Reliable and developmentally appropriate study end points are needed to achieve drug development for treatment of pediatric pulmonary arterial hypertension

OBJECTIVE

To identify suitable end points and surrogates for pediatric pulmonary arterial hypertension (PAH) as the lack of developmentally appropriate end point and clinical trials contribute to the unmet medical need.

STUDY DESIGN

Reviewed the efficacy end points and surrogates for all trials (1995 to 2013) that were submitted to the Food and Drug Administration (FDA) to support the approval of PAH therapy and conducted literature search.

RESULTS

An increase in the 6 min walking distance (6MWD) was used as a primary end point in 8/9 adult PAH trials. This end point is not suitable for infants and young children because of performance limitations and lack of control data. One adult PAH trial used time to the first morbidity or mortality event as a primary end point, which could potentially be used in pediatric PAH trials. In the sildenafil pediatric PAH trial, the change in pulmonary vascular resistance index or mean pulmonary artery pressure was used as a surrogate for the 6MWD to assess exercise capacity. However, two deaths and three severe adverse events during the catheterizations made this an unacceptably high-risk surrogate. The INOmax persistent pulmonary hypertension of the newborn trial used a reduction in initiation of extracorporeal membrane oxygenation treatment as a primary end point, which is not feasible for other pediatric PAH trials. A Literature review revealed none of the existing noninvasive markers are fully validated as surrogates to assess PAH efficacy and long-term safety.

CONCLUSIONS

For pediatric PAH trials, clinical end points are acceptable, and novel validated surrogates would be helpful. FDA seeks collaboration with academia, industry and parents to develop other suitable and possibly more efficient efficacy end points to facilitate pediatric PAH drug development.

Inhaled nitric oxide use in preterm infants in California neonatal intensive care units

OBJECTIVE

To describe inhaled nitric oxide (iNO) exposure in preterm infants and variation in neonatal intensive care unit (NICU) use.

STUDY DESIGN

This was a retrospective cohort study of infants, 22 to 33+6/7 weeks of gestational age (GA), during 2005 to 2013. Analyses were stratified by GA and included population characteristics, iNO use over time and hospital variation.

RESULTS

Of the 65 824 infants, 1718 (2.61%) received iNO. Infants, 22 to 24+6/7 weeks of GA, had the highest incidence of iNO exposure (6.54%). Community NICUs (n=77, median hospital use rate 0.7%) used less iNO than regional NICUs (n=23, median hospital use rate 5.8%). In 22 to 24+6/7 weeks of GA infants, the median rate in regional centers was 10.6% (hospital interquartile range 3.8% to 22.6%).

CONCLUSION

iNO exposure varied with GA and hospital level, with the most use in extremely premature infants and regional centers. Variation reflects a lack of consensus regarding the appropriate use of iNO for preterm infants.

Survey of neonatology training programs: 2002 to 2003

The Committee on Research in Neonatology from the Section on Perinatal Pediatrics, American Academy of Pediatrics presents an overview of the update of the Neonatal-Perinatal Training Program Survey obtained in 2002 to 2003. Our goal was to update the last survey in 1996 and to begin to assess research resources and the potential for training life-career physician scientists (basic and clinical investigators).

Fewer spontaneous arousals during prone sleep in preterm infants at 1 and 3 months corrected age

OBJECTIVE

This study was performed to determine if there were fewer spontaneous arousals in prone sleep than in supine sleep.

STUDY DESIGN

Home polysomnography/video recordings were done during daytime naps in 14 preterm infants: four at corrected age of 1 month, nine at both 1 and 3 months, and one only at 3 month. A body movement lasting 3 to 60 s during sleep was used as an indicator of spontaneous arousals.

RESULTS

Most arousals had a heart rate increase and change in respiration pattern. The mean duration of the intervals between successive arousals in active and quiet sleep was significantly longer in prone at 1 and 3 months of age. The duration of arousals was significantly shorter at 3 months corrected age compared with one month corrected age during active sleep. The duration of arousals was shorter during quiet sleep at one month compared with active sleep.

CONCLUSION

There were fewer spontaneous arousals that is, longer interval between successive arousals in prone, which may, in part, explain the increase in risk of Sudden Infant Death Syndrome.

Diffusion tensor brain imaging findings at term-equivalent age may predict neurologic abnormalities in low birth weight preterm infants

BACKGROUND AND PURPOSE

Low birth weight preterm infants are at high risk of brain injury, particularly injury to the white matter. Diffusion tensor imaging is thought to be more sensitive than conventional MR imaging for detecting subtle white matter abnormalities. The objective of this study was to examine whether diffusion tensor imaging could detect abnormalities that may be associated with later neurologic abnormalities in infants with otherwise normal or minimally abnormal conventional MR imaging findings.

METHODS

We prospectively studied 137 low birth weight (<1800 g) preterm infants. Neonatal conventional MR imaging and diffusion tensor imaging were performed near term-equivalent age before discharge, and neurologic development of the infants was later followed up at 18 to 24 months of age.

RESULTS

Among the preterm infants who were fully studied, 63 underwent normal conventional MR imaging. Three of these infants developed cerebral palsy, and 10 others showed abnormal neurologic outcome. Diffusion tensor imaging results for these infants showed a significant reduction of fractional anisotropy in the posterior limb of the internal capsule in neurologically abnormal infants (including those with cerebral palsy) compared with control preterm infants with normal neurologic outcomes.

CONCLUSION

These results suggest that neonatal diffusion tensor imaging may allow earlier detection of specific anatomic findings of microstructural abnormalities in infants at risk for neurologic abnormalities and disability. The combination of conventional MR imaging and diffusion tensor imaging may increase the predictive value of neonatal MR imaging for later neurologic outcome abnormalities and may become the basis for future interventional clinical studies to improve outcomes.

Cisapride decreases gastroesophageal reflux in preterm infants

OBJECTIVE

Gastrointestinal prokinetic agents, such as cisapride, are commonly used in pediatric practice to improve gastric emptying, to decrease emesis, to improve lower esophageal sphincter tone, and to improve irritability and feeding aversion associated with gastroesophageal reflux (GER). Although cisapride seems to be effective in infants from 2 months to 14 years old, data for younger and preterm infants are not available. Whether reflux is a significant cause of reflex apnea or feeding intolerance in the preterm infant is controversial. The objective of this 1-year prospective study, started in 1998, was to determine the efficacy of cisapride for treatment of reflux and reflux-associated apnea (RAAP) in preterm infants. Before this study, the diagnosis of reflux was often made clinically and the effect of therapy on reflux or the decision to increase the dose of cisapride was made empirically. The clinical bias was that persistent apnea, not responding to caffeine, was caused by GER. We reasoned that a systematic approach to the diagnosis and treatment of reflux would improve the care of preterm infants and reduce the risk of toxicity, especially if an increased dose of cisapride showed no improvement in reflux or apnea.

STUDY DESIGN

Twenty-four preterm infants (24-36 weeks' gestational age) had clinical apnea/pH studies when they were referred by the attending neonatologist for suspected GER. These infants were born at 28.8 +/- 3.1 weeks with birth weight of 1169 +/- 387 g (range: 631-2263 g). Each infant was studied before and 8 days after starting cisapride treatment. Cisapride dose was 0.09 to 0.25 mg/kg every 6 hours enterally. Treatment decisions regarding dose of cisapride were the responsibility of the attending neonatologist. The pH was recorded continuously for 24 hours at 0.25 Hz and was analyzed using EsopHogram software. A single sensor pH catheter was inserted to ~2 cm above the esophageal gastric junction. GER was defined as a drop in esophageal pH below 4.0 for a least 5 seconds, or pathologic GER was defined as a reflux index (RI) >2 standard deviation (SD) from the mean based on published norms for term infants. The following parameters were calculated from the pH recording: number of reflux events per 24 hours, duration of the longest episode, number of episodes >5 minutes per 24 hours, and RI, ie, percentage of time with pH <4.0. Each study had a combined time-lapse video recording and multichannel digital recording. Recorded parameters were: continuous pulse oximetry, electrocardiogram, respiratory effort (piezo sensor), and airflow (temperature sensor at nostrils and mouth). The recording was scored for central apneas of 10 to 14 seconds and >/=15 seconds (prolonged) and >/=10 seconds for obstructive and mixed apneas. RAAP was scored when an apnea (irrespective of the type) occurred within 1 minute of a GER event. Baseline, after cisapride, and follow-up electrocardiograms were performed because of concern about prolonged QTc and cardiac arrhythmias. The infants were 35.6 +/- 4.5 weeks postconceptional age when first studied. Twelve infants (mean birth weight: 1821 +/- 749 g; gestational age: 32 +/- 2 weeks; postconceptional age: 35.6 +/- 2.6 weeks) were identified retrospectively as controls because their baseline GER parameters were within the normal range using Vandenplas' criteria.

RESULTS

Overall, cisapride treatment significantly improved the RI from 16.6 +/- 15.2 to 9.1 +/- 8.4 SD. The number of reflux episodes >/=5 minutes was reduced from 7.1 +/- 5.8 to 4.3 +/- 4.4 SD. No significant effect was seen on the total number of refluxes (/24 hours). Eight infants (33%) had no decrease in the RI after a week of treatment. Three of these infants improved after cisapride dose was increased from 0.09 to 0.25 mg/kg/dose every 6 hours. Although 0.09 mg/kg/day is the minimum effective dose, 67% of our infants did respond to this low dose. Cisapride was discontinued in 3 infants because of prolonged QTc >/=0.450 seconds (0.473 in 1 and 0.470 in 2). More data about the effect of cisapride on QTc interval are reported in Pediatrics in a separate article. Only 1 infant showed no improvement with increased dose. Caffeine treatment had no effect on the baseline or follow-up GER values. Although apnea indexes for central and obstructive apnea were similar before and after cisapride, mixed apnea was less during treatment. There was a significant decrease (0.32 +/- 0.40 to 0.12 +/- 0.17/hour) in RAAP when the one infant who had increased reflux on increased dose of cisapride was excluded as an outlier. The statistical difference, before and after cisapride, for the group is significant with the outlier omitted. The clinical significance is unclear because ~50% of the infants had minimal changes in their apnea indexes. Furthermore, ~40% of infants did not have RAAP. (ABSTRACT TRUNCATED)

Influence of light in the NICU on the development of circadian rhythms in preterm infants

The fetal biological clock is an endogenous clock capable of generating circadian rhythms and responding to maternal entraining signals. By at least the third trimester of pregnancy fetal diurnal rhythms are entrainable by maternal day-night rhythms. Maternal illness during pregnancy and premature birth are obvious clinical factors that may adversely affect circadian rhythm development. Premature birth of the fetus has a most dramatic impact on maternal fetal interactions. The effect on biorhythms appears to be temporary and is greatest on the most immature infants. The results to date support the importance of fetal circadian rhythms and the relative lack of these rhythms in the preterm infant. It is well known that growth and development in the prematurely born infant are influenced by a multitude of factors; clearly, the neonatal intensive care unit is not a surrogate for the maternal placental unit. This article reviews what is known about circadian development in the human infant with an emphasis on the unique circumstances of the preterm infant. The research on the short- and long-term effects of environmental interventions on circadian, sleep, and neurologic development is discussed. Although an earlier onset of circadian development did not result with cycled lighting in the neonatal nursery, there may still be important biological effects that have not been studied. There are sufficient data to state that there is no reason for continuing a chaotic, noncircadian environmental approach for the care of the prematurely born infant.

Predictive value of neonatal neurological tests for developmental outcome of preterm infants

BACKGROUND

There is a need to identify, as early as possible, infants who are at risk for long-term neurological morbidity.

METHODS

To predict neurodevelopment outcome of preterm infants <30 weeks' gestation in a population of 100 infants, we used several neonatal and neurobehavioral tests, including cranial ultrasonography, the Prechtl neurological test, quality of spontaneous general movements, and quality of sleep-wake organization.

RESULTS

The Prechtl test at corrected term age and findings on cranial sonograms both had high specificity, but the Prechtl test had better overall positive predictive power for normal neurological and developmental outcomes at 2 years' corrected age. Developmental changes in sleep and the amount of indeterminate sleep did not correlate with outcome. Scoring general movement quality did not predict outcome and did not augment the positive predictive power of the Prechtl test.

CONCLUSIONS

The Prechtl test at corrected term age (independent of the other tests) is the best positive predictor of normal neurological outcome and Bayley test results at 2 years' corrected age.

More awakenings and heart rate variability during supine sleep in preterm infants

OBJECTIVE

The Task Force of The American Academy of Pediatrics (1996) recommends the nonprone sleeping position for asymptomatic preterm infants to prevent sudden infant death syndrome. The mechanism by which the nonprone sleeping position reduces the rate of sudden infant death syndrome is unclear for full-term infants and the precise effect of sleeping position on sleep and cardiorespiratory characteristics has never been addressed in preterm infants. The purpose of the present study was to clarify the effect of sleeping position on sleep and cardiorespiratory characteristics in preterm infants at an age when they are ready for discharge.

STUDY DESIGN

Sixteen asymptomatic preterm infants were studied in both supine and prone sleeping positions at 36.5 +/- 0.6 weeks' postconceptional age using videosomnography. Sleep, respiratory, and heart rate characteristics were compared between the two positions using each infant as his/her own control.

RESULTS

More awakenings (ie, arousals >/=60 seconds) were seen during all sleep states in the supine sleeping position but overall the total sleep and percent sleep state were not affected by sleeping position. After each feeding, the first quiet sleep was significantly shorter, with more heart rate variability and awakenings in the supine position. There were no significant differences in the occurrence of arousals (<60 seconds) or the incidence or severity of apnea and periodic breathing. No clinically significant apnea (>/=15 seconds), bradycardia, or oxygen desaturations were seen.

CONCLUSION

In 36-week-postconceptional age preterm infants, the supine sleeping position had less quiet sleep and was associated with greater heart rate variability during the first sleep cycle after the feeding. More awakenings were seen during all sleep states in the supine position. These data support the American Academy of Pediatrics recommendation for "Back to Sleep" for asymptomatic preterm infants because more awakenings and lower threshold for arousal may provide some benefit for the infant responding to a life-threatening event. However, further studies are needed to address positional effect on the physiologic measures in preterm infants at older ages (later stages of development). Precisely what constitutes the most healthy or advantageous sleep for newborn infants remains an important question.

Survey of sleeping position after hospital discharge in healthy preterm infants

OBJECTIVE

To evaluate the prevalence of nonprone (supine or side) versus prone sleeping position in healthy preterm infants.

STUDY DESIGN

A questionnaire on sleeping position was mailed to mothers of 167 preterm infants discharged from the intermediate nursery at Packard Children's Hospital at Stanford. The prevalence of nonprone sleeping at 1 month (term corrected age) and 3 months (2 months corrected age) after nursery discharge was analyzed by an unpaired t test.

RESULTS

Nonprone position sleeping occurred in 64% initially and dropped to 35% at 2 months corrected age.

CONCLUSIONS

Overall, nonprone sleeping was widespread in our healthy preterm infants after hospital discharge but may not persist. A majority of these infants were sleeping prone during a high-risk period for sudden infant death syndrome.

Developmental care does not alter sleep and development of premature infants

OBJECTIVE

The Neonatal Individualized Developmental Care Program (NIDCAP) for very low birth weight (VLBW) preterm infants has been suggested by Als et al to improve several medical outcome variables such as time on ventilator, time to nipple feed, the duration of hospital stay, better behavioral performance on Assessment of Preterm Infants' Behavior (APIB), and improved neurodevelopmental outcomes. We have tested the hypothesis of whether the infants who had received NIDCAP would show advanced sleep-wake pattern, behavioral, and neurodevelopmental outcome.

METHODS

Thirty-five VLBW infants were randomly assigned to receive NIDCAP or routine infant care. The goals for NIDCAP intervention were to enhance comfort and stability and to reduce stress and agitation for the preterm infants by: a) altering the environment by decreasing excess light and noise in the neonatal intensive care unit (NICU) and by using covers over the incubators and cribs; b) use of positioning aids such as boundary supports, nests, and buntings to promote a balance of flexion and extension postures; c) modification of direct hands-on caregiving to maximize preparation of infants for, tolerance of, and facilitation of recovery from interventions; d) promotion of self-regulatory behaviors such as holding on, grasping, and sucking; e) attention to the readiness for and the ability to take oral feedings; and f) involving parents in the care of their infants as much as possible. The infants' sleep was recorded at 36 weeks postconceptional age (PCA) and at 3 months corrected age (CA) using the Motility Monitoring System (MMS), an automated, nonintrusive procedure for determining sleep state from movement and respiration patterns. Behavioral and developmental outcome was assessed by the Neurobehavioral Assessment of the Preterm Infant (NAPI) at 36 weeks PCA, the APIB at 42 weeks PCA, and by the Bayley Scales of Infant Development (BSID) at 4, 12, and 24 months CA.

RESULTS

Sleep developmental measures at 3 months CA showed a clear developmental change compared with 36 weeks PCA. These include: increased amount of quiet sleep, reduced active sleep and indeterminate sleep, decreased arousal, and transitions during sleep. Longest sleep period at night showed a clear developmental effect (increased) when comparing nighttime sleep pattern of infants at 3 months with those at 36 weeks of age. Day-night rhythm of sleep-wake increased significantly from 36 weeks PCA to 3 months CA. However, neither of these sleep developmental changes showed any significant effects of NIDCAP intervention. Although all APIB measures showed better organized behavior in NIDCAP patients, neither NAPI nor Bayley showed any developmental advantages for the intervention group. The neurodevelopmental outcome measured by the Bayley at 4, 12, and 24 months CA showed 64% of the NIDCAP intervention group at the lowest possible score compared with 33% of the control group. These findings could not be explained by the occurrence of intraventricular hemorrhage or the socioeconomic status of the parents, which showed no significant group effect.

CONCLUSION

The results of this study, including measures of sleep maturation and neurodevelopmental outcome up to 2 years of age did not demonstrate that the NIDCAP intervention results in increased maturity or development. Buehler et al (Pediatrics. 1995;96:923-932) have reported that premature infants (N = 12; mean gestational age 32 weeks, mean birth weight 1700 g) who received developmental care compared with a similar group of infants who received routine care showed better organized behavioral performance on an APIB assessment at 42 weeks PCA. None of the medical outcome measures were significantly different in this study. Although our APIB results are in agreement, the results of the NAPI, the Bayley and sleep measures do not show an increase in neurodevelopmental maturation. In the earlier report by Als et al (Journal of the American Medical Associatio

Dew-point hygrometry system for measurement of evaporative water loss in infants

Evaporation of water from the skin is an important mechanism in thermal homeostasis. Resistance hygrometry, in which the water vapor pressure gradient above the skin surface is calculated, has been the measurement method of choice in the majority of pediatric investigations. However, resistance hygrometry is influenced by changes in ambient conditions such as relative humidity, surface temperature, and convection currents. We have developed a ventilated capsule method that minimized these potential sources of measurement error and that allowed second-by-second, long-term, continuous measurements of evaporative water loss in sleeping infants. Air with a controlled reference humidity (dew-point temperature = 0 degree C) is delivered to a small, lightweight skin capsule and mixed with the vapor on the surface of the skin. The dew point of the resulting mixture is measured by using a chilled mirror dew-point hygrometer. The system indicates leaks, is mobile, and is accurate within 2%, as determined by gravimetric calibration. Examples from a recording of a 13-wk-old full-term infant obtained by using the system give evaporative water loss rates of approximately 0.02 mgH2O.cm-2.min-1 for normothermic baseline conditions and values up to 0.4 mgH2O.cm-2. min-1 when the subject was being warmed. The system is effective for clinical investigations that require dynamic measurements of water loss.

Randomized multicenter trial comparing synchronized and conventional intermittent mandatory ventilation in neonates

OBJECTIVE

To compare synchronized intermittent mandatory ventilation (SIMV) and conventional intermittent mandatory ventilation (IMV) in neonates.

STUDY DESIGN

Prospective, multicenter, randomized clinical trial.

SETTING

Level III neonatal intensive care units at six university or children's hospitals.

PATIENTS

Three hundred twenty-seven infants receiving conventional IMV for respiratory distress syndrome, pneumonia, or meconium aspiration pneumonitis were randomly assigned a 7.5 +/- 6 hours of age to either continue with IMV or change to SIMV. Infants assigned to each mode of ventilation had similar birth weight (BW), gestational age, and Apgar scores at birth, and similar oxygenation indexes at randomization. They received similar surfactant therapy and had similar incidence of sepsis, seizures, secondary pneumonia, and necrotizing enterocolitis. In the infants with BW less than 1000 gm, more infants receiving IMV had surgical ligation of their patent ductus arteriosus than did those receiving SIMV (27 vs. 7 %; p = 0.02).

ANALYSIS

Data was analyzed overall for all infants and also separately within three BW groups: less than 1000 gm, 1000 to 2000 gm, and more than 2000 gm. The 1000 to 2000 gm BW group was further analyzed in subgroups weighing 1000 to 1499 gm and 1500 to 2000 gm.

RESULTS

In all infants, at 1 hour after randomization, the infants receiving SIMV had a lower mean airway pressure than those receiving IMV (8.08 +/- 2.15 vs. 8.63 +/- 2.59; p<0.05), with similar fractions of inspired oxygen and oxygenation indexes. Infants whose BW was 1000 to 2000 gm at 0.5 hour required a lower fraction of inspired oxygen with SIMV than with IMV (0.52 +/- 0.20 vs. 0.62 +/- 0.27; p<0.05) and had better oxygenation at 1 hour, as shown by lower oxygenation indexes with SIMV than with IMV (6.14 +/- 4.17 vs. 9.42 +/- 8.41; p = 0.01). Infants whose BW was 1000 to 2000 gm received a lower number of unit doses of sedative/analgesic drugs per infant during the first 4 days of SIMV than did infants receiving IMV (3.8 +/- 3.4 vs 6.3 +/- 5.5 unit doses; p = 0.02). Infants whose BW was more than 2000 gm had a shorter duration of mechanical ventilation with SIMV than with IMV (median, 72 vs 93 hours; p = 0.02). Three of the forty-six infants receiving IMV but none of the 47 infants receiving SIMV required extracorporeal membrane oxygenation. In the infants with BW less than 1000 gm, fewer infants treated with SIMV required supplemental oxygen at 36 weeks of postconceptional age than did those treated with IMV (47 vs 72%; p<0.05). In 83 infants whose lungs were mechanically ventilated for 14 days or longer, all with BW less than 2000 gm, those treated with SIMV regained their BW earlier than those treated with IMV (median, 21.5 vs 29 days; p<0.01). There were no differences in the rates of death, intraventricular hemorrhage (grades III and IV), air leak, need for pharmacologic paralysis, or need for supplemental oxygen at 28 days.

CONCLUSIONS

We found that SIMV was at least as efficacious as conventional IMV, and may have improved certain outcomes in BW-specific groups.

Biological rhythmicity in preterm infants prior to discharge from neonatal intensive care

OBJECTIVE

The study of biological rhythms and the influence of environmental factors in the timing and synchronization of different rhythmic events have important implications for neonatal health. Preterm infants in the neonatal intensive care unit (NICU) are deprived of the patterned influences of maternal sleep, temperature, heart rate, and hormonal cycles. The impact of the NICU and nursing interventions on the development of the circadian system was studied in 17 stable preterm infants in the Intermediate Intensive Care Nursery at Stanford University for three consecutive days at about 35 weeks postconceptional age.

OUTCOME MEASUREMENTS

Rectal temperature, abdominal skin temperature, heart rate, and activity were simultaneously recorded at 2-minute intervals during each 3-day study by a small microcomputer (Vitalog).

RESULTS

Very low amplitude circadian rhythms were found for rectal and skin temperatures (maximum range 36.8 to 37.0 degrees C); population mean values for heart rate (158 bpm) and activity (3.5 counts per 2-min bin) did not differ significantly as a function of time of day. Rectal temperature, averaged in 6-hour bins over the 24-hour day as a function of both postconceptional age and postnatal age, was significantly higher during the first part of the circadian cycle. In all infants, rhythmicity in each variable was dominated by ultradian periodicities that were coincident with feedings and related interventions; moreover, several physiological variables charted during feeding differed significantly from values obtained during periods in which caregiving interventions did not occur.

CONCLUSION

Quantitative data on the preterm infant circadian system may facilitate evaluation of factors that improve therapeutic responses, recovery, and outcome of neonatal intensive care patients.

Biological rhythmicity in normal infants during the first 3 months of life

OBJECTIVE

The mammalian "biological clock," which resides in the hypothalamic suprachiasmatic nucleus, has an important role in both the timing and organization of sleep and in the coordination of sleep with other physiological rhythms such as temperature regulation and respiratory control. We wished to describe the development of the circadian system in normal infants during the first 3 months of life.

METHODS

Ten healthy full term infants were studied in the infant's home for three consecutive days at 1 month and 3 months postnatal age. Rectal temperature, abdominal skin temperature, heart rate, and activity were recorded at 2-minute intervals during each study using a small microcomputer.

RESULTS

Circadian periodicity for most variables was seen at 1 month of age and significantly increased at 3 months. Differences in the pattern of rhythmicity during these two developmental periods were highlighted by an increase in activity during the subjective day and a decrease in Trec during the subjective night at 3 months compared to 1 month. Correlational analysis revealed that all pairs of variables, exclusive of Tsk, showed a significantly higher association at 3 months relative to 1 month. The lengthening of the interfeeding interval at 3 months of age corresponded with an increased consolidation of sleep during the night and a relatively lower nocturnal body temperature minima compared to 1 month of age.

CONCLUSION

The results of this study underscore the subtle changes in the nature and interaction of several infant variables during this critical developmental period, which may reflect maturation of the circadian system and its coupling with homeostatic effector systems that are developing in parallel.

Light variability in the modern neonatal nursery: chronobiologic issues

The role that nursery light variability may play in modulating infant biological rhythms is being studied in Stanford Medical Center's Neonatal Intensive Care (NICU) and Intermediate Care (IN) Nurseries. In this investigation, spatial and temporal variability in illuminance was determined at 20 sites within each nursery over a 5-day period. The analysis of 240 measurements at 30 min intervals from each site revealed marked variability in illumination with respect to both time and position in the nursery. These aperiodic lighting patterns differed greatly from the published characterization of NICUs as having 'constant' illumination. Light pulses of variable frequency, intensity, and duration were common at each of the 40 bedsites studied. Given the powerful impact of light on circadian rhythmicity and sleep in adults, the results from this study suggest that modern NICU lighting, while implemented to facilitate intensive care, may have adverse effects on infant development. Future studies on the influence of light on biological rhythmicity and sleep are essential to provide a framework for clinical and environmental interventions, which may play a significant role in improving developmental outcome in hospitalized preterm or term infants.

Delayed compliance increase in infants with respiratory distress syndrome following synthetic surfactant

Recent research has demonstrated that Exosurf (EXSF), a newly synthesized artificial surfactant, increases survival when administered endotracheally to premature infants with RDS. This study examines the effects of EXSF on static respiratory system compliance (Crs). Thirty-four patients received two doses of EXSF in this rescue protocol. Crs (mL/cmH2O/kg) did not significantly change within the first 4 hours after either dose. However, Crs values did increase significantly (paired Student's t-test, P = 0.005) when data collected after the second dose (0.36 +/- 0.13 mL/cmH2O/kg) were compared to first week follow-up data (0.51 +/- 0.21 mL/cmH2O/kg). Crs data collected between 2 and 4 weeks after treatments were again not significantly different from non-concurrent control data collected at 3-4 weeks of life. The measurement of Crs in infants receiving EXSF may have been affected by an increase in lung inflation, which could mask an increase in Crs. We speculate that improved lung inflation may occur with less barotrauma in the first week of life due to surfactant replacement treatment and may in part explain the improved Crs seen at 1 week of age. Many investigators using different surfactants, dosing schedules, and pulmonary function methodologies to evaluate lung mechanics have reported that the improvement in compliance after surfactant treatment usually follows the clinical improvement in gas exchange. Additional studies are needed to explain the mechanism of early improvement following surfactant replacement in infants with RDS.

Noninvasive methods for estimating in vivo oxygenation

Clinical signs of hypoxia and hyperoxia are nonspecific and unreliable, yet both are potentially injurious. Noninvasive methods of oxygen assessment fill the gap between clinical observation and invasive tests, helping physicians deliver sufficient oxygen with minimum toxicity. Potential sites for oxygen measurement vary between the blood and the mitochondria; each method measures at a different site and detects different types of hypoxia and hyperoxia. Thus, values obtained by two different methods are not equivalent, giving each method unique strengths and weaknesses. We review two clinical methods (pulse oximetry and transcutaneous oximetry), as well as four experimental methods (near-infrared spectrophotometry, magnetic resonance spectroscopy, magnetic resonance saturation imaging, and time-of-flight absorbance spectrophotometry). The principles of each method and the clinical situations in which each succeeds or fails are discussed. A fundamental understanding of each method can help in deciding which methods, if any, are appropriate for a given patient and how best to correct observed oxygenation problems once they are discovered.

Incidence of bronchopulmonary dysplasia, growth failure, and pulmonary dysfunction assessed by clinical scoring

A clinical scoring system was used to determine retrospectively whether the severity of bronchopulmonary dysplasia (BPD) in 67 preterm infants at 21 to 27 days of age would predict the need for home supplemental oxygen or growth retardation (weight less than 5th percentile at 12 months of age). The scoring system was composed of five variables, including fractional inspiratory oxygen, partial pressure of CO2, respiratory rate, chest retractions, and growth rate. The score did not predict the need for home supplemental oxygen or growth retardation (P = .87 and .79, respectively); in contrast, the number of hours of oxygen greater than 80% was significantly correlated with home O2 use (P = .0001) and growth retardation at 1 year of age (P = .013). Since there is no simple predictive score that can be used to determine the functional severity of BPD, each at-risk infant must be clinically evaluated for the degree of pulmonary dysfunction, the need for O2 supplementation, and other supportive pulmonary care prior to discharge.

Plasma dopamine, norepinephrine, epinephrine and DOPAC levels in preterm infants prior to and immediately after a sleep ventilation hypercarbia test

The postnatal maturation and the adaptational ability of the sympathoadrenal system has been investigated in preterm neonates (n = 8), and in sick preterm neonates with respiratory disorders (n = 10). Plasma levels of dopamine (DA), norepinephrine (NE), epinephrine (E) and 3-4 dihydroxyphenylacetic acid (DOPAC) were evaluated at rest during the first month of life, and following an inhalation of a 5% carbon dioxide-21% oxygen mixture for 10 min. During the first month of life the sick preterm neonates exhibited similar NE, E, and DOPAC plasma levels but higher DA amounts than healthy infants. Plasma DA levels were inversely correlated with the transcutaneous oxygen tension (r = -0.636) indicating that hypoxemia was able to enhance the release of DA. Immediately following the hypercarbia test, there were no significant changes of plasma catecholamine levels in the sick preterms, but there was a significant increase of E plasma levels (+140%, p less than 0.05) and a moderate elevation of NE and DA amounts in the healthy preterms. It is concluded that preterm neonates who have had respiratory disorders did not exhibit an immaturity of the sympathoadrenal system at rest, but had a defect in the release of E following hypercarbia exposure, which may be secondary to an alteration in chemoreceptor function and/or reduced catecholamine stores.

A controlled trial of aerosolized ribavirin in infants receiving mechanical ventilation for severe respiratory syncytial virus infection

BACKGROUND

Although the antiviral agent ribavirin improves the course of lower respiratory tract disease in spontaneously breathing infants with respiratory syncytial virus infection, it is not known whether ribavirin can benefit infants with severe respiratory syncytial virus disease who require mechanical ventilation.

METHODS

We conducted a randomized, double-blind, placebo-controlled evaluation of ribavirin (20 mg per milliliter) administered continuously in aerosolized form to infants receiving mechanical ventilation for respiratory failure that was caused by documented respiratory syncytial virus infection.

RESULTS

Of the 28 infants (mean [+/- SD] age, 1.4 +/- 1.7 months) enrolled, 7 had underlying diseases predisposing them to severe infection (mean age, 3.0 +/- 2.6 months), and 21 were previously normal (mean age, 0.8 +/- 0.9 month). Among the 14 infants who received ribavirin, the mean duration of mechanical ventilation was 4.9 days (as compared with 9.9 days among the 14 who received placebo; P = 0.01), and the mean length of supplemental oxygen use was 8.7 days (as compared with 13.5 days; P = 0.01). The mean length of the hospital stay was 13.3 days after treatment with ribavirin and 15.0 with placebo (P = 0.04). When only the 21 previously normal infants were considered, the mean length of the hospital stay was 9.0 days for the ribavirin recipients and 15.3 days for those who received placebo (P = 0.005).

CONCLUSIONS

In infants who require mechanical ventilation because of severe respiratory syncytial virus infection, treatment with aerosolized ribavirin decreases the duration of mechanical ventilation, oxygen treatment, and the hospital stay.

Neonatal tuberous sclerosis: magnetic resonance appearance of subependymal tubers

A case of tuberous sclerosis in a neonate, with cerebral and cardiac hamartomas evaluated by MR imaging, is presented. Intracranial subependymal tubers in this neonate exhibit increased signal intensity on short TR images. This differs from the signal characteristics of subependymal tubers in older patients.

Fatal postoperative Legionella pneumonia in a newborn

This is a case of postoperative Legionella pneumonia in a full-term infant with hypoplastic left heart syndrome. The infant had an uncomplicated prenatal history, normal vaginal delivery, Apgars of 8 at 1 and 5 minutes, but was cyanotic at birth. At 3 days of age she had a stage 1 Norwood surgical procedure to palliate her congenital heart disease. A synthetic patch was placed over the thoracic midline because of difficulty in reapposing the sternum. Peritoneal dialysis was used to manage renal failure. At 20 days of age she had disseminated intravascular coagulopathy and pneumonia associated with sepsis. Four days later she died. Legionella pneumophila serogroup 1 was isolated from a lung culture taken at autopsy.

Periodic breathing in preterm infants: incidence and characteristics

The prevalence and characteristics of periodic breathing in preterm infants were measured by 24-hour impedance pneumograms in 66 preterm infants before discharge from the nursery. Four periodic breathing parameters (percentage of periodic breathing per quiet time, number of episodes of periodic breathing per 100 minutes of quiet time, mean duration of periodic breathing, and longest episode of periodic breathing) were compared to data available from healthy term infants and from term infants who subsequently died of sudden infant death syndrome (SIDS). Periodic breathing was found in all preterm infants studied and mean periodic breathing parameter values (12.0%, 8.6 episodes, 1.2 minutes, and 7.3 minutes, respectively) in our preterm population were substantially higher than values from healthy term infants and SIDS victims. Most periodic breathing parameters decreased significantly in infants studied at 39 to 41 weeks' postconceptional age compared with earlier postconceptional age groups. No relationship was found between central apneas of greater than or equal to 15 seconds' duration and postconceptional age or any periodic breathing parameter. Periodic breathing is a common respiratory pattern in preterm infants that is usually not of pathologic significance. Associations between elevated levels of periodic breathing and respiratory dysfunction or SIDS should be made with caution.

The effect of dexamethasone on chronic pulmonary oxygen toxicity in infant mice

The effect of dexamethasone (0.1, 1, and 5 mg/kg/d given subcutaneously from d 14-18) was tested in infant mice continuously exposed from birth to either humidified air or 80% oxygen. Dexamethasone significantly decreased lung wet wt (p less than 0.01), lung water (p less than 0.021), lung dry wt, protein, and DNA (p less than 0.001) in both air- and oxygen-exposed animals. Dexamethasone, however, had no effect on lung compliance measured after animals were killed on d 18. It also had no effect on the increase in the blood-air barrier thickness or decrease in the blood-air exchange surface area seen in the 80% oxygen-exposed mice. Dexamethasone decreased thymus gland wt (p less than 0.001), body wt gain (p less than 0.001), brain wt (p less than 0.001), and lung lymphocytes (p less than 0.05) in both air- and oxygen-exposed animals. The effect of 1 mg/kg and 5 mg/kg of the drug could not be differentiated. During the 4 d of drug administration, one air- and one oxygen-exposed animal died; both received 5 mg/kg/d of dexamethasone; microscopic and culture evidence of infection was not found. If dexamethasone causes similar effects in human infants with bronchopulmonary dysplasia, it should be used with great caution even for short-term clinical management.

Periodic breathing cycle duration in preterm infants

Periodic breathing cycle duration (PCD), the time interval from the beginning of one respiratory pause to the beginning of the next pause within an episode of periodic breathing (PB), was measured by examination of 24-h impedance pneumograms in 51 preterm infants. Calculations of the SD of PCD within a given PB episode (approximately 3 s) and comparison of PCD values between two PB episodes in each infant (r = 0.68) revealed considerable variability in PCD. This variability was not related to the number of cycles in the PB episode or to the amount of PB in the recording. Contrary to the decrease in PCD from 15.0 s at 1 wk to 12.4 s at 12 wk in term infants reported previously, PCD did not vary as a function of postconceptional, gestational, or postnatal age in our preterm population. PCD has limited value as an indicator of chemoreceptor maturation in the preterm infant, and most likely reflects transient adjustments in respiratory system control.

Periodic breathing parameter values depend on specific pneumogram scoring criteria

Periodic breathing (PB) has been related to both normal and pathologic respiratory system control in infants. However, comparison of the results of separate studies has been limited by the variability in procedures used by different investigators to quantify PB. In this study we scored 15 24-hr impedance pneumograms using the criteria of Parmelee et al. (Neuropediatrie 3:294-304, 1972), Christova-Gueorguieva (Biology of the Neonate 44:325-332, 1983), and Curzi-Dascalova, Kelly and Shannon (Pediatrics 63:355-360, 1979) and analyzed the resulting differences in several commonly used PB parameters. Scoring criteria consistently and significantly influenced three PB parameters: the %PB, number of episodes of PB/100 min recording time, and mean duration of PB episode length showed average changes of 74%, 179%, and 36%, respectively, when the methods with the most extreme differences were compared. In contrast, the duration of the longest episode of PB showed no significant change as a function of scoring criteria. Awareness of the particular method of PB scoring is therefore essential in interpreting PB parameter values.

Periodic breathing in preterm infants: influence of bronchopulmonary dysplasia and theophylline

Periodic breathing (PB) has been studied extensively in both normal term infants and term infants presumed to be at high risk for sudden infant death syndrome (SIDS); however, little is known about the incidence and significance of PB in preterm infants. Twenty-four hour impedance pneumograms were obtained from 108 preterm infants prior to their discharge from the nursery and four PB parameters (%PB, No. of episodes of PB/100 min, mean duration of PB episode length, and duration of the longest episode of PB) were quantified in each recording. Control infants who were asymptomatic for apnea had the highest PB parameter values (%PB, 12.0; No. episodes/100 min, 8.6; mean duration, 1.2 min; and longest episode, 7.3 min); infants with bronchopulmonary dysplasia (BPD) showed dramatic decreases in all PB parameters, with a median %PB of 1/16 of the control population. Theophylline use was associated with a significant decrease in PB parameter values only in infants without BPD. Central apneas greater than 15 s did not vary significantly as a function of BPD, theophylline, or postconceptional age. We conclude that the clinical status of preterm infants significantly influences PB parameter values and must be taken into account in the interpretation of pneumograms, for decision-making about home cardiorespiratory monitoring, and in assigning risk for SIDS.

A randomized, placebo-controlled trial of effects of dexamethasone on hypothalamic-pituitary-adrenal axis in preterm infants

As part of a blinded, randomized, placebo-controlled study of dexamethasone therapy in 27 preterm infants with bronchopulmonary dysplasia, we investigated the effect of 7 days of high-dose glucocorticoid therapy on the hypothalamic-pituitary-adrenal axis. Before therapy the median basal cortisol concentration in all infants was 8.2 micrograms/dl (226 nmol/L). After stimulation with 1-24 ACTH, the serum cortisol concentration rose in all infants to a median concentration of 23.5 micrograms/dl (649 nmol/L), resulting in a median rise of 13.4 micrograms/dl (37 nmol/L). Immediately after 7 days of glucocorticoid therapy basal and peak cortisol concentrations were significantly decreased in the dexamethasone group. The rise in serum cortisol following 1-24 ACTH, however, remained equivalent in both groups. Ten days after the end of therapy basal and peak cortisol concentrations in the dexamethasone group had returned to levels equivalent to those seen in the placebo group. Weight gain was markedly diminished while the infants were receiving dexamethasone. Weight gains were, however, equivalent 10 days after the end of treatment. These data indicate that 7 days of dexamethasone therapy has significant but short-term effects on cortisol secretion and possibly on weight gain.

Interference of fetal hemoglobin with the spectrophotometric measurement of carboxyhemoglobin

We measured the concentration of carboxyhemoglobin (HbCO) in blood samples from 32 neonates by spectrophotometry (IL282 CO-Oximeter) and gas chromatography, finding a strong positive correlation (r = 0.89) between the concentration of fetal hemoglobin (Hb F) and HbCO as measured by spectrophotometry, but not by gas chromatography. Thus, Hb F interferes with the determination of HbCO by spectrophotometric techniques by falsely increasing apparent HbCO in direct proportion to Hb F. We conclude that, when Hb F is known or suspected to be present, blood HbCO cannot be reliably determined by methods based on spectrophotometry.

Dissociation of mean airway pressure and lung volume during high-frequency oscillatory ventilation

Eight kittens were studied during high-frequency oscillatory ventilation (HFOV) using an airway vibrator. HFOV was performed at 1000 and 1800 cycle/min at three present oscillatory amplitude settings and with lungs normal and injured by saline lavage. Change in lung volume (LV) during HFOV was compared to change in LV obtained during static inflation at matched mean airway pressure (Paw) of 5, 10, 15 and 20 cm H2O. LV during HFOV was significantly higher than during static inflation, and increased as oscillatory amplitude increased. LV was significantly lower after lung injury for matched HFOV settings, and was not affected by rate. Dissociation of Paw and LV during HFOV is observed implying that mean alveolar pressure (Palv) exceeds Paw during HFOV in this experimental model. The safe clinical application of HFOV may involve measurement of Palv or LV.

Interference of fetal hemoglobin with the spectrophotometric measurement of carboxyhemoglobin

We measured the concentration of carboxyhemoglobin (HbCO) in blood samples from 32 neonates by spectrophotometry (IL282 CO-Oximeter) and gas chromatography, finding a strong positive correlation (r = 0.89) between the concentration of fetal hemoglobin (Hb F) and HbCO as measured by spectrophotometry, but not by gas chromatography. Thus, Hb F interferes with the determination of HbCO by spectrophotometric techniques by falsely increasing apparent HbCO in direct proportion to Hb F. We conclude that, when Hb F is known or suspected to be present, blood HbCO cannot be reliably determined by methods based on spectrophotometry.

Rapid assessment of ventilation by measurement of carbon dioxide elimination during high-frequency ventilation of kittens

Monitoring of the effectiveness of ventilation is a significant problem during high-frequency ventilation (HFV). The time necessary to achieve equilibrium of the arterial tension of carbon dioxide (Paco2) following step changes in ventilation is appreciable, because of large body stores of CO2. Waiting for Paco2 to reach equilibrium is not only time-consuming but a potentially dangerous means of monitoring ventilator adjustments during HFV. Five kittens of mean +/- SD 1,082 +/- 383 gm weight were studied during HFV, both with normal lungs and lungs injured by saline lavage-induced surfactant depletion. The transcutaneous tension of carbon dioxide (Ptcco2) was monitored continuously to determine the time required to achieve equilibrium of Paco2 following a step change in ventilation. The rate of pulmonary CO2 elimination (VECO2) was measured immediately before and immediately after (less than 12 sec) step changes in ventilation and was used to predict the change in Paco2 achieved once equilibrium was reestablished. With normal lungs, equilibration time following step changes in ventilation was found to be approximately 20 minutes. After step decreases in ventilation of the injured lung, achieving equilibrium state took significantly longer, approximately 30 minutes. The Paco2 predicted was significantly related to the change in Paco2 achieved at equilibrium for both normal and injured lung studies. We concluded that direct monitoring of VECO2 during HFV may be a useful clinical monitoring technique, allowing rapid and accurate assessment of the efficiency of ventilation following step changes in ventilation and potentially assisting in optimizing ventilator settings.

Placental pathology is not predictive for sudden infant death syndrome (SIDS)

A previous report has suggested an increased incidence of chorioamnionitis in the placentae of sudden infant death syndrome (SIDS) victims. To further evaluate placental pathology in SIDS, 27 cases were identified from coroner's records and matched to two control groups. Both control groups were matched for birthweight, gestational age, and season, with the second also matched for maternal race, infant sex, blood type B, and maternal parity. No significant increase in chorioamnionitis or other placental abnormalities were found in SIDS victims when controlling for prematurity, which is a factor related to chorioamnionitis. An increased incidence of vaginal bleeding (P less than 0.04) and possibly substance abuse or anemia at delivery was found in SIDS mothers. There were more premature and black infants found in the SIDS group compared with the general birth population, and also lower five-minute Apgar scores (P less than 0.02) compared to matched controls. Analysis of the second control group match, including infant Apgar scores, maternal hematocrit, maternal age, and complications of pregnancy and delivery, did not influence any of our conclusions. The data suggests that matching for prematurity may be important in identifying the strength of additional risk factors for SIDS, since the risk factors for SIDS and premature delivery are similar.

Apnea during sleep in the pediatric patient

Pediatric respiratory disorders during sleep are primarily apneic problems that can be associated with a number of abnormalities. When apnea is secondary to a disease process, the main focus should be on the identification of that disease process and on the institution of appropriate therapy. When the apnea persists or when it is idiopathic, additional evaluation may be required to identify an appropriate course of management.

Sequelae of acquired cytomegalovirus infection in premature and sick term infants

To assess the risk of long-term sequelae after acquired cytomegalovirus (CMV) infection in premature and sick term infants, 55 CMV infected patients were matched prospectively with 55 control patients and these matched pairs were evaluated at 3 years of age. Sensorineural hearing losses were present in four of 43 CMV infected patients (all mild-moderate) and in two of 43 controls (one severe). The incidence of neurologic sequelae was not increased in CMV infected patients with birth weight greater than 2000 gm. Among patients with birth weight less than 2001 gm, moderately abnormal EEGs were found in four (17%) of 23 CMV infected patients and in one (4%) of 23 controls, and severe handicaps occurred in four (14%) of 29 CMV infected patients and in two (7%) of 29 controls. Severe handicaps in premature infants were significantly (P less than 0.05) associated with early onset of CMV excretion (less than 8 weeks of age) and severe cardiopulmonary disease. Among the premature infants who were documented early excretors, three of 13 had severe neuromuscular impairment, four of 13 had severe handicaps (DQ less than 70, severe neuromuscular impairment, or profound loss of vision or hearing), and an additional four had DQs of 70 to 79. Among their matched control subjects, none of 13 had severe neuromuscular impairment, two of 13 had severe handicaps, and an additional two had DQs between 70 and 79. None of the premature infants who were documented late excretors (greater than or equal to 8 weeks of age) had any neurologic sequelae. The risk of neurologic sequelae and handicap may be increased in premature infants with onset of CMV excretion in the first 2 months of life.

Use of sodium nitroprusside in neonates: efficacy and safety

Sodium nitroprusside was administered to 58 neonates, including 11 with severe respiratory distress syndrome, 15 with persistent pulmonary hypertension of the newborn, 28 with clinical shock, three with systemic hypertension, and two with pulmonary hypoplasia, all refractory to conventional intensive therapy. Nitroprusside was infused at 0.2 to 6.0 micrograms/kg/min for periods of 10 minutes to 126 hours. Infants with severe respiratory distress syndrome had increased PaO2 and decreased PaCO2 or peak inspiratory pressure, and nearly all (82%) survived. Infants with persistent pulmonary hypertension of the newborn had variable responses; improvement did not correlate with survival, but survival (47%) was identical to that in an earlier series of infants given tolazoline. Infants in shock had improved perfusion, urine output, and serum bicarbonate levels, and these responses were significantly related to survival. Hypertension was controlled in all three hypertensive infants. Adverse effects were very uncommon. Toxic effects were not observed. Sodium nitroprusside is effective and can be used safely in circulatory disorders in the neonate.

Evaluation and management of infantile apnea

Knowledge regarding the etiology and optimal management of prolonged apnea and its relationship to SIDS is still limited. The majority of infants with prolonged apnea do not die of SIDS, although the risk of SIDS in this group is greater than in the general population. Many infants with prolonged apnea who are perceived by parents and physicians as having had a "life-threatening" event may be at risk for another. Appropriate assessment following this event includes a careful history and physical examination to determine cause and severity. Etiologies to be considered include infections, metabolic aberrations, seizure problems, cardiac arrhythmias or congenital heart disease, anatomic airway abnormalities, gastroesophageal reflux and impaired regulation of breathing. If a specific cause has been identified for the infant's apnea, appropriate treatment often will lead to resolution of the apnea problem. If a specific etiology has not been identified or if the risk of "life-threatening" prolonged apnea seems to persist, electronic cardiorespiratory monitoring may be considered. Appropriate treatment for asymptomatic infants who are at increased statistical risk of SIDS is controversial. Asymptomatic infants may be candidates for home monitoring, but as yet, there are no reliable tests to predict which infants are at risk for prolonged apnea. Monitoring at home must be prescribed by the physician and should be continued until judged no longer appropriate by the attending physician. Skilled caregivers are crucial to the continuous observation and management of these patients in the hospital and at home. Therefore parents should be taught monitor use and also CPR.(ABSTRACT TRUNCATED AT 250 WORDS)