Ultrasound Guided Bilateral Retrolaminar Block as Analgesia for Adolescent Idiopathic Scoliosis Correction

-Preoperative: Evaluation of patients will be carried out through proper history taking, clinical examination and routine laboratory investigation and patients will be trained to use the Numerical Rating Scale (NRS 0= no pain, 10= intolerable pain) used for evaluation of pain intensity.

The patient is allowed to fast for 8 hours for solids and 2h for clear fluid. Before the study, all patients will be interviewed and will be briefed on the wake-up test procedure. They will be informed that they will be asked to open their eyes, move their fingers (hold the anesthesiologist's hand), move their toes, and finally, to remember a given color.

-Intraoperative: On arrival to operating roome, a 20 G peripheral IV cannula will be inserted. Electrocardiogram (ECG), noninvasive mean arterial blood pressure (MAP) and peripheral oxygen saturation will be attached and baseline data will be monitored and documented. Sedation will be given intravenously in the form of midazolam 0.02 mg/kg and IV fliud according to calculation of deficit and maintaince calculation.

After preoxygenation, anesthesia with IV propofol 2 mg/ kg and fentanyl 2 µg/kg will be administered for analgesia and cisatracurium 0.5 mg/ kg will be given intravenously to facilitate endotracheal intubation.

Central venous catheter will be inserted and attached for monitoring of CVP. Also, enotropy will be connected on the patientꞌs forehead and maintained between 40-60.

44 patients will be equally divided to two equal groups (22 patients for each group) Group 1: will receive sham bilateral bilevel ultrasounded guided retrolaminar block at T4 and T10 after induction of anaesthesia in prone position.

Group 2: will receive real bilateral bilevel ultrasounded guided retrolaminar block at T4 and T10 after induction of anaesthesia in prone position. The total desired volume used in the whole injection will be 40 ml containing 3mg / kg bupivacaine with adrenaline 2.5 2 µg/ml. The total 40 ml volume will be divided into 10 ml for each injection.

Maintaince of anaesthesia will be 50 : 50 % O2 to air and sevoflurane 2% and cisatracurium incremental every 30 min at dose of 0.1 mg/kg. I.V analgesia in form of incremental fentanyl 1 ug /kg when entropy increases more than 60 during surgery and 30 min before the wake-up test.

Wake up test: Before continuation of anesthesia, patients will be given a color to remember. After finishing the wake-up test, anesthesia will be induced using 3 mg/kg propofol and 0.1 mg/kg cisatracurium, whereas anesthesia will be maintained as described previously.

At the end of surgery, inhalational anesthetic agent will be turned off, residual neuromuscular block will be reversed with neostigmine 0.05 mg/kg and atropine 0.01 mg/kg then patients will be extubated and will be transferred to post anesthesia care unit (PACU).

Postoperative multimodal analgesia: will received paracetamol 10 mg/kg every 6 hours and intravenous diclofenac 1.5 mg/kg every 8 hours regularly.

All observations will be carried out by a single investigator, who is blinded to the study groups.

-In all groups, the following will be measured: -

1. Demographic data.
2. Time of the first dose of rescue analgesia (morphine at dose of 0.1 mg/kg).
3. Total doses of postoperative morphine consumption.
4. Number of patients received rescue analgesia.
5. Numerical Rating Scale (NRS) for pain that ranged from (0 = no pain) to (10 = intolerable pain). If score is >3 will need analgesia in the form of morphine 0.1 mg/kg will be given till NRS decreases to ≤3. NRS will be assessed and recorded on arrival to the Recovery Unit, 2, 4, 8, 12, 18, 24 h after the operation, by an anesthesiologist, who is blinded to the study groups.
6. Total doses intraoperative consumption of fentanyl.
7. Wake-up profile: On the surgeons' request for the intraoperative wake-up test, administration of sevoflurane will be stopped. (the quality of wake-up, return of spontaneous breathing, ability to open eyes on command, and ability to move hands and feet) and postoperative amnesia. Patients will be asked repeatedly during the wake-up test, at least every 15 s, to open their eyes and to move their hands and feet. The time elapsed from the interruption of anesthesia to the start of spontaneous breathing (T1), from the return of spontaneous breathing to eye opening on command (T2), and from eye opening to movement of hands and feet (T3) will be recorded in seconds using a stopwatch. The quality of the wake-up test will be evaluated on a three-point rank scale (7).
8. First time of postoperative mobilization.