Radial artery puncture is a medical procedure that is performed in order to obtain arterial blood sampling for gas analysis. A needle is inserted into the radial artery and spontaneously fills with blood. The syringe that is used is prepacked and contains a small amount of heparin, to prevent coagulation or needs to be heparinised, by drawing up a small amount of heparin and squirting it out again. Most commonly radial artery puncture is performed in order to obtain arterial blood sampling for gas analysis. The partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2) and the pH of arterial blood are important in assessing pulmonary function, since these data indicate the status of gas exchange between the lungs and the blood.
Contradictions
Cellulitis or other infections over the radial artery Absence of palpable radial artery pulse Positive Allen test (see below), indicating that only one artery supplies the hand Coagulation defects (relative) ''''Allen Test'
It is very important to perform Allen Test to confirm the patency of the ulnar artery, because in case there is no collateral flow through the ulnar artery, radial artery puncture is contraindicated since it can result in a gangrenous finger or loss of the hand from spasm or clotting of the radial artery. The Allen Test is performed with the patient sit with her hands supinated on her knees. Then stand at the patient's side with your fingers around her wrist; compress the tissue over both radial and ulnar arteries. Allow a few minutes for the blood to drain from the hand while the patient opens and closes her hands several times. Release the pressure on the ulnar artery while keeping the radial artery occluded. normal skin color should return to the ulnar side of the palm in 1-2 seconds, followed by quick restoration of normal color to the entire palm. A hand that remains white indicates either absence or occlusion of the ulnar artery, and radial artery puncture is contraindicated.
Anatomical Review
The radial artery runs along the lateral aspect of the volar forearm deep to the superficial fascia. The artery runs between the styloid process of the radius and the flexor carpi radialis tendon. The point of maximum pulsation of the radial artery can usuall be palpated just proximal to the wrist. See figure 1 for anatomical relations.
Necessary Equipment
1) Materials for skin cleansing ( Alcohol and cotton )
2) Syringe with 3 to 5 mL of Lidocaine 1% and a 23- to 25-gauge neddle.
3) Preheparinised 3 to 5 mL syringe with 23 to 25 gauge neddle. To heparinize the syringe, aspirate 0.5 mL of heparin into the syringe, hold the syringe upright, pull the plunger all the way out to the end, and then return all of the heparin to the original container. This can be done with buttrfly wings.
4) Gloves
5) Ice for transport.
Procedure
1)Wash your hands and put on disposable gloves.
2)Locate the approximate position of the artery by slowly rolling your index finger from side to side.
3)Clean the skin over the proposed site of puncture.
4)Anesthetize the skin over the proposed site of puncture with the the 1% lidocaine 3 to 5 mL
5)Identify again the point of maximal pulsation of the radial artery.
6)With your dominant hand hold the syringe and needle puncture ( preheparinised ) and insert the needle into the anesthetized area at 45 degrees to the skin with needle's bevel uppermost.
7)Guide the needle slowly toward the point of maximum pulsation. When you hit the artery there will be a sudden gush of arterial blood into the hub of the needle. Then you need to make a small amount of suction to obtain an adequate blood sample ( only 1-2 mL ). If no blood is obtained with these maneuvers, withdraw the needle to a position just under the skin and try again. Make at least 3 attempts before giving up and trying another site. This can be done with butterfly wings if you prefer.
8)Once you have taken blood sample remove the needle from the artery and apply direct pressure over the site for 5 minutes.
9)Expel all air bubbles from the sample holding the syringe upright and allowing the bubbles to collect near the needle hub. Then evacuate it by pushing on the plunger.
10)Carefully cap the needle with a rubber stopper. Don't forget to label the tube with patient's name. Place the sample in the bag containing ice and send it to the lab.
It is very important to return about 20 minutes later to check for adequated perfusion of the hand and for possible haematoma formation.