Intravenous magnesium.
OBJECTIVE
To review the function and use of intravenous magnesium in magnesium depleted and non-magnesium depleted patients.


METHODS
A review of studies reported from 1966 to 1998 and identified through a MEDLINE search of the English-language literature on the use of intravenous magnesium.


RESULTS
Magnesium is a metalo-coenzyme that participates in numerous enzymatic reactions including all reactions that involve the formation and utilization of ATP. The cardiovascular, neurological and metabolic disorders caused by magnesium deficiency are associated with an increase in morbidity and mortality and can be rapidly corrected by magnesium therapy. There is also evidence that intravenous magnesium alters ion channels, NMDA receptors, and calcium metabolism, causing effects that are beneficial in a range of cardiovascular, respiratory and metabolic disorders, in the absence of magnesium deficiency. In these disorders intravenous magnesium sulphate is usually administered as an initial bolus varying between 8 - 16 mmol over 5 min, followed by an infusion of 2 - 4 mmol/h, to keep the plasma magnesium between 1.5 - 3 mmol/L.


CONCLUSIONS
Magnesium is required in patients who are magnesium depleted and is also of benefit in non-magnesium depleted patients with pre-eclampsia. It may also be of benefit in non-magnesium depleted patients with acute coronary syndromes, arrhythmias, acute asthma, stroke, seizures and spinal cord injury.
Connolly
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E
Department of Critical Care Medicine, Flinders Medical Centre, Adelaide, SA Australia.
Worthley
L I
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