Calcium Ion Activity in the Sick Neonate: Effect of Bicarbonate Administration and Exchange Transfusion

Abstract

ExtractCalcium ion activity was measured in plasma obtained by venous or arterial puncture using a calcium-selective flow-through electrode. Mean level of ionized calcium in umbilical venous plasma was 2.48 ± 0.04 mEq/liter. Within 30 hr after birth, the values decreased in sick infants to 1.35 ± 0.11 mEq/liter. Total calcium concentra tions were in the normal adult range at birth (5.20 ± 0.08 mEq/liter), showing a subsequent decline to subnormal values (3.47 ± 0.28 mEq/liter at age 30-40 hr). A calcium ion activity of less than 1.4 mEq/liter was associated with total calcium level" at or below 3 mEq/liter in 80% of patients. Symptoms and signs attributable to hypocalcemia (ionized fraction) or hypornagnesemia, or both, were found only in infants in whom plasma levels of both divalent cations were below the lower limit of normal. Administration of NaHGOs for acidosis caused a slight rise in pH (from 7.20 to 7.28 rnEq/liter) and a decrease in plasma calcium ion activity (from 1.68 to 1.51 mEq/liter). During exchange transfusion with acid-citrate-dextrose (ACD)-Tham buffered blood, calcium ion activity decreased significantly from 1.90 ± 0.08 to 1.20 ± 0.09 mEcj, liter, whereas total calcium levels increased consistently (from 4.22 db 0.13 to 5.33 ± 0.15 mEq/liter). SpeculationThe temporary hypocalcemia, observed in sick newborn infants, may also occur in healthy newborns. It is thought to initiate normal calcium homeostasis by stimulating parathormone secretion and by bringing into play the two feedback mechanisms for calcitonin and parathormone secretion.

Calcium Metabolism in Newborn Infants THE INTERRELATIONSHIP OF PARATHYROID FUNCTION AND CALCIUM, MAGNESIUM, AND PHOSPHORUS METABOLISM IN NORMAL, “SICK,” AND HYPOCALCEMIC NEWBORNS

“…It is not clear why the sick group had lower levels of plasma P than the normal group and did not demonstrate a rise in plasma P levels as did the normal infants. It is of interest that Radde, Parkinson, Hoffken, Apiah, and Hanley (36) made a similar observation in a group of sick infants. A possible explanation is that, due to poor feeding, the dietary intake of P was less in the sick infants than in the normal group.…”

pH and the Level of Calcium in the Blood of Fetal and Neonatal Albino Rats

“…This finding along with the observation that ionized calcium falls following bicarbonate administration in human infants led Radde et al (25) to suggest that care should be exercised to avoid overcorrection of acidosis in the early postnatal period. In line with this suggestion is the observation that acidotic infants which were normocalcemic before NaHC03 therapy, became hypocalcemic when blood pH was normalized (35).…”

Metabolic and Hormonal Consequences of Exchange Transfusion via the Umbilical Artery or Vein

“…If blood preserved with acid citrate and dextrose (ACD) is used, problems of acid-base balance, blood glucose homeostasis and lowered ionized calcium levels may result (2,8,9) whereas if heparin is em ployed there may be complications due to anticoagulation and excessive rise following transfusion in unconjugated unbound bilirubin (3). The work reported here was undertaken to investigate which route of transfusion was better for glucose homeostasis and which was the less stressful.…”