Effect of bicarbonate on neonatal serum ionized magnesium in vivo.

Sodium bicarbonate is used to treat metabolic acidosis or to induce metabolic alkalosis in sick neonates. The aim of this study was to quantify the decrease in serum concentration of ionized magnesium ([Mg(2+)]) when sodium bicarbonate is administered in vivo. We administered 1 mEq/kg body weight sodium bicarbonate 4.2% for correction of metabolic acidosis (n = 11) for management of persistent pulmonary hypertension (n = 3). After sodium bicarbonate treatment, serum pH increased by an average of 0.046 (P < 0.001), serum [Mg(2+)] decreased by an average of 0.07 mmol/L (P < 0.01), and serum [Ca(2+)] decreased by an average of 0.06 mmol/L (P = 0.04). There was a significant correlation between baseline [Mg(2+)] and baseline [Ca(2+)] (R(2) = 0.328, P = 0.032). Sodium bicarbonate therapy in infants causes a significant decrease in [Mg(2+)] and serum [Ca(2+)]. We suggest that infusion of sodium bicarbonate be effected while monitoring serum [Mg(2+)] and serum [Ca(2+)].