Radial artery access for coronary interventions

Radial artery access

Anatomy

1. The radial artery is branch of brachial artery below the elbow and runs on the lateral aspect of forearm to the wrist. 
2. At the level of wrist, it lies on the top of styloid process of radius bone and the scaphoid bone. 
3. The artery joins the deep communicating branch of ulnar artery to form deep palmer arch. 

Advantages of radial access over femoral access:

1. The bleeding complications are uncommon with radial artery puncture as it can be easily compressed. 
2. Prolonged bed rest is not required.  
3. It can be helpful in cases with difficult femoral access such as morbid obesity and peripheral vascular disease. 
4. The hand has collateral flow from the ulnar artery via palmer arch. 
5. Patient can be mobilised soon after the procedure. 
6. Left radial access is preferred compared to right radial access for cannulation of left internal mammary artery (LIMA) to left anterior descending (LAD) graft post coronary artery bypass surgery.

Allen's test

• Before taking radial artery access, Allen's test is performed to assess ulnar collateral flow in the palmer arch. 

Technique of Allen's test

1. Simultaneously radial and ulnar arteries are occluded while patient make a fist. 
2. Patient is asked to open the hand. The palm will appear pale due to blanching. 
3. Pressure over ulnar artery is released while pressure over radial artery is maintained. 
4. If palm regains pink colour within 6 to 10 seconds, the result is positive and there is satisfactory ulnar flow and radial access can be safely performed. 
5. The test is negative or abnormal if it takes more than 10 seconds for the palm to return to its pink colour.
6. Ulnar flow can also be assessed with the help of plethysmography using a pulse oximeter. 
7. The oximeter probe is attached to thumb or forefinger and both radial and ulnar arteries are compressed. 
8. The plethysmograph waveform will flatten.
9. Then, pressure from ulnar artery is removed and pressure over radial artery is maintained. 
10. In a normal test, waveform with return to normal. 
11. The test is considered negative if the waveform doesn't return or if there is delay of more than 8 seconds. 
12. Radial access is contraindicated in patients lacking radial pulse or with Raynaud's disease. 

Patient preparation for radial access

1. The patient's intravenous line is placed in opposite arm. 
2. The patient is explained regarding procedure and is comfortably sedated to decrease anxiety.  
3. The patient's wrist is positioned and extended while supporting dorsum of wrist with a small towel or roll of gauze or a commercially available positioning device. 
4. The radial area is cleaned with prepping solution and draped with sterile towels. 
5. A small of amount of local anaesthetic (1-2 ml) is infiltrated along the puncture site using a 25-gauge needle. 
6. The ideal puncture site is 1-2 cm proximal to the flexor crease of the wrist. 

Technique of radial puncture

1. A through and through or double wall puncture technique
2. Single wall (anterior) puncture technique
3. Double wall puncture technique is preferred for radial artery access. 
4. A micropuncture needle may be used for a single wall puncture with 21-gauge needle and 0.018 guide wire. 
5. A hydrophilic sheath (5F - for diagnostic procedure or 6F- for performing interventions) is advanced into the radial artery over guide wire.

 

Cocktail

1. Before a catheter is advanced through radial sheath, it is common to administer a cocktail (nitroglycerin, a calcium channel blocker, and heparin) through side arm of sheath to decrease risk of radial artery spasm. 
2. Anticoagulation is required in radial access to prevent arterial thrombosis. 

Note

1. Stop advancing the guide wire if any resistance is felt. Angiography may be performed to define anatomy. 
2. There may be presence of radial artery loop or an accessory artery.