MONONUCLEAR BLOOD-CELL MAGNESIUM CONTENT AND SERUM MAGNESIUM CONCENTRATION IN CRITICALLY ILL HYPOMAGNESEMIC PATIENTS AFTER REPLACEMENT THERAPY

Magnesium (Mg) deficiency, commonly diagnosed as hypomagnesemia based upon low serum Mg concentrations, is a frequent electrolyte abnormalit y in critically ill patients. Intravenous replacement therapy is empir ic and serum Mg concentrations have traditionally been used as guideli nes for measuring efficacy. Recent studies have shown that the Mg cont ent of mononuclear blood cells (MBCs) may provide a better index for M g status than serum concentrations. The purpose of this study was to e valuate the effects of intravenous Mg replacement therapy on MBC Mg co ntent and serum Mg concentrations in critically ill hypomagnesemic pat ients. Adult patients admitted to the trauma intensive-care unit (ICU) with serum Mg concentration less than or equal to 0.6 mmol/L (less th an or equal to 1.5 mg/dl) were considered for study entry. Patients wi th severe renal disease (S-cr > 133 mu mol/L), pregnancy, or those who were seropositive for HIV were excluded. Ten patients with moderate ( > 0.4-0.6 mmol/L [> 1.0-1.5 mg/dL]) and severe (less than or equal to 0.4 mmol/L [less than or equal to 1.0 mg/dL]) hypomagnesemia received 0.5 and 0.75 mmol/kg of intravenous MgSO4, respectively, over 24 h. MB C Mg content and serum concentrations of magnesium, phosphorus, calciu m, sodium, potassium, blood urea nitrogen, creatinine, glucose, and al bumin were measured at baseline (0 h), end of infusion (24 h), 36 h, a nd 48 h. Data were analyzed using ANOVA with repeated measures and a P value < 0.05 was considered significant. Serum Mg concentrations incr eased significantly from baseline to 48 h (0.5 +/- 0.1 to 0.8 +/- 0.2 mmol/L, P < 0.001). MBC Mg content did not change significantly within the study period (2.6 +/- 1.0 to 3.0 +/- 1.3 fmol/cell, P > 0.7). The doses of MgSO4 (0.5-0.75 mmol/kg) used in this study increased serum Mg concentrations, but did not result in a statistically significant c hange of MBC Mg content in this group of trauma ICU patients. (C) Else vier Science Inc. 1997.