Early neonatal hyperkalaemia in the extremely premature newborn infant

Abstract

The incidence of hyperkalaemia in 43 consecutive infants born at less than 28 weeks gestation and cared for in our neonatal intensive care unit was documented. Plasma K levels were related to indices of renal function as well as to the degree of illness in the infants. The mean gestational age was 26.0 weeks (range 24-27 weeks) and the mean birthweight was 815 g (range 395-1170 g). Twenty-six of infants (60%) had at least one plasma K > 5.5 mmol/L and 13 (30%) had a maximum plasma K > 7 mmol/L. The mean postnatal age at which the plasma K exceeded 7 mmol/L was 25 h (range 10-39 h). Five infants with plasma K > 7 mmol/L developed cardiac arrhythmias and four died to this complication. Only one infant had a large intraventricular haemorrhage. Only two of 16 infants with an initial plasma K < 5 mmol/L had a maximum plasma K > 7 mmol/L, compared with eight of 10 with an initial plasma K > 6 mmol/L (P < 0.005). Plasma K also correlated directly with plasma urea (P < 0.001) and plasma creatinine (P < 0.025), and inversely with urine volume (P < 0.05). Plasma K did not correlate with K intake, arterial pH, presence of asphyxia, severity of respiratory illness, gestation or birthweight. The rapidity with which the plasma K concentration reached potentially hazardous levels in some infants makes it imperative to measure plasma K within 6 h of birth and to continue to monitor levels at least every 6 h for the first 48 h in all infants born at less than 28 weeks gestation.