Ketamine Versus Dexmedetomidine as an Adjuvant in Scalp Block in Supratentorial Brain Tumor Excision Surgeries

Overview

Supratentorial brain tumor surgeries are associated with significant nociceptive stimulation and postoperative pain, which may adversely affect patient outcomes. Scalp block has emerged as an effective regional anesthetic technique to improve analgesia and reduce opioid consumption. Objective: To compare efficacy of ketamine versus dexmedetomidine as adjuvants to bupivacaine in scalp blocks for supratentorial brain tumor surgeries, focusing on analgesia, opioid consumption, and hemodynamic stability. Methods: This randomized double-blinded controlled trial included 80 patients undergoing supratentorial tumor excision, allocated equally into two groups: Group K received bupivacaine with ketamine (2 mg/kg), and Group D received bupivacaine with dexmedetomidine (1 µg/kg). Intraoperative hemodynamics, fentanyl consumption, postoperative pain scores (NRS), analgesic requirements, and complications were assessed.

The study was designed as a prospective, double-blind, randomized controlled clinical trial to evaluate efficacy of Ketamine versus Dexmedetomidine as an adjuvant to Bupivacaine in Scalp Block in Adults undergoing Supratentorial Brain Tumor Excision Surgeries for Hemodynamic and Pain Control. The study was carried out in neurosurgery operating rooms at Cairo University Hospital, Faculty of Medicine, Cairo University. The study was approved by the Ethics Committee of Faculty of Medicine, Cairo University, MS-483-2025 Egypt. The trial was preregistered on clinicaltrials.gov, NCT06168903.Written informed consent was obtained from all patients. The Consolidated Standards of Reporting Trials (CONSORT) guidelines were adhered Informed written consent was obtained from each patient. There are adequate provisions to maintain participants' privacy and confidentiality of the data. Randomization will be performed using computer-generated numbers. Allocation concealment will be maintained using serially numbered, opaque, and sealed envelopes. Investigators will remain blind to the sequence, with group assignments contained in envelopes marked only with case numbers. Before each case, a study nurse or assistant will open the corresponding numbered envelope to reveal the patient's group assignment. * Dexmedetomidine (D):): Patients will receive a scalp block with a 20 ml syringe containing 1 mg/kg of 0.5% bupivacaine and 1 µg/kg of dexmedetomidine, with the remainder filled with saline. * Ketamine (K): Patients will receive a scalp block with a 20 ml syringe containing 1 mg/kg of 0.5% bupivacaine and 2 mg/kg of ketamine, with the rest filled with saline. The syringes will be prepared by an anesthesia technician and handed blindly to the anesthetist to administer the block. Study Protocol: Patients visited the pre-anesthesia room before the procedure. All patients received explanation of Numerical Rating Scale (NRS) for pain assessment, which ranges from 0 (no pain) to 10 (most severe pain) \[17\]. Standard monitoring was applied, including electrocardiography (ECG), non-invasive, invasive blood pressure, and Oxygen Saturation (SaO₂), and baseline vital signs were recorded, including heart rate, systolic and diastolic blood pressure, mean arterial pressure, and oxygen saturation. Anesthesia was induced with intravenous propofol 2 mg/kg, fentanyl 2 µg/kg, and atracurium 0.5 mg/kg, with mask ventilation for 3 minutes followed by tracheal intubation. Intraoperative signs of inadequate analgesia, such as tachycardia or hypertension exceeding 20% of baseline, were managed with additional 50 µg doses of fentanyl, and total fentanyl consumption was recorded. Anesthesia was maintained using intermittent positive pressure ventilation with isoflurane 0.8-1.2 MAC in an oxygen/air mixture, and atracurium infusion 0.5 mg/kg, while end-tidal CO₂ was monitored. After induction, bilateral scalp blocks were performed using a 23G needle, with local anesthetic infiltrated around supraorbital, supratrochlear, zygomaticotemporal, auriculotemporal, lesser occipital, greater occipital, and great auricular nerves, 2-3 mL per nerve. Scalp Block Techniques Supraorbital Nerve Block Patient was seated with the head slightly forward and eyes closed. The supraorbital notch was palpated, and a needle was inserted approximately 1 cm above the notch. 2 ml of local anesthetic were injected at this site. Supratrochlear Nerve Block With the patient in the same position, the injection site was located one finger's breadth medial to the supraorbital nerve. The needle was redirected medially, and 3 mL of local anesthetic was administered. Zygomaticotemporal Nerve Block The patient's head was turned so that the target side was facing upward. Landmarks included the orbital rim and zygomatic arch. A dual injection technique was used, with 1 mL injected deeply and 2 mL subcutaneously. Auriculotemporal Nerve Block The injection site was 1-1.5 cm anterior to the ear, above the tragus, taking care to avoid superficial temporal artery. 3ml of local anesthetic were injected subcutaneously. Greater Occipital Nerve Block With the head turned or the patient seated, the occipital artery was palpated, approximately 3-4 cm lateral to the external occipital protuberance. The needle was inserted perpendicular to the skin medial to the artery, and 3 mL of local anesthetic was injected subcutaneously. Lesser Occipital Nerve Block Injection site was located about 2.5 cm lateral to the greater occipital nerve block site. 3 ml of local anesthetic were administered subcutaneously. Great Auricular Nerve Block (Postauricular Branches) The injection site was 1.5 cm posterior to the ear at the level of the tragus. The needle was inserted perpendicular to the bone, withdrawn slightly, and 3 mL of local anesthetic was injected subcutaneously \[5\]. Hemodynamic Monitoring HR and BP were recorded baseline before induction, 1 and 5 minutes after induction, at intubation, 5 minutes after the scalp block, 5 minutes after pin insertion, 5minutes after skin incision, at 15min, 20min, 25min, 30min,35min, 40min,60min, 95min, 3hour, 4hour and after extubating as well as in post-anesthesia care unit (PACU) and upon arrival in surgical ICU. Deviations from baseline were managed according to protocol: * Bradycardia (\<20% below baseline) was treated with atropine 0.04 mg/kg * Hypotension (\<20% below baseline) with ephedrine 5 mg IV * Hypertension or tachycardia (\>20% above baseline) with fentanyl 50 µg IV. At the end of surgery, residual neuromuscular blockade was reversed using atropine 0.01 mg/kg and neostigmine 0.05 mg/kg. Extubating was performed when the patient met standard criteria, including a Glasgow Coma Scale \>8, adequate cough and gag reflex, sufficient motor strength, a train-of-four (TOF) ratio \>0.9, ability to hold head tilt or hand grip for 5 seconds, adequate tidal volume and oxygenation and hemodynamic stability. In PACU, standard monitoring was continued, pain was assessed using NRS. Patients were discharged when modified Aldrete Score exceeded 9 \[18\]. Paracetamol and ketorolac were given as rescue analgesia when NRS score was more than 4. The time from extubating to the first analgesic request was recorded, and total postoperative analgesic consumption was documented. Any hemodynamic instability, including hypertension, tachycardia, bradycardia, or hypotension, as well as nausea, vomiting, and other complications, were recorded. Hemodynamic monitoring (MAP in mmHg) was Pain assessment using NRS (0-10) was conducted upon PACU arrival, 2, 4, 6, 8, 12and 24 hours postop