What is the technique of femoral central line?

According to research, ultrasound guidance is associated with a higher success rate and fewer complications for central venous access compared to the traditional landmark method. This comprehensive guide will explain what is the technique of femoral central line, outlining the steps for safe and effective catheter placement.

Quick Summary

The technique involves placing a central venous catheter into the femoral vein, typically using the Seldinger method with either landmark or ultrasound guidance. The process includes patient positioning, site preparation, vessel puncture, and threading the catheter, followed by confirmation and securement.

Key Points

• Ultrasound Guidance: The preferred method for placing a femoral central line, as it significantly increases the success rate and reduces complications by providing real-time visualization.

• Seldinger Technique: The standard procedural approach, involving a sequence of steps including needle entry, guidewire insertion, tract dilation, and catheter placement over the wire.

• Anatomical Landmarks: In the absence of ultrasound, the femoral vein is located medial to the palpable femoral artery pulse, below the inguinal ligament.

• Risk of Arterial Puncture: A major risk of the landmark technique is accidentally puncturing the femoral artery, which is significantly reduced with ultrasound guidance.

• Sterile Technique: Strict adherence to sterile procedures is essential to prevent catheter-related bloodstream infections, a serious complication.

• Post-Placement Confirmation: Proper catheter placement is confirmed using methods such as ultrasound, blood aspiration, and the FLUSH test.

Understanding Femoral Central Venous Access

Central venous access is a critical procedure used in many medical situations, including the administration of medications, fluids, and blood products, as well as for hemodynamic monitoring. While other sites like the subclavian or internal jugular are often preferred, the femoral vein is a common alternative, especially in emergencies or when other sites are inaccessible. The technique of placing a femoral central line involves careful, systematic steps to ensure patient safety and catheter function.

Preparing for the Procedure

Successful central line placement begins with meticulous preparation. This phase is crucial for minimizing the risk of infection and complications.

1. Informed Consent: Whenever possible, obtain informed consent from the patient or their legal representative, explaining the procedure, its risks, and benefits.
2. Patient Positioning: The patient is placed in a supine position. If the patient is obese, an assistant may need to retract the pannus to expose the groin area fully. A reverse Trendelenburg position can sometimes be used to reduce venous pressure.
3. Sterile Preparation: The entire area around the insertion site is thoroughly cleansed using an antiseptic solution, such as chlorhexidine. A wide area is prepped to ensure a large sterile field. The clinician and any assistants don sterile caps, masks, gowns, and gloves.
4. Draping: A sterile drape with a fenestration (opening) is placed over the target area to maintain the sterile field.
5. Equipment Preparation: The central line kit is opened and organized. Each lumen of the catheter is flushed with sterile saline and clamped. If ultrasound guidance is used, the probe is covered with a sterile sheath containing a small amount of gel to prevent air artifacts and maintain sterility.

The Seldinger Technique

The most common method for placing a central line is the Seldinger technique, which involves inserting a guidewire into the vessel to facilitate catheter placement. This method can be performed using either anatomical landmarks or ultrasound guidance.

Landmark-Guided Approach

For the landmark-guided technique, the clinician relies on palpating anatomical structures to locate the vein.

1. Locate the Femoral Artery: Palpate the femoral artery pulse approximately two finger-breadths below the inguinal ligament. The femoral vein lies just medial to the femoral artery (remember the mnemonic NAVEL: Nerve, Artery, Vein, Empty space, Lymphatics, from lateral to medial).
2. Anesthetize the Site: Infiltrate the skin and subcutaneous tissue with a local anesthetic at the planned insertion site.
3. Insert the Needle: The insertion needle, attached to a syringe, is inserted medial to the femoral pulse at a 45-degree angle. Gentle negative pressure is applied to the syringe as the needle is advanced.
4. Confirm Venous Puncture: A flash of dark, non-pulsatile blood in the syringe confirms entry into the femoral vein. If bright, pulsatile blood is aspirated, the needle is in the artery and must be withdrawn.

Ultrasound-Guided Approach

The ultrasound-guided technique has largely replaced the landmark approach due to its higher safety and success rates.

1. Visualize Anatomy: The ultrasound probe is placed over the groin to visualize the femoral artery and vein in a transverse view. The vein is typically medial and fully compressible, while the artery is lateral and pulsatile.
2. Align the Vessel: The femoral vein is centered on the ultrasound screen.
3. Insert the Needle: Under real-time ultrasound guidance, the needle is inserted, and its tip is followed as it advances toward the vein. This allows for precise, direct venipuncture.
4. Aspirate Blood: Confirmation of venous access is achieved by aspirating blood into the syringe, just as in the landmark technique.

Advancing the Catheter

Once venous access is confirmed, the remaining steps of the Seldinger technique are followed.

1. Insert the Guidewire: The syringe is removed while the needle is stabilized. The thumb is placed over the needle hub to prevent air embolism. The J-tipped guidewire is then inserted through the needle and advanced into the vessel. If resistance is met, the wire is removed and placement is reconfirmed.
2. Remove the Needle: The needle is carefully withdrawn over the guidewire, which is held securely throughout the process.
3. Make a Skin Incision: A small incision is made at the guidewire entry point with a scalpel to allow for easier passage of the dilator and catheter.
4. Dilate the Tract: The dilator is threaded over the guidewire and advanced into the vessel with a twisting motion to enlarge the tract. The dilator is then removed.
5. Thread the Catheter: The central venous catheter is advanced over the guidewire. As it enters the vein, the guidewire will emerge from the catheter's distal port. The wire is grasped and the catheter is fully advanced into the vessel.
6. Secure the Catheter: The guidewire is completely removed, and the lumens are clamped. The catheter is secured to the skin using sutures and a dressing is applied.

Post-Procedure Care and Confirmation

After the line is secured, proper care and confirmation are necessary to ensure functionality and safety.

1. Flush the Catheter: Each port is checked by aspirating a small amount of blood and then flushing with sterile saline to ensure patency.
2. Confirm Placement: A chest X-ray is typically used to confirm the position of central lines in the chest. However, for femoral lines, bedside ultrasound is often used to ensure proper placement and check for complications. The FLUSH test, involving agitated saline and cardiac ultrasound, can also confirm positioning. For detailed information on this and other emergency procedures, consult authoritative resources like WikEM (WikEM - Central line: femoral).

Comparison of Techniques

Feature	Landmark-Guided Technique	Ultrasound-Guided Technique
Accuracy	Relies on anatomical palpation, which can be difficult in certain patients (e.g., obese, hypotensive).	Real-time visualization ensures precise needle placement into the vein, increasing accuracy.
Success Rate	Lower first-pass success rate, especially for less experienced operators.	Significantly higher first-pass success rate, even for inexperienced operators.
Complications	Higher risk of arterial puncture, nerve damage, and hematoma formation.	Lower risk of arterial puncture and related complications due to direct visualization.
Time	Can be faster for experienced operators in ideal conditions.	May take slightly longer initially but reduces procedure time by preventing failed attempts.
Equipment	Requires minimal equipment.	Requires an ultrasound machine and a sterile probe cover.
Best For	Situations where ultrasound is unavailable, but use is becoming less common.	Standard of care in most settings due to improved safety and efficacy.

Conclusion

The technique of femoral central line placement is a vital skill in modern medicine, with the ultrasound-guided Seldinger method now considered the gold standard for safety and success. From meticulous site preparation to confirming catheter position, each step plays a crucial role. While landmark methods are still relevant in specific situations, the visual precision offered by ultrasound minimizes risks, ensuring the best possible outcome for patients requiring this critical procedure.

Frequently Asked Questions

Why is the femoral vein often chosen for central line placement?

The femoral vein is a common site because it is large, easily accessible, and has a low risk of pneumothorax, which can occur with chest sites like the subclavian vein. It is particularly useful in emergency situations or when other sites are not available.

What is the Seldinger technique in the context of a femoral line?

The Seldinger technique is a medical procedure used to obtain safe access to blood vessels. For a femoral line, it involves using a needle to puncture the vein, passing a guidewire through the needle, removing the needle, dilating the access site, and finally threading the central line catheter over the guidewire into the vein.

What is the difference between landmark and ultrasound guidance?

Landmark guidance relies on palpating the patient's anatomy to estimate the vessel's location, while ultrasound guidance uses an ultrasound machine to provide real-time visualization of the vessels. Ultrasound is generally safer and more effective.

Is it painful to have a femoral central line placed?

The procedure is performed under local anesthesia, so the patient should not feel pain during the insertion. They may feel a pressure sensation. After the local anesthetic wears off, there may be some discomfort at the insertion site, which is typically managed with pain medication.

What are the common complications associated with a femoral central line?

Complications can include infection, bleeding, hematoma, nerve damage, and accidentally puncturing the femoral artery. The risk of these complications is minimized by using ultrasound guidance and strict sterile technique.

How is the position of a femoral central line confirmed?

While a chest X-ray is standard for chest central lines, femoral line placement is typically confirmed at the bedside using ultrasound. The FLUSH test, where agitated saline is injected while using a cardiac ultrasound, can also be used to confirm proper venous positioning.

How long can a femoral central line stay in place?

The duration depends on the patient's clinical condition and hospital protocol. Due to the higher risk of infection and thrombosis, femoral central lines are often removed or replaced with a line in a different location as soon as clinically possible, typically after a few days.