A central line, formally known as a central venous catheter (CVC), is a thin, flexible tube inserted into a large vein, with its tip positioned near the heart in the superior or inferior vena cava. This intravenous access is reserved for situations requiring prolonged therapy or the delivery of specialized medications that cannot be safely administered through a standard peripheral intravenous (IV) line. The procedure is performed under sterile conditions by trained healthcare professionals to ensure patient safety and effective treatment.
Defining Central Lines and Their Purpose
A central line differs from a standard peripheral IV, which is a short catheter placed in a small, superficial vein. Peripheral IVs are suited for short-term fluid administration and routine medications. In contrast, the central line tip rests in a large vein with a high blood flow rate. This rapid dilution prevents irritation and damage to the vessel wall, making central lines necessary for delivering caustic medications, such as chemotherapy drugs and vasopressors, which would otherwise harm smaller peripheral veins.
Central lines allow for the administration of high-concentration nutritional support (Total Parenteral Nutrition or TPN), which is too hypertonic for peripheral veins. They are also used for frequent or long-term treatments, like extended courses of antibiotics, and for repeated blood sampling. Central lines can be categorized into non-tunneled catheters for short-term use and tunneled lines or implanted ports for longer-term access. Furthermore, a central line allows for the measurement of central venous pressure (CVP), providing information about the heart’s function and fluid status.
Essential Preparation Before Insertion
Safe insertion begins with meticulous preparation and adherence to strict sterile technique. Informed consent must be obtained from the patient, detailing the reason for placement and the potential risks involved. The clinician selects an insertion site, commonly the internal jugular vein (neck), the subclavian vein (collarbone), or the femoral vein (groin). The internal jugular and subclavian sites are preferred due to a lower risk of infection compared to the femoral site.
The patient is positioned to optimize venous filling and access, often using the slight head-down (Trendelenburg) position for neck or chest insertions. A comprehensive central line kit, containing the catheter, guidewire, and dilator, is prepared onto a sterile field. Maximal sterile barrier precautions are mandatory, requiring the operator to wear a sterile gown, mask, cap, and gloves, and use a large sterile drape. A portable ultrasound machine is also prepared, as imaging guidance is the standard of care for visualizing the vein and reducing complications.
The Seldinger Insertion Technique
The Seldinger technique is a standardized, wire-guided method preferred for placing central venous catheters. The procedure begins with ultrasound guidance to locate the target vein and distinguish it from the adjacent artery. Once the vein is identified, a local anesthetic is injected to numb the skin and surrounding tissue.
A small puncture is made through the skin, and a thin, hollow access needle is inserted into the target vein under real-time ultrasound visualization. Successful entry is confirmed by aspirating non-pulsatile, dark venous blood into the attached syringe. The syringe is then removed, and a flexible guide wire is threaded through the needle and advanced into the central circulation.
The access needle is removed, leaving only the guide wire in the vein. A small incision is made at the entry point to widen the skin opening. Next, a plastic vessel dilator is threaded over the guide wire and advanced to create a tract through the subcutaneous tissue.
The dilator is immediately removed, and the central venous catheter is threaded over the guide wire and advanced to the predetermined distance. The guide wire is then withdrawn from the catheter. Proper placement is temporarily checked by aspirating blood and flushing each lumen with saline. Finally, the catheter is secured to the skin with sutures or a securement device, and a sterile dressing is applied.
Post-Procedure Care and Verification
Immediately following insertion, verification of the catheter’s exact position is required to ensure safety and function. For lines inserted in the neck or chest, a chest X-ray is the traditional method used to confirm the catheter tip is correctly situated in the superior vena cava, just above the right atrium. The X-ray also rules out mechanical complications, such as a pneumothorax (collapsed lung).
Alternative verification methods, such as bedside ultrasound with a saline “bubble study,” offer faster confirmation that the catheter is within the venous system. Once placement is confirmed, a sterile, transparent dressing is placed over the insertion site for protection and inspection. The line must be securely fastened to the skin to prevent migration or accidental removal. Routine maintenance includes flushing the catheter lumens with saline to maintain patency and prevent blockages.
Understanding Major Insertion Risks
Although performed by skilled personnel, central line placement carries several specific risks. One frequent complication is inadvertent arterial puncture, occurring when the needle enters the adjacent artery instead of the vein. This risk has been significantly reduced by the routine use of ultrasound guidance, but it can still lead to hematoma formation or vascular injury.
A serious risk, particularly with subclavian and internal jugular approaches, is a pneumothorax, where the needle punctures the lung lining, causing the lung to collapse. Ultrasound helps avoid this by visualizing the pleura during the procedure. An air embolism is a rare but catastrophic complication that occurs if air enters the vein, especially if the insertion site is open during the procedure. This risk is mitigated by placing the patient in a head-down position and occluding the needle hub during wire exchange.
Other potential issues include nerve injury and catheter malpositioning, where the line tip ends up in a smaller vessel or is directed into the wrong area.