RESUMO
This study tests the hypothesis that increasing the calcium and phosphorus content of formulas for very low birth weight (VLBW) infants to the level required to decrease the incidence of rickets has a negative impact on magnesium balance. Using formulas variously supplemented with these minerals, we measured absorption and retention in two groups of preterm infants: (1) VLBW infants, less than 1500 gm and at less than 32 weeks of gestational age, with 3-day mineral balances begun at days 10, 20, 30, and 40; and (2) low birth weight infants appropriately grown and at 32 to 34 weeks of gestational age, with a single 3-day balance begun at day 10. Magnesium did not affect calcium balance in VLBW or low birth weight infants but promoted phosphorus retention in VLBW infants from day 20 onward. Absorption and retention of magnesium increased with postnatal age in VLBW infants, but this effect was obvious only when calcium or phosphorus intakes were low or when magnesium intake was high. Calcium and phosphorus supplementation further reduced magnesium absorption and retention in VLBW infants to the extent that they were in negative balance throughout the study; however, magnesium supplementation improved absorption and retention in VLBW infants. The low birth weight infants absorbed and retained more magnesium than VLBW infants at the same postnatal age whether or not magnesium was supplemented. We conclude that magnesium deficits occur at currently recommended intakes of 10 mg/kg/day for VLBW infants with calcium and phosphorus intakes that allow retentions equivalent to in utero accretions; however, with magnesium intakes approaching 20 mg/kg/day, appropriate retention can be achieved.
Assuntos
Envelhecimento/metabolismo , Cálcio/farmacologia , Idade Gestacional , Recém-Nascido de Baixo Peso/metabolismo , Magnésio/metabolismo , Fósforo/farmacologia , Absorção , Animais , Cálcio/administração & dosagem , Cálcio/sangue , Estudos de Coortes , Nutrição Enteral , Humanos , Alimentos Infantis , Recém-Nascido , Magnésio/administração & dosagem , Magnésio/sangue , Magnésio/farmacologia , Magnésio/urina , Masculino , Leite , Fósforo/administração & dosagem , Fósforo/sangueRESUMO
Axial movement of the right hemidiaphragm during tidal breathing was recorded using real-time ultrasonography in 46 healthy term infants. Displacement was 2.6 +/- 0.1, 3.6 +/- 0.2, and 4.5 +/- 0.2 mm (mean +/- SEM) for the anterior, middle, and posterior thirds, respectively. Diaphragmatic movement was significantly greater in the middle and posterior segments than in the anterior segment (P less than 0.0001). Excursion of the diaphragm was similar in sleeping and awake infants, and during quiet and active sleep, as identified by behavioral criteria. Diaphragmatic movement was also assessed in nine infants who required mechanical ventilation and pharmacologic paralysis because of respiratory disease. In these infants, axial movement of the right hemidiaphragm was less in the middle and posterior thirds (P less than 0.05 and P less than 0.01, respectively) than in spontaneously breathing infants, and posterior movement was not predominant. Normative data for axial diaphragmatic movement may be of clinical value in the assessment of defects of the diaphragm, rib cage, or abdomen in newborn infants and may allow further understanding of the direct effects of therapeutic interventions on the respiratory system in infancy.
Assuntos
Diafragma/fisiologia , Doença da Membrana Hialina/fisiopatologia , Recém-Nascido/fisiologia , Síndrome de Aspiração de Mecônio/fisiopatologia , Diafragma/efeitos dos fármacos , Diafragma/fisiopatologia , Humanos , Pancurônio/farmacologia , Respiração Artificial , UltrassonografiaRESUMO
Seventy-four infants weighing less than 1500 gm at birth were fed enterally from birth until day 47. Group A (18 infants) were given SMA Gold Cap: group B (18 infants), supplementary calcium to 21 mmol/L (84 mg/dl); group C (16 infants), further calcium supplementation to 31.2 mmol/L (125 mg/dl); and group D (22 infants), milk with calcium content 31.2 mmol/L (125 mg/dl) and phosphorus supplementation to 15.7 mmol/L (49 mg/dl). The addition of calcium reduced the radiologic evidence of rickets, and combined calcium and phosphorus supplementation maintained plasma alkaline phosphatase activity within the normal range for 6 weeks.