Magnesium in brachial plexus blocks: A meta-analysis, meta regression, and trial sequential analysis

Area of Science:

• Anesthesiology
• Pharmacology

Background:

• The efficacy of magnesium sulphate (MgSO4) in accelerating sensory block onset for brachial plexus blocks (BPBs) remains debated.
• This meta-analysis investigates the impact of MgSO4 as an adjunct to local anesthetics (LA) in BPBs.

Purpose of the Study:

• To evaluate the effect of adding MgSO4 to LA on the onset time of sensory block in BPBs.
• To assess secondary outcomes including sensory and motor block durations, and analgesia duration.

Main Methods:

• A systematic meta-analysis of randomized clinical trials comparing MgSO4 with control in BPBs.
• Searches included Medline, Embase, Google Scholar, and bibliographies.
• Primary outcome: sensory block onset. Secondary outcomes: block durations and analgesia duration. Random-effects model and subgroup analysis by MgSO4 dose were used.

Main Results:

• MgSO4 significantly accelerated the onset of sensory block (SMD = -1.00) and motor block (SMD = -1.15).
• MgSO4 prolonged the duration of analgesic effect (SMD = 4.22).
• Higher MgSO4 doses (>200 mg) showed prolonged sensory and motor block durations and longer analgesia compared to lower doses (≤200 mg).

Conclusions:

• Adding MgSO4 to LA in BPBs results in a faster onset of sensory block.
• MgSO4 also enhances the duration of analgesia, with doses ≤200 mg potentially offering optimal benefits.