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Acute Pain | Chronic Pain | General

Analgesic adjuncts for brachial plexus block

Clinical bottom line:

There is no convincing evidence from this review that adjunct analgesics are of any benefit.

Brachial plexus nerve blocks with local anaesthetic may be used for relief of postoperative pain. Combination of local anaesthetic with other drugs has the goal of prolonging analgesic effect with the disadvantage of systemic effects or prolonged motor block. It may also allow for a reduction in the amount of local anaesthetic used.

A major methodological is detecting whether adjunct drugs produce their action through a local effect, or through a systemic effect after absorption from the injection site. For this reason, the use of a systemic control group is regarded by many as a methodological necessity.

Systematic review

DB Murphy, CJ McCartney, VW Chan. Novel analgesic adjuncts for brachial plexus block: a systematic review. Anesthesia & Analgesia 2000 90: 1122-1128.

Date review completed: December 1999

Number of trials included: 17

Number of patients: 796

Control group: various, including five with systemic analgesic control group

Main outcomes: postoperative pain measures

Inclusion criteria were studies analysing the effect of novel analgesic adjuncts in brachial plexus block. Only prospective, randomised, double-blind and controlled studies were selected. Studies also had to have a measure of postoperative pain.

Searching included MEDLINE and EMBASE to December 1999 using a variety of MeSH terms including brachial plexus or nerve block and the names of a variety of drugs likely to be used as analgesic adjuncts.

Studies were classified as supportive if the analgesic adjunct demonstrated significant analgesic benefit versus control and negative if they did not.


There were 17 studies in a variety of surgical settings. Blocks were by axillary (11), supraclavicular (5) and interscalene (1) approaches. Opiates were used in 13 study arms, clonidine in six and neostigmine in one. The studies were small. There were 47 different treatment arms in 17 studies, with an average of only 17 patients per treatment arm. Five studies included a systemic analgesic control group.

Twelve of the studies were supportive, but only three had a systemic control group. Two of the three negative studies had a systemic control group.

For opioids in 10 studies, six were supportive and four negative. Two studies with a systemic control group were supportive, and two negative.

For clonidine in six studies, five were supportive and one negative. One study with a systemic control group was supportive.

The single study with neostigmine was negative. It did not have a systemic control group.


Though properly randomised and double blind, the trials were predominantly (12/17) methodologically flawed because they lacked a systemic control group and all were small. There is no convincing evidence from this review that adjunct analgesics are of any benefit.