Applications of magnesium sulfate in obstetrics and anesthesia.

BACKGROUND AND OBJECTIVES Magnesium is predominantly an intracellular ion. Its blocking effects on NMDA receptors are responsible for the analgesic and sedative characteristics of this ion. The objective of this study was to review the physiology, pharmacology, and decreased plasma levels of magnesium, as well as its applications in obstetrics and anesthesia. CONTENTS Magnesium is an intracellular cation with multiple functions: it is a cofactor for enzymes of the glucose metabolism and those that participate in the degradation of nucleic acids, proteins, and fatty acids; it regulates the movements of transmembrane ions; and it intervenes in the activity of several enzymes. Critical patients have a tendency to develop hypomagnesemia, and the treatment consists in correcting the cause, whenever possible, and replacement of magnesium. A reduction in the minimum alveolar concentration (MAC) of inhalational agents in animals and the use of opioids in humans under anesthesia has been demonstrated. CONCLUSIONS Magnesium sulfate has been used in obstetrics with good results, inhibiting premature labor and in the treatment of eclampsia-associated seizures. It is potentially analgesic and sedative, and could be used as adjuvant during general anesthesia, attenuating the blood pressure response to tracheal intubation and decreasing the need of anesthetics.