Effectiveness of low dose epidural magnesium sulphate in labour analgesia

Abstract

Magnesium sulphate is common adjuvant in central neuraxial blocks because of its analgesic action due to antagonistic action on N-methyl-D-aspartate receptors. It has been earlier used as epidural adjuvant in labour analgesia in dose of 50 mg. In current study magnesium sulphate was used epidurally in 25 mg dose and its effectiveness was assessed. The current randomized control trial, double blind study was conducted in 100 parturients, divided in group M and C with 50 in each. All the parturient received 15 microgm of fentanyl intrathecally and bolus dose of 8ml 0.1% bupivacaine epidurally followed by epidural infusion of 0.1% bupivacaine at rate of 8ml/hr. In addition to above, group M received 50mg of magnesium sulphate epidurally and group C received volume adjusted sterile saline. The pilot study conducted on 5 parturients, all parturients in group M developed motor block, which was attributed to magnesium sulphate so the dose of it decreased to 25 mg. The synergistic action of magnesium sulphate was evaluated by pain assessment by Visual analogue scale and number of breakthrough pain. The faster onset of analgesia and better pain relief was found in group M. The breakthrough pain was less in group M in both stage 1 and stage 2 of labour. The duration of labour, incidence of instrumentation, need of caesarean section and neonatal outcome were comparable in both the groups.Magnesium sulphate is an effective epidural adjuvant in labour analgesia even in 25mg dose without any adverse effect.