Difference between the single wall and the double wall technique
What is a single wall technique?
A single wall technique shall be used for radiography whenever practical. To perform a single-wall technique, only the ventral wall of the vessel is punctured to gain entry to the vessel.
What is a double wall technique?
When it is not practical to use a single wall technique, a double walled technique shall be used. A double-wall puncture (Seldinger technique) is performed by puncturing the dorsal and ventral walls of the vessel and subsequently withdrawing the needle.
When pulsatile blood is encountered, the tip of the needle is in an intraluminal position, and a guidewire can be placed safely.
What is Seldinger technique?
Seldinger technique (thin-wall needle technique) is commonly used procedure to obtain safe access to central vein.
The desired vessel is punctured with a sharp hollow needle, syringe is detached and guidewire is advanced through the lumen of the needle, and then the needle is withdrawn.
After desired vessel puncture, guiding sheath is instantly slid over the needle into the vessel.
The needle is withdrawn, guidewire is advanced through the guiding sheath, central catheter is placed into the vessel.
Needle puncture with subsequent guidewire introduction into vessel through needle; needle exchanged for sheath/catheter over wire•
The Seldinger technique for venous cutdown can also use a small, 1- to 2-mm, venotomy and a Seldinger wire-guided catheter (found in prepackaged central line set).
Central catheter is then passed over the guidewire into the vessel.
Contrarily, modified Seldinger technique(guiding sheath-over-the-needle technique) use needle that is covered with guiding sheath.
The Seldinger unit comes assembled with dilator and catheter.
The catheter-over-needle is advanced through the skin, 1 cm distal to the incision and then through the venotomy. The needle is removed and the wire advanced into the vein through the catheter.
Available access routes○
Internal/external jugular vein○
Common femoral vein○
Subclavian vein○
Popliteal vein○
Greater/lesser saphenous vein○
Translumbar IVC○
Transhepatic IVC or portal vein
Preprocedure
Review indications to determine best route of access•
Review prior imaging for patency of planned route of access
Procedure
US guidance is preferred during needle access○
21-g needle for 0.018″ wire/micropuncture○
18-g needle for direct 0.035″ system•
Confirm venous blood return through needle•
Introduce wire fluoroscopically○
Place microaccess sheath; upsize wire to 0.035″•
Place desired sheath/catheter
Post-Procedure
•Obtain hemostasis•
Observe for location-specific potential complications
