External Oblique Intercostal Block vs Subcostal Transversus Abdominis Plane Block in Open Nephrectomy

This randomized controlled double blinded study will be done on 80 patients (40 in each group), patients will be randomly classified by computer generated numbers. Through a sealed opaque envelope technique, a blinded nurse who will not participate in the study or data collection, will read the number contained in the envelope and make group assignments.

All patients will be seen in the anesthesia clinic, optimization of general condition and all required investigations will be done before surgery. Patients will be premedicated with 1.5 mg midazolam and 4 mg granisetron. Basic monitoring will be applied to the patients such as Pulse oximetry (SPO2), Non-invasive blood pressure (NIBP), Electrocardiogram (ECG), Capnogram and temperature probe.

After adequate preoxygenation, induction of general anesthesia will be done through wide bore cannula using 1 mic/kg fentanyl, 1-2 mg/kg titration of propofol, 0.5mg/kg atracurium. Patients were mechanically ventilated using volume-controlled ventilation (VCV) with adjustment of end tidal carbon dioxide (ETCO2) to be 32-35 mmHg, 50% inspired oxygen in air and sevoflurane concentration to be 1MAC. The patients will receive either block before skin incision that will be done 20 minutes after the block. 0.5 mic/kg fentanyl will be injected when heart rate or blood pressure increases more than 20% of baseline. By the end of the surgery, 1gm paracetamol will be administered with fully reversal of muscle relaxants at the end of the surgery.

Group E This group of patients will receive external oblique intercostal block in supine position. A high-frequency linear transducer will be placed in sagittal plane between the midclavicular and anterior axillary line at the level of the 6 to 8th rib. The pointing mark of the probe will be directed cranially and may be slightly tilted medially for better identification of external oblique muscle and intercostal muscles.

After sterilization of skin and through the in-plane technique directing from cranial to caudal, a needle will be used to pierce the skin, subcutaneous tissue then external oblique muscle to hydrodissect the fascial plane between external oblique muscle and intercostal muscles with 25 ml bupivacaine 0.25 % and 4 mg dexamethasone added to it.

Group T Subcostal transversus abdominis plane block will be applied to this group and patients will be supine. A high-frequency linear transducer will be placed directly below and along costal margin. After sterilization of skin, with in-plane technique and from lateral to medial, a needle will be used to pierce the skin, subcutaneous tissue then rectus muscle and 25 ml of 0.25 % bupivacaine with 4 mg dexamethasone will be injected between rectus muscle and transversus abdominis muscle.

After extubation, the patients will be transferred to PACU (Post-Anesthesia Care Unit) for monitoring. Numerical rating scale (NRS) will be used for pain assessment while 0 is no pain and 10 is severe agonizing pain. Patients will be given a rescue analgesia of 0.05 mg / kg morphine if NRS ≥ 4 and repeated if needed after 20 minutes. 1 gm paracetamol every 8 h and 30 mg ketorolac (if not contraindicated) every 12 h will be given regularly.