Comparative Efficacy of Two Different Dosages of Intrathecal Magnesium Sulphate Supplementation in Subarachnoid Block

Abstract

INTRODUCTIONRegional anaesthesia is a safe, inexpensive technique, widely used for lower limb orthopaedic surgery due to the advantage of prolonged post-operative pain relief. Combination with adjuncts [1][2][3][4][5] like epinephrine, clonidine, neostigmine, opioids, midazolam and magnesium [6][7][8][9][10][11][12][13][14][15][16][17][18][19] have been used to prolong analgesia and reduce the incidence of adverse events. These spinal adjuvants allow the use of lower dose of local anaesthetic agents, prolong and intensify the subarachnoid block and offer hemodynamic stability. Opioids such as fentanyl are commonly used as additive to local anaesthetics to prolong the duration and intensify the effects of subarachnoid block. However significant side effects of opioids such as pruritis, urinary retention, respiratory depression, hemodynamic instability and occasionally severe nausea and vomiting may limit their use. Newer methods of prolonging the duration of subarachnoid block and reducing post-operative analgesic requirements are of special interest in major surgical procedures.One of the mechanisms implicated in the persistence of postoperative pain is central sensitization, which is an activity-dependent increase in the excitability of spinal neurons . Central sensitization has been shown to depend on the activation of dorsal hornNmethyl-D aspartate (NMDA) receptors by excitatory amino acid transmitters such as aspartate and glutamate. NMDA receptor antagonists prevent central sensitization induced by peripheral nociceptive stimuli by blocking dorsal horn NMDA receptor activation. Magnesium (Mg 2+) is a non-competitive N-methyl-Daspartate (NMDA) receptor antagonist that blocks ion channels in a voltage dependent fashion. Koining reported that intravenous magnesium administration led to significant reduction in fentanyl consumption in peri and post-operative periods. Studies have evaluated use of magnesium intrathecally and shown to prolong the action of subarachnoid anaesthesia [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. However, most of these studies used an opioid along with magnesium, which could have contributed to the prolongation of blockade after subarachnoid block [6-13], Magnesium alone with LA in a dose of 50 mg and maximum upto 100 mg has been used in a few studies [14][15][16][17][18][19]. Although the results of adding MgSO 4 50 mg to IT bupivacaine are conflicting, the effect of increasing the dose of additional MgSO 4 has not been fully investigated. We used a dose of about 0.7mg/ kg (50 mg) to ≤ 1mg/kg (75 mg) of intrathecal magnesium and found similar results. The primary outcome was the duration of spinal anaesthesia, beginning of sensory and motor block, time to maximal sensory block, and duration of sensory and motor block. The secondary outcomes included hemodynamic variations and post-operative analgesic requirements . MATeRIAlS AND MeThODSWe conducted a randomized double blind study on 90 patients of either sex, belonging to ASA physical status I and II scheduled for orthopaedi...

Intrathecal magnesium sulfate does not reduce the ED50 of intrathecal hyperbaric bupivacaine for cesarean delivery in healthy parturients: a prospective, double blinded, randomized dose-response trial using the sequential allocation method

“…Several previous studies [13, 19, 21, 22] reported that the duration of spinal anesthesia was significantly prolonged by intrathecal magnesium sulfate, which is consistent with the findings in the present study. The present study also showed that adding magnesium sulfate intrathecally could significantly prolong the duration of spinal anesthesia with bupivacaine and sufentanil (184 min vs 148 min, P  < 0.001).…”

“…The ED 50 of intrathecal hyperbaric bupivacaine for cesarean delivery, determined using Dixon and Massay up-down sequential method [19, 20], was 4.7 mg (95% CI, 4.4–5.0 mg) in the Control group, and 4.9 mg (95% CI, 4.6–5.2 mg) in the Magnesium group. There was no significant difference in the ED 50 of bupivacaine between the Magnesium group and the Control group ( P  = 0.53).…”

Comparison of two different doses of magnesium sulphate for spinal anaesthesia: a prospective, randomized double-blind study

“…There was no nausea in magnesium sulphate group as reported in other studies. 17,18,23 This finding suggests t hat magnesium sulphate probably has inhibitory action on nausea which may be advantageous compared to intrathecal opioids .…”

“…Similar findings were observed in other studies. 17,[21][22][23] Among these studies, two studies 17,23 compared magnesium sulphate as adjuvant to intrathecal bupivacaine where as in the other two studies 21,22 intrathecal fentanyl was also added and concluded the same. The duration of motor block was same in both the groups in another study.…”

Comparative Evaluation of Intrathecal Dexmedetomidine and Magnesium Sulphate as Adjuvants to Bupivacaine for Lower Abdominal and Lower Limb Surgeries

“…7 Intrathecal magnesium has shown promising results by prolonging the duration of analgesia in various surgical procedures like lower limb surgeries. 8,9 The aim of study was to compare the effects of intrathecal dexmedetomidine and magnesium sulphate as adjuvants to bupivacaine for lower abdominal and lower limb surgeries in relation to characteristics of sensory block, motor block and sedative effect.…”