Mechanism of action of the erector spinae plane block: distribution of dye in a porcine model

Abstract

This study aimed to describe the anatomical distribution of dye injected in the erector spinae plane (ESP) in a porcine living model, which could aid to reveal factors potentially relevant to the unexplained clinical effects of the ESP block. Six pigs received 0.6 mL/kg of 0.25% new methylene blue at the level of the sixth thoracic vertebra through either a cranial-to-caudal or a caudal-to-cranial in-plane ultrasound-guided bilateral ESP injection 20 min before euthanasia.Spread of dye evaluated through transverse cryosections (four injections) extended from T5 to T10 and from T5 to T8 when a cranial-to-caudal direction of injection was used, and from T5 to T9 and from T5 to T8 when the opposite direction of injection was used. A median of 4.5 medial and lateral branches of the dorsal rami was observed stained through anatomical dissection (eight injections), regardless of the direction of injection. No evidence of dye was found in the thoracic paravertebral or epidural spaces, where the dorsal root ganglia, ventral rami and rami communicantes are located. In all the cases, dye solution was found in the prevertebral thoracic lymph nodes.In this study, ESP injection resulted in a median spread over five spinal segments (12 injections), staining the lateral and medial branches of the dorsal rami of the spinal nerves, regardless of the direction of the needle used.

<p>Erector Spinae Plane Block and Paravertebral Block for Breast Surgery: A Retrospective Propensity-Matched Noninferiority Trial</p>

“…Most cadaveric studies examining the spread of ESPB have shown extensive longitudinal and lateral spread of dye deep and superficial to and inside the erector spinae muscles, but little spread to the paravertebral space that is the main target of TPVB because that area includes both the ventral and dorsal rami of the thoracic nerves. [18][19][20][21][22][23] One of the most apparent advantages of ESPB is its lower demand for technical expertise. We showed that ESPB was performed in a shorter period of time than TPVB, as previous studies have shown.…”

“…[15][16][17] Injectate administered by ESPB is expected to make a wide spread in the craniocaudal direction, yet the results of cadaveric studies show inconsistent and unpredictable dye spread with little spread to the paravertebral space. [18][19][20][21][22][23] Accordingly, this retrospective propensity-matched study was conducted to see if ESPB could provide comparable analgesic effects to TPVB in patients undergoing breast surgery using data saved in our departmental registry. We also compared the distribution of sensory blockade after TPVB and ESPB.…”

The erector spinae plane block causes only cutaneous sensory loss on ipsilateral posterior thorax: a prospective observational volunteer study

“…However, other studies have raised concerns and objections. Otero PE et al [24] according to inject dye in the erector spinae plane in a porcine living model, found there is no evidence of anterior spread of dye involving thoracic paravertebral or epidural spaces. The cadaver study by Ivanusic et al [25] also demonstrated that there was no spread of dye anteriorly to the paravertebral space to involve the origins of the ventral and dorsal branches of the thoracic spinal nerves.…”

“…The diffusion of local anesthetic drugs in the thoracolumbar fascia helps to modulate the somatic and visceral pain. Recently, Otero PE et al [24] found that the thoracic lymph nodes were stained when exploring the mechanism of ESP block in a porcine model. They considered it might be that the local anesthesia entered the lymphatic reflux and desensitized the sensory nerve fibers connected to the lymphatic finger, contributing to clinical analgesic effects.…”

Postoperative Thoracic Pain Treatment: Serratus Anterior or Erector Spinae Plane Block?

“…documented the absence of solution spread into the paravertebral area in a cadaveric study, Adhikary et al 19 stated that the solution they used reached both the epidural and paravertebral areas. Also, Otero et al 20 reported a new perspective on the ESPB efficacy mechanism. They injected six pigs with dye using the ESPB technique at the T6 level while they were alive and sacrificed them after 20 minutes to evaluate the distribution of the dye by studying the cadavers.…”