Calcium nutrition and metabolism during infancy.

Calcium is a vital mineral for the developing newborn infant. This review discusses perinatal and neonatal calcium metabolism, with an emphasis on enteral calcium absorption and the nutritional factors affecting calcium bioavailability including the three major endocrine hormones involved in calcium metabolism: parathyroid hormone, vitamin D, and calcitonin. The placenta transports calcium to the fetus throughout pregnancy, with the largest amount of fetal calcium accumulation occurring in the third trimester. At birth, the newborn transitions to intestinal absorption to meet the body's calcium needs. Most calcium is absorbed by paracellular passive diffusion in the small intestine. Calcium intestinal absorption is affected by the type and amount of calcium ingested. It is also affected by the amount of intestinal calcium that is bound to dietary fats and proteins. One major consequence of decreased calcium absorption is metabolic bone disease in which there is a failure of complete mineralization of the bone osteoid.

Gestational therapy with an angiotensin II receptor antagonist and transient renal failure in a premature infant.

The fetotoxic effects of angiotensin converting enzyme inhibitors when used during the second half of pregnancy are well known. The more recently developed angiotensin II receptor antagonists appear to yield similar fetal abnormalities. We report a premature infant born to a 41-year-old mother with a long history of infertility who had received losartan therapy for hypertension throughout an undetected pregnancy. Ultrasound examination 2 days prior to delivery identified a single fetus at 29 weeks gestation, anhydramnios, and an empty fetal bladder. The neonatal course was complicated by oliguria, hyperkalemia, marked renal dysfunction, respiratory failure, joint contractures, and a large anterior fontanelle with widely separated sutures. Hypotension (mean arterial pressure<25 torr) on day 1 responded to volume expansion, dopamine, and hydrocortisone. Serum creatinine reached a maximum of 2.7 mg/dL on day 6 and decreased to 0.4 by day 56. No formal urinalysis was performed, but the urine was reported to be visually clear throughout the course. Although a renal ultrasound on day 2 was normal, a follow-up study at 7 months revealed bilateral generalized parenchymal echogenicity, consistent with medical renal disease. Since then, weight and length have been at the 5th percentile or less, with apparent renal tubular acidosis necessitating the addition of sodium citrate supplements. This case emphasizes the importance of maintaining a high index of suspicion for potential pregnancy when contemplating the use of a drug of this class, and considering serial testing for pregnancy when using such drugs, even in patients with a longstanding history of infertility.

Intracranial pressure changes during intermittent CSF drainage.

Premature very-low-birth-weight infants with posthemorrhagic hydrocephalus are often managed with intermittent cerebrospinal fluid drainage from a ventricular reservoir. There are little data regarding intracranial pressure changes during intermittent drainage to determine the amount and frequency of cerebrospinal fluid removal or to determine the correct resistance of future programmable shunts. The objective of this study was to determine the feasibility of using a commercially available intracranial pressure transducer to measure changes in pressure associated with this procedure. Continuous intracranial pressure was measured in three infants with a transducer placed at the time of ventricular reservoir insertion. Daily reservoir taps began 48 hours after placement and intracranial pressure was monitored for 7 days. Intracranial pressure before the initial tap was comparable to levels previously reported as normal. The daily removal of 10 cc/kg of cerebrospinal fluid was sufficient to lower intracranial pressure below baseline, however it was associated with wide swings in pressure and, in one patient, sustained negative pressure. The use of direct intracranial pressure monitoring may be useful in determining the optimal amount and frequency of cerebrospinal drainage from infants with posthemorrhagic hydrocephalus managed with a ventricular reservoir, as well as determining resistance settings of subsequent programmable shunts.