An implanted port, often called a port-a-cath, is a small medical appliance placed entirely beneath the skin, typically in the chest. It consists of a small reservoir connected to a flexible catheter threaded into a large central vein near the heart. Patients requiring chemotherapy, frequent blood transfusions, or long-term intravenous (IV) medication often receive a port. This allows repeated access to the bloodstream without puncturing peripheral veins, minimizing discomfort and damage. The port’s design, including a self-sealing silicone septum, helps reduce the risk of infection compared to external lines.
Understanding Port Access and Preparation
Accessing an implanted port requires strict sterile technique to prevent introducing microorganisms into the bloodstream. The clinician confirms the patient’s identity and port type before starting. Both the patient and provider must wear a mask, and thorough hand hygiene is performed before preparing a sterile field.
The skin overlying the port is meticulously cleaned, most commonly with a chlorhexidine antiseptic solution. Cleaning involves a vigorous scrubbing motion for about 30 seconds, followed by allowing the area to air dry completely. This contact time ensures the antiseptic is effective. The port is then stabilized by placing fingers on opposite edges to hold it steady beneath the skin.
The port is accessed using a specialized non-coring Huber needle. This needle has a deflected tip designed to slice the silicone septum, preserving the integrity of the self-sealing membrane. The Huber needle is inserted firmly at a 90-degree angle directly into the center of the port until the tip contacts the back of the reservoir. Successful placement is confirmed immediately by gently aspirating, which produces a distinct “flashback” of blood into the extension tubing.
The Process of Blood Sample Collection
Once the port is accessed and blood return is confirmed, the first step is to withdraw and discard a specific volume of blood, known as the waste or clearance sample. This discard volume clears the catheter of residual flushing solution, such as saline or heparin lock fluid. Contamination can lead to inaccurate laboratory results, especially for coagulation tests. A common recommendation is to discard 5 to 10 milliliters of blood, though the exact volume varies by policy.
After the clearance volume is discarded, the required specimens are collected using an appropriate method, such as a syringe or specialized blood draw device. If multiple tubes are needed, they must be drawn in a specific sequence to prevent cross-contamination from additives. Coagulation tubes are typically drawn immediately after the discard sample for accurate results. If blood cultures are required, they are collected first, before the discard, as this represents the most accurate sample for detecting bloodstream infections.
Blood aspiration should be performed using a slow and gentle technique, especially when using a syringe, to minimize shear stress on red blood cells. Forceful pulling can cause hemolysis (rupture of red blood cells), which compromises sample integrity and can lead to falsely elevated lab values. Aspirate only the necessary volume to accurately fill the collection tubes, ensuring the proper blood-to-additive ratio.
Post-Procedure Care and Recognizing Complications
After all blood samples are collected, the port must be flushed to clear the line of remaining blood cells. This flushing is typically performed with 10 to 20 milliliters of normal saline, using a pulsatile or “push-pause” technique. This turbulent flow effectively dislodges cellular debris from the catheter walls.
Following the saline flush, a locking solution is administered to maintain patency until the next use. This solution is commonly a small volume of diluted heparin, an anticoagulant that prevents clot formation. The non-coring needle is removed while maintaining positive pressure on the syringe plunger during the final injection of the lock solution. This technique prevents negative pressure from drawing blood back into the catheter tip, a common cause of blockage.
A sterile dressing is applied if the port remains accessed for ongoing therapy; otherwise, a small bandage covers the puncture site after the needle is removed. Patients must monitor the site for signs of complications, such as infection. Redness, swelling, warmth, pain, or systemic fever and chills indicate potential infection requiring medical attention. Difficulty drawing blood, resistance upon injection, or inability to easily flush the port are signs of a possible occlusion that warrants clinical assessment.