Increased incidence of neonatal vitamin K deficiency resulting from maternal anticonvulsant therapy.

OBJECTIVE: The null hypothesis of our study is that the incidence of vitamin K deficiency in mother-infant pairs exposed to anticonvulsant drugs is not higher than in controls. STUDY DESIGN: In this multicenter observational case-control study, 25 pregnant women receiving anticonvulsant therapy and 25 pregnant controls were studied for PIVKA-II (protein induced by vitamin K absence of factor II) and vitamin K1 concentrations at 32 weeks' gestation and at delivery. RESULTS: PIVKA-II was detectable in 54% of cord samples of the anticonvulsant group and in 20% of controls (chi 2, p = 0.01). In both groups vitamin K1 cord blood levels were predominantly below the detection limit. Maternal vitamin K1 concentrations were lower in women with epilepsy than in controls (Wilcoxon's rank sum test, p < 0.05), but PIVKA-II was rarely present. CONCLUSIONS: The incidence of vitamin K deficiency is increased in neonates exposed to anticonvulsant drugs prenatally. Their mothers, however, are rarely vitamin K deficient.

31P nuclear magnetic resonance and zero-point titration compared for measuring free magnesium concentration in erythrocytes.

Intracellular ionized magnesium concentrations ([Mg2+]i) were measured in erythrocytes by 31P nuclear magnetic resonance (NMR) and zero-point titration in 14 controls and seven patients with renal magnesium loss. The mean intracellular ionized magnesium concentration in controls measured by 31P NMR was 0.20 (SD 0.03) mmol/L cell water, compared with 0.55 (SD 0.12) mmol/L cell water by zero-point titration. Total erythrocyte magnesium content measured with the lysate method was 0.63 mmol/L cell water higher than estimated by 31P NMR, probably because not all magnesium complexes are fully visible to the NMR technique. We found a positive correlation between plasma ultrafiltrable magnesium and [Mg2+]i irrespective of the [Mg2+]i assay used. [Mg2+]i measured with 31P NMR correlated modestly but significantly with [Mg2+]i determined by zero-point titration (r = 0.58, P less than 0.02). Washing erythrocytes before the zero-point titration decreased the ATP content and the cell water fraction, which led to overestimation of [Mg2+]i by zero-point titration. Although absolute values for [Mg2+]i differ with the assay used, both methods determined significantly lower values for [Mg2+]i in patients with isolated renal magnesium loss.

Reference values of magnesium and potassium in mononuclear cells and erythrocytes of children.

Reference values for magnesium and potassium contents of mononuclear cells and erythrocytes were estimated in cord blood and in children from infancy through adolescence. No differences were detected between results for boys and girls. The mononuclear magnesium content was independent of age and was within the adult range of values. No significant correlation was shown between magnesium in serum and in mononuclear cells. Mononuclear potassium also showed no age-related differences. The correlation between magnesium and potassium contents in mononuclear cells was significant: however, the correlation was lower when the magnesium and potassium contents were expressed in terms of protein potent: micromoles or millimoles per gram of protein, respectively. The concentration of magnesium in erythrocytes was significantly lower in cord blood and during the first month of life, compared with that at older ages, and showed no significant correlation with serum magnesium. The concentration of erythrocyte potassium was independent of age and showed a low but significant correlation with erythrocyte magnesium content.