Depth of cervical plexus block and phrenic nerve blockade: a randomized trial

Area of Science:

• Anesthesiology and Pain Medicine
• Regional Anesthesia Techniques
• Surgical Anesthesia

Background:

• Cervical plexus blocks are frequently used for awake carotid endarterectomy (CEA).
• Blocks are categorized as superficial, intermediate, or deep based on fascial planes.
• The impact of block depth on phrenic nerve blockade and diaphragmatic motion is not fully understood.

Purpose of the Study:

• To investigate the effect of cervical plexus block depth on phrenic nerve blockade.
• To assess the impact of block depth on hemi-diaphragmatic motion during awake carotid endarterectomy.
• To evaluate injectate spread and clinical outcomes associated with different block depths.

Main Methods:

• A randomized controlled trial involving 45 patients undergoing elective awake CEA.
• Patients received superficial, intermediate, or deep cervical plexus blocks with ropivacaine and MRI contrast.
• Diaphragmatic movement was measured using transabdominal ultrasound before and after block placement.
• MRI evaluated injectate spread, and lung function was assessed.

Main Results:

• Significant differences in ipsilateral hemi-diaphragmatic motion were observed between block groups (p<0.001).
• Deep blocks resulted in the most pronounced diaphragmatic dysfunction (2.04±1.20 cm) compared to intermediate (3.86±1.24 cm) and superficial (4.34±1.06 cm) blocks.
• No significant differences were found in lung function, oxygen saturation, complication rates, or patient satisfaction.

Conclusions:

• The depth of cervical plexus block injection significantly impacts diaphragmatic function.
• Deep cervical plexus blocks are associated with more pronounced diaphragmatic dysfunction.
• Anesthesiologists should consider block depth when performing cervical plexus blocks for awake CEA to minimize phrenic nerve involvement.