An intravenous (IV) line blood draw collects a blood sample directly from an existing catheter placed in a vein. This technique is often preferred over traditional venipuncture, especially for patients requiring frequent laboratory testing. Drawing blood from a vascular access device helps preserve peripheral veins and minimizes the pain and anxiety associated with repeated needle insertions. This procedure requires meticulous sterile technique and specialized medical training to ensure patient safety and accurate laboratory tests.
When to Use IV Line Blood Draws
The decision to collect a blood sample from an IV line is reserved for situations where standard venipuncture is difficult or unnecessary due to a reliable access point. This method is frequently used in critically ill patients, those with difficult venous access, or individuals with indwelling central venous catheters, such as peripherally inserted central catheters (PICCs). While central lines are designed for both infusion and blood collection, peripheral IVs carry a higher risk of complications, including hemolysis, and are often discouraged for routine draws.
Before drawing blood, temporarily stop any fluids or medications infusing through the line. The infusion pump should be paused for a minimum of two minutes to allow the infused solution to circulate and equilibrate with the bloodstream. This waiting period minimizes the risk of diluting the blood sample or contaminating it, which could lead to inaccurate test results. After the pause, the line must be flushed with sterile saline to clear any residual infusate from the catheter.
Essential Supplies for the Draw
Performing a blood draw from a vascular access device requires a specific set of sterile supplies to maintain a closed system and prevent infection. These materials must be readily available at the patient’s bedside:
- Appropriate personal protective equipment, such as clean, non-sterile gloves.
- An effective antiseptic solution, like a chlorhexidine or alcohol swab, for disinfecting the connection port.
- Pre-filled syringes of sterile 0.9% sodium chloride (typically 10 mL) for flushing the line.
- A discard syringe to aspirate and remove the initial volume of blood containing residual flush solution and contaminants.
- A specialized syringe or a vacuum tube holder (Vacutainer) with a Luer-lock adapter for blood collection.
- The necessary blood collection tubes, identified by their color-coded tops.
- A designated sharps disposal container.
Detailed Procedure for Collection
The procedure begins with meticulous hand hygiene and the donning of gloves to ensure an aseptic environment. The needleless connector, or hub, of the IV line must be vigorously scrubbed with an antiseptic for five to ten seconds and allowed to air dry completely. This action reduces the microbial load on the access site before opening the system.
Next, attach the discard syringe to the clean hub and unclamp the catheter. Slowly withdraw the initial volume of blood, which is contaminated with saline flush and possibly infusate, and discard it. A standard discard volume of 3 to 5 mL is common to ensure the removal of the catheter’s dead space and residual fluid.
After removing the discard syringe, immediately attach the blood collection device to the hub. Aspirate the required volume of blood into the collection tubes. Once all samples are collected, remove the device and thoroughly flush the line with a new syringe of saline. A final 10 mL flush is typically recommended, administered using a push-pause technique to create turbulence that helps clear the line. The infusion can then be restarted, and the access port secured with a new sterile cap.
Maintaining Safety and Sample Quality
Preventing contamination and preserving sample integrity are primary concerns when drawing blood from an IV line. Aseptic technique, including vigorous scrubbing of the hub and strict adherence to the order of draw, minimizes the risk of introducing bacteria into the bloodstream. Using a smaller syringe (e.g., 3 mL) for aspiration helps reduce negative pressure on red blood cells, preventing mechanical hemolysis.
If blood return is sluggish or non-existent, the technician must never apply excessive force or attempt to “milk” the line, as this can damage red blood cells or the catheter. Instead, gentle repositioning of the patient’s limb or a re-attempt with a smaller syringe may be considered. Adequate removal of the waste volume is a quality control measure, as insufficient removal can dilute the sample, leading to falsely low lab values. All procedures, including the volume collected and the draw location, must be carefully documented in the patient’s medical record.