Central Venous Access for Hemodialysis

The Role of Central Venous Access

In the United States, more than 5 million central venous catheters (CVCs) are placed every year, translating to more than 15 million days of treatment with CVCs for different purposes. CVCs are useful tools to administer medications and fluids, and to collect blood samples and exert a pivotal role in the setting of hemodialysis (HD) treatments in patients affected by either acute kidney injury (AKI) or end-stage kidney disease (ESKD). Data from the Dialysis Outcomes and Practice Patterns Study (DOPPS) study indicate that 15% of HD patients in the United States are dialyzed with catheters; in other countries, the use of catheters differs significantly, ranging from 45% in Canada to 25% in Italy, 16% in the United Kingdom, and 6% in Japan.

The Kidney Disease Outcomes Quality Initiative (KDOQI) considers arteriovenous (AV) access to be preferable to a CVC in most incident and prevalent HD patients due to a lower risk of infection and an association with lower all-cause mortality. Hence, if not contraindicated, incident HD patients starting dialysis with a CVC should convert to AV access as soon as possible. In a world that counts more than 2 million prevalent patients treated with HD, CVC remains the most rapid method to guarantee kidney replacement therapy when AV access is not immediately available. CVC must provide the prescribed HD treatment with an adequate flow, preferably in excess of 400mL/min. CVCs must guarantee adequate biocompatibility, flexibility, and resistance, remaining chemically neutral. Their function should represent a bridge to more longer-term vascular access, such as an AV fistula (AVF) or AV graft (AVG). The ancillary use of a CVC may be necessary while waiting for a planned living donation of a kidney transplant or in patients undergoing peritoneal dialysis who have to interrupt their treatment for complications. The most common placement sites are the internal jugular, subclavian, and femoral veins, cannulated mainly with the Seldinger technique (see later).

Types of Catheters

The principal types of HD CVCs are tunneled (or cuffed) and nontunneled catheters. The use of tunneled CVCs is preferred due to the lower risk of infections compared with nontunneled CVCs and their better performance in terms of delivered dialytic dose. A recent alternative, used in selected cases, is represented by a hybrid prosthesis-tunneled catheter device, HD reliable outflow—HeRO device, or the Surfacer Inside-Out Access Catheter System. Both these devices are useful for patients with either central venous stenosis or obstruction, two complications occurring in 25% to 40% of patients using CVCs.

Silicone is the main material choice for tunneled CVCs because of its intrinsic softness and flexibility associated with thicker catheter walls. Polyurethane or copolymers, such as polyurethane/polycarbonate (Carbothane), are the prevalent choice for nontunneled ones. Polyurethane has thermoplastic properties that guarantee flexibility, but its synthesis process may also confer mechanical stiffness, pressure strength, chemical stability, and biocompatibility. Polyurethane presents a superior tensile strength than silicone, so CVCs are designed with larger inner lumen maintaining the same outer diameter. This peculiarity improves the overall catheter flow rate and reduces the possibility of catheter fractures in comparison with silicone CVCs. Carbothane presents all the advantages of polyurethane with higher resistance to body fluids, strength, and better biocompatible properties and, for these reasons, is the most commonly used.

Inner CVC configuration depends on the number of lumens, which can be single, double, or triple. Double-lumen CVCs are characterized by cylindric lumens resembling a double O or by a symmetric disposition resembling a double specular D; other double-lumen devices may also have the distal part divided. Other relevant differences among these devices regard the tip, which may be coaxial, split, step-tip, or Z shaped.

Randomized controlled trials and meta-analyses have failed to demonstrate a significant difference between the different types of devices.

Central Venous Catheter Placement