Tehran University of Medical Sciences Archives of Anesthesiology and Critical Care 2423-5849 0 0 2025 12 29 1395 1395 Mojgan Rahimi Department of Anesthesiology and Intensive Care, Imam Khomeini Hospital Complex, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Mohamad Sorani Department of Anesthesia, School of Allied Medicine, Tehran University of Medical Sciences, Tehran, Iran. Afzal Shamsi Department of Anesthesia, School of Allied Medicine, Tehran University of Medical Sciences, Tehran, Iran. Myasar Mohamad Department of Anesthesiology and Intensive Care, Al-Shifaa Private Hospital, College of Mediicne, University of Diyala, Diyala, Iraq. Noah Awad Hussain Department of Anesthesiology and Intensive Care, Al-Shifaa Private Hospital, College of Mediicne, University of Diyala, Diyala, Iraq. 2025 09 03 2025 09 14 Background: Spinal anesthesia is a very commonly used procedure in modern-day anesthesia practice. Today most of the lower limb surgeries are performed under spinal anesthesia. Midazolam, dexmedetomidine, and fentanyl are common intravenous adjuvants used during anesthesia to allay anxiety and sedation. The aim of this study was to compare the effects of intravenous dexmedetomidine-midazolam versus fentanyl-midazolam in terms of analgesic characteristics, sedation, and adverse effects. Methods: This is a randomized prospective study that included 35 patients in each group, posted for lower limb orthopedic surgery. Intravenous dexmedetomidine, fentanyl, and midazolam were administered after subarachnoid block. Data for sedation, analgesia, hemodynamic parameters, and adverse effects were recorded. Results: RR for FM group showed significant intra-group variability in RR across perioperative stages (p<0.05), whereas the DM group maintained greater respiratory stability (p=0.243). HR for DM group exhibited significantly lower intraoperative and postoperative HR compared to FM group (p<0.001), with notable within-group changes, unlike the FM group. MAP for both groups remained stable over time (DM: p= 0.283, FM: p= 0.260), although the FM group had slightly higher values in the postoperative recovery phase. Sedation (RSS): DM produced deeper and more sustained sedation intraoperatively and postoperatively (p<0.001), while FM showed quicker sedation decline. Patient satisfaction was significantly higher in the DM group (VAS: 3.0 vs. 4.0, p= 0.001), although surgeon satisfaction did not differ notably. Adverse events were rare and comparable, though hypotension was more frequent in the DM group (22.9% vs. 8.6%). Conclusion: Dexmedetomidine plus midazolam provided superior sedation quality and patient satisfaction, with more stable cardiopulmonary parameters during orthopedic surgery under spinal anesthesia. Despite a slightly higher rate of hypotension, DM appears to offer a more favorable sedative profile compared to fentanyl plus midazolam. https://aacc.tums.ac.ir/index.php/aacc/article/view/1395