Craner, Ryan

Background and objectives Few cadaveric studies have evaluated the dye spread with superficial parasternal intercostal plane (SPIP) blocks. In this study, we examined the dye spread of an ultrasound-guided SPIP block in a human cadaveric model with single and double injection techniques. Methods Seven single and four double ultrasound-guided SPIP blocks were performed in seven unembalmed human cadavers using an in-plane approach with the transducer oriented parasagitally 1 cm lateral to the sternum. For the single SPIP, 20 mL of 0.166% methylene blue was injected in the second or third intercostal space into the plane between the Pec major muscle and internal intercostal muscles. For the double SPIP, 10 mL of 0.166% methylene blue was injected in the SPIP at one intercostal space with an additional 10 mL injected in the SPIP two intercostal spaces caudally. The extent of dye spread was documented. Results For all SPIP injections, there was consistent mediolateral spread from the sternum to the mid-clavicular line, with many extending laterally to the anterior axillary line. There was craniocaudal spread to a median of 2 intercostal muscles with a single SPIP and 3 intercostal muscles with a double SPIP. There was a median spread to 1 intercostal nerve for the single SPIP and 1.5 intercostal nerves with the double SPIP. Conclusions The SPIP block demonstrated limited spread in this cadaver study. A single injection of this block may be of limited value and multiple SPIP injections may be needed to have adequate spread for anterior thoracic procedures.

Background and objectives Studies show variable spread with thoracic erector spinae plane (ESP) injections. Injection sites vary from lateral end of the transverse process (TP) to 3 cm from the spinous process, with many not describing the precise site of injection. This human cadaveric study examined dye spread of ultrasound-guided thoracic ESP block at two needle locations. Methods Ultrasound-guided ESP blocks were performed on unembalmed cadavers. Methylene blue (20 mL, 0.1%) was injected in the ESP at the medial TP at level T5 (medial transverse process injection (MED), n=7) and the lateral end of the TP between T4 and T5 (injection between transverse processes (BTWN), n=7). The back muscles were dissected, and the cephalocaudal and medial-lateral dye spread documented. Results Dye spread cephalocaudally from C4-T12 in the MED group and C5-T11 in the BTWN group, and laterally to the iliocostalis muscle in five MED injections and all BTWN injections. One MED injection reached serratus anterior. Dorsal rami were dyed in five MED and all BTWN injections. Dye spread to the dorsal root ganglion and dorsal root in most injections, though more extensively in the BTWN group. The ventral root was dyed in 4 MED and 6 BTWN injections. Epidural spread in BTWN injections ranged from 3 to 12 levels (median: 5 levels), with contralateral spread in two cases and intrathecal spread in five injections. Epidural spread in MED injections was less extensive (median (range): 1 (0–3) levels); two MED injections did not enter the epidural space. Conclusion An ESP injection administered between TPs exhibits more extensive spread than a medial TP injection in a human cadaveric model.