The magpie trial

Posterior reversible encephalopathy syndrome (PRES) and hypomagnesemia: A frequent association?

Posterior reversible encephalopathy syndrome (PRES) is a serious neurological condition encountered in various medical fields. Pathophysiological factor(s) common to PRES cases of apparently unrelated etiologies are yet to be found. Based on the hypothesis that hypomagnesemia might participate in the cascade leading to PRES, our study sought to verify whether hypomagnesemia is frequently associated with PRES regardless of etiology. From a retrospective study of a cohort of 57 patients presenting with PRES of different etiologies, presented here are the findings of 19 patients with available serum magnesium levels (SMLs) during PRES. In the acute phase of PRES, hypomagnesemia was present in all 19 patients in spite of differences in etiology (including immunosuppressive drugs, hypertensive encephalopathy, eclampsia, systemic lupus erythematosus, iatrogenic etiology and unknown). SMLs were within normal ranges prior to PRES and below normal ranges during the first 48h of PRES, with a significant decrease in SMLs during the acute phase. In this retrospective study, constant hypomagnesemia was observed during the acute phase of PRES regardless of its etiology. These results now require larger studies to assess the particular importance of acute hypomagnesemia in PRES and especially the possible need to treat PRES with magnesium sulfate.

[Magnesium sulfate in obstetrics: current data]

OBJECTIVE

To review the available evidence regarding history, pharmacology, physiology, maternal/fetal side effects, and efficacy of magnesium sulfate in pregnant women.

DATA SOURCES

The literature in Medline was searched from 1966 through April 2003 using the terms "magnesium sulfate," "tocolytic," "preeclampsia," "eclampsia," and "pregnancy." Reviews of bibliographies of retrieved articles provided additional references.

RESULTS

Magnesium sulfate (MgSO4) has long been used for prophylaxis of preterm delivery (tocolytic affect) and eclampsia prophylaxis (neuroprotective effect). Randomized controlled trials and systematic reviews have demonstrated the efficacy of magnesium sulfate in preventing eclampsia in patients with preeclampsia or in patients with eclampsia. Whether magnesium sulfate should be administered to patients with severe preeclampsia or to mild preeclampsia is discussed in the manuscript. Inversely, it appears that magnesium sulfate is ineffective in delaying birth or preventing preterm birth when it is used as a tocolytic. Furthermore, there is evidence that high cumulative doses of magnesium sulfate may be associated with increased infant mortality.

CONCLUSION

The evidence to date confirms the efficacy of magnesium sulfate therapy for women with eclampsia and preeclampsia. However, magnesium sulfate should not be used in order to treat preterm labor.

Second overview of relationships between antenatal pharmacologic magnesium sulfate and neurologic outcomes in children

In the last ten years, the body of scientific knowledge concerning the use of antenatal pharmacologic magnesium sulfate (MgSO4) has become substantially larger. Several randomized controlled trials have provided compelling evidence that MgSO4 is the drug of choice for maternal seizure prophylaxis in toxemia. In contrast, the recent Cochrane Systematic Review, as well as other studies, have shown there is no evidence basis for the use of MgSO4 for tocolysis. Furthermore, when tocolytic-strength doses of MgSO4 are employed, there is an excess risk for total pediatric mortality (Cochrane Systematic Review and our own previous work). It is conceivable, nonetheless, that low doses of MgSO4, when used as prophylaxis in some selected cases of preterm labor, may ultimately be shown to be neuroprotective for a relatively small number of children. Unfortunately, the indiscriminate use of high-dosage MgSO4 for attempted tocolysis in preterm labor is much more likely to cause harm than do good.