A Peripherally Inserted Central Catheter, or PICC line, is a thin, soft tube inserted through a vein in the upper arm and advanced until its tip rests in a large vein near the heart, typically the superior vena cava. This device provides a reliable, long-term access point for administering medications, intravenous fluids, and nutritional support. Drawing blood from a PICC line avoids the need for repeated needle sticks, improving patient comfort and preserving other vascular access sites. Accessing a PICC line for any reason, including blood withdrawal, is a complex, sterile medical procedure that must only be performed by trained healthcare professionals.
Preparation Before Accessing the Line
Before initiating the blood collection, meticulous preparation of the environment and equipment is necessary to prevent contamination and ensure accurate lab results. Supplies typically include antiseptic wipes, sterile gloves, a syringe for the waste volume, the appropriate blood collection tubes, a transfer device, and pre-filled syringes of normal saline flush solution. The minimum syringe size used for a central line should be 10 milliliters to prevent excessive pressure that could damage the catheter’s integrity.
Thorough hand hygiene is performed, and the healthcare professional must don appropriate personal protective equipment, including a mask and clean gloves, to minimize the risk of infection. Patient safety begins with confirming the patient’s identity using two distinct identifiers and verifying the physician’s order for the blood draw. If the patient is receiving continuous infusions through the PICC line, those infusions must be temporarily stopped for at least one minute before accessing the line for the blood sample.
A sterile field is established on a clean surface, organizing all equipment using an aseptic non-touch technique. The injection port, or needleless connector, is then vigorously cleaned. This “scrub the hub” action involves using an antiseptic solution, such as 2% chlorhexidine with 70% alcohol, and mechanically scrubbing the surface for 15 to 30 seconds before allowing it to air dry completely.
The Precise Technique for Blood Collection
The mechanical process of blood collection begins by accessing the disinfected port with an empty 10-milliliter syringe. The line clamp, if present, is opened, and gentle aspiration is applied to withdraw a volume of blood to be discarded, often called the “waste” or “discard” volume. This step is necessary to clear the catheter lumen of any residual infusates, such as saline or medications, which could dilute or contaminate the blood sample and lead to inaccurate test results.
The volume of blood to be discarded is typically 3 to 5 milliliters, though institutional protocols may suggest a range up to 10 milliliters, particularly if the line was locked with a heparin solution. Once the waste blood is aspirated, the line is clamped before the syringe is disconnected to prevent blood reflux or air entry. The syringe containing the waste blood is then properly discarded.
A fresh syringe or a specialized blood collection transfer device is then connected to the access port, and the clamp is reopened. The required amount of blood for the laboratory tests is then withdrawn. If multiple blood tubes are needed, they should be collected in a specific order of draw to prevent cross-contamination from the additives present in different tubes.
The general order of draw starts with:
- Blood culture bottles
- Tubes for coagulation studies (e.g., light blue top)
- Serum tubes
- Heparin tubes
- EDTA tubes (e.g., lavender top)
Using a closed system, such as a transfer device, to fill the vacuum tubes directly from the PICC line minimizes the risk of needle-stick injuries and potential contamination. After the final sample is collected, the line is clamped again before the collection device is removed.
Maintaining the PICC Line After the Sample is Taken
Immediately following the blood collection, the integrity and patency of the PICC line must be restored through a thorough flushing process. First, the needleless connector is scrubbed again with an antiseptic wipe and allowed to dry. A new pre-filled 10-milliliter syringe of normal saline is attached to the port.
The line is unclamped, and the saline is infused using a “push-pause” technique, which involves rapidly injecting small bursts of saline and pausing briefly between each push. This turbulent flow action helps to dislodge any blood or fibrin residue from the catheter walls, promoting a cleaner lumen and reducing the risk of clot formation. The total volume of saline flush is often 10 to 20 milliliters, depending on the catheter type and institutional policy.
The final step in the flushing process is the positive pressure technique, which involves maintaining pressure on the syringe plunger while simultaneously clamping the line and disconnecting the syringe. This action prevents backflow of blood into the catheter tip as the pressure drops, reducing the chance of occlusion. The line is then secured with a locking solution, typically a saline lock or a heparin lock, as per physician orders.
The procedure concludes with ensuring the access cap is secure and restarting any paused intravenous infusions. The PICC site should be observed for any signs of adverse reactions, such as swelling, pain, or redness. Accurate documentation of the procedure, including the amount of waste blood discarded, the volume of samples collected, and the locking solution used, is necessary for patient safety.