Erector Spinae Plane Block

This is a prospective randomized controlled study which will be conducted in the Anesthesiology Department at Theodor Bilharz Research Institute after approval by the institutional review board and obtaining patient informed consent. 46 patients will be enrolled in the study and will be randomized to be equally divided into two groups: ESPB group(E group) and control group (C group).

Anesthetic technique:

A preoperative assessment, including a history, physical examination, review of laboratory data, and assignment of ASA classification will be performed on all patients prior to the procedure. After premedication with intravenous midazolam 2 mg, patients will be transferred to the operating room.

Standard monitors such as noninvasive blood pressure, electrocardiography (ECG), and pulse oximetry (SpO2) will be attached. Anesthesia will be induced using propofol 1-2 mg/kg, fentanyl 1-2 µg/kg and sevoflurane. After adequate manual ventilation, atracurium 0.5 mg/kg will be administered to facilitate endotracheal intubation. Ventilation will be started with oxygen and medical air (FiO2 = 0.6). Patients will be positioned in the lateral position to perform the ESPB and for preparation for surgery.

Erector SpinaePlane Block technique:

After skin sterilization and draping, a high-frequency linear array ultrasound probe will be placed on the back in a transverse orientation to identify the tip of the T7 transverse process. The tip of the transverse process will be centered on the ultrasound screen and the probe will then be rotated into a longitudinal orientation to produce a parasagittal view, in which the following layers will be visible superficial to the acoustic shadows of the transverse processes: skin and subcutaneous tissue, trapezius and erector spinae muscle.The rhomboid major muscle has its lower border a tthe T5-6 vertebral level and its absence will be used as additional confirmation that the T7 transverse process is being viewed. An echogenic 22-G block needle will be inserted in-plane to the ultrasound beam in a cranial-to-caudal direction until contact is made with the T7 transverse process. Correct location of the needle tip in the fascial plane deep to erector spinae muscle will confirmed by injecting 0.5-1 ml normal saline and seeing the fluid lifting the erector spinae muscle off the transverse process without distending the muscle.

ESPB group:

A total of 25 ml bupivacaine 0.5% will be injected into the ESP.

Control group:

The ESPB will not be performed. Surgical technique and postoperative care will follow standard local clinical practice.

Pain management:

Numerical Rating Scale (NRS) pain score will be used immediately postoperatively and then at 30 minutes, 1, 2, 4, 6, 12 and 24 h. Scores (1-3) are considered mild pain, (4-6) moderate pain and (7-10) severe pain. Rescue analgesia with intravenous pethidine (25 mg) will be prescribed if the patient's resting NRS score is more than three or on patient demand. Additional intravenous doses of 25 mg of pethidine will be given if needed to achieve a score below 4. The second rescue analgesic plan will be intravenous ketorolac 30 mg diluted in 100 ml normal saline and administered slowly, if NRS remained persistently >3 after 15 min of the first rescue analgesic administration.

Data collection

• Age
• Sex
• BMI
• ASA Classification
• Intraoperative and postoperative arterial blood pressure
• Intraoperative and postoperativeheart rate
• Numerical Rating Scale (NRS) pain score immediately postoperatively and then at 30 minutes, 1, 2, 4, 6, 12 and 24 h.
• Postoperative analgesia consumption
• The overall degree of patient satisfaction will be assessed using a three-point scale (good, moderate, and bad) on the first postoperative day.
• Block related complications (e.g Pneumothorax)
• Postoperative opioid related complications (e.g. Nausea, vomiting, constipation, sedation)

Statistics:

The patients will be randomly divided into two groups; group (E) and group (C). Forty-six patients will be prospectively enrolled for each study of patients who had been diagnosed to be able to reject the null hypothesis that the population means of the groups are equal with Power calculations suggested that a minimum of 23 subjects per group will be required to detect 10% difference in time for first rescue analgesia between groups (taking type I or α error of 5%, type II or β error of 20% and Standard Deviation=10). To be on a safer side, patients will be included in each group (n=23).

Statistical analyses will be performed using JMP ver. 12.0 (SAS Institute Inc., Cary, NC, USA). The number of patients who will be reported complications corresponding percentage (%) for nominal variables; for continuous variables with normal distribution, and the Mann-Whitney U test will be used for nonparametric variables. The level of significance for both the tests set at p<0.05.

Inclusion criteria

• Patient is able to provide a written informed consent.
• ASA I-II.
• Patient is scheduled to perform an elective open renal surgery through a flank incision.

Exclusion criteria

• ASA III-IV
• Pregnancy.
• Patient is allergic to bupivacaine local anesthetic.
• Impaired coagulation (Platelet count< 150,000 cells/mcl and/or INR ≥ 1.4).
• Infection at site of injection.
• Prior same side flank surgery.