A Randomized Comparison Between 0.67 mcg/kg, 1 mcg/kg, and 1.33 mcg/kg of Perineural Dexmedetomidine for Ultrasound-Guided Infraclavicular Block

Inclusion Criteria: * patients undergoing upper limb surgery at or below the elbow * age between 18 and 75 years * American Society of Anesthesiologists classification 1-3 * body mass index between 18 and 35 kg/m2 Exclusion Criteria: * adults who are unable to give their own consent * allergy or contraindication to dexmedetomidine * exposure to dexmedetomidine during the previous 48 hrs * pre-existing neuropathy (assessed by history and physical examination) * coagulopathy (assessed by history and physical examination and, if deemed clinically necessary, by blood workup i.e. platelets ≤ 100, International Normalized Ratio ≥ 1.4 or partial prothrombin time ≥ 50) * renal failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work-up i.e. creatinine. eGFR \< 90) * hepatic failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work-up i.e. transaminases ≥ 100) * allergy to LA * pregnancy (as institutional policy, female patients with childbearing potential undergoing non urgent surgery are tested preoperatively for pregnancy with blood tests) * breast feeding * prior surgery in the infraclavicular region * chronic pain syndromes requiring opioid intake at home