Evaluation of Sensory and Motor Blockade of Ultrasound-Guided Parasacral Ischial Plane Block in Lower Extremity Surgery

Sympatholysis resulting from central neuraxial block or general anesthesia in lower extremity surgeries may lead to adverse hemodynamic changes and increased perioperative mortality, particularly in high-risk patients. In such patients, lower extremity procedures can be successfully performed solely under sciatic and femoral nerve blocks. Depending on the surgical indication, the sciatic nerve block may be utilized alone or in combination with a lumbar plexus or femoral nerve block.A novel ultrasound-guided (USG) fascial plane approach targeting the sacral plexus, termed the Parasacral Ischial Plane (PIP) block, has been successfully investigated in a limited number of patients. The sacral plexus is located within a fascial plane formed by the pelvic fascia anteriorly, the sacrum medially, the piriformis and gluteus maximus muscles posteriorly, and the ischium bone laterally. The piriformis muscle has no attachment to the ischium; instead, it attaches laterally to the greater trochanter. A fascial plane exists between the piriformis muscle and the ischium, which extends directly to the sacral plexus.

Venkataraju et al. stated that during the demonstration of the PIP block, the needle should be directed and positioned toward the posteromedial surface of the ischium. Following bony contact, the injectate was administered, and its spread was observed beneath the piriformis muscle toward the sacral plexus (SP). This method is considered to be technically more straightforward and carries a lower risk profile.