Thoracic-paravertebral blocks: comparative anatomical study with different injection techniques and volumes

Area of Science:

• Anesthesiology
• Anatomy
• Regional Anesthesia

Background:

• Thoracic-paravertebral blocks (TPVB) are crucial for thoracic analgesia.
• Injection techniques and volumes may influence dye spread and block efficacy.
• Understanding dye distribution is key to optimizing TPVB procedures.

Purpose of the Study:

• To investigate how different injection techniques and volumes affect dye spread in TPVB.
• To determine if an alternating injection technique ensures complete staining of adjacent intercostal nerves.
• To compare landmark-guided versus ultrasound-guided TPVB dye distribution.

Main Methods:

• Comparative anatomical study using 10 or 20 mL Alcian Blue dye.
• Performed on 10 donor cadavers (54 injections) for education/research.
• Utilized both landmark-guided and ultrasound-guided TPVB techniques.

Main Results:

• Ultrasound-guided TPVB correctly identified the thoracic-paravertebral space (TPVS) in all cases.
• Sympathetic trunk staining occurred in 84.6% of injections, unaffected by technique or volume.
• Higher injection volumes (20 vs. 10 mL) significantly increased stained intercostal nerves (p=0.04).
• Medial needle placement increased epidural spread (p≤0.001); lateral/cranial injections reduced it.

Conclusions:

• Higher injection volumes in ultrasound-guided TPVB enhance intercostal nerve staining.
• Specific injection angles (lateral/cranial) and ultrasound guidance minimize unwanted epidural spread.
• Landmark-guided TPVB showed less reliable TPVS identification and higher epidural spread risk.