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A patient is scheduled for forearm surgery to be performed under an axillary plexus block using ropivacaine. Based on the results of a recent study, which of the following is MOST likely to occur with the addition of intravenous dexamethasone to an axillary plexus block?
(A) Shorter time to motor recovery
(B) Shorter time to sensory recovery
(C) Longer time to first analgesic intake
(D) Greater postoperative analgesic drug use
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Discussion
Dexamethasone has been described as an adjuvant that prolongs the duration of several types of peripheral nerve blocks. Its effect may vary based on several factors, including the type of block, the local anesthetic used, and whether it is administered perineurally or intravenously (IV). A recent study assessed the impact of IV dexamethasone on an axillary plexus block with ropivacaine. This study was timely as concerns have been raised recently regarding the safety of off-label use of perineural dexamethasone.
The axillary brachial plexus block with dexamethasone (ADEXA) study was a double-blind, randomized, placebo-controlled study of 98 patients scheduled for hand or forearm surgery. Patients were randomized to receive an IV bolus of either 8 mg/2 mL of dexamethasone or 2 mL of saline (control group) at the time of axillary plexus block placement. The syringe with either dexamethasone or saline was prepared by an independent staff member; thus, its content was blinded to both the investigator and patient. For the axillary plexus block, 0.125 mL/kg of 0.475% ropivacaine was injected under ultrasound guidance (to a maximum of 40 mL). No additional intraoperative analgesic was used.
A total of 100 patients were initially enrolled, resulting in 50 patients randomized to each study group. However, 2 patients in the dexamethasone group were excluded from the final analysis because of either consent withdrawal or lack of study drug availability. The primary outcome was the time of first analgesic administered after axillary plexus block. Secondary outcomes included motor and sensory block duration, use of postoperative analgesics during the initial 48-hour postoperative period, and block-related complications.
A total of 6 patients (12.5%) in the dexamethasone group and 2 patients (4%) in the control group required no additional analgesic dose in the first 48 hours postoperatively. Of the remaining patients, the time to first analgesic intake after axillary plexus block was longer in the dexamethasone group than in the control group (20.9 vs 14.7 hours, respectively). Times to motor and sensory recovery were also longer in the dexamethasone group compared with those in the control group. Fewer patients in the dexamethasone group required analgesic drugs (acetaminophen, ketoprofen, or tramadol) in the first 48 hours postoperatively compared with those in the control group. Blood glucose levels 2 hours after axillary plexus block were higher in the dexamethasone group, although the difference between groups was unlikely to be clinically important.
In summary, the addition of IV dexamethasone to an axillary plexus block significantly prolongs block duration and therefore reduces postoperative analgesic use. Further studies are necessary to delineate weight-based dosing of dexamethasone, as well as to evaluate the impact of using lower doses of local anesthetic agents.
Reference
1. Clement JC, Besch G, Puyraveau M, et al. Clinical effectiveness of single dose of intravenous dexamethasone on the duration of ropivacaine axillary brachial plexus block: the randomized placebo-controlled ADEXA trial. Reg Anesth Pain Med. 2019;44(3):370-374. doi: 10.1136/rapm-2018-100035.
