Comparison between adenosine and magnesium sulphate as adjuvants for transversus abdominis plane block: a prospective randomized controlled trial.

Background: Various adjuvants have been employed during different nerve blocks. We aimed to evaluate the effect of adding adenosine versus magnesium sulfate to bupivacaine on the quality and duration of transversus abdominis plane (TAP) block.

Methods: Participants were randomized to TAP block using either 20 mL of bupivacaine hydrochloride 0.375% + 12 mg adenosine in 2 mL of saline 0.9% (adenosine group), 20 mL of bupivacaine hydrochloride 0.375% + 500 mg magnesium sulphate in 2 mL saline 0.9% (magnesium group) or 20 mL of bupivacaine hydrochloride 0.375% + 2 mL saline 0.9% (control group). Primary outcome measure included postoperative pain as assessed by Visual Analog Scale (VAS) for pain scoring on movement and secondary outcomes included analgesia duration, postoperative morphine need and any adverse effects.

Results: VAS in adenosine and magnesium groups was significantly less than in control group at 6 and 12 hours postoperatively whereas it was comparable in adenosine and magnesium groups at all time points. Analgesia duration was significantly longer in adenosine and magnesium groups in comparison to the control group and it was relatively longer in the magnesium group when compared to adenosine group (401 vs. 447 vs. 320 minutes in adenosine, magnesium and control groups, respectively; P=0.003).

Conclusions: Both adenosine and magnesium improved the quality and duration of TAP block, but the duration was relatively longer with magnesium.