Ultrasound Guided Modified Versus Conventional Serratus Anterior Plane Block as a Preemptive Analgesia for Unilateral Video-Assisted Thoracoscopic Surgery

After sterilization of the skin and draping, the high frequency linear probe of Sonosite M Turbo ultrasonography (FUJIFIM sonosite, Inc., Bothell, WA, USA) will be placed at the level of the midclavicular line in a sagittal plane. The second rib will be recognized at the axillary artery. The probe will be moved downward to count the ribs until the level of the fifth rib in the mid-axillary line. At this time, the latissimus dorsi muscle (lying superficial) and the serratus anterior muscle (lying deep) will be clearly visualized under ultrasound . Next, A 22-gauge, 80 mm needle (Stimuplex D, B-Braun, Germany) will be inserted in plane relative to the ultrasound probe between the latissimus dorsi and the serratus anterior muscle. After confirming negative aspiration of blood, 1 ml normal saline will be injected for hydro-dissection sign to verify the needle tip, then a volume of 25 ml 0.25% bupivacaine will be injected superficially to serratus anterior muscle. .

The patient will be placed in the lateral decubitus position according to the selected site of surgical intervention. After sterilization of the skin and draping, the high frequency linear probe of Sonosite M Turbo ultrasonography ( FUJIFIM sonosite, Inc., Bothell, WA, USA) will be placed horizontally midway between tip of the scapula and posterior axillary line to identify the view of latissimus dorsi(lying superficial) and serratus anterior muscle(lying deep) over either the sixth or seventh rib. A 22-gauge, 80 mm needle (Stimuplex D, B-Braun, Germany) will be inserted in plane relative to the ultrasound probe from posteromedial to anterolateral direction toward posterior axillary line till reaching the interfacial plane between latissimus dorsi and serratus anterior muscle . After confirming negative aspiration of blood, 1 ml normal saline will be injected for hydro-dissection sign to verify the needle tip, then a volume of 25 ml 0.25% bupivacaine will be injected .