Effects of perineural administration of dexmedetomidine in combination with bupivacaine in a femoral-sciatic nerve block

Background and Aim: Perineural administration of dexmedetomidine, a a2-adrenoceptor agonist, prolongs the duration of analgesia. We hypothesized that adding dexmedetomidine to bupivacaine would prolong postoperative analgesia after below knee surgery. Materials and Methods: After ethical approval, 60 patients scheduled for below knee surgery under combined femoral-sciatic nerve block were randomly allocated into two groups to have their block performed using bupivacaine 0.5% alone (group B) or bupivacaine 0.5% combined with 100 mg bupivacaine-dexmedetomidine (group BD). Motor and sensory block onset times; durations of blockades and analgesia were recorded. Results: Sensory and motor block onset times were shorter by 20% in group BD than in group B (P < 0.01). Sensory and motor blockade durations were longer in group BD (45% and 40%, respectively) than in group B (P < 0.01). Duration of analgesia was longer in group BD by 75% than in group B (P < 0.01). Systolic, diastolic arterial blood pressure levels, and heart rate were significantly less in group BD, six patients in group BD, and no patients in group B developed bradycardia (P < 0.05). Conclusion: The addition of dexmedetomidine 100 mg to bupivacaine 0.5% during ultrasound-guided combined femoral and sciatic block for below knee surgery was associated with a prolonged duration of analgesia. However, this may be associated with significant bradycardia requiring treatment.