Evaluating the Intraoperative Analgesic Effect of Ultrasound Guided Erector Spinae Plane Block in Parturient Undergoing Elective Cesarean Section for Placenta Accreta Under General Anesthesia.

All included subjects will be randomly allocated using sequentially numbered, sealed opaque envelope technique. into two groups; (Group A): will receive preoperative ultrasound guided erector spinae plane block and (Group B): will receive fentanyl bolus(1mic/kg) following delivery of the fetus (conventional group).

There will neither be restrictions nor stratification in the randomization process. The allocation envelope will be opened by the anesthetist who will perform the block while another anesthetist who will be blinded of the intervention will be responsible for data collection both intra and post-operative.

1. Pre-operative preparation All patients will be anaesthetized in accordance with the local policy of Cairo university gynecology \& obstetrics hospital. Except for oral clear fluid intake 3 hours before surgery, all patients will be instructed to fast for 6 hours. Patients will be transferred to the preparation room one hour before surgery to record their demographic data and allocate them to either group. (Group A) Patients in this anesthetic group, bilateral ESPB will be performed under ultrasound guidance by an anesthesiologist in the preparation room thirty minutes before induction of general anesthesia in the following steps: The parturient will be instructed to remain in the sitting position. A high-frequency linear ultrasound probe (Philips, HD11 XE) will be placed in a cephalocaudal orientation over the midline of the back at the spinous process of the 9th thoracic vertebra along the short axis. and slightly moved in the lateral direction until the transverse process is visible. After standard disinfection of skin and subcutaneous infiltration of 3 mL of 2% lidocaine, a 22G blunt needle (TuoRen Medical Instrument Finty Company, Zhengzhou, China) will be introduced from the outside towards the transverse process (T9) using the in-plane method until the needle tip crosses all the muscles. Subsequently, 20 ml of 0.25% Bupivacaine (11) (Harvest Pharmaceutical Co. Ltd., Shanghai, China) will be injected between the transverse process and the deep surface of the erector spinae on each side. The block performance time for each side is expected to be around (146-243) seconds with an average of 185 seconds in expert hand. (12) The local anesthetic is assumed to spread four levels cephalad and caudal from the site of injection at level of T9, thus the expected dermatomal block would be from T5 to L1. General complications of ESPB should be considered during block performance, these include pneumothorax, nearby vessel or nerve injury, local anesthetic systemic toxicity (LAST) and block failure. Testing for loss of tactile sensation and discrimination in the expected dermatome will be done 20 min after the injection of drugs. If no loss of sensation was attained within 30 min this will be considered an unsuccessful block and the parturient will be excluded from the study and managed according to the theater protocol. The patients with successful block enrolled in the study will be also given a 10 ml syringe containing saline that will be injected after the delivery of the baby. (Group B): Patients in this group will be given 1mic/kg fentanyl diluted to 10 ml by IV injection by the attending anesthetist after delivery of the fetus.
2. Intra-operative management Upon arrival to OR the patients will be placed supine with left uterine displacement. Standard monitors: ECG, peripheral oxygen saturation (SpO2) and noninvasive arterial blood pressure (NIBP) will be applied. An IV access will be obtained.

General anesthesia will be induced in both groups after adequate preoxygenation using propofol 2.5 mg/kg, rocuronium 1 mg/kg. After securing the endotracheal tube (6.5mm), anesthesia will be maintained using 1 MAC isoflurane, timed rocuronium and volume-controlled ventilation 6-8ml/kg to obtain normocarbia. 1gm tranexamic acid will be infused. Two 18g cannula will be inserted as well as radial artery cannulation for invasive blood pressure monitoring.

Goal directed fluid therapy using invasive arterial blood pressure monitoring will take place, keeping mean arterial pressure (MAP) 65-90 mmHg and urine output >0.5 ml/kg/h.

Fluid maintenance according to the patient's weight and fasting hours will take place, taking in consideration third space loss and replacement at a rate of 8ml/kg/hr.

Intraoperative blood loss will be assessed visually and clinically and resuscitation will take place with proper blood and its products replacement for each patient as needed with target Hematocrit >30%.

After delivery of the fetus the patients will be given an oxytocin bolus (0.5 IU) for over five seconds, followed by infusion at a rate of 2.5 IU/hr. They will also receive the medication in syringe that was prepared in the preparation room. for group A, 10 ml normal saline while for group B,1 mic/kg fentanyl diluted to 10 ml. Tachycardia more than 20% not associated with hypotension will be treated in both group by giving blouses of 1mic/kg fentanyl as rescue analgesia as needed with a maximum dose of 4mic/kg. (13) Heart rate (HR) and mean arterial pressure (MAP) will be recorded every five minutes. The following timings will also be recorded and analyzed, In the preparation room (T0), at the induction of anesthesia (T1), at skin incision (T2), at fetal delivery (T3), and at the end of the operation (T4). Fetal delivery time, emergence time, episodes of hypertension or tachycardia and total fentanyl consumption will be recorded.

After patients' awakeness from anesthesia, they will be extubated after the administration of adequate doses of sugammadex (2-4 mg/kg/dose) regarding stable hemodynamics, consciousness (obey simple commands), ventilation (spontaneous breathing, RR 10-18, TV >8ml/kg) and muscular strength (lift the head and hold for 30 sec.), then will be transferred to a post-anesthesia care unit.

c-Postoperative All patients will be transferred to the post anesthesia care unit (PACU). All patients will be prescribed paracetamol 1gm IV /8hrs, Diclofenac 75 mg IV /6hrs and 8mg of dexamethasone as a single dose.

The visual analogue scale (VAS) score of patients will be measured both at rest and with cough or movement after instructing them how to use them at 2 h, 6 h, 12 h, and 24 h postoperative. The VAS score is ranked on a point system from 0-10; 0 points: no pain; less than 3 points: mild pain, which the patient can tolerate; 4-6 points: pain that affects sleep but can be tolerated; 7-10 points: the patient has increasingly severe pain that is unbearable.

Those with VAS score of more than 4 will receive rescue nalbuphine. For breakthrough pain, nalbuphine with an initial dose of 10mg every 4 to 6 hours as needed with maximum single dose 20 mg and maximum daily dose of 160 mg (14).

Adverse effects of opioids and local anesthetics will be recorded including respiratory depression (respiratory rate <90%), bradycardia, hypotension, postoperative nausea and vomiting scores (0- none, 1-mild, 2-moderate, and 3-

severe), time to first rescue analgesia and the total opioid consumption within 24h after surgery. All data will be obtained by an anesthesiologist, who will be blinded to the group assignment and will not be involved in implementing the nerve block.

Measurement tools

• Intraoperative hemodynamics.
• Total intraoperative fentanyl consumption.
• Total opioid (Nalbuphine) consumption in the first 24 hours postoperative.
• Time of first rescue analgesia used in the first 24 hours postoperative.
• Visual analogue pain score (VAS).
• Post-operative adverse effects such as nausea, vomiting, LA toxicity, bleeding and collapse.