A midline catheter is an intravenous (IV) line used to deliver fluids and medications. A common question is whether blood samples can be drawn from them. This article discusses considerations for blood collection from midlines.
Understanding Midline Catheters
A midline catheter is a thin, flexible tube inserted into a peripheral vein in the upper arm. Longer than a standard peripheral intravenous (PIV) line, it ranges from 8 to 25 centimeters. The catheter’s tip is positioned in larger upper arm veins, ending below the armpit, and does not extend into central circulation. This means midlines are not central venous catheters (CVCs) or PICC lines. Midlines are primarily used for administering medications, fluids, and sometimes blood products for several weeks when standard PIVs are unsuitable. They reduce the need for frequent needle sticks, remaining in place longer. Their design makes them appropriate for non-irritating medications compatible with peripheral veins, providing stable access for intermediate-term therapy.
Drawing Blood from a Midline
While technically possible, drawing blood from a midline catheter is generally not recommended for routine collection. The primary function of a midline is to deliver infusions, and frequent blood draws can introduce complications. Many healthcare facilities have policies against routine blood draws from midlines due to these risks.
One significant concern is potential damage to the catheter itself. Midlines are designed for forward infusion, and the negative pressure created during blood aspiration can compromise the catheter’s integrity, leading to blockages or a shortened lifespan. Additionally, the long, narrow lumen of a midline can affect blood sample quality. Hemolysis, the breakdown of red blood cells, is a known risk, which can lead to inaccurate laboratory test results and necessitate repeat draws. Dilution of the blood sample with flush solutions used to maintain catheter patency can also occur, further skewing test outcomes.
Drawing blood from a midline can also increase the risk of complications for the patient. Repeated manipulation of the catheter hub during blood draws elevates the risk of infection and phlebitis, which is inflammation of the vein. Some manufacturers indicate midlines can be used for blood sampling, and some studies suggest low rates of hemolysis, but consistent good samples are often questioned. In rare, specific situations, such as when other venous access is difficult or in emergencies, a healthcare provider might consider attempting a blood draw if institutional policy permits. When performed, proper technique, including flushing the line and discarding an initial waste volume of blood to prevent dilution, is crucial.
Other Blood Collection Methods
When a patient has a midline catheter in place, the safest and most common method for blood collection remains peripheral venipuncture. This involves drawing blood directly from a different, healthy vein, typically in the opposite arm, hand, or foot. This approach minimizes risks associated with manipulating the midline and provides reliable, accurate laboratory results.
For patients who require frequent blood draws or have limited peripheral venous access, other types of vascular access devices might be considered. Central venous catheters, such as PICC lines, are often designed with lumens specifically for blood sampling. If a patient already has a CVC or PICC line, blood can typically be drawn from these lines as they are placed in larger, central veins, allowing for easier and safer aspiration of blood samples.
Guidance for Patients and Caregivers
Patients and caregivers play an important role in understanding their medical care, including midline catheter use. Communicate openly with the healthcare team about the line type and its intended uses. Policies regarding blood draws from midlines can vary between hospitals and clinics.
Patients should promptly notify their nurses or doctors if they experience any unusual symptoms around their midline catheter, such as pain, swelling, or redness, especially following any procedure involving the line. Asking questions or expressing concerns if a blood draw is being attempted from the midline, or if a different site for collection is preferred, can contribute to safer care. Open dialogue ensures the most appropriate and safest methods for blood collection are utilized.