A NEW METHOD FOR PARENTERAL CALCIUM AND PHOSPHORUS ADMINISTRATION IN THE NEWBORN:

The low solubility of calcium phosphate makes it difficult to maintain normal bone mineralization in low birthweight infants during prolonged parenteral alimentation. We postulated that alternating calcium(Ca) and phosphate(P) administration at short intervals might permit substantial accretion of both without excessive fluctuations in serum concentration. We used two solutions of 2.1% amino acid in 5% dextrose; one had 50mEq of calcium per liter and the other 28mEq of phosphorus per liter. These were given alternately for one hr periods by infusion pump to anesthesized lambs. Serum calcium and phosphorus were measured hourly in 5 lambs, weighing 2.3-4.0 kg for a total of 33 periods. Ca was given at 5-10 mg/kg/hr and P at 4-8mg/kg/hr. Serum Ca changed less than 1.2 mg/dl during 15 Ca infusions and 15 P infusions. During one phosphorus period Ca decreased 1.4 mg/dl. Serum phosphorus was not significantly changed by either Ca or P infusions. Urine Ca analyses indicated that 87% of the Ca given was retained. Ca infusion at 10 mg/kg/hr for 12 hrs daily would thus give a balance of 120 mg/kg/d x .87=104 mg/kg/d accretion rate.