Pericapsular Nerve Group Block Versus Intrathecal Morphine for Pain After Hip Surgery

Overview

Pain after hip replacement surgery is often severe and is commonly treated with opioids, which may cause nausea, vomiting, sedation, difficulty passing urine and slow breathing. This study will compare two ways of controlling pain in adults having hip surgery under spinal anesthesia. One group will receive morphine added to the spinal injection. The other group will receive an ultrasound-guided pericapsular nerve group (PENG) block, in which local anesthetic is injected near the nerves that carry pain signals from the hip joint. Participants will be assigned to one of the two groups by chance. Sixty-four adults aged 18 to 65 years will take part, with 32 in each group. Pain scores at rest and during movement, the total amount of morphine used through a patient-controlled pump, the time until the first request for extra pain medicine, the amount of additional paracetamol used, side effects such as nausea and vomiting, and complications related to the block will be compared between the groups during the first 48 hours after surgery.

Postoperative pain after total hip arthroplasty is frequently severe and limits early mobilization. Systemic opioids remain widely used but are associated with respiratory depression, sedation, urinary retention, constipation and postoperative nausea and vomiting. Intrathecal morphine added to spinal anesthesia provides prolonged analgesia but shares these opioid-related adverse effects. The pericapsular nerve group (PENG) block, first described by Giron-Arango and colleagues, targets the articular branches of the femoral, obturator and accessory obturator nerves that supply the anterior hip capsule by injecting local anesthetic into the fascial plane between the psoas tendon anteriorly and the pubic ramus posteriorly. Because the block spares motor fibers, it may provide effective analgesia without impairing early mobilization. Direct comparisons of the PENG block with intrathecal morphine in hip arthroplasty are limited. This will be a prospective, randomized, controlled, open-label, single-center study conducted at Selcuk University Faculty of Medicine Hospital. Local ethics committee approval has been obtained, and written informed consent will be obtained from every participant before enrollment. Sixty-four patients aged 18 to 65 years with an American Society of Anesthesiologists physical status of I to III scheduled for unilateral hip surgery under spinal anesthesia will be allocated to one of two equal groups of 32 patients using a sealed-envelope randomization method, so that the allocation sequence is concealed from the investigator enrolling the patient. Owing to the nature of the interventions, participants, treating anesthesiologists and outcome assessors will not be blinded to group allocation. Before surgery, demographic data (age, height, weight, body mass index), comorbidities, physical status classification, type of surgery and fracture location will be recorded. Peripheral venous access will be obtained with an 18 or 20 gauge cannula. Standard non-invasive monitoring of heart rate, systolic, diastolic and mean arterial pressures and peripheral oxygen saturation will be applied and recorded at predefined intervals from the intraoperative period until the 48th postoperative hour, with intraoperative measurements every 5 minutes. Spinal anesthesia will be performed in the sitting position under aseptic conditions at the L3-L4 or L4-L5 interspace using a 25 to 27 gauge, 90 mm Quincke spinal needle, after confirming free and clear cerebrospinal fluid flow. Patients in Group 1 will receive 10 mg of hyperbaric bupivacaine 0.5% together with 100 micrograms of morphine hydrochloride into the intrathecal space. Patients in Group 2 will receive 10 mg of hyperbaric bupivacaine 0.5% intrathecally without morphine, followed by an ultrasound-guided PENG block on the operative side. For the block, patients will be placed supine and the area will be prepared with aseptic technique. A low-frequency (2 to 5 MHz) curvilinear ultrasound probe will be placed over the anterior inferior iliac spine and rotated approximately 45 degrees counterclockwise to align with the iliopubic eminence, visualizing the anterior inferior iliac spine, iliopubic eminence, iliopsoas tendon and femoral artery. A 21 gauge, 80 to 100 mm insulated, echogenic short-bevel needle will be advanced in-plane from lateral to medial until the tip lies in the plane between the iliopubic eminence and the iliopsoas tendon. After negative aspiration for blood and sonographic confirmation of needle position, 20 mL of 0.5% bupivacaine will be injected. Adequacy of the neuraxial block will be confirmed before surgery begins. Postoperative analgesia will be provided with intravenous patient-controlled analgesia using morphine, programmed to deliver a 1 mg bolus dose with a 10-minute lockout interval and no background infusion. Intravenous paracetamol 1000 mg will be administered on demand as rescue analgesia, without exceeding a total daily dose of 4000 mg. Pain intensity at rest and on movement will be assessed with a Visual Analog Scale at the 1st, 3rd, 6th, 12th, 24th and 48th postoperative hours. Analgesic consumption, patient-controlled analgesia demand and delivery ratios, time to first rescue analgesic request, the incidence of nausea and vomiting, and block-related complications such as arterial puncture, hematoma, paresthesia during injection and signs of local anesthetic systemic toxicity will be recorded during the 0 to 1, 1 to 3, 3 to 6, 6 to 12, 12 to 24 and 24 to 48 hour intervals. Total analgesic consumption over 48 hours will also be recorded. Before every regional block, the expiry date and availability of 20% lipid emulsion will be checked, and the anesthesia machine, circuit leak test, defibrillator and emergency drug trolley will be verified. The primary outcome will be cumulative morphine consumption during the first 24 postoperative hours. Secondary outcomes will include cumulative morphine consumption over 48 hours, pain scores at rest and on movement at each assessment point, time to first patient-controlled analgesia demand, total paracetamol consumption, incidence of postoperative nausea and vomiting and block-related complications.