Dialysis catheter

Catheter for hemodialisis

A dialysis catheter is a catheter used for exchanging blood to and from the hemodialysis machine from the patient.

The dialysis catheter contains two lumens:

• Venous
• Arterial

This is a confusing terminology for layperson, because both lumens are in the vein. The arterial lumen (typically red) withdraws blood from the patient and carries it to dialysis machine, while the venous lumen (typically blue) returns blood to the patient (from the dialysis machine). Flow rates of dialysis catheters range between 200 to 500 ml/min.

If a patient requires long-term dialysis therapy, a chronic dialysis catheter will be inserted. Chronic catheters contain a dacron cuff that is tunneled beneath the skin approximately 3–8 cm. The tunnel is thought to add a barrier to infection. The most popular dialysis catheter sold on the market today is the split-tip dialysis catheter. This catheter comprises two free floating tips.

Catheter placement

The catheter is placed in one of the large veins. A common site is superior vena cava or SVC. An SVC catheter is placed by puncturing the internal jugular vein in the neck (most often on the right side), and the catheter is then advanced downwards toward the chest. Alternatively an SVC catheter can be inserted via subclavian veins right behind the clavicle (the collar bone), often on the right. If the access of SVC is difficult, the femoral veins can be used. This is an inferior option, however, because the groin site is more prone to infection and also because patient cannot sit upright.

Complications

Some common malfunctions of dialysis catheters include: clotting, infection, and kinking. One of the most common errors of tunnel hemodialysis catheter insertions is failure to locate the arterial limb of the catheter medially and the venous limb laterally. This must be done, due to the fact that most catheters have a memory in the plastic, which will cause the catheter to try to resume it's natural straight form. If the arterial limb is placed laterally, this will cause the arterial inlet to float up against the vein wall, or even up against the rim of the inlet of the atrium. This has the same effect as your vacuum cleaner hose sucking up against your curtains. This results in poor blood flows, and can force the dialysis staff to reverse flow, using the venous limb of the catheter as the arterial. This will result in more inefficient dialysis, as there will be add-mixing of blood from the catheter (cleaning the same blood, over again).

Fistulas versus catheters

Surgically created arteriovenous fistulas are preferred over catheters for patients with chronic renal failure,^[1] as the risk of infections (e.g. endocarditis, bacteremia), hospitalization and death are lower.^[2][3] One of the most common errors of tunnel hemodialysis catheter insertions is failure to locate the arterial limb of the catheter medially and the venous limb laterally. This must be done, due to the fact that most catheters have a memory in the plastic, which will cause the catheter to try to resume it's natural straight form. If the arterial limb is placed laterally, this will cause the arterial inlet to float up against the vein wall, or even up against the rim of the inlet of the atrium. This has the same effect as your vacuum cleaner hose sucking up against your curtains. This results in poor blood flows, and can force the dialysis staff to reverse flow, using the venous limb of the catheter as the arterial. This will result in more inefficient dialysis, as there will be add-mixing of blood from the catheter (cleaning the same blood, over again).

References

1. ^ Huijbregts HJ, Blankestijn PJ. Dialysis access--guidelines for current practice. Eur J Vasc Endovasc Surg. 2006 Mar;31(3):284-7. PMID 16500586.
2. ^ McGill RL, Marcus RJ, Healy DA, Brouwer DJ, Smith BC, Sandroni SE. AV fistula rates: changing the culture of vascular access. J Vasc Access. 2005 Jan-Mar;6(1):13-7. PMID 16552677.
3. ^ Allon M, Daugirdas J, Depner TA, Greene T, Ornt D, Schwab SJ. Effect of change in vascular access on patient mortality in hemodialysis patients. Am J Kidney Dis. 2006 Mar;47(3):469-77. PMID 16490626.