A peripherally inserted central catheter, commonly known as a PICC line, is a thin, flexible tube inserted into a vein in the upper arm, extending to a large vein near the heart. Its primary purpose involves delivering long-term medications, fluids, or nutrition directly into the bloodstream. A PICC line can also be used to collect blood samples for laboratory testing, offering a convenient alternative to repeated needle sticks.
How Blood Samples Are Collected
Collecting blood from a PICC line involves a specific, careful procedure performed by trained healthcare professionals. The line is flushed with a sterile saline solution to clear any medications or fluids. An initial volume of blood, typically 3 to 10 milliliters, is then withdrawn and discarded. This “waste” volume prevents dilution of the sample, ensuring accurate test results.
Following the discard, the required amount of blood for laboratory tests is collected using a syringe or a vacuum collection system. Aseptic technique must be maintained to prevent contamination. Once the sample is obtained, the PICC line is flushed again with sterile saline to prevent clotting and maintain patency.
Why Use a PICC Line for Blood Draws?
Utilizing a PICC line for blood draws offers several advantages, particularly for patients requiring frequent lab tests. Enhanced patient comfort is a significant benefit, as it eliminates the need for multiple peripheral needle sticks. Patients requiring numerous blood samples experience less pain and anxiety. This approach is particularly beneficial for individuals with difficult venous access, whose peripheral veins may be fragile or hard to locate.
The practice also contributes to vein preservation, protecting smaller veins from repeated punctures and potential damage. For healthcare providers, drawing blood from a PICC line offers convenience, streamlining sample collection without searching for new venipuncture sites.
Important Considerations for Accurate Results
Several factors require careful consideration to ensure the accuracy and safety of results. Dilution can occur if the initial discard volume is insufficient, affecting laboratory values and necessitating repeat draws. Hemolysis, the breakdown of red blood cells, is a concern if blood is drawn too forcefully or through a catheter that is too small. Hemolyzed samples can lead to erroneous test results.
Infection risk exists if aseptic technique is breached, potentially leading to a central line-associated bloodstream infection (CLABSI). Strict sterile protocols mitigate this risk. PICC lines can also become occluded or clotted, making blood withdrawal difficult or impossible. This interferes with timely lab collection and may require interventions to restore patency.
Situations Where Other Methods Are Better
In some situations, drawing blood from a PICC line may not be preferred or possible. If the PICC line is not functioning properly (e.g., sluggish blood return, inability to aspirate), a peripheral venipuncture may be necessary.
If a PICC line infection is suspected, blood cultures from a peripheral site, in addition to the PICC line, are recommended to diagnose the source. For highly sensitive laboratory tests requiring minimal dilution or contamination (e.g., specific coagulation studies, precise medication levels), a peripheral blood draw may be chosen.
The decision to use an alternative method is made by the healthcare team, considering the patient’s condition, the specific tests required, and the integrity of the PICC line. For patients with chronic kidney disease, PICC lines are avoided to preserve arm veins for potential future dialysis access.