John B Paton

Follow-up of infants screened by auditory brainstem response in the neonatal intensive care unit

Auditory brainstem response screening at 40 and 60 dB was conducted in 100 infants in the neonatal intensive care unit to determine initial failure rate and prevalence of abnormality on follow-up. Of our NICU population, 20% failed one or both of the screening levels: 9% failed at 60 dB in both ears, and 11% failed at 40 dB in one or both ears. On follow-up, half of the 60 dB failure group were found to have sensorineural or conductive impairment and represent the 2% to 4% prevalence of serious otologic-audiologic problems generally found in an NICU population. Subsequent improvement (reversal) of the retest ABR records of the remaining infants in the 60 dB failure group was thought to be related to neural changes in the brainstem associated with recovery from hypoxic episodes. A transient or reversible conductive deficit appeared to account for the majority of failures at 40 dB. We recommend the screening protocol be expanded to include threshold and latency measures in infants who fail the initial screening. The transient nature of many ABR abnormalities makes postdischarge ABR, otologic, audiologic, and neurologic examinations mandatory before any inferences are made about hearing loss or neurodevelopmental disorders.

Gram-negative bacilli in human milk feedings: Quantitation and clinical consequences for premature infants

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Effects of positive pressure ventilation on intrarenal blood flow in infant primates.

Extract: Measurement of intrarenal distribution of renal blood flow by injection of radionuclides in 3—5-day-old infant monkeys showed a preponderance of outer cortical over inner cortical flow with flow rates of 4.23 and 2.54 ml/min/g, respectively. Intermittent positive pressure ventilation (IPPV) causes a reversal of this flow pattern. The theoretical difference in nephron function in these two areas suggests that this reversal in intrarenal flow induced by IPPV may have important clinical implications.Speculation: Extrarenal stimuli such as IPPV causes a redistribution of intrarenal blood flow in infant primates. Any stimuli that results in increased production of epinephrine or similar compounds may be responsible for this redistribution by a local effect on outer cortical blood vessels. Our data further suggest that antidiuretic hormone may influence intrarenal blood flow in addition to altering tubular membrane permeability.

Early state organization and follow-up over one year

Evaluations of state organization at 36 weeks postconceptional age (PCA) were conducted in the special care nursery on 24 low birth weight preterm neonates who were subsequently assessed on three dimensions of outcome at 1 year postterm. Half the subjects (N = 12) had been cared for in an alternative supportive nursery from 32 to 36 weeks PCA; the other half had remained in the regular intermediate care nursery. Although subjects from the alternative nursery demonstrated superior state organization before nursery discharge at 36 weeks PCA (p < .05), they were not superior on any outcome measures at 1 year postterm. Subjects demonstrating superior state organization within their nursery group were compared with subjects demonstrating inferior state organization within their nursery group. Significant differences in 1-year outcome were found between these two groups of good and poor neonatal state organizers on gross morbidity, on the Bayley motor scale, and on a measure of recovery of state organization observed in the Strange Situation (p < .05). J Dev Behav Pediatr 13:83–88, 1992.

The effect of phenobarbital on asphyxia in the newborn monkey.

Extract: This study characterizes the circulatory changes associated with asphyxia in the newborn monkey and examines the effect of phenobarbital on asphyxia. The time to last gasp and duration of total asphyxia as well as heart rate at the start of resuscitation were the same in the phenobarbital-treated and untreated infants. Initial cardiac output was the same in both groups; there was a profound drop in cardiac output with asphyxia which was the same in both groups. Organs which preferentially receive a greater percentage of cardiac output during asphyxia are heart, total brain, and adrenal glands. Organs receiving a decreased percentage of cardiac output during asphyxia are kidneys, liver, and gastrointestinal tract. Cerebral hemisphere flow as a percentage of cardiac output is maintained during asphyxia, whereas paleoencephalon flow as a percentage of cardiac output increases significantly. These data confirm the circulatory redistribution of cardiac output in response to asphyxia described previously in the monkey fetus. The treated infants did not show the prolongation of time to last gasp reported in the monkey fetus; the dose of phenobarbital we used, although adequate to produce sedation, may have been too low to demonstrate the protective effect.Speculation: The long term survival status of infants with neonatal diseases such as severe meconium aspiration or hyaline membrane disease which are frequently accompanied by varying degrees of asphyxia might be improved by including phenobarbital in the treatment regimen if a protective effect were conclusively demonstrated.

Organ blood flows of fetal and infant baboons

Baseline values for total and selected regional blood flows are presented for 77 studies of baboons from 92 days of gestation to 61 days of postnatal age. Systemic blood flow rose from 231.3 +/- 21.4 ml/min/kg to 330.4 +/- 122.4 ml/min/kg in late gestation and from 124.0 +/- 29.9 ml/min/kg on day 1 to 162.8 +/- 20.5 ml/min/kg at the 8th week. In both fetal and infant periods, blood flow to brain, heart, kidneys, and gastrointestinal tract changed to reflect both anatomic and functional requirements. When compared to late gestation levels, blood flows on day 1 to brain, myocardium and gastrointestinal tract decreased proportionally to systemic blood flow. In contrast, renal blood flow on day 1 was maintained at the predelivery level and represented about twice the proportion of systemic blood flow of late gestation. The data presented provide a developmental profile of systemic and selected organ blood flows from mid-gestation to the 8th week of postnatal life in the baboon. As such, they may form the basis for further investigation and understanding of perinatal maladaptation from preterm delivery and disease.

Amniotic fluid, epinephrine, and norepinephrine. I. Comparison between the human and baboon.

Abstract Comparisons were made of amniotic fluid amines (epinephrine [E] and norepinephrine [NE]) between 9 baboons and 8 human subjects. No significant difference was noted between baboon and human amniotic fluid NE when equated as micrograms of amines per milligram of creatinine. Values for E were significantly different, with 1.55 μg per milligram of creatinine observed in baboons as contrasted to 0.27 μg per milligram creatinine in the human subject. The E/NE ratios in the human subjects were 1.23 as compared to 4.34 in the baboon. The baboon fetus produces 6 times more E and twice as much NE than the human fetus. It can be inferred that the development of the adrenal gland and its innervation in the baboon fetus is more complete than in the human fetus, since higher levels of E are found in the baboon. The more mature adrenal gland in the baboon may be related to the mobilization of these stress hormones for a necessary homeostatic mechanism after birth.

Gluconeogenesis from Lactate in the Chronically Catheterized Baboon Fetus

Gluconeogenesis from lactate may be qualitatively identified in the chronically catheterized baboon fetus in the maternal fed and fasted state. Infusion of 250 microCi U-14C-lactate to the fetus over a 150-min period leads to the appearance of 14C-glucose in the fetal circulation. Little 14C-lactate or glucose appears in the maternal circulation, supporting fetal production of glucose from lactate. Maternal glucose infusion seems to inhibit fetal gluconeogenesis. The mean plateau in percent disintegrations per minute of glucose compared to lactate in the maternal fed state is 14.7 +/- 2.2 compared to 16.1 +/- 3.0 in the maternal fasting state and 11.1 +/- 0.6 during maternal glucose infusion. It is clear that the primate fetus is capable of gluconeogenesis before term. Quantitation of this capacity awaits development of a model permitting assessment of maternal-placental and fetal substrate flux.

Meeting the Special Nutritional Needs of Sick Infants with a Percutaneous Central Venous Catheter Quality Assurance Program

Adequate nutrition is important in infancy because it can affect brain growth. A critical period for brain growth is the end of the fetal growth period and the first 2 years of life. Delivery of nutrition to infants in the neonatal intensive care unit is challenging because illness and prematurity increase nutritional need and create access difficulties. One technique, percutaneous central venous catheter (PCVC) placement, eliminates access difficulties. Nevertheless, safe delivery of parenteral nutrition through PCVCs is dependent on minimizing infectious and mechanical complications. With the implementation of a PCVC quality assurance program, problems can be identified early, and appropriate, timely interventions can be initiated.

Placental Transfer and Fetal Effects of Maternal Sodium ß -Hydroxybutyrate Infusion in the Baboon

ABSTRACT: We examined the effects of maternal sodium ß-hydroxybutyrate (NaBOHB) on the primate fetus to investigate the impact of ketosis not associated with acidosis on fetal metabolism. After a loading dose (600 mg/ kg), NaBOHB was infused for 70 min (300 mg/kg hr) into the maternal femoral vein of eight pregnant baboons, and placental transfer and fetal and maternal metabolic changes were observed during an acute experimental protocol. Maternal arterial levels rose from 0.70 ± 0.21 to 5.42 ± 0.93 mM (p<0.001), and fetal arterial levels from 0.34 ± 0.09 to 2.76 ± 0.64 mM (p<0.01). A maternalfetal gradient of approximately 2:1 was observed in both baseline and steady-state infusion conditions and is similar to the human maternal-fetal ketone gradient. This is in contrast to the sheep where significantly higher gradients have been described. The elevated lactate, from 1.90 ± 0.34 to 2.88 ± 0.54 mM (p<0.05) and somewhat decreased pO2 values in the fetus from 54.8 ± 8.9 to 45.0 ± 3.8 mm Hg (p>0.05<0.1), without change in oxygen consumption (2.00 ± 0.28 versus 1.73 ± 0.15 mM/min) are features common to conditions of increased levels of fetal energy substrate. NaBOHB does not appear to contribute to oxidative energy metabolism of the whole fetus but may contribute to lipid stores. The significance of higher levels of BOHB in the primate fetus compared to the sheep fetus remains to be elucidated.