Postoperative Opioid Consumption of Serratus Posterior Superior Intercostal Plane Block Versus Thoracic Paravertebral Block After Open Thoracotomy: A Randomized Prospective Trial

Prospective double-blind randomized clinical trial. All patients will be randomly allocated into two equal groups:

Group S (Serratus Posterior Superior Intercostal Plane Block group) Group P (Paravertebral Block group) Using computer generated randomization table, each group consists of 24 patients.

• All patients will be hospitalized and visited a day before the surgery, full history with physical examination and routine investigation will be done, the nature and complications of the study will be explained in detail to the patient and informed written consent will be obtained from all patients.
• Age, sex, body mass index (BMI), and ASA data will be recorded. All patients in both groups will be informed about the numerical rating scale (NRS) for post-operative pain assessment prior to surgery. The NRS is a numerical scale ranging from 0 to 10, where 0-2 mean no pain, 3 mean mild pain, 4-7 mean moderate pain, 8 mean severe pain, and 9-10 mean unbearable pain.11 Also respiratory function will be assessed using spirometry and the forced expiratory volume in 1st second (FEV1).
• All patients will be kept nil orally 8 hours before the operation except for clear fluid 2-3 hours preoperative.
• In the operating room, standard monitors including non-invasive blood pressure (NIBP), digital pulse oximetry and electrocardiogram (ECG) will be connected to the patients, 18 G venous cannula will be inserted with ringer lactate infusion 10 ml/kg/h, also arterial cannula will be inserted for invasive blood pressure monitoring. Capnogram and temperature probe will be applied to each patient and central venous catheter will be inserted after induction of anesthesia.
• All patients will be premedicated with 0.03mg/kg midazolam. General anesthesia will be induced by 2 µg/kg fentanyl, 1.5 mg/kg propofol and 0.6 mg/kg rocuronium will be injected i.v to facilitate tracheal intubation with a left double-lumen endotracheal tube (35-37 French) for one lung ventilation. Patients will be connected to the operating room ventilator immediately after intubation with FIO2 =1, tidal volume =6-8 ml/kg and respiratory rate to maintain Etco2= 35-40mmHg. Anesthesia will be maintained with opioid (fentanyl 1µg/kg/hr), neuromuscular blocking agent (rocuronium 0.6 mg/kg in repeated boluses), and isoflurane (minimum alveolar concentration 1-1.5).
• At the end of the surgery, all patints will take 1 g paracetamol i.v infusion followed by 30 mg/kg ketolac i.v. Also, all patients will take 8 mg ondansteron i.v to prevent postoperative nausea and vomiting (PONV). After that, both groups will undergo regional blocks following the surgical closure and before the reversal of residual neuromuscular blockade in the lateral decubitus with the operative side up and the skin will be prepared with 10% povidone-iodine.
• The blocks will be performed by the same anesthesiologist (performer) who is experienced by at least 20 successful uncomplicated blocks before. The post-operative assessment will be performed by a blinded second anesthesiologist (evaluator). The patient and the evaluator will be blinded to the performed block. The performer anesthesiologist may know the patients included in the block group due to the nature of the study. Both blocks will be performed by a high-frequency (7-12 MHz) linear ultrasound probe, using in-plane technique, 80 mm block needle, and 30 ml of 0.25% bupivacaine for injection.

1. All patients will be turned into the supine position, and then neuromuscular reversal (with 4mg/kg sugammadex i.v.) and extubation will be performed in the supine position. Patients will be transferred to the recovery room and they will be assessed for pain site and pain score (NRS) at rest and during coughing. Need for analgesia will be defined as NRS ≥ 3 when 0.1 mg/kg i.v. morphine will be given as a rescue analgesia and that will be beside regular i.v. 1 g paracetamol every 8 hours from the initial intraoperative dose for all patients (as a standard analgesia with maximum dose 4 g/ 24 h). The rescue analgesic morphine dose may be repeated 10 minutes later if the pain score is still ≥ 3 with caution for avoidance of sedation or respiratory depression. The NRS will be recorded at 2, 4, 6, 12, 18, 24 hours postoperative while the patient resting (NRS static) and coughing (NRS dynamic). The 1st time for rescue analgesia, the total first 24 hours opioid consumption and its side effects such as nausea, vomiting and pruritus will be recorded. Also respiratory functions (FEV1) will be re-assessed using spirometry and recorded at the same NRS timing in the in-hospital period, and patient satisfaction at 24 hours postoperative by five-point Likert scale.