Peripheral Intravenous (PIV) lines are short, small-bore catheters typically placed in a peripheral vein, often in the arm or hand. When a patient requires a blood sample, healthcare providers often seek to use the existing PIV to avoid the discomfort and risk of an additional needle stick. Drawing blood from a peripheral IV line is a common practice in clinical settings, though it is highly conditional.
The Feasibility and Conditions for Use
Drawing blood from a PIV is a feasible technique, but its success and safety depend entirely on specific patient and catheter conditions. The most significant factor is the catheter’s diameter. A larger gauge is generally preferred to reduce the risk of red blood cell damage during aspiration. Many clinical guidelines suggest using catheters of 20 gauge or larger, though success rates can vary even with these sizes.
The location and age of the PIV also influence the decision. Newly inserted lines often have a much higher success rate for blood collection than those in place for a longer period. Using an existing PIV is often preferred for patients with difficult venous access to spare them the pain and anxiety of multiple failed venipunctures. However, policies are not universal, and some institutional guidelines recommend against routine blood draws due to the potential for sample error.
Maintaining Sample Integrity During Collection
A strict procedural protocol must be followed to ensure the collected blood sample provides accurate results and prevents dilution or contamination. If intravenous fluids or medications are actively infusing through the line, the infusion must be temporarily stopped. Providers are advised to pause the infusion for at least two minutes before drawing the sample, allowing circulating blood to clear the catheter hub of the infusing solution.
The next important step involves drawing and discarding a specific volume of blood, often called the “waste tube,” to clear the catheter of any residual IV fluid or saline flush. This discard volume typically ranges from 3 to 10 milliliters, depending on institutional policy, and is essential to prevent erroneous lab results caused by fluid contamination. The required blood sample is then collected using a technique that minimizes turbulence and excessive negative pressure, such as a vacuum-powered collection tube holder or a small syringe.
Potential Complications and Contraindications
The most common and serious complication of drawing blood from a PIV is hemolysis, which is the physical destruction of red blood cells. This damage occurs when blood is forced through a small catheter bore or subjected to excessive suction, which can happen with larger syringes or forceful aspiration. Hemolysis causes the release of intracellular components, such as potassium, which can lead to falsely elevated or inaccurate lab results, often resulting in the sample being rejected by the laboratory.
Beyond sample quality, the procedure can also negatively affect the PIV line itself and the patient’s vein. The aspiration process increases the risk of catheter occlusion or clotting within the catheter, potentially rendering the line unusable for future infusions. Excessive manipulation and the necessary application of a tourniquet may also increase the risk of phlebitis, which is inflammation of the vein.
Certain clinical situations strictly prohibit drawing blood from a PIV, as it is considered a contraindication. The line should not be used for blood collection if it shows signs of local infection, infiltration (fluid leaking into surrounding tissue), or phlebitis. Additionally, drawing blood for specific tests, like blood gas analysis, is generally not recommended due to the increased unreliability of the results compared to direct venipuncture.