Increased renal net acid excretion in prematures below 1,600 g body weight compared with prematures and small-for-date newborns above 2,100 g on alimentation with a commercial preterm formula.
In 76 low birth weight infants with an actual body weight ranging from 1,210 to 2,540 g and fed a commercial preterm formula, urine samples were collected and blood acid base status was measured on day 38 (+/- 17, mean +/- SD) of life. Infants with an actual body weight below 1,600 g demonstrated a higher daily weight gain (22 +/- 3 vs. 14 +/- 5 g/kg/day), lower blood pCO2 (35.4 +/- 5.0 vs. 38.9 +/- 3.8 mm Hg), lower urine pH (5.8 +/- 0.5 vs. 6.5 +/- 0.3), higher renal net acid (1.86 +/- 0.38 vs. 1.28 +/- 0.55 mmol/kg/day) and higher phosphorus excretion (0.67 vs. 0.52 mmol/kg/day) than infants with an actual body weight above 2,100 g. Urinary ionogram data of these 2 groups of infants show that the increased renal net acid excretion of the smaller prematures is the result of a lower urinary excretion of sodium, potassium and chloride, due to a higher daily weight gain, probably a higher retention of these minerals, and a higher urinary phosphorus excretion probably due to an age-specific lower intestinal calcium absorption, and therefore a lower rate of calcium and phosphorus retention. Considering the low renal capacity for hydrogen ion excretion, very low birth weight infants still run a considerable risk for disturbances of acid base metabolism due to the high mean level of net acid excretion in nutrition with preterm formulas and an additional age-specific augmentation of renal acid load.
Kalhoff
H
H
Children's Hospital, Dortmund, Germany.
Wiese
B
B
Kunz
C
C
Diekmann
L
L
Stock
G J
GJ
Manz
F
F
D000136:Acid-Base Equilibrium; D001724:Birth Weight; D002118:Calcium / Q000652:urine; D003404:Creatinine / Q000652:urine; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007231:Infant, Newborn; D007234:Infant, Premature / Q000378:metabolism*; D007236:Infant, Small for Gestational Age / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D008297:Male; D010758:Phosphorus / Q000652:urine; D011188:Potassium / Q000652:urine; D012964:Sodium / Q000652:urine; D014556:Urine
D010758:Phosphorus; D012964:Sodium; D003404:Creatinine; D011188:Potassium; D002118:Calcium