This study will compare three different doses of perineural dexmedetomidine 0.67 mcg/kg, 1 mcg/kg, and 1.33 mcg/kg as adjuvants to local anesthetics for ultrasound-guided infraclavicular brachial plexus blocks (ICBs). Our research hypothesis is that 1.33 mcg/kg will provide a 15%-longer duration than 1mcg/kg, which in turn will provide a 15%-longer duration than 0.67 mcg/kg. Since analgesic duration and sensory duration can be influenced by intake of pain medications and surgical trauma to small cutaneous nerves, respectively, we will select motor block duration as the main outcome to better target the action of dexmedetomidine on the brachial plexus.
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
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)
Parallel
dexmedetomidine (perineural) 0.67 mcg/kg
DrugPerineural dexmedetomidine 0.67 mcg/kg will be added to the local anesthetic used to block the cords of the brachial plexus with an infraclavicular approach.
dexmedetomidine (perineural) 1 mcg/kg
DrugPerineural dexmedetomidine 1 mcg/kg will be added to the local anesthetic used to block the cords of the brachial plexus with an infraclavicular approach.
dexmedetomidine (perineural) 1.33 mcg/kg
DrugPerineural dexmedetomidine 1.33 mcg/kg will be added to the local anesthetic used to block the cords of the brachial plexus with an infraclavicular approach.
Motor block duration
The elapsed period in minutes between the ending time of the local anesthetic injection and the time of return of hand and fingers movement
Sensory block duration
The elapsed period in minutes between the ending time of the local anesthetic injection and the time of the return of hand and fingers sensation
Analgesic block duration
The elapsed period in minutes between the ending time of the local anesthetic injection and the time of the first sensation of pain in the surgical area
Block performance time
Sum of: 1- the acquisition time of the ultrasonographic image. and 2- the time to perform the block itself (from the skin anesthesia to the end of local anesthetic injection)
Intensity of pain during block procedure
Evaluated with the Numeric Rating Scale for Pain. This scale is graduated from 0 to 10 points. A 0-point score represents the absence of pain, and a 10-points score represents the worst imaginable pain. Patients will be asked to rate their pain verbally with this scale. The blinded assessor will register the score reported.
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