What is a peripheral nerve block?
A nerve block prevents or relieves pain by interrupting pain signals that travel along a nerve to the brain. It involves an injection of local anaesthetic (a numbing agent) around a nerve either during or immediately after surgery. Pain relief from nerve block may last only a few hours after surgery, after which people may experience moderate to severe pain.
What is dexamethasone?
Dexamethasone is a steroid that may reduce pain and the inflammatory response to tissue damage after surgery (heat, pain, redness and swelling). In people receiving nerve block, dexamethasone may be given with the local anaesthetic around the nerve (perineural) or into a vein (intravenous) to prolong the pain relief from the peripheral nerve block.
What did the researchers investigate?
We looked for randomized controlled trials that investigated whether perineural or intravenous dexamethasone prolongs the length of time people experience pain relief from the peripheral nerve block when undergoing upper and lower limb surgery and reduces the intensity of pain after surgery. We also investigated whether perineural or intravenous dexamethasone cause any side effects or harms. We searched the medical literature for articles that included either adults or children undergoing upper or lower limb surgery with peripheral nerve block published up until 25 April 2017. We also assessed the quality of evidence for each outcome.
What did the researchers find?
We included 35 studies involving 2702 aged 15 to 78 years.
When compared with placebo, the duration of sensory block was prolonged in the perineural dexamethasone group by 6 and a half hours (27 studies, 1625 participants, low-quality evidence) and in the intravenous dexamethasone group by six hours (8 studies, 499 participants, moderate-quality evidence). When perineural and intravenous dexamethasone were compared, the duration of sensory block was longer in the perineural dexamethasone group by three hours (9 studies, 720 participants, moderate-quality evidence).
Postoperative pain intensity at 12 hours after surgery was lower in the perineural dexamethasone group compared with placebo (5 studies, 257 participants, very low-quality evidence) and at 24 hours after surgery (9 studies, 469 participants, low-quality evidence). When we compared intravenous dexamethasone with placebo, postoperative pain intensity was also lower in the intravenous dexamethasone group than in the placebo group at 12 hours (3 studies, 162 participants, low-quality evidence) and 24 hours (5 studies, 257 participants, low-quality evidence). The amount of opioid pain medication required was also lower in participants receiving perineural and intravenous dexamethasone. There was no difference in postoperative pain intensity or the amount of opioid pain medication required when perineural and intravenous dexamethasone were compared. We concluded that one way of administering dexamethasone does not provide better pain relief over the other.
Five serious adverse events were reported in three studies. One block-related adverse event (pneumothorax or collapsed lung) occurred in one participant in a trial comparing perineural dexamethasone and placebo; however group allocation was not reported. The remaining events were non-block-related and occurred in two trials comparing perineural dexamethasone, intravenous dexamethasone and placebo. Two participants in the control group required hospitalization within one week of surgery; one for a fall and one for a bowel infection. One participant in the placebo group developed a chronic pain syndrome called Complex Regional Pain Sydrome, and one participant in the intravenous dexamethasone group developed pneumonia. The quality of evidence for safety issues was very low.