Sonoanatomy

Ultrasound probe selection: linear high frequency probe

Mapping/scout scan: look between the intervertebral spinous processes and laminae:

1)Probe position transverse over the sacral cornua (-> frog’s eyes US view)
2)Then rotate probe 90 degrees for a longitudinal view
Identify:
•Sacral cornua
•Sacrum
•Sacrococcygeal membrane
•End of the dural sac (hyperechoic (<-> CSF are anechoic (black) 
•Caudal epidural space
•Assess the position of the dural sac in relation to the sacrococcygeal membrane
 

NOTE: Ultrasound can't see through bone; so with increasing age (= increasing angulation of the spinous processes and increasing ossification of the laminae) the size of the echo window will diminish -> you might need to scan paramedian
TIP: use a large linear probe (50mm) – this will allow you to visualise more vertebrae in one image for easier monitoring of needle approach and LA spread