Step 3: Position and advance needle

  1. Palpate radial artery gently to landmark for puncture.
  2. Hold syringe in dominant hand like a pencil, with the plunger set to collect a 1 ml sample. The syringe is “vented” at the plunger to allow the sample to enter under the pressure of the artery. It is not necessary to draw the sample up into the syringe.
  3. Rest dominant hand on patient’s thenar eminence to steady syringe.
  4. Holding syringe at about 45 degrees, puncture the skin just distal to where the index finger is palpating the radial pulsation.
  5. Slowly advance the needle until you get a "flash" of blood in the hub of the needle, then "freeze" the needle and syringe in that position.
  6. Allow the syringe to fill with blood to approximately one ml. The vented syringe will fill on its own.

The radial artery at the wrist is very superficial and in fact this is one of the reasons it is so frequently used for arterial blood gas sampling. One of the most common reasons for missing a puncture is that the student misses the artery on the way through. This is often followed by attempts to find the artery even deeper by "poking around". This will be unsuccessful and much to the displeasure of the patient. If you don't encounter the artery in the superficial subcutaneous tissue you should pull the needle back and try again.