The Effect of Intrathecal Magnesium Sulphate on Bupivacaine-Fentanyl Subarachnoid Block for Infraumbilical Surgeries

Local anaesthetics with additives in a wide range, affect the versatility of spinal anaesthesia. Amongst a diverse class of drugs, phenylpiperidine derivative fentanyl, NMDA receptor blocker magnesium have been added as adjuvants to amide local anaesthetic hyperbaric bupivacaine for spinal anaesthesia in an attempt to prolong analgesia.METHODS70 patients of either gender were selected randomly and were divided into two groups of 35 each. Administered intrathecally in Group S (control) 12.5 mg of hyperbaric bupivacaine, 25 mcg of fentanyl, 1 mL of normal saline and in Group M (study) 12.5 mg of hyperbaric bupivacaine, 25 mcg of fentanyl, 50 mg of magnesium sulphate.RESULTSInsignificant haemodynamic variability was observed following the addition of magnesium to the spinal block agent. Onset (min.) of sensory block was 7.8 ± 1.2 in group M, 5.3 ± 1.0 in group S which was statistically significant with p-value of < 0.00001. Onset (min.) of motor block was 13.2 ± 1.5 in group M, 10.4 ± 2.1 in group S which was statistically significant (p- value < 0.00001). Duration of analgesia (min) was 290.3 ± 9.5 in group M and 261.3 ± 12.2 in group S which was statistically significant with p- value <0.00001. The recovery from the motor block (min) was 242.5 ± 9.4 in group M, 236.5 ± 5.5 in group S, the difference was statistically significant (p- value of 0.002). At 8th hr mean of VAS was 3.65 ± 0.90 in Group M, 4.62 ± 0.68 in Group S, statistically significant, with p-value of <0.00001CONCLUSIONSMagnesium added to hyperbaric bupivacaine with fentanyl for spinal anaesthesia significantly prolongs the onset and duration of analgesia, onset and recovery from motor block, less score of VAS, without significant haemodynamic variations and adverse effects.