Total magnesium, ionized calcium, potassium and sodium concentrations in mixed umbilical cord blood and venous blood serum at a median (min.-max.) age of 33 h (24-48 h) were assessed colorimetrically in 46 asphyxiated and 35 healthy term infants. Asphyxiated infants without any signs or with signs of mild hypoxic-ischaemic encephalopathy (HIE) had significantly higher, and infants with severe HIE lower umbilical cord blood serum total magnesium (mean (95%CI) 0.81 (0.75-0.87) mmol/l and 0.64 (0.47-0.87) mmol/l, respectively, p < 0.05) compared with the control group (0.72 (0.69-0.76)mmol/l). An increase in serum total magnesium in spite of normalized acid-base status in asphyxiated infants suffering from severe HIE compared with the control group infants was found by the second day of life (0.97 (0.87-1.07) mmol/l and 0.86 (0.81-0.9) mmol/l, respectively, p < 0.05). At the age of 24-48 h hypermagnesaemia (>2 SD) was discovered in 36%, hyponatremia (<2 SD) in 38%, and hypocalcaemia (<2 SD) in 23% of asphyxiated infants. Derangements (>2 SD) in at least two electrolytes by the second day of life were significantly associated with poor outcome.
Conclusions: Magnesium, calcium and sodium derangements are a frequent finding in asphyxiated infants, and these abnormalities are significantly associated with poor outcome. For a better outcome prediction, the routine determination of magnesium in addition to other electrolytes in asphyxiated infants is recommended.