System	Condition	Evidence base
Central nervous system	Acute pain	l Perioperative IV magnesium reduced opiate consumption postoperatively and led to reduced pain scores [46]
	Chronic pain	l IV and PO magnesium increased range of movement and reduced pain scores in chronic back pain with a neuropathic component [48]
	Memory dysfunction	l Increased brain magnesium enhanced learning and memory in rats [72] but no research in humans to date
	Neuromuscular blockade	l Potentiates the effects of non-depolarising neuromuscular blocking agents [73] - [76] l Blunts the serum potassium rise induced by suxamethonium [77]
	Postoperative shivering and thermoregulation	l Reduction in hypothermic shivering threshold from 36.6˚C to 36.3˚C (not clinically significant) [78] , some reports of reduced postoperative shivering [79] - [81] but not borne out in a systematic review [82]
	Insomnia	l PO supplementation gave improved sleep quality, sleep time and ease of getting to sleep [49]
Cardiovascular system	Arrhythmias	l Treatment for torsades de pointes, digoxin toxicity, most atrial and ventricular arrhythmias where hypokalaemia is present [50] l Superior to amiodarone in cardioversion of atrial tachyarrhythmias in intensive care [51]
	Myocardial infarction	l Reduced infarct size in canine model [83] l LIMIT-2 study showed reduced 28-day mortality in magnesium treated group [84] l Larger and more recent ISIS-4 and MAGIC-2 trials showed no survival benefit [85] [86]
	Cardiothoracic surgery	l Prophylactic magnesium reduced incidence of postoperative atrial fibrillation from 28% to 18% [53] and ventricular arrhythmias by 48% [54] l Magnesium in cardioplegic solution reduced postoperative ischaemia [55]
	Phaeochromocytoma anaesthesia	l Case series reported 15 out of 17 cases with good haemodynamic stability at induction and tracheal intubation, with 4 cases requiring additional pharmacological support for blood pressure control during tumour handling [59]
Respiratory system	Acute severe asthma	l Scottish Intercollegiate Guidelines Network (SIGN) and British Thoracic Society (BTS) 2012 recommend intravenous magnesium for patients with acute asthma, non-respondent to inhaled short-acting beta-2 agonists, inhaled anticholinergics, corticosteroids and oxygen [60] l Reduced admission rates in acute severe asthma but not in non-severe [61]
	Respiratory muscle weakness	l Improved respiratory muscle power in hypomagnesaemic patients given supplementation [62]
Gastrointestinal system	Mendelson’s syndrome	l Magnesium trisillicate is superior to cimetidine in achieving a higher gastric pH [66] in prophylaxis against Mendelson’s syndrome (pulmonary aspiration of gastric contents in obstetric anaesthesia)
Obstetrics	Eclampsia	l Reduced risk of maternal death and seizure recurrence compared to diazepam [67]
	Pre-eclampsia	l Reduced risk of developing eclampsia compared to placebo, phenytoin and nimodipine [68]