The objective of this study was to clarify the relationship between the blood
potassium and
calcium levels, and the efficacy of prophylactic
calcium (Ca) administration early in life for nonoliguric
hyperkalemia in extremely low
birthweight (ELBW) infants. This was a retrospective study including 55 ELBW infants with gestational age less than 26 weeks (mean, 24.4 weeks; mean
body weight, 681 g). The plasma
potassium concentration and whole blood ionized
calcium (iCa) concentration were measured every 2 to 3 hours. Laboratory data obtained up to 24 hours after birth were collected. The infants were divided into two groups based on whether or not Ca
gluconate was administered prophylactically starting at admission (prophylactic and nonprophylactic group). There was a negative correlation between the plasma
potassium and iCa levels at 12 and 24 hours, and the maximum plasma
potassium level was higher in the
hypocalcemia group (minimum iCa level, < 0.9 mmol/L) than in the normocalcemia group. The iCa level was significantly higher and the plasma
potassium level was significantly lower in the prophylactic group than in the nonprophylactic group at 12 and 24 hours. The increment in the plasma
potassium level at 24 hours compared with that at admission was significantly lower in the prophylactic than in the nonprophylactic group. Nonoliguric
hyperkalemia may be attenuated by maintaining the iCa level within normal limits by prophylactic Ca administration early in life. Prospective studies are needed to confirm this.