Fundamental principles of performing an ESP (erector spinae plane) block (as per our understanding in 2022).
1. Identify and clearly visualize the transverse processes (TPs) and fascial planes at the desired level. A curved probe (vs linear) can be helpful if depth is more than 4cm.
2. Needle visualization with an inplane approach can be tricky. Make small controlled dynamic scanning probe movements, and look for tissue motion to help localize the needle tip.
3. Aim to land on the edge of the TP (vs the middle), so that the needle can be advanced off the bone to slide deeper into the intertransverse tissue complex if necessary, to cleanly lift the investing muscle fascia off the bony TPs.
4. Injecting nonactive fluid to hydrolocate and place the needle tip into the correct plane will help prevent "wasted" injections of LA into the wrong location.
5. Make small sliding probe motions to dynamically scan and assess LA spread during injection, to confirm that spread is indeed occurring deep to the fascia of the ES muscle. This is essential for LA to penetrate anteriorly to the paravertebral space and the ventral rami/dorsal root ganglia.