The Optimal Time of IV Dexamethasone Administration for Prolongation of Peripheral Nerve Block

Overview

The purpose of this study is to determine the optimal timing of IV dexamethasone for prolongation of ultrasound (US) guided supraclavicular brachial plexus block (SCB) in patients undergoing unilateral hand or forearm surgery at the Toronto Western Hospital. Investigators seek to answer which timing of IV dexamethasone will provide the maximum block prolongation. Investigators hypothesize that IV dexamethasone administered either before or after the block will further extend the duration of analgesia provided.

This is a prospective double-blind randomized trial to evaluate the optimal timing of IV dexamethasone. All patients undergoing isolated hand or forearm surgery under anesthetic will be approached to participate. The patients will be consented on the day of surgery; all patients will be fully informed of the procedures involved in the study. Once the patient has consented to the study, they will be randomized to receive dexamethasone at one of four different times: 1 hour before the block, during the block, 1 hour after the block and 2 hours after the block. In accordance with routine pre-block management, non-invasive blood pressure, electrocardiogram and pulse oximetry will be applied and intravenous access secured on the non-operative side for infusion of a 0.9% saline solution. Prior to block performance all patients will receive intravenous midazolam 1 - 4mg IV and / or fentanyl 25mcg IV for anxiolysis and analgesia, respectively, as needed. The US-guided SCB will be performed under sterile conditions by a staff regional anesthetist, regional anesthesia fellow or a directly supervised resident with experience of at least 10 US-guided SCB performed for each approach. Ultrasound examination above the clavicle will be performed using a high frequency linear probe (5 - 12 MHz range) with either a Philips, Sonosite or GE ultrasound machine. The brachial plexus, subclavian artery, first rib and pleura will be identified in the supraclavicular fossa. A 22 - gauge insulated 50mm needle (Stimuplex, Braun Medical, Bethlehem, PA) will be introduced in plane with the US and advanced to puncture the brachial plexus sheath. Typically this is accompanied by a palpable 'fascial click'. A small amount (0.5-1ml) of local anesthetic will be incrementally injected for needle tip hydro-location and/or hydro-dissection at the discretion of the operator. After placing the needle tip near the intersection of the first rib and the lateral aspect of the subclavian artery ('corner pocket') 30mls of 0.5% bupivacaine will be injected incrementally in 5ml aliquots with intermittent aspiration for blood. A blinded research associate will evaluate sensory loss and motor blockade every 5 minutes until surgery starts. Supplemental mask oxygen IV fluid replacement and full monitoring will be continued intraoperatively. Intravenous sedation will be used at the discretion of the attending anesthetist and according to the patient's wishes as is the standard of care at our institution. The dose of sedative and / or analgesic drugs will be recorded. Attendants will be asked to avoid any intraoperative steroid therapy. Surgical duration will be recorded for comparative analysis and exclusion of cases \<30 or \>180 minutes. Following surgery, patients will be transferred to the post-operative care unit (PACU) or fast-tracked for discharge directly from the day case unit. The onset time of surgical pain (if applicable) and first analgesic request will be recorded. Once oral intake is established, patients will receive one of two analgesic preparations as needed; Tylenol#3® (acetaminophen 300mg/codeine 30mg/caffeine 15mg per tablet) or Percocet® (acetaminophen 325mg/oxycodone HCl 5mg) if intolerant to codeine. Patients will be evaluated at 1 and 2 hours postoperatively noting pain scores, analgesics received, block density and recovery criteria. On discharge from hospital, patients will receive a prescription of Tylenol#3® as needed or Percocet® if intolerant to codeine. Patients will be given a home diary to complete. Patients will be requested to record the time at which they first experience pain at the surgical site, the time of first analgesic use and the time when they regain normal (or baseline equivalent) strength in their fingers. Patients will be asked to complete diary entries at 8 hrs, 24hrs, 48hrs and 7 days post operatively. They will be asked to document their visual analogue (VAS) pain score, cumulative analgesic consumption, side effects (numbness / tingling in the operative arm, weakness in the operative arm, pain around the injection site, bruising around the injection site, nausea and vomiting) and current VAS for satisfaction pertaining to the analgesia received. Patients will be telephoned at the aforementioned times to collect data from the diary, which was found the most reliable method of data collection during a previous study. Finally, patients will be phoned at 3 months to ensure no long - term numbness or weakness related to the nerve block. The doses of oral codeine or oxycodone consumed by each patient will be converted into equi-analgesic doses of oral morphine sulphate in order to facilitate comparison between groups. Sample size for the study: A total of 220 participants will be randomized to receive dexamethasone at one of four different time points: 1 hour before the block, during the block, 1 hour after the block and 2 hours after the block.