Quadratus Lumborum Block Versus Thoracic Paravertebral Block

All patients will be medically checked in the preoperative assessment clinic {history, physical examination, investigations (e.g. complete blood picture, coagulation profile , liver \& kidney functions , ECG for patient above 40 years, chest x-ray for patients above 60 years and any other necessary investigations required for risky patients. ) }.

The patients will be randomly allocated into two equal groups(25 patients for each group) with a computer-generated list (www.Random.org).

QLB group: will receive 0.3ml/Kg bupivacaine 0.25% ( keeping in mind not to exceed the maximum recommended toxic dose of plain bupivacaine which is 2.5 mg/Kg \& 3mg/Kg with epinephrine).

PVB group: will receive 0.25ml/Kg/side of 0.375% bupivacaine with epinephrine 5ug/ml, yielding the same dose of bupivacaine of 1.875mg/ml at the level of T10.

• In the recovery room, the patients will be continuous monitored for pulse, blood pressure, oxygen saturation.
• Humidified oxygen 3L/min. by nasal prong will be delivered to all patients.
• Portable ultrasound machine , nerve stimulator, pressure injector monitor ,resuscitation equipment \&drugs (e.g. epinephrine, lipid emulsion ), sterile gloves and surgical towels should be available.
• Intravenous(IV) 18 gauge cannula will be inserted. Midazolam 0.02 mg/Kg will be administered.

While the patients in the supine or lateral position, they will receive bilateral single injection ultrasound guided QLBs under complete sterilization of the abdomen with sterile solution (iodine povacryl \& isopropyl alcohol solution). All patients will be monitored throughout the performance of the block \& all data will be recorded. A linear ultrasound transducer probe (6-13MHZ), or curved probe (according to patients BMI). ( Sonosite M-turbo; Inc., Bothell, WA, USA) in a sterile cover will be placed at the level of the anterosuperior iliac spine and moved cranially until the three muscle layers of the abdomen will be identified: external oblique, internal oblique, and transversus abdominis muscles. The external oblique muscle will be followed posterolaterally until its posterior border visualize (hook sign) leaving underneath the internal oblique muscle, like a roof over the QL muscle. The probe will be tilted down to identify a bright hyperechoic line that corresponded with the intermediate layer of the thoracolumber fascia(Blanco et al.,2015).

A 21 gauge blunt, insulated, echogenic needle will be inserted in plane . The optimal point of injection will be determined using hydrodissection (3-5 mL normal saline). The site of the needle will be confirmed in place by ultrasound guided, nerve stimulator (B- Braun) \& pressure injector monitor.

After negative aspiration, we will inject 0.3mL/Kg bupivacaine 0.25% in each side in QLB group. The patients will be monitored for about 20-30 minutes before induction of anesthesia.

While the TPVB will be performed by single injections at the level of T10 vertebra. The patients will be placed in the sitting position, and the spinal process of T10 will be palpated. Then a linear ultrasound transducer probe (6-13 MHZ).

( Sonosite M-turbo; Inc., Bothell, WA, USA) in a sterile cover will be placed at the corresponding transverse process to be clearly visualized and the skin-transverse process distance will be measured on both sides. After infiltration of the skin and subcutaneous tissue with 1% lidocaine with epinephrine 5ug/ml, an 18G Touphy needle will be inserted perpendicular to the skin, approximately 2.5 cm from midline, until contact with the transverse process will be established ( It is important to visualize the pleura very clearly at all times ). The needle will then slightly withdrawal \& reinserted 1-1.5 cm deeper either caudally or cranially for the transverse process (TP). The site of the needle will be confirmed in place by ultrasound guided, nerve stimulator (B- Braun) \& pressure injector monitor.

After careful aspiration, patients will be received a slow injection of 0.25mL/Kg/side of 0.375% bupivacaine with epinephrine 5ug/ml at the level of T10. The patients will be monitored for about 30 minutes before induction of anesthesia. Induction of general anesthesia will be done.

After full awakening from anesthesia, the patient will be transferred to the recovery room. In the recovery room, the patient will be continuous monitored \& humidified oxygen will be applied for about 1 hour. Then a standardized analgesic regimen consisting of regular IV/oral paracetamol 1g every 6 hours combined with PCA morphine (on demand) will be initiated. Patients required additional analgesia will be received IV ketorolac(15-30mg).

A trained anesthetist not involved in the study \& blinded to the patient group will measure the VAS, morphine requirements \& patient satisfaction.