Ultrasound-guided Genicular Nerve Block for Total Knee Arthroplasty.

After the administration of spinal anesthesia, the anatomical structures of the proximal and distal region of the knee will be explored through an M- ultrasound machine Turbo® with a high-frequency 6-13 MHz linear probe. The ultrasound transducer will be placed in a coronal orientation to the axis of the knee in the corresponding area to be blocked according to anatomical landmarks of superior medial genicular nerve (SMGN), inferior medial genicular nerve block (IMGN), superior lateral genicular nerve (SLGN), inferior lateral genicular nerve (ILGN), and recurrent genicular nerve (RGN). It should be noted that the visualization of the genicular arteries in the femoral epicondyles and in the area of the tibial plateau, represents an accurate guide to where the sensory afferents are, however; its display is not constant. 4 ml of 0.2% ropivacaine will be administered, with adrenaline 1: 100 000 in each of the five nerves.

100 ml of ropivacaine 0.2% with 1 mg of epinephrine during the period of intraoperative ischemia and, before the closure of the surgical wound, 50 ml of ropivacaine 0.2%.