An implanted port, or vascular access device, is a small medical device placed beneath the skin, usually in the chest, connected to a catheter threaded into a large central vein. This system provides reliable, long-term access for administering intravenous medications, fluids, blood products, and for drawing blood samples. After accessing the port with a specialized needle, healthcare professionals must attempt to withdraw blood, known as establishing blood return. This fundamental safety check ensures the device is functioning correctly and is safely positioned within the bloodstream. The inability to draw back blood, despite the port flushing easily, is a common problem requiring careful investigation before the device can be used.
Confirming Correct Placement
Successful aspiration of blood confirms two major facts about the device. First, it proves the catheter tip is correctly positioned within the central venous circulation, typically in the superior vena cava (SVC). Second, the ability to draw blood demonstrates the patency of the entire catheter lumen, confirming there are no internal obstructions preventing the flow of blood or medication. The port’s function is to deliver therapies directly into the high-flow central bloodstream for rapid dilution. Achieving blood return confirms the catheter is not kinked, fractured, or lodged against the vessel wall, assuring that subsequent infusions will be delivered safely.
Potential Causes for Aspiration Failure
A lack of blood return, despite successful flushing, is often called a persistent withdrawal occlusion (PWO). The most frequent cause is an intraluminal obstruction, such as a fibrin sheath or a small blood clot, formed at the catheter tip. This buildup acts like a one-way valve: positive pressure allows flushing, but negative pressure causes the obstruction to collapse against the opening, preventing blood withdrawal.
Another common reason is catheter malposition, where the tip has migrated or is resting against the vein wall. This physical obstruction prevents blood aspiration, although flushing pressure can momentarily push the tip away to allow fluid passage. Less common causes include mechanical issues like “pinch-off syndrome,” where the catheter is compressed between the clavicle and the first rib, or a disconnect between the catheter and the port body.
Troubleshooting Steps Before Use
When an implanted port fails to produce blood return, a sequential and systematic approach is necessary to attempt to restore function.
Positional Adjustments
The first actions involve simple physical maneuvers to reposition the catheter tip within the vein. The patient can be asked to change position, as altering intrathoracic pressure may shift the catheter tip away from the vessel wall. Positional changes include:
- Sitting up
- Lying down
- Raising the arm on the side of the port
- Performing a deep cough or a Valsalva maneuver (bearing down)
Mechanical Checks
If repositioning does not resolve the issue, all external connections, including the Huber needle and extension tubing, must be checked for kinks or loose connections. A gentle push-pull technique can be attempted using a 10 mL syringe filled with saline, applying intermittent, slight negative pressure to draw back blood. It is important to never forcefully inject fluid into a port that has resistance or questionable blood return, as this action risks worsening a problem like a fracture or dislodgement.
Pharmacological Intervention
If the PWO persists after mechanical and positional adjustments, the next step involves using a pharmacological agent to dissolve a suspected clot. A fibrinolytic drug, such as alteplase (tissue plasminogen activator), may be ordered by a physician and instilled into the catheter lumen. This medication is left to dwell for a specified period, often 30 minutes to two hours, before aspiration is attempted again. If the port remains non-functional, imaging like a dye study (port-a-gram) may be required to confirm the catheter’s integrity and tip location before further use is considered.
Risks of Using a Port Without Blood Return
The question of whether to use a port without blood return carries clinical risk, and caution is the standard of practice. The primary danger is the possibility of extravasation, which occurs when the infused medication leaks out of the vein into surrounding tissue. Without blood return, there is no guarantee that the catheter tip is safely within the vein.
A fractured catheter or a tip that has eroded through the vessel wall will cause the drug to be delivered subcutaneously. This risk is especially serious when administering vesicant medications, such as certain chemotherapy drugs, which can cause severe tissue damage, blistering, and necrosis if they extravasate.
Even if the medication is non-vesicant, the compromised function suggests the therapy is not being delivered into the high-flow central circulation as intended, which can lead to inaccurate drug concentration and ineffective treatment. Furthermore, a port that lacks blood return due to a fibrin sheath or clot is already a site of potential bacterial colonization, increasing the risk of a systemic bloodstream infection.
If troubleshooting measures fail to restore blood return, the port should not be used for infusion, particularly for high-risk therapies like chemotherapy. The safest approach is to seek radiographic confirmation of device integrity or to access an alternative venous site.