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Perineural dexamethasone added to local anesthesia for brachial plexus block improves pain but delays block onset and motor blockade recovery.

BACKGROUND
Multiple studies have shown that perineural dexamethasone improves postoperative analgesia. However, some studies have shown minimal benefit, and have raised concerns regarding adverse physio-chemical effects of perineural dexamethasone. Furthermore, there is a paucity of studies wherein control (IV) dexamethasone was considered.


OBJECTIVE
The purpose of this meta-analysis was to evaluate the effectiveness of different concentrations of perineural dexamethasone injection on postoperative analgesia, as well as complications from its use for brachial plexus blocks.


METHODS
A systematic literature search was conducted using the Cochrane Central Registry of Controlled Trials, PubMed, and Scopus. Trials comparing control and local dexamethasone-treated groups, and those which reported duration of analgesia and/or pain scores/opioid consumptions were selected. Meta-analysis was performed using the Review Manager (RevMan) software 5.1.


RESULTS
Fourteen studies consisting of a total of 1,022 patients were included. Perineural dexamethasone significantly prolonged the duration of postoperative analgesia in patients receiving both low-dose (4 - 5 mg) [SMD 2.41 (95% CI: 1.47, 3.35 P = 0<0.00001) I² = 82%], and higher-doses (8 - 10 mg) [SMD 4.46 (95% CI 3.54, 5.38 P < 0.00001) I² = 94%]. However, the duration of motor block was also prolonged [SMD 2.52 (95% CI: 1.06, 3.98 P = 0.0007) I² = 97%] and dexamethasone delayed latency of onset of sensory [SMD -0.49 (95% CI: -0.89, -0.09 P = 0.02) I² = 76%] and motor [SMD -0.56 (95% CI: -1.13, 0.00 P = 0.05) I² = 87%] blocks. Postoperative pain scores were improved at both 24 hours [SMD -1.46 (95% CI: -2.43, -0.50 P = 0.003) I² = 95%] and 48 hours [SMD -1.20 (95% CI: -2.26, -0.13 P = 0.03) I² = 95%] in dexamethasone-treated groups, whereas opioid consumption was reduced only at 48 hours [SMD -2.97 (95% CI: -4.17, -1.76 P < 0.00001) I² = 88%]. Complications were comparable between control and dexamethasone-adjuvant groups, except for the excessively prolonged nerve block that was observed predominantly in the dexamethasone-adjuvant group.


LIMITATIONS
The limitations include different definitions used for the measurements of certain parameters such as the duration of analgesia and duration of motor block, number of studies assessing certain parameters having high heterogeneity, and varying types of local anesthetics used in various studies.


CONCLUSIONS
Perineural dexamethasone addition to local anesthetic solutions significantly improved postoperative pain in brachial plexus block without increasing complications. However, perineural adjuvant dexamethasone delayed the onset of sensory and motor block, and prolonged the duration of motor block. Smaller doses of dexamethasone (4 - 5 mg) were as effective as higher doses (8 - 10 mg).