Dexmedetomidine Added to Ropivacaine Single Shot vs Continuous Interscalene Nerve Block

"For the single shot group with dexmedetomidine added to ropivacaine group (Group D), after local analgesia with 3 mL of 1% lidocaine, the block will be performed under ultrasound guidance using an in-plane approach with a 22 G 80-mm ultrasound needle (Pajunk SonoTAP II, Germany).~The perineural solution will be pre-mixed in a 30 mL syringe before the realization of the block.~A total of 150 mg of ropivacaine 0.5% will be prepared, 125 mg (25mL) will be mixed with a dose of 2 mcg/kg IBW of dexmedetomidine (100 mcg/mL dexmedetomidine hydrochloride; Precedex, Hospira Inc, Lake Forest, IL). The total of 25 mL (125 mg or ropivacaine 0.5%) with dexmedetomidine will be injected perineurally at the level of the roots and a 5 mL (25 mg) will be injected between the sternocleidomastoid muscle and anterior scalene for the superficial cervical plexus block."

The block will be performed under ultrasound guidance using an in-plane approach with a 17G Tuohy needle (Arrow FlexBlock). A total of 100 mg (20 mL) of ropivacaine 0,5% will be injected perineurally at the level of the roots using the Tuohy needle. The 19 G arrow catheter will then be introduced through the Tuohy needle and we will leave 4 cm of the catheter perineurally. An additional 25 mg (5 mL) of ropivacaine 0,5% will be injected using the catheter to make sure the catheter is in a correct position. An additional 5 mL (25 mg) of ropivacaine 0.5 % will be injected between the sternocleidomastoid muscle and anterior scalene for the superficial cervical plexus block using an ultrasound in-plane approach with a 22 G 80-mm ultrasound needle (Pajunk SonoTAP II, Germany) or with a standard 25G 1 1/2 inches needle. After the surgery, an infusion of ropivacaine 0,2% at a standard rate of 5 mL/h will be started using an elastomeric pump of 300 mL (Baxter Corporation, Mississauga, Ontario).