Early-onset neonatal hyperkalemia associated with maternal hypermagnesemia: a case report

Kenichi Tanaka, Hiroko Mori, Rieko Sakamoto, Shirou Matsumoto, Hiroshi Mitsubuchi, Kimitoshi Nakamura, Masanori Iwai

Neonatal nonoliguric hyperkalemia (NOHK) is a metabolic abnormality that occurs in extremely premature neonates at approximately 24 h after birth and is mainly due to the immature functioning of the sodium (Na+)/potassium (K+) pump. Magnesium sulfate is frequently used in obstetrical practice to prevent preterm labor and to treat preeclampsia; this medication can also cause hypermagnesemia and hyperkalemia by a mechanism that is different from that of NOHK. Herein, we report the first case of very early-onset neonatal hyperkalemia induced by maternal hypermagnesemia. A neonate born at 32 weeks of gestation developed hyperkalemia (K+ 6.4 mmol/L) 2 h after birth. The neonate's blood potassium concentration reached 7.0 mmol/L 4 h after birth, despite good urine output. The neonate and his mother had severe hypermagnesemia caused by intravenous infusion of magnesium sulfate given for tocolysis due to pre-term labor. The early-onset hyperkalemia may have been caused by the accumulation of potassium ions transported through the placenta, the shift of potassium ions from the intracellular to the extracellular space in the infant due to the malfunctioning of the Na+/K+ pump and the inhibition of renal distal tube potassium ion secretion, there is a possibility that these mechanisms were induced by maternal and fetal hypermagnesemia after maternal magnesium sulfate administration. Because neonatal hyperkalemia poses a significant risk for the development of life-threatening cardiac arrhythmia, this case highlights the necessity of maternal blood magnesium monitoring during magnesium sulfate administration and neonatal blood potassium monitoring when there is severe maternal hypermagnesemia at delivery.