Palpate the course of the radial artery. Place index, middle and ring fingers over the maximal pulsation of the radial artery. After having found the proper course of the artery, lift the index finger and puncture there, from lateral to medial under an angle of 45 degrees. By puncturing from lateral to medial, the operator can stabilize the artery by pressing the vessel against the flexor tendons of the thumb. Puncture as distal as possible, but at least 1 cm proximal from the styloid process. This prevents perforation of the retinaculum flexorum and inadvertent puncture of a small superficial branch of the radial artery. In addition, this allows successive more proximal attempts in case of a first failure.

This thin  needle comes in a kit, together with a 10 cm 6F hydrophilic sheath and a 0.025" hydrophilic wire. A small cannula contains the needle, which has a small longitudinal groove at its distal end. Once the needle has an intraluminal position blood flows in a transparent tube, fixed to the needle. Then the needle needs to be advanced until blood can be seen between the needle and the sheath (via the groove).

When the needle is removed, blood spurs out of the cannula and the wire can be introduced.

Success rates are high.

This system allows stabilization of the needle with a guidewire, once the artery is punctured. The wire enhances accurate placement of the cannula into the lumen.

1. Remove protective shield and try to advance the wire through the needle via actuating lever to insure proper feeding. The actuating lever must be retracted proximally as far as possible prior to puncture so as not to inhibit blood flashback.

2. Puncture vessel in a continuous, controlled, slow forward motion. Blood flashback in clear hub of needle indicates successful entry into the vessel. Avoid transfixing both vessel walls, since this may lead to sub-arterial placement.

3. Stabilize position of introducer needle and carefully advance spring guidewire via actuating lever. The reference mark on the clear feed tube indicates the lever position at which point the soft tip of the spring wire coincides with the tip of the needle. If resistance is encountered while advancing the spring guidewire, do not forcefully advance the wire. Retract the wire fully and attempt further advancement after slight changes in angulation and depth of needle in relation to the artery.

4. Once the wire is inserted completely, rotate the cannula as it is advanced into the subcutaneous tissue to prevent stripping of this cannula over the wire.

5. Once the cannula is inserted, remove needle, wire and tube

Many types of open needles can be used. It is important to keep the needle immobile during wire insertion, because access can be lost following slight movement of the exterior end of the needle.

1. ARROW needles are compatible with 0.025" wires, most open needles with 0.035" wires.
2. Shape a "J" in the wire, since this will ease manipulation out of sidebranches or over tortuous segments.
3. It is recommended to use exchange wires during early experience. Initially more guide exchanges are required. A long wire allows to maintain distal access.
4. Never force the wire against resistance. You might have entered a small branch or the wire might become blocked in a spastic or tortuous segment. Inject a small amount of contrast to understand the problem. Especially hydrophilic wires need to be handled with care, since they can easily enter small branches without noticeable friction.
5. If the wire enters the descending instead of the ascending aorta, ask the patient to take a deep breath and readvance.