Magnesium and calcium are the most abundant cations, after sodium and potassium, in the body. Magnesium ions (Mg2+) are involved as a cofactor in about 300 known enzymatic reactions and in several important processes, whereas intracellular calcium regulates many important physiologic functions, including muscle contraction, hormone secretion, glycogen metabolism, and cell division. Of particular relevance to the anesthetist are the effects of calcium on the myocardium, vascular smooth muscle and blood coagulation. Mg2+ blocks the N-methyl-D-aspartate (NMDA) receptor and its associated ion channels; this property of Mg2+ as an antagonist of NMDA receptors is the basis for studies of its adjuvant effect in perioperative analgesia. The calcium inhibitory effect causes central arteriolar vasodilatation and acts against vasospasm. Magnesium has a stabilizing effect on membranes; it can be used in the treatment of cardiac rhythm disorders. Magnesium sulfate is a safe supplement to a general anesthetic regimen as it reduces the total anesthetic requirements, cost, post-operative pain score and post-operative analgesic requirements. Thus, magnesium seems to have a potential role in anesthesia related to knee surgery, hysterectomy, caesarean section, lumbar surgery, cardiac surgery etc, as suggested by several clinical studies. This clearly indicates that anesthetists may repose increasing confidence in magnesium in the near future.
