Tehran University of Medical Sciences Archives of Anesthesiology and Critical Care 2423-5849 9 1 2023 02 08 59 63 Ahmad Egbali Department of Anesthesiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Amir Shafa Department of Anesthesiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Seyed Sajjad Razavi Department of Anesthesiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Alireza Mahdavi Department of Anesthesiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Tahere Chavoshi Department of Anesthesiology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. 2022 04 24 2022 05 28 Background: This study aimed to compare the effect of dexmedetomidine-fentanyl (DF) and midazolam-ketamine (MK) combination on the level of sedation in children undergoing bone marrow biopsy. Methods: This study was a single-blind randomized clinical trial. The patients were divided into two groups of 35. Five minutes before undergoing bone marrow biopsy, the first group underwent sedation with a combination of 0.1 mg/kg midazolam with 1 mg/kg ketamine, and the second group underwent sedation with a combination of 2 μg/kg dexmedetomidine with 1 μg/kg fentanyl. The mean arterial pressure (MAP), heart rate, SpO2, the level of sedation, and the incidence rates of complications were recorded in both groups and compared to each other. Results: There was no significant difference between the two groups in terms of age (P= 0.687), gender (P= 1.00), and weight (P= 0.839). However, there was a significant difference in the average length of stay in recovery (P= 0.015) and surgeon satisfaction (P= 0.000), with a longer recovery period in the midazolam-ketamine (MK) group. The Repeated measures ANOVA showed significant differences in heart rate (P= 0.008), sedation score (P = 0.038), and the percentage of oxygen saturation (P= 0.00) during surgery. Conclusion: The combination of dexmedetomidine and fentanyl (DF) compared to the combination of midazolam and ketamine (MK) can provide more patient sedation and surgeon satisfaction along with more stable hemodynamics for patients undergoing bone marrow biopsy. https://aacc.tums.ac.ir/index.php/aacc/article/view/528