Spreading pattern of epidurally administered contrast medium in rabbits

Area of Science:

• Anesthesiology
• Radiology
• Veterinary Medicine

Background:

• Understanding epidural drug spread is vital for effective spinal anesthesia and pain management.
• Optimizing epidural injection techniques requires precise knowledge of contrast medium distribution patterns.
• Previous studies have not fully elucidated the volume-dependent spread of epidural agents at specific spinal levels.

Purpose of the Study:

• To precisely map the spread of epidurally administered contrast medium in a rabbit model.
• To determine the optimal injection volume for achieving specific epidural spread patterns.
• To identify ideal epidural catheter placement for targeting different spinal cord segments.

Main Methods:

• Epidural catheter placement in rabbits at either T7 or T12 spinal levels under anesthesia.
• Gradual injection of contrast medium in small increments (0.1 ml/kg) up to 0.6 ml/kg.
• Radiographic assessment of contrast medium spread in both rostral and caudal directions.

Main Results:

• Epidural contrast medium spread increased with injected volume in both T7 and T12 groups (P < 0.0001).
• Spread was not linearly dependent on volume, with distinct polynomial relationships observed (y = 4.0 + 41.8x - 28.1x² for T7; y = 0.2 + 57.7x - 43.5x² for T12).
• Contrast spread was equal rostrally and caudally at T7, but significantly more rostral spread occurred at T12 (P < 0.05).

Conclusions:

• Catheter placement 1-3 segments below the target is recommended for lower thoracic/lumbar levels due to rostral spread.
• For mid-thoracic targets (T7), placement at the target segment is advised.
• Small volume titrations are essential for achieving predictable epidural spread and targeted delivery.