, or in the subclavian vein, where the vessel may be compressed by the clavicula. By inserting the catheter in the internal jugular vein, the authors retained the advantage of the floppy catheter, but inserted it into a larger vein, with a much higher blood flow. A second mechanism for thrombogenicity is the endothelial toxicity of the drug delivered at the catheter tip. This risk is reduced by positioning the tip of the catheter in the larger part of the superior vena cava, just above the right atrium, and by checking its position systematically in the catheterization laboratory.

Tran and colleagues may have devised a near perfect route for intravenous infusion in patients with leukemia, with an almost zero risk of thrombosis. Provided these results are confirmed in other studies, this challenges us to change our practice, as the safety of our patients is essential.