The relationship between serum magnesium levels and the occurrence of convulsions in women treated with magnesium sulphate for severe preeclampsia and eclampsia

Abstract

Maternal mortality and morbidity in eclampsia is directly related to the number of convulsions thus optimum prevention of convulsions in eclampsia and severe pre-eclampsia is vital. Magnesium sulphate has been shown to be to be supreme in control of these convulsions but despite this, a number of patients continue to convulse during therapy. Studies done show that the levels of serum. magnesium achieved during treatment with magnesium su Iphate dose regimen vary depending on the body mass index and that patients with higher body mass index do not achieve therapeutic levels. It is thus prudent to determine the serum levels of Magnesium in patients treated with magnesium sulphate to determine the frequency of subtherapeutic levels and whether this contributes to the recorded failure to control convulsions seen in some of these patients. OBJECTIVE: To determine if sub-therapeutic levels of serum magnesium III patients with severe preeclampsia/eclampsia on treatment with magnesium sulphate are associated with occurrence of convulsions. METHODOLOGY' This was a prospective cohort study of patients in two serum magnesium categories (therapeutic • and subtherapeutic magnesium levels) on treatment with magnesium sulphate for severe preeclampsia and eclampsia. A baseline survey of magnesium levels after administration of the loading dose (4 grams over 5 to 15 minutes as per the protocol) was done at recruitment was done and 101 patients with subtherapeutic levels and 69 with therapeutic levels were followed up to determine the occurrence of convulsions. RESULTS With the magnesium sulphate regimen of 4 grams loading dose and a maintenance dose of 1 gram hourly that was used in the study 101(59.4%) of the 170 patients with severe preeclampsia/eclampsia had subtherapeutic levels while 69(40.6%) of them had therapeutic levels. Of the patients who convulsed while on these standard dosing regimen, 78.1% had subtherapeutic serum magnesium levels while 21.9% had therapeutic serum magnesium levels. The odds for convulsions for patients with subtherapeutic serum magnesium levels was 2.91 that for those patients with therapeutic serum magnesium levels ( 95% CI 1.10 to 7.98, P = 0.016). The body mass index was inversely proportional to the serum magnesium levels and the two were highly correlated (p<0.05). The odds of subtherapeutic serum magnesium levels with a high BMI (Overweight or more) was 86.5 times that for those patients with a normal BMI ( 95% CI 13.6- 355.5, P = 0.001). 9 CONCLUSIONS The standard dose regimen of magnesium sulphate used of 4 grams loading dose and 1 gram hourly for maintenance failed to give therapeutic levels of serum magnesium in a majority of patients. Many of the patients who convulsed while on treatment with magnesium levels had subtherapeutic serum magnesium levels. A high body mass index in the patients was associated with subtherapeutic levels. RECOMMENDA TIONS Studies testing drug regimens based on body mass index or higher doses should be formulated with a goal to improve the control of convulsions in patients with eclampsia/severe eclampsia .