The targets of PECS II block include the medial and lateral pectoral nerves, including the lateral cutaneous branches of the TICNs (Figure 6).
This agent can block the lateral cutaneous branches of the TICN in the interfascial plane between the pectoralis minor and serratus anterior muscles but cannot block the anterior cutaneous branch of the TICN.
The dermatomal sensory innervation to the breast is provided by the third to fifth lateral cutaneous branches
to the lateral breast region, the second to fifth anterior cutaneous nerves to the medial side and minor contribution from the intermediate group of supraclavicular nerve to the superior and lateral aspect of the breast (see Figure 9).
The lateral cutaneous branches depart near the angle of the rib posteriorly .
Since the lateral cutaneous branches leave the TAP posterior to the midaxillary line, posterior injection of local anesthetics is suggested if analgesia for both the anterior and lateral abdominal wall is required .
While subcostal and lateral TAP injections do not always cover the lateral cutaneous branches of the segmental nerves , the posterior approach deposits the injectate posterior to the midaxillary line and may provide better analgesia to the lateral abdominal wall .
Versatility of lateral cutaneous branches
of intercostal vessels and nerves: Anatomical study and clinical application.
In Type III (10%), lateral cutaneous branches
of T2 and T3 fuse as a common trunk and then split immediately after exiting the intercostal space to form an ICBN.