There arc a number of reasons thai there is growing interest in the umc of alpha 2-adrcnoeeptor agonists as sedatives. One is the availability of a drug with a shorter half-life (dexmedetomidinc). Secondly, in addition to sedation, there arc oilier favorable effects of alpha 2-adrenoceplor agonists, e.g., analgesia and maintained cardiorespiratory function. Finally, antagonists to the effects of alpha 2-adrenoceptor agonists have been described that make quick reversal of sedation an option. A randomized study was designed to compare dexmedetomidine as a primary sedative agent with a commonly used drug in patients undergoing awake carotid endarterectomy (CEA). Forty patients (ASA class 1I-IV) undergoing elective carotid endarterectomy were included in the study. Patients were randomized into two groups (Group Dex and Group P), to receive either dexmedetomidine or propofol. Patient in Group Dex , received a bolus of 1 pg/kg dexmedetomidine over ten minutes. After the bolus, the infusion was set at 0.2-0.7 pg /kg /hr. Patient in Group P received propofol I mg/kg/h . Sedation level was assessed using Observer's Assessment of Alertness-Sedation [OAA/S] scale. The primary outcomes were defined as the number of patients with an OAA/S score of 4 intraoperatively and an OAA/S score of 5 postoperatively. Cardiorespiratory parameters were compared, as well as pain score and additional analgesia, intra- and postoperative side effects, and complications. Chi-square tests were used to analyze the primary endpoints. All secondary parameters were analyzed using the Wilcoxon rank sum test. P< 0.05 considered significant. There were no differences in respiratory end points between treatment groups in the intraoperative period. Patients receiving dexmedetomidine had significantly lower heart rates compared with the propofol group (P < 0.05). Arterial pressures in the two groups were similar at baseline and over the study period. Five patients in the dexmedetomidine group (25%) (P< 0.001) had an OAA/S score of 4 at all six time points assessed intraoperatively, while no patient in the control group had a score of 4 at all the time points considered. Ten patients (50%) (P<0.01) in the dexmedetomidine group had a score of 4 at three or more time points compared with four patients (20%) in the control group, five patients in the control group (25%) and one patient in the dexmedetomidine group (5%) (P< 0.05) did not achieve a score of 4 at any of the six critical intraoperative time points. More patients in the propofol group required treatment with Nitroglycerin 1-5 mg/h (45% vs 12%, P < 0.01) for control of hypertension. Postoperatively .there were no differences in arterial pressures between the groups for this period and no rebound phenomena were seen. The patients sedation for their surgical procedure was equally satisfactory between treatment groups. During recovery, patients who had received dexmedetomidine during the surgery had significantly smaller needs for rescue analgesia by 50% (P< 0.01) compared with the Propofol-Treated group. In conclusion the present study show that the use of dexmedetomidine in patients undergoing carotid endarterectomies under superficial cervical plexus block resulted in fewer fluctuations from the desired sedation level. Patients receiving dexmedetomidine required less andhypertensive therapy compared with patients receiving propofol.
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