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]


l PO supplementation gave improved sleep quality, sleep time and ease of getting to sleep [49]

Cardiovascular system


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)



l Reduced risk of maternal death and seizure recurrence compared to diazepam [67]


l Reduced risk of developing eclampsia compared to placebo, phenytoin and nimodipine [68]