Positioning
POSITIONING
The block can be performed with the patient in either the sitting or lateral decubitus position. The probe should be placed in a sagittal plane about 3cm lateral to the midline.
Figure 1: a) patient in the lateral position with sagittal probe orientation and in-plane needle approach for mid thoracic erector spinae block.
Preliminary Scan
PRELIMINARY SCAN
Select the vertebral level in the middle of the desired dermatomal spread. For example, if you wish to block levels T3-T7 then aim to place the injection at the level of the T5 transverse process (TP). Place the transducer in the midline using a saggital orientation. Identify the superficial hyperechoic shadows of the spinous processes in the midline. Scan laterally to visualise the square hyperechoic outline (‘tombstone’) of the transverse processes. Scanning further laterally this square outline of the TP will be replaced by a curved outline of the corresponding rib. Now move medially again to position over the lateral TP. Immediately superficial to the transverse processes you will visualise the erector spinae muscle seen it its long axis. Superficial to this the rhomboid major muscle is seen above T6 vertebral level (this level approximates to the inferior tips of the scapulae), and superficial to the rhomboid is the trapezius muscle. The erector spinae muscle fibres will be seen as horizontal striations running across the screen. Position the TP of the desired vertebral level in the middle of the screen.
Figure 2: a) saggital plane ultrasound image showing the erector spinae muscles sitting superficial to the Transverse processes of T5 and T6 vertebrae b) annotated ultrasound image (Trap=trapezius muscle, Rhomb=rhomboid muscle, ES=erector spinae muscle, IC=intercostal muscles, TP5=T5 transverse process, TP6=T6 transverse process)
Technique
TECHNIQUE
Using an in-plane approach direct your needle tip towards the TP at the desired level. Inject a small amount of local anaesthetic (1ml) to position the needle tip just super cial to the TP, con rming correct needle tip position with local anaesthetic spreading deep to the erector spinae muscle. Further injection of local anaesthetic should reveal cranio-caudal spread along the length of the erector spinae muscle superficial to adjacent TP’s
Text and images have been reproduced from the 2nd edition of the RA-UK Handbook, which can be purchased on Amazon, or is received on joining RA-UK. This excellent resource also contains practical descriptions of all of the advanced blocks referenced in the editorial.