Effect of Low Dose Midazolam with Low Dose Dexmedetomidine on Bradycardia and Sedation after Spinal Block: A Prospective Case Control Study

Introduction: Sedation makes it convenient for the patient, the anaesthesiologist and the surgeon during surgeries under regional anaesthesia. Midazolam in doses of 0.05mg/Kg produces good sedation and excellent amnesia but has no specific analgesic properties and causes depression of upper airway muscle tone in the elderly, resulting in a higher incidence of airway obstruction. Midazolam is commonly used drug for sedation during regional anaesthesia, which produces good sedation and excellent amnesia but causes upper airway obstruction and respiratory depression. Dexmedetomidine has been used as a sedative for various surgical and medical procedures, but loading dose of 1μg/kg has been associated with higher incidences of bradycardia, whereas lower doses produce inadequate sedation. Aim: To evaluate the effect of low dose midazolam on bradycardia and sedation during low dose dexmedetomidine infusion after spinal block. Methodology: In this prospective case control study, 80 patients undergoing surgeries under spinal anaesthesia were studied under two groups, Group D (n=40) who received 1mcg/kg dexmedetomidine as loading dose and Group DM (n=40) who received inj.midazolam 0.025mg/kg along with 0.5mcg/kg dexmedetomidine as loading dose. Both the groups were maintained by continuous infusion of dexmedetomidine at 0.04mcg/kg//hr. All patients were monitored for heart rate, mean arterial pressure, respiratory rate, oxygen saturation, Observer's Assessment of Alertness/Sedation Scale (OAA/S) and complications. Results: Mean heart rate was significantly lower in group D compared to group DM after 5 and 10 min of loading (P < 0.0001). Incidence of bradycardia requiring Atropine was significantly higher (P=0.0011)in group D (22/40) than group DM (7/40). OAA/S score was significantly lower in group DM at 5 minutes (P=0.0049) and 10 minutes (P=0.0004). Other hemodynamic variables were comparable in both groups. Conclusion: Low dose Midazolam with low dose Dexmedetomidine offered better results for bradycardia and sedation compared to routine dose of Dexmedetomidine alone.