Types of Catheters for Dialysis

Non-tunneled catheters

Designed for short term access and immediate need for access such as acute kidney injury, thrombosed hemodialysis access or poisoning. 

If the pt may need temporary access but for a longer period of time (1-2 weeks) you may use a non-tunneled cuffed catheter. This would be a pt who needs dialysis (has chronic kidney disease) but has not had permanent access placed or an AV fistula has not matured. 

Many different non-tunneled catheters are available (polyethylene, polyvinyl chloride and silicone). The catheter has a cone shaped tip. It will be rigid at room temperature but will soften at the body's internal temperature. Non-tunneled catheters are usually short (9-20 cm) to avoid the catheter from entering the right atrium of the heart. 

Infections are always a risk with catheters and the risk increases with the time a catheter is in place. The duration of time that a non-tunneled catheter can be in place varies depending on the placement. Non-tunneled catheters placed in the Internal Jugular vein and Subclavian vein can remain in place for 2-3 weeks safely. Femoral catheters, however, are only safe for either one dialysis session or 3-7 days in a bed bound patient. 

There is a higher risk of a pneumothorax when placing a catheter in the subclavian vein than in the internal jugular vein. 

Tunneled Catheters

Tunneled catheters are primarily used for intermediate or long-term (>2 weeks). Although chronic hemodialysis using arteriovenous access is preferred, some pts are poor candidates. In the following situations, prolonged use of tunneled catheters are appropropriate.

-A bridge while awaiting AV access

-Pt has unsuitable vascular anatomy

-AV access may place increase the pt's risk for complications (high output cardiac failure, myocardial ischemic events or steal syndrome-pain or numbness in the hand indicated decreased blood flow)

Tunneled catheters generally have a polyester cuff that is tunneled under the skin from about 3-8 cm. This tunnel is thought to allow tissue ingrowth that will seal off the catheter. This is thought to decrease the risk of infection. Tunneled catheters have a larger lumen as well and allow for higher blood flow than the non-tunneled variety. 

The duration of time that a tunneled catheter can be in place is variable. With proper care the tunneled catheter may remain in place for 1-2 years. 

Arteriovenous Access 

This is the preferred access for chronic hemodialysis. When compared with tunneled catheters, AV access has a lower rate on infection/bacteremia, decreases rate of hospitalizations, increased events of adequate dialysis and a decreases risk of death. There are two main types: arteriovenous fistula and arteriovenous graft. 

Arteriovenous fistula-a type arteriovenous access. An AV fistula is created by connecting an artery directly to a vein, most often in the forearm. Connecting the artery to the vein causes more blood to flow into the vein which causes the vein grows larger and stronger, making repeated needle insertions for hemodialysis treatments easier. 

An AV fistula requires advance planning because a fistula takes a while after surgery to develop (4-24 months). But a properly formed fistula is less likely than other kinds of vascular access to form clots or become infected. Also, properly formed fistulas tend to last many years—longer than any other kind of vascular access. 

How do you know when it is mature? My attending told me that you will be able to easily visualize a prominant vein up the forearm, hear a bruit and there will be a palpable thrill. 

Arteriovenous graft-If you have small veins that won’t develop properly into a fistula, you can get a vascular access that connects an artery to a vein using a synthetic tube, or graft, implanted under the skin in your arm. The graft becomes an artificial vein that can be used repeatedly for needle placement and blood access during hemodialysis. Since you are placing a graft, it doesn't need to mature like a fistula does and can be used fairly soon after placement, often within 2 or 3 weeks.

Compared with properly formed fistulas, grafts tend to have more problems with clotting and infection and need replacement sooner. However, a well-cared-for graft can last several years.

I am leaving out many details but this was a brief overview to help this non-surgically oriented medical student (Internal Medicine, woohoo!) with some basics.