Magnesium requirements in patients with chronic inflammatory disease receiving intravenous nutrition

Assessment of magnesium (Mg) status by serum and 24 hr urine estimations has been used to study 25 patients with severe Crohn's disease. Mg depletion was found to be present in 21 (84%), of whom eight (32%) had both low serum and low urine Mg levels. Only four patients (16%) had normal serum and normal urine Mg. Fifteen of the 25 patients required intravenous nutrition (IVN). A combined low serum and urine Mg was found in five of 14 patient-weeks in which less than 5 mmol Mg/24 hr was given but in none of 42 patient-weeks in which 5-10 mmol/24 hr was given and none of 65 patient-weeks in which greater than 10 mmol Mg IV/24 hr was given. Mg deficiency was statistically significantly more likely to occur in patients taking less than 5 mmol IV Mg/24 hr. After discharge, five patients who had been treated with IVN were found to have recurrent low serum Mg levels over some months, and symptoms in this group were common--muscle cramps, tetany, and bone pain. A high dose of Mg supplements was required, of the order of 60 mmol oral Mg/24 hr, to prevent magnesium deficiency in these patients.