The deep serratus anterior plane block for intensive care management of rib fractures: a cadaveric study on spread patterns.

BACKGROUND: In intensive care unit management, the serratus anterior plane block is sometimes meant to be inefficient for treating rib fractures, despite its proven efficacy in thoracic surgery analgesia. This cadaveric study aimed to investigate the anatomical distribution of local anesthetic by evaluate its dissemination on fractured and non-fractured sides. The primary outcome was the distribution pattern of dye as visualised by CT imaging and confirmed by anatomical dissection. METHODS: Cadaveric study. Single-centre study conducted in the Department of Anatomy Two formalin-fixed female cadavers aged 89 and 65 years, with no prior thoracic interventions. Bilateral deep serratus anterior plane blocks were performed under ultrasound guidance using methylene blue and contrast solution, following controlled unilateral rib fractures. CONCLUSIONS: Both cadavers had anterolateral rib fractures. In the first cadaver, dye spread was observed toward the pleura but did not stain nerves. Dissemination was restricted due to a breast mass and thickened fascia. In the second cadaver, pleural penetration of the dye occurred on the fractured side, while the intact side showed no dye presence. Lateral cutaneous branch of the intercostal nerve, thoracodorsal nerve and long thoracic nerves staining occurred only on the non-fractured side. CT and dissection results were concordant. CONCLUSIONS: The predictability of serratus anterior plane block efficacy may be compromised in the setting of rib fractures associated with blunt trauma due to variability in drug distribution. Given the small number of formalin-fixed cadavers used, these findings should be interpreted as preliminary anatomical observations requiring validation in fresh or Thiel-embalmed models.