Relationship between injectate volume and disposition in erector spinae plane block: a cadaveric study

Area of Science:

• Anesthesiology
• Anatomy
• Pain Management

Background:

• Erector spinae plane (ESP) blocks are utilized for analgesia after thoracoabdominal and lumbar spine surgeries.
• The impact of injectate volume and location on anesthetic spread in ESP blocks requires further clarification.

Purpose of the Study:

• To investigate the relationship between injectate volume and the cephalocaudal spread of anesthetics in ESP blocks.
• To determine the optimal injectate volume for effective analgesia.

Main Methods:

• Ultrasound-guided ESP injections were performed on cadavers using contrast dye and saline.
• Real-time fluoroscopy assessed cephalocaudal spread after incremental injections.
• Cadaveric dissection documented dye distribution within anatomical structures.

Main Results:

• Larger injection volumes correlated with more extensive cephalocaudal spread.
• Dissection revealed staining ventral to the erector spinae muscle spanning 4-7 levels with 30-40 mL injections, and 12-13 levels with 60-80 mL injections.
• No spread to the lamina, transverse processes, paravertebral space, epidural space, or pleura was observed.

Conclusions:

• Increased injectate volume in ESP blocks leads to greater cephalocaudal spread.
• Anesthetic spread reached the dorsal rami and ventral erector spinae muscle.
• 30 mL injections may be optimal for achieving 4-7 level analgesia.