Fat digestion in the newborn. Characterization of lipase in gastric aspirates of premature and term infants.

We have measured lipolytic activity in gastric aspirates obtained at birth in a group of 142 infants. The infants ranged in gestational age from 26 to 41 wk. Lipolytic activity, measured by the hydrolysis of long chain triglyceride ([tri-(3)H]oleate), and expressed as nanomoles FFA per milliliter gastric aspirate per minute was 333+/-66 in 55 small premature infants (gestational age 26-34 wk and body wt 750-2,000 g) and 558+/-45 in a group of 87 larger infants (gestational age 35-41 wk and body wt 2,020-4,000 g). No activity was detected in seven infants with an unusually low pH in the gastric aspirate, 2.88+/-0.44 (compared with a mean pH level of 5.59+/-0.22 in the other 135 infants). Attempts to characterize this lipase showed that it has a molecular weight of 44-48,000, pH optimum of 3.0-5.0, that FFA acceptors (albumin) stimulate activity, whereas bile salts, taurocholate and glycocholate, cause marked inhibition at concentration >3 mM. Our survey shows that enzyme activity is present as early as 26 wk of gestation, increases with gestational age, and has the same characteristics throughout gestation. The data show that the lipase in gastric aspirates differs from pancreatic lipase, but closely resembles human and rat lingual lipase. Because the lipase has a low pH optimum and does not require bile salts, it can act in the stomach where it initiates the hydrolysis of dietary fat. We suggest that intragastric lipolysis is probably of major importance in the newborn and especially in the premature infant where it compensates not only for low pancreatic lipase, but in addition, helps to overcome the temporary bile salt deficiency through the formation of amphiphilic reaction products.

Results of controlled double-blind study of thyroid replacement in very low-birth-weight premature infants with hypothyroxinemia.

The nature of hypothyroxinemia in sick very low-birth-weight (VLBW) infants was evaluated by assessment of the hypothalamic-pituitary axis and by the clinical response to thyroxine (T4) therapy. Twenty-three very low-birth-weight infants of gestational age 26 to 28 weeks, whose serum T4 concentrations were 4 micrograms/dL on two occasions, and thyrotropin less than 20 microU/mL, were included in a double-blind study. Following a thyrotropin-releasing hormone stimulation test, babies were given either T4 or placebo. Nine babies were thyrotropin-releasing hormone tested prior to therapy; four babies, two from each group, were tested 1 to 2 weeks after therapy. In 11 untreated babies, mean base line serum thyrotropin of 7.0 +/- 1.4 rose to 23.7 +/- 4.1 microU/mL in 30 minutes. This response was not significantly greater than the observed response in full-term babies, 23.7 +/- 4.1 v 16.6 +/- 0.97 microU/mL, respectively, P greater than .05. In two babies treated with T4 the thyrotropin response to thyrotropin-releasing hormone was completely suppressed. Serial serum T4 determinations showed normalization in both groups after a similar time interval. There was no beneficial effect of T4 therapy on growth of head circumference, length, or weight. Developmental data revealed no significant differences in the mental, motor, or gross neurologic outcome in the treated and nontreated infants after 1 year of follow-up. These observations imply that hypothyroxinemia in sick preterm infants is not a direct consequence of hypothyroidism. Despite the lack of demonstrable short-term beneficial effects of T4 therapy, follow-up studies are necessary to resolve the question of long-term benefits.

Fat digestion in very low-birth-weight infants: effect of addition of human milk to low-birth-weight formula.

The possible compensatory role of human milk lipase in the digestion of dietary fat was examined in a group of very low-birth-weight infants. Fat excretion was studied in 15 preterm infants of gestational age 26 to 33 weeks and birth weight 660 to 1,695 gm. The amount and composition of fecal fat were determined in stools collected for 72 hours. Eight infants were fed Similac 24 LBW exclusively and seven infants were fed a mixture of fresh human milk (40%) and formula (60%). Fat excretion was lower in infants fed a mixture of human milk and formula than in infants fed formula only (4.7% -+/- 0.50% vs 11.9% +/- 1.4% of intake, respectively). Excretion of calcium soaps, when expressed as percent of total fat, was higher in the group fed the human milk-containing diet (18.9% +/- 13.5%), than in the group fed formula only (6.8 +/- 2.5%); however, the absolute amounts excreted were similar in both groups (65 +/- 46 and 45 +/- 17 mg/kg/day, respectively). The lower fat excretion in infants fed a mixture of fresh human milk and formula could be related to the lipase present in human milk. These data suggest that human milk lipase probably contributes to the digestion and absorption of dietary fat in the "tiny premature" infant.

A prospective study of the oxytocin challenge test and newborn neurobehavioral outcome.

In a prospective study, infants of high-risk mothers delivered over a 1-year period were evaluated by clinical, biochemical, and behavioral methods. Of 67 newborns whose mothers had oxytocin challenge tests (OCTs), 54 were delivered after negative tests, and 13 after positive tests. Infants with positive OCTs had poor state organization and reflexive performance when compared with negative-OCT babies. These infants also showed evidence of intrauterine malnutrition, but did not have any greater asphyxiation than the negative OCT group. These results are consistent with the hypothesis that a positive OCT implies pathological placental respiratory insufficiency, which may be superimposed, in many instances, on impairment in utero of the placenta's nutritional function. The clinical manifestation of such dysfunction is the alteration in subtle neonatal neurobehavior.

Use of intravenous fluids before cesarean section: effects on perinatal glucose, insulin, and sodium homeostasis.

Perinatal glucose, insulin, and sodium homeostases were assessed in relation to antepartum intravenous infusions administered to 59 normal mothers undergoing cesarean section at term without labor under epidural anesthesia. Group A (N = 20) received 1 L of Ringer's lactate without dextrose during one hour; group B (N = 20), 1 L of 5% dextrose in water during one hour; and group C (N = 19), 1 L of 5% dextrose in water during two and one half hours. Mean maternal and fetal serum glucose and insulin and sodium concentrations at delivery differed among all groups in direct relationship to the rate of glucose infusion. Neonatal hypoglycemia (30 mg/dL or less) correlated with the presence of a glucose infusion, a maternal glucose concentration of 117 mg/dL or greater, and an umbilical venous insulin concentration of 26 microU/mL or greater. Among group A patients who received sodium, and group B and C patients who did not, fetal hyponatremia (umbilical venous sodium 130 mEq/L or less) correlated with the absence of sodium in the prepartum infusion. The results suggest that the antepartum administration of a balanced electrolyte solution without excess glucose infusion can minimize the incidence of fetal hyperglycemia and hyponatremia and neonatal hypoglycemia.

Effect of theophylline on neurotransmitters in preterm infants with apnea.

Urinary excretion of various catecholamine metabolites (4-hydroxy-3-methoxymandelic acid, homovanillic acid, 3-methoxy-4-hydroxphenylglycol) was studied in preterm infants with idiopathic apnea treated with theophylline. Relief of apnea in these infants was not associated with significant increase in the urinary excretion of various metabolites. We suggest that theophylline does not seem to relieve apnea of prematurity by the stimulation of peripheral catecholamine systems.

Study of neurotransmitters in premature infants with or without apnea of prematurity.

Twelve-hour urinary excretion of 4-hydroxy-3-methoxymandelic acid (VMA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) was studied in 20 premature infants, 8 without apnea and 12 with apnea. All infants were studied at 1-3 days of postnatal age (before apnea). Nonapneic infants were restudied at 10-15 days of postnatal age. Apneic infants were also restudied 24 h after apnea. Apnea was not associated with decreased urinary excretion of VMA and MHPG. Only HVA, when expressed as microgram/kg body weight, was significantly lower after the onset of apnea. This difference disappeared when HVA was expressed as microgram/mg creatinine. We suggest that apnea of prematurity may not be related to the immaturity of catecholamine pathways.

Permanent presence of managed care and outcome of critically ill infants.

In the era of managed care, the potential for high-risk patients of all ages to receive less than optimal care exists because the mechanism for reimbursement is designed to promote savings. The specific ways managed care payment mechanisms actually differ from indemnity insurance or fee-for-service are conceptually quite simple. This article reviews mechanisms such as utilization review, setting length-of-stay bench marks, preapproval for referrals to specialists, specific treatments, procedures, and hospital days.

Protective apathy, a hypothesis about the behavioral organization and its relation to clinical and physiologic status of the preterm infant during the newborn period.

This article describes the behavioral organization and its change in relation to physiologic and clinical variables in a group of infants whose birthweight was less than 1.5 kg and who were experiencing and recovering from acute cardiorespiratory illness. The authors used the Brazelton Premature Sale, which was designed for use with a wide range of gestational ages (27 to 35 weeks). Examinations began 1 week after birth and were obtained serially during the initial recovery period of these infants.

The impact of perinatal and neonatal events on the early behavior of the extremely premature human.

Observations were performed on 45 very low birth weight (VLBW) newborns at 7 and 21 days of life, using a Neonatal Behavioral Assessment Scale specifically modified for the extremely premature infant. Findings were analyzed using multiple and stepwise regression techniques to determine the influence of intrapartum and neonatal factors which might influence neurobehavior . Perinatal asphyxial descriptors accounted for significant variance on day 7 behavior; however, their impact was muted for day 21. At this time, jaundice and postnatal nutrition revealed a prominent and independent behavioral influence on the VLBW survivor.