What is a Central Venous Catheter (CVC)?
For patients requiring immediate hemodialysis, a central venous catheter (CVC) is the standard of care. A CVC is a flexible tube inserted into a large central vein, most commonly in the neck (internal jugular), chest (subclavian), or groin (femoral). This method provides immediate access to the bloodstream, which is critical in emergency situations, such as acute kidney injury, or while waiting for a more permanent access site to mature. The CVC has two lumens or ports: one to withdraw blood from the patient to be filtered by the dialysis machine and another to return the filtered blood to the body.
Non-Tunneled vs. Tunneled Catheters
Central venous catheters can be classified into two main types: non-tunneled and tunneled. The choice depends on the anticipated duration of short-term use and the patient's condition.
Non-Tunneled Catheters
Non-tunneled catheters are used for urgent or emergent dialysis for a very short period, typically less than two weeks. They are inserted directly into the vein, without being passed under the skin. The exit site is close to the insertion site, making them less stable and more susceptible to infection compared to tunneled catheters. Non-tunneled catheters are the fastest and simplest to place, making them the default choice when dialysis must begin immediately. Placement can be performed at the patient's bedside with the help of real-time ultrasound to minimize complications.
Tunneled Catheters
If a patient requires temporary access for more than a few weeks—for example, while a permanent AV fistula or graft is maturing—a tunneled catheter may be used. These catheters are passed under the skin for several inches before entering the vein. This 'tunneling' helps anchor the catheter and provides a barrier against infection, making it a safer option for more extended use, from several weeks to months. A cuff on the catheter promotes tissue growth, which helps hold it in place and further minimizes the risk of infection.
Why are catheters not used for long-term dialysis?
While essential for short-term and emergency needs, catheters are not the preferred long-term solution for hemodialysis due to significant risks and drawbacks.
- High infection risk: Catheters have the highest risk of infection of any vascular access type. Bacteria can enter the bloodstream through the catheter's exit site, potentially leading to a serious bloodstream infection. This risk is higher with non-tunneled catheters but persists even with tunneled ones.
- Risk of clotting and poor blood flow: Blood clots can form within or around the catheter, causing blockages and restricting blood flow. Poor blood flow can lead to inadequate dialysis treatment and can trigger alarms on the dialysis machine.
- Vein damage: The presence of a catheter in a central vein can cause scarring and narrowing of the vein (stenosis). This can make it more difficult or impossible to place future vascular access options in the same area.
- Lower efficiency: Catheters generally provide a lower rate of blood flow compared to a mature AV fistula, potentially requiring longer or less efficient dialysis sessions to properly filter the blood.
Comparing Vascular Access Options
| Feature | Central Venous Catheter (CVC) | Arteriovenous (AV) Fistula | Arteriovenous (AV) Graft |
|---|---|---|---|
| Use Case | Short-term; urgent/emergency dialysis; bridge to long-term access | Long-term, permanent dialysis | Long-term; for patients with poor veins for a fistula |
| Procedure | Minimally invasive; bedside procedure | Surgical procedure to connect an artery and vein | Surgical procedure using a synthetic tube to connect an artery and vein |
| Time to Use | Immediate | 2–3 months to mature | 2–3 weeks after surgery |
| Infection Risk | Highest risk | Lowest risk | Higher risk than fistula, but lower than catheter |
| Lifespan | Weeks to months | Years | 2–3 years, potentially longer |
| Blood Flow | Adequate for immediate use, but often lower than fistulas | Provides excellent, high-volume flow | Provides good flow, though slightly less durable than a fistula |
The process of placing a temporary catheter
Before a temporary catheter is placed, a healthcare provider will conduct an assessment, which may include imaging like ultrasound to map the patient's veins. During the procedure, the patient will receive a local anesthetic and possibly sedation to remain comfortable. A vascular specialist or nephrologist will then insert the catheter into the selected vein using image guidance to ensure proper placement. After insertion, an X-ray is often used to confirm the catheter's tip is in the correct position.
Following the procedure, strict care is required to prevent complications:
- Keeping the site clean and dry: The dressing over the exit site must be kept clean and dry at all times. Regular dressing changes are performed by healthcare professionals.
- Monitoring for infection: Patients and caregivers should be vigilant for signs of infection, including redness, swelling, fever, or pain at the catheter site, and report them immediately.
- Handling with care: The catheter should not be pulled or tugged, and sharp objects should be kept away from the line.
What happens after the temporary catheter?
The goal is to transition away from a catheter as soon as possible due to the associated risks. If kidney function does not recover and the patient needs long-term dialysis, a plan is made to create a permanent access, such as an AV fistula or AV graft. Once the permanent access is ready for use, the temporary catheter is removed. In some cases where permanent access is not possible, a tunneled catheter may be used long-term despite the higher risks. According to a study in the journal Nephrology Dialysis Transplantation, using a non-tunneled catheter for more than two weeks significantly increases infection rates.
Conclusion
For patients who need immediate or temporary hemodialysis access, a central venous catheter is the typical and most practical solution. However, healthcare providers prioritize transitioning to a more permanent option, like an AV fistula or graft, whenever possible to reduce the risk of serious complications such as infection and clotting. The type of catheter used—non-tunneled for very short-term, urgent needs or tunneled for slightly longer periods—is determined by the patient's specific clinical situation and the expected duration of treatment. Awareness of the risks and proper care protocols are crucial for managing temporary vascular access safely.
For more detailed clinical guidelines, you can consult the National Kidney Foundation's KDOQI guidelines on vascular access.
