MRI of axillary brachial plexus blocks: a randomised controlled study

Area of Science:

• Anesthesiology
• Regional Anesthesia
• Medical Imaging

Background:

• Ultrasound guidance is standard for axillary plexus blocks, but alternative methods are needed when equipment is unavailable.
• The necessity of three injections for non-ultrasound-guided axillary blocks has been debated.

Purpose of the Study:

• To investigate if MRI-observed local anesthetic distribution explains success rate differences between single, double, and triple injection axillary block methods.
• To compare the clinical efficacy of single, double, and triple deposit axillary block techniques.

Main Methods:

• A blinded, randomized controlled trial involving 45 patients undergoing surgery.
• Patients were randomized into three equal groups receiving single, double (transarterial), or triple injections of local anesthetic.
• Magnetic Resonance Imaging (MRI) assessed local anesthetic distribution, followed by clinical evaluation of sensory block success.

Main Results:

• The triple-deposit method demonstrated a significantly higher success rate (100%) compared to single and double-deposit methods (67% each) for blocking nerves distal to the elbow (P=0.04).
• MRI analysis indicated that patients in the triple-deposit group generally had superior local anesthetic distribution scores.
• While the triple-deposit group showed the highest overall success, single and double-deposit groups achieved comparable MRI scores for specific nerves or cords.

Conclusions:

• The triple-deposit axillary plexus block technique is more effective for achieving sensory block distal to the elbow.
• MRI findings provide partial explanation for the superior clinical outcomes observed with the triple-deposit method, highlighting the importance of local anesthetic spread.