Dexametasone Versus Dexametasone Plus Dexmedetomidine in Nerve Blocks

This study will compare perineural dexamethasone 2mg and perineural mixture of dexamethasone 2mg plus dexmedetomidine 50mcg DX plus DXD as adjuvants to local anesthetics for ultrasound-guided infraclavicular brachial plexus blocks (ICBs). The protocol is designed as a superiority trial and hypothesizes that the mixture of both drugs results in longer block duration. Furthermore, since analgesic and sensory duration can be influenced by the intake of pain medications and surgical trauma to small cutaneous nerves, respectively, motor block duration was selected as the main outcome to better target the action of both adjuvants on the brachial plexus.

With the approval of Ethics Committee of the Hospital Clínico Universidad de Chile, a total of 50 patients undergoing upper extremity surgery (elbow and below) will be recruited. Recruitment will be carried out by an investigator not involved in patient care in the preoperative clinic or during routine preoperative visits.

All ICBs will be supervised by one of the coauthors and conducted preoperatively in an induction room.

After skin disinfection and draping, the ICB will be performed with a previously described technique. In both groups, a proven 90% effective volume of 35 mL of local anesthetic solution will be injected. As LA solution, it will be used a mixture of lidocaine 1.0%-bupivacaine 0.25% with epinephrine 5 µ/mL. The injectate will be slowly injected through the block needle.

Patients will be randomized to receive the study drug, either PN 2 mg dexamethasone or a combination of PN 2 mg dexamethasone with 50 ug dexmedetomidine, mixed with the above-mentioned LA solution.

A research assistant (licensed anesthesiologist) will prepare the local anesthetic solutions and will add the study drug following the randomization order. The operator, patient and investigator assessing the block will be blinded to group allocation.

The primary outcome will be the duration of the motor block (defined as the temporal interval between the end of LA injection through the block needle and the return of movement to the hand and fingers) for patients with successful ICBs. Patients will be provided with a data sheet and asked to record the time at which motor function returns. An investigator blinded to group allocation will collect this data sheet in person (inpatients) or by phone (outpatients) on postoperative day 1.

Eligibility Criteria:
Inclusion Criteria:

* American Society of Anesthesiologists classification 1-3
* Body mass index between 20 and 35

Exclusion Criteria:

* Adults who are unable to give their own consent
* Pre-existing neuropathy (assessed by history and physical examination)
* Coagulopathy (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. platelets ≤ 100, International Normalized Ratio ≥ 1.4 or prothrombin time ≥ 50)
* Renal failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. creatinine ≥ 100)
* Hepatic failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. transaminases ≥ 100)
* Allergy to local anesthetics (LAs)
* Pregnancy
* Prior surgery in the infraclavicular region
* Chronic pain syndromes requiring opioid intake at home