Thoracic paravertebral and erector spinae plane block: A cadaveric study demonstrating different site of injections and similar destinations

[...]this cadaveric study was planned to examine the mechanism of action and drug spread after a thoracic ESP block using methylene blue dye. In five formalin-based prone cadavers a left-sided ESP block was performed with 20 ml injectate [0.1 ml methylene blue dye (1 ml = 10 mg methylene blue) and 19.9 ml normal saline] under US guidance. Using similar volumes right sided thoracic PV injections were also administered under US guidance in all five cadavers. [...]in total there were ten injections made: five ESP block on left side and five PV injections of right.