Neurotoxicity after spinal anaesthesia induced by serial intrathecal injections of magnesium sulphate  An experimental study in a rat model

Abstract

SummaryWe have previously demonstrated in a rat model that the lumbar intrathecal injection of 0.02 ml 6.3% magnesium sulphate, a concentration iso-osmolar with rat plasma, produces a state of spinal anaesthesia and general sedation which reversed completely after 6 h, without evidence of neurotoxicity, immediately or during the week thereafter. Using the same model and five groups of six animals in each, we administered the same volume and concentration of magnesium sulphate and compared its clinical effects with those of 0.02 ml 12.6% magnesium sulphate, 0.02 ml 2% lignocaine and 0.02 ml 0.9% sodium chloride solution, given as a series of 15 injections on alternate days for a period of 1 month. The animals were then killed and their spinal cords and meninges examined histologically. No significant differences were noted in the times of onset, durations of sensory and motor blockade and the times to full recovery throughout the entire period of 1 month's observation in the animals receiving intrathecal 6.3% magnesium sulphate. In the group receiving 12.6% magnesium sulphate, the time of onset of sensory and motor blockade was shorter and the duration of both parameters was significantly longer than in the former group. Full clinical recovery and resumption of normal eating and drinking took place in both groups throughout the entire series of 15 successive intrathecal injections. Identical, mild, uniform histopathological changes in the spinal cord were seen in all the five groups, including the group in which only the intrathecal catheter was implanted. The complete recovery and benign consequences of repeated intrathecal injections of iso-osmolar magnesium sulphate in a rat model indicate a lack of neurotoxicity and provide an impetus for further trials in larger animal species, before initial clinical trials of this substance, given intrathecally, in humans.Keywords Anaesthetics, local; lignocaine. Ions; magnesium. Anaesthetic techniques, regional; intrathecal. ...................................................................................... Correspondence to: Dr M. Bahar Accepted: 22 September 1996 The recent increased interest in the neurological effects of magnesium deficiency and a renewed concern with magnesium metabolism [1] prompted us to examine the results of intrathecal administration of magnesium sulphate (MgSO 4 ) in an animal model previously described by us [2]. We have also previously demonstrated in this same rat model that the intrathecal injection of a 0.02-ml bolus of 6.3% MgSO 4 , a concentration iso-osmolar with human and rat plasma [3][4][5], produced a state of spinal anaesthesia and general sedation lasting approximately 1 h. This

Le magnésium ajouté à la bupivacaïne prolonge la durée de l’analgésie après un bloc interscalénique

“…Several studies have found magnesium to be safe in intrathecal and epidural blockades. Chanimov et al 13 showed that intrathecal injection of 6.3% magnesium sulphate 0.02 mL (4.6 mgÁkg -1 ) did not cause neurotoxicity, while 12.6% magnesium sulphate 0.02 mL (9.2 mgÁkg -1 ) caused moderate vacuolation and severe histopathological demyelinization. Another report 14 described that the inadvertent epidural injection of larger doses (8.7 g, 9.6 g) of magnesium sulphate did not cause neurologic toxicity in pregnant woman.…”

Serum electrolyte and blood gas changes after intrathecal and intravenous bolus injections of magnesium sulphate An experimental study in a rat model

“…These results show that intrathecally administered magnesium sulphate has little effect on electrolyte homeostasis. The increasing interest in magnesium as a physiological N-methyl-D-aspartate antagonist and its role in a variety of clinically important disorders characterised by intracellular calcium excess and magnesium deficiency [1][2][3][4][5] has prompted us to investigate the use of intrathecal magnesium sulphate in an experimental animal model.We have previously shown that when injected intrathecally in a rat model, magnesium sulphate, in a concentration iso-osmolar with rat plasma, will produce a state of segmental spinal anaesthesia which is both completely reversible and free of neurotoxic side-effects [6,7]. However, the same volume and concentration which resulted in spinal anaesthesia, when injected intravenously, did not produce general anaesthesia sufficient for a laparotomy procedure to be carried out painlessly.…”

“…We have previously shown that when injected intrathecally in a rat model, magnesium sulphate, in a concentration iso-osmolar with rat plasma, will produce a state of segmental spinal anaesthesia which is both completely reversible and free of neurotoxic side-effects [6,7]. However, the same volume and concentration which resulted in spinal anaesthesia, when injected intravenously, did not produce general anaesthesia sufficient for a laparotomy procedure to be carried out painlessly.…”

The effect of intrathecal magnesium sulphate on nociception in rat acute pain models

“…Intrathecal administration of magnesium sulphate (MgSO 4 ) has recently been shown to produce spinal anaesthesia [1][2][3]. Using the tail-pinch method, we have reported that intrathecal administration of MgSO 4 did not induce complete analgesia in the presence of motor paralysis [4] although differentiation of analgesia from motor paralysis may be difficult.…”