This study was designed to evaluate the effect of scalp block combined with general anesthesia on the intraoperative consumption of fentanyl and time of extubation of patients undergoing elective craniotomy. Scalp block will be applied to three groups with differences of the administered solution to the scalp and one group will be placebo group.

Regional scalp block (RSB) is an established technique that involves infiltration of local anesthetic (LA) at well-defined anatomical sites targeting the major sensory innervation of the scalp. Regional techniques minimize anesthetic requirements and their effects may be beneficial. There is a lack of consensus and evidence concerning alternative analgesia strategies for cranial neurosurgery.

Patients undergoing elective craniotomy for tumor dissection will be randomly divided into four groups to receive scalp block as an adjuvant to general anesthesia. After a standard induction sequence using propofol, fentanyl and a single dose of rocuronium, patients will be intubated. Bilateral scalp block will be given immediately after induction, except patients in control group who will not have a scalp block. Drugs for scalp block will be 20ml ropivacaine 0.5%, 20ml xylocaine 1% and dexmedetomidine 1mcg/kg.Anaesthesia will be maintained with propofol and remifentanyl infusion. Intraoperatively, propofol infusion at 75 to 100 μg/kg/h up to dura closure and reduced to 50-75 μg/kg/h up to skin closure. Five minutes before head pinning scalp block was performed by blocking the supraorbital, supratrochlear, auriculotemporal, occipital, and postauricular branches of the greater auricular nerves.Routine monitoring of electrocardiogram, heart rate (HR), and mean arterial blood pressure (MAP) will record at two-minute intervals from the beginning of anesthesia until 10 minutes after incision, followed by 5-minute intervals throughout the remaining course of the surgery. Monitoring of the depth of anesthesia will also performed using the Bispectral Index. Sample size was calculated based on Type I error of α = 5% and power = 80% and minimum difference d = 30%, which is clinically significant in the pilot study. All quantitative variables will be reported as mean and standard deviation, and qualitative variables will be listed as number (percentage). Mann-Whitney test and Chi-square test will be used for comparison of endpoints. Linear mixed model will be used to evaluate the differences of hemodynamics variables. Statistical Package for Social Sciences (SPSS, version 19.0; SPSS Inc., Chicago, USA) will be used for all calculations. p values less than .05 will be considered significant.

Inclusion Criteria:

• patients with American Society of Anesthesiologists Physical status classification 1-3
• patients who are scheduled for elective craniotomy for brain tumor
• patients who have provided consent for participation in the study

Exclusion Criteria:

• Patients who have allergy to local anesthetics and dexmedetomidine
• Glasgow coma scale <15
• tumor>4cm
• any contraindication for receiving dexmedetomidine
• severe mental impairment
• pregnant women
• uncontrolled hypertension, arrhythmia, coagulation disorder