Sonographic assessment of renal size and growth in premature infants.

BACKGROUND: Low birth-weight infants are at risk for renal disease when renal insults occur in the neonatal period. Renal growth as measured by sonography over time is utilized by many nephrologists as predictors of future renal disease. OBJECTIVE: To identify infants at risk by defining normal renal growth for the very premature infant. MATERIALS AND METHODS: Renal growth was evaluated in 30 infants whose birth weight was 1,500 g or less and gestational age was <31 weeks. During a 2-month time period, three US measurements were taken (first week of life, age 28 days, and age 56 days or earlier if discharged). Infants were divided according to birth weight: the extremely low birth-weight group (ELBW) was <1,000 g (n = 14), and the very low birth-weight group (VLBW) was 1,000-1,500 g (n = 16). RESULTS: In both groups, the right and left renal lengths were similar. In the ELBW group, the initial mean length was 3.25 cm and grew to 4.16 cm, while the mean volume was 4.85 cm and grew to 10.39 cm. In the VLBW group the initial mean length was 3.69 cm and grew to 4.35 cm while the mean volume was 7.25 cm and grew to 11.83 cm. CONCLUSION: These data establish normal expected growth for future studies.

Meconium stained fluid: approach to the mother and the baby.

Meconium aspiration syndrome is a common problem that most pediatricians will encounter in the delivery room and normal newborn nursery. Approximately 13% of all live births are complicated by meconium-stained amniotic fluid. Like many aspects of the perinatal period, optimal care of an infant born through meconium-stained amniotic fluid involves collaboration between obstetrician and pediatrician, each with separate but important roles. As always, effective communication and advanced preparation and anticipation of potential problems form the cornerstone of this partnership. Together the health of infants may be improved.

Controversies in the treatment of meconium aspiration syndrome.

MAS remains an infrequent but challenging condition confronting neonatologists. Avoidance of postterm pregnancies, improved intrapartum monitoring,and amnioinfusion have been beneficial. Studies have not demonstrated conclusively that any form of ventilation is superior to others, but strategies that recruit alveoli are desirable. Surfactant lavage or replacement may be beneficial. When hypoxic respiratory failure progresses, iNO may improve oxygenation and avoid ECMO.

A new model of oxidative stress in rat pups.

BACKGROUND: With current evidence, no specific oxygen concentration can yet be recommended in the resuscitation of the depressed term neonate. OBJECTIVES: To design a neonatal rat model of resuscitation that mimics birth hypoxia and allows the study of the effects of resuscitation on outcome. METHODS: Several key determinants were established utilizing P12 Sprague-Dawley rat pups. These include the ventilatory settings necessary to maintain normocarbic conditions and the amount and duration of hypoxia required to cause significant disruption of oxidative metabolism in the subjects' brains. Biochemical and cellular markers of oxidative injury were then compared in response to normoxic versus hyperoxic resuscitation. RESULTS: Oxidative stress is produced in 12-day-old intubated rat pups with 15 min of 5% oxygen followed by 30 min of 100% oxygen or room air. Oxidized glutathione levels increased immediately after hypoxia and resuscitation then returned to control values at 24 h regardless of the resuscitate. Reduced glutathione levels were, however, significantly decreased 24 h after resuscitation with pure oxygen compared with the room air-resuscitated group (391 +/- 35 vs. 508 +/- 71 nmol/ml; p = 0.037). Stress from either resuscitate did not translate into evidence of oxidative modification detected by immunocytochemistry at 30 days. CONCLUSIONS: We have demonstrated the ability to ventilate, create hypoxic stress, and resuscitate neonatal rats. While resuscitation with 21 or 100% oxygen results in a transient increase in oxidative glutathione levels, the oxygen-resuscitated group alone demonstrated a reduction in reduced glutathione 24 h later. Furthermore, these pups can then be returned to their dams for rearing, allowing ongoing evaluation of long-term effects of hypoxia and various modes of resuscitation.

Consequences of neonatal resuscitation with supplemental oxygen.

There has been considerable controversy surrounding the optimal inspired oxygen concentration for resuscitation of term and preterm infants. We have developed a rat pup model to quantify both physiologic and biochemical parameters associated with normoxic vs. hyperoxic resuscitation. We have confirmed existing human data that hyperoxic resuscitation of rat pups is associated with a significant delay in onset of spontaneous respiratory efforts. Both 40% and 100% inspired oxygen delayed onset of respiratory activity when compared to 21% oxygen. We have also documented, in the rat pup model, that hyperoxic resuscitation is associated with reduced levels of glutathione at 24 hours post resuscitation. The implications of these and other findings for human infants are that term asphyxiated babies can be safely resuscitated in 21% oxygen and that supplementary oxygen can be reserved for non-responders. In contrast, resuscitation of extremely low gestational age infants does appear to require an initial low inspired oxygen concentration (eg, 30%) with subsequent pulse oximetry titration to optimize oxygenation status.

Effect of supplemental oxygen on reinitiation of breathing after neonatal resuscitation in rat pups.

To test our hypothesis that resuscitation with 21% and 40% oxygen (O2) would shorten time to onset of respiratory activity when compared with resuscitation with 100% O2, diaphragmatic electromyogram (EMG) electrodes were inserted in Sprague-Dawley rat pups, age 8-10 d before intubation and mechanical ventilation with 5% O2 to induce cessation of respiratory activity. Each animal was then resuscitated with 100% and 21% O2 (n = 10) or 100% and 40% O2 (n = 11) for 30 s before the ventilator was disconnected. Recovery of diaphragm activity was compared between resuscitation groups. Blood gas status and heart rate data were characterized in additional rat pups. Time to first respiratory effort was 36 +/- 21 s (mean +/- SD) for room air resuscitation and 72 +/- 22 s for 100% O2, (p = 0.002). In contrast, there was no difference in time to onset of diaphragm activity when resuscitation with 40% O2 was compared with 100% O2: 84 +/- 27 s versus 76 +/- 23 s, respectively (p > 0.05). Resuscitation with 100% and 40% O2 both resulted in hyperoxia and hypocapnia when compared with room air, without effect on heart rate. Our findings indicate that even modest hyperoxic resuscitation will result in a delayed onset of respiration compared with normoxic gas, via a mechanism that may involve both hyperoxemic and hypocapnic inhibition of chemoreceptors.