LAUSR

The Subpectoral interfascial plane (SIP) block, which was first described in 2016 by Raza et al. [ 1], involves the injection of a local anesthetic into the space between the pectoralmajormuscle (PMM) and the external intercostal muscle (EIM). It anesthetizes the anterior rami of the T2 to T6; therefore, SIP block may be effective for the postoperative analgesia of themedian sternotomy such as that following a cardiac surgery [2]. However, the spread of local anesthetic injected by the SIP block has still not been investigated. In this time, we investigated the spread of the SIP block.We studied five cadavers, that had been subjected to the Thiel's embalming technique, to investigate how widely the injectate spreads by evaluating the spread of blue dye. Ultrasound-guided blue dye injections were performed as follows: 20 mL of blue dye was injected into the fascial plane between the left PMM and the left EIM 2 cm lateral to the sternal edge. Ten minutes after the injection, we assessed the spread of the blue dye. In conclusion, all dye had spread from the anterior rami of T2 to T4. However, all dye didn't spread at