A midline catheter provides a way to deliver medications and fluids directly into the bloodstream over an extended period. This device offers a practical solution for patients needing intravenous access for several weeks. Understanding where and how these catheters are placed helps to demystify this common medical procedure.
Understanding the Midline Catheter
A midline catheter is a thin, flexible tube designed for intravenous therapy that is longer than a standard peripheral intravenous (IV) line but shorter than a peripherally inserted central catheter (PICC) line. While a typical peripheral IV is usually a few centimeters long, a midline catheter can range from approximately 7.5 to 20 centimeters in length. Its purpose is to provide intravenous access for a duration between one to four weeks.
A midline catheter’s tip ends in a larger vein of the upper arm, at or below the armpit (axilla), and remains a peripheral device. This differs significantly from a PICC line, which is threaded further into the body until its tip reaches a large central vein near the heart, such as the superior vena cava. Because the midline does not enter the central venous system, it has a lower risk of serious complications compared to central lines.
Common Placement Locations
Midline catheters are primarily placed in the upper arm, targeting larger, deeper veins. The most common veins selected for insertion include the basilic, cephalic, or brachial veins. These veins are chosen due to their size and accessibility, facilitating easier insertion and reducing complication risks like vein irritation.
The basilic vein is preferred because of its straighter course and larger diameter, which can reduce the catheter bending or becoming blocked. While the cephalic vein can also be used, it may be less ideal due to a more tortuous path or a tendency to narrow as it approaches the shoulder. Regardless of the specific vein, the catheter is advanced so that its tip rests in the upper arm, stopping before it reaches the larger central veins in the chest.
The Insertion Procedure
Inserting a midline catheter is a medical procedure performed by trained healthcare professionals under sterile conditions. Before placement, the healthcare provider numbs the insertion site with a local anesthetic to ensure patient comfort. The area is then thoroughly cleaned with an antiseptic solution, and a sterile drape is placed over the arm to maintain a clean field.
Ultrasound guidance is used during the procedure to visualize the veins and surrounding structures. This real-time imaging allows for precise needle insertion into the selected vein, reducing the risk of accidental puncture of arteries or nerves. Once the catheter is successfully inserted and its position confirmed, the device is secured with a device or tape, and a sterile dressing is applied to protect the insertion site. The process is quick, usually taking around 20 minutes.
Clinical Indications for Midline Use
Midline catheters are a choice for patients requiring intravenous therapy for an intermediate duration, ranging from one to four weeks. They are useful when a standard peripheral IV would require frequent changes, but a central venous catheter is not needed or carries higher risks. For example, midlines are used for prolonged courses of antibiotics, extended hydration needs, or pain management therapies.
This type of catheter allows for the administration of medications and solutions that are well-tolerated by peripheral veins, such as those with a pH between 5 and 9 or osmolarity less than 800-900 mOsm/L. Midlines offer several advantages, including reducing the number of needle sticks a patient experiences and preserving smaller veins that might otherwise be damaged by repeated IV insertions. Their peripheral nature also means a lower risk of complications like central line-associated bloodstream infections compared to central catheters.