Physical and social environment of newborn infants in special care units.

Infants in newborn intensive and convalescent care units are exposed to large amounts of sensory stimulation of various sorts. Although infants in these units do not lack visual, auditory, and tactile stimulation, they receive relatively infrequent coordinated sensory experiences. Furthermore, there is no diurnal rhythmicity in physical and social stimulation across days.

Decreasing trend in postneonatal mortality.

OBJECTIVE: The objective was to evaluate the postneonatal mortality rate at our institution from 1999 to 2006 as a follow-up to a previous report from our hospital covering 1993 to 1998 and to investigate the causes of death in infants dying in the postneonatal period. STUDY DESIGN: We identified all infant deaths before discharge from the nursery aged > or =28 days. Clinical data for all cases and autopsy records where available were reviewed and the cause of death was determined for each infant. RESULT: Total nursery deaths for the 7 years were 211, of which 14 (6.6%) occurred after the neonatal period. This represents a decreasing trend from the 12% reported in 1993 to 1998. Causes of death were the complications of prematurity and congenital defects. The five infants whose cause of death was the complications of prematurity had chronic lung disease, four had abdominal surgery for perforation and resection and two had intraventricular hemorrhage (IVH) Gr IV. All infants had multiple organ failure by the time of death and the final event was infection and/or renal failure. The nine congenital defects included two trisomy 21 with complications, one CHARGE association with heart defects, one hypertrophic cardiomyopathy and two others with multiple congenital heart defects. Of the three remaining infants, the anomalies included one with hydranencephaly, one with caudal regression and one with multiple vascular liver tumors. CONCLUSION: Along with the general decrease in infant mortality, postneonatal mortality is decreasing as a percentage of nursery deaths. The causes of death include complications of prematurity and congenital defects.

Mercury vapor contamination of infant incubators: a potential hazard.

In a survey of 42 infant incubators 18 showed detectable concentrations of mercury vapor. In 12 instances the concentrations of mercury vapor in the thermometer holder exceeded industrial safety standards. In 16 incubators the contamination was traced to broken mercury-in-glass thermometers used to monitor incubator ambient temperatures. Use of alcohol thermometers or thermistors in place of mercury-in-glass thermometers would eliminate this potential hazard.

Hyperammonemia associated with perinatal asphyxia.

Twelve infants with severe perinatal asphyxia were found to have elevated blood ammonia levels (302 to 960 microgram/100 ml). In the seven survivors, hyperammonemia was associated with CNS irritability, hyperthermia, hypertension, and wide neonatal heart rate oscillations. Follow-up examinations revealed severe neurologic dysfunction in five of seven infants. CNS depression, hyperthermia, hypertension, and a nonreactive, fixed heart rate characterized the infants that died. These findings suggest a clinical entity secondary to perinatal asphyxia whose signs and symptoms may be related to hyperammonemia.

Factors affecting heart rate variability in preterm infants.

Neonatal heart rate variability (NHRV) was studied in 92 preterm infants (birth weight, 750 to 2,500 gm; gestational age, 28 to 36 weeks). Each infant was monitored continuously during the first 6 hours and for one hour at 24, 48, and 168 hours of life. During each hour NHRV was quantified and related to the following parameters: sex, gestational age, postnatal age, heart rate, and the presence and severity of respiratory distress syndrome (RDS). NHRV in healthy preterm infants was inversely related to heart rate level and directly related to the infant's postnatal age. In healthy babies with gestations of 30 to 36 weeks there was no significant correlation between NHRV and gestation. Decrease in NHRV was significantly related to the severity of RDS, and the reappearance of NHRV in infants with RDS was associated with a good prognosis. Decreased NHRV significantly differentiated the infants with RDS who survived after the fifth hour of life. The data reveal that NHRV (1) should be corrected for heart rate level and postnatal age; (2) is decreased in RDS; and (3) can be used as an indicator of morbidity and mortality in preterm infants with RDS.

Lack of identifiable risk factors for kernicterus.

In recent years kernicterus at autopsy has been observed in sick premature infants in the absence of markedly elevated levels of serum bilirubin. Potentiating factors have been suggested to explain kernicterus in such a setting. In order to establish which factors are associated with increased risk for kernicterus in these small babies, this retrospective matched control study was undertaken. Thirty-two infants with kernicterus at autopsy were matched for gestational age, birth weight, length of survival, and year of birth to 32 control infants without kernicterus. Multiple historical, clinical, and laboratory factors were compared, including therapy, sepsis, hypothermia, asphyxia as reflected by Apgar score, hematocrit, acidosis, hypercarbia, hypoxia, hypoglycemia, and hyperbilirubinemia. No statistically significant differences between the kernicteric and nonkernicteric infants were demonstrated for any of these factors, including peak total serum bilirubin levels. Multivariant analysis also failed to determine a group of factors associated with increased risk for kernicterus. It was not possible to separate those infants with and without kernicterus at autopsy on the basis of the clinical factors evaluated.

Sudden infant death syndrome: sleep apnea and respiration in subsequent siblings.

Subsequent siblings of infants who died of the Sudden Infant Death Syndrome are at a four- to six-times increased risk to die of this syndrome. This study compares the respiratory development during sleep state of this epidemiologic high risk group with that of normal infants during the first six months of life. Subsequent siblings exhibited higher respiratory rates in all states at 3 months of age. Quiet sleep and indeterminate respiratory rates were elevated at 1 week of age compared to control infants. Indeterminate respiratory rates remained higher at 6 months of age. These differences were accompanied by a reduced incidence of total breathing pauses of two to five seconds and six to nine seconds duration in siblings. Study groups could not be differentiated on the basis of either breathing pauses of more than ten seconds of central apnea of six seconds or more. Obstructive and mixed apnea (6 seconds or more) were infrequently observed in these study groups. A high degree of intersubject variability characterized all data on breathing pauses.

Polygraphic studies of normal infants during the first six months of life: III. Incidence of apnea and periodic breathing.

The incidence of apnea and periodic breathing was studied in full-term infants between birth and 6 months of age. Apnea was defined as a pause equal to or exceeding six seconds, periodic breathing as two cessations of breathing within a 20-second period, each equal to or longer than three seconds but less than six seconds. Sleep and cardiopulmonary variables were monitored. Apnea was common in the normal full-term infant. The incidence of apnea was highest in the newborn period and apneas exceeding 15 seconds were limited to this age. A reduction in apnea incidence occurred between birth and 3 months of age; thereafter, the incidence remained unchanged. The majority of apneas occurred during active sleep (AS). Few minutes were classified as indeterminate; the number of apneas during these minutes was comparable to those during AS. The incidence of apneas during quiet sleep was low. Periodic breathing remained stable across the ages, occurring primarily in AS. Apnea exceeding 15 seconds in rare in infancy. The tabulation of shorter apnea may be of limited value in identifying infants at risk for abnormal apnea due to extreme variability among infants. The sleep-waking state of the infants must be considered in order to evaluate apnea counts.

Respiratory behavior in near-miss sudden infant death syndrome.

Seventeen infants with unexplained prolonged apnea that has been designated near-miss sudden infant death syndrome were monitored for sleep and cardiorespiratory variables during a 12-hour, all-night recording session. Infants were matched for gestational age, sex, and age at recording with control infants. Respiratory variables studied included respiratory rate, respiratory variability, apnea duration, apnea density, and periodic breathing. No statistically significant differences were found in sleep state or respiratory variables between near-miss and control infants. Eight infants (47%) had no recurrence of prolonged apnea, whereas three (17.6%) had recurrent apneic episodes for six weeks to eight months following the original episode. No clinical or polygraphic finding predicted which infant would exhibit recurrent apnea. None of the infants was monitored at home. All infants were developing normally when examined at 1 to 2 years of age.

Temporal distribution of sleep states, somatic activity, and autonomic activity during the first half year of life.

Twelve-hour, all-night polygraphic recordings were obtained from 25 normal infants at 1 week and 1, 2, 3, 4, and 6 months of age. The objectives of the study were to provide a description of the emerging temporal distribution of quiet sleep (QS), active sleep (AS), and motility, and to describe the maturation of a circadian influence upon heart rates. With increasing age, increased percentages of AS began to cluster toward the end of the night and increased percentages of QS toward the beginning. A circadian influence upon heart rates was observed in AS and indeterminate sleep prior to its existence in QS. At 2 and 3 months of age motility in AS and QS increased linearly during the night.

Developmental patterns of heart rate and heart rate variability during sleep and waking in normal infants and infants at risk for the sudden infant death syndrome.

The developmental sequence of heart rate and heart rate variability was examined during sleep and waking states in 22 normal infants, and 22 siblings of sudden infant death syndrome (SIDS) victims, using 12-h polygraphic recordings at 1 week and at 1, 2, 3, 4, and 6 months of age. Heart rate was higher in siblings of SIDS victims than in normal infants during quiet sleep over the first 6 months of life and was higher in the waking state at 3 months of age. The sibling group also had lower variability at 1 week during quiet sleep. Gender contributed no significant differences to heart rate, but females at risk for SIDS had lower waking cardiac variability than males.

Fetal heart rates in siblings of infants with sudden infant death syndrome.

This study examined fetal heart rate (FHR) variables during maternal sleep in subsequent siblings of infants who died of sudden infant death syndrome (SIDS) and who are thus at increased statistical risk for SIDS, and controls. Four findings differentiated the tracings of subsequent siblings of SIDS infants and controls: 1) FHR variability in subsequent siblings of SIDS infants ranged between 11 and 25 beats/min, compared with 6 to 10 beats/min in controls (P less than .001). 2) Bradycardia was more frequent in subsequent siblings of SIDS infants. 3) FHR accelerations (more than 150 beats/min) followed by heart rates below 120 beats/min were elevated in subsequent siblings of SIDS infants (P less than .01). 4) Strong respiratory arrhythmia was more frequent in subsequent siblings of SIDS infants. These siblings exhibited more reactive FHR patterns. Although these data cannot be interpreted as clinical markers to identify the infant who will die of SIDS, they are compatible with the hypothesis that mild chronic hypoxia is associated with risk for SIDS.

Obstructive apnea, associated patterns of movement, heart rate, and oxygenation in infants at low and increased risk for SIDS.

Repetitive polysomnograms were recorded between 40 weeks post-conceptional age and 6 months in a total of 49 infants, 19 healthy preterm infants, 14 normal term infants, and 16 subsequent siblings of infants who died of sudden infant death syndrome (SIDS). These nighttime recordings lasted 2-4 hours, except at 3 months when an overnight 12-hour recording was performed. Obstructive apneas (OA) > 3 seconds were divided into 3 categories: 1) clear obstructive, 2) mixed and 3) unclear because of movement artifacts. More than half belonged in category 3 and were excluded from further analysis unless accompanied by a transient episode of bradycardia (TEB), defined as heart rate < or = 100 beats per minute. Each OA with TEB was also examined for changes in transcutaneous oxygen tension (PtcO2). Most pauses were brief (median, 4 seconds), the longest (27 seconds) seen only once in the youngest premature infant. The majority of OA were accompanied by heart rate accelerations. The number of clear obstructive and mixed apneas was similar. The scores were combined to calculate a density (number per 100 minutes of recording). OA were not common: Their density decreased from 2 in 100 minutes at 40 weeks in the preterm to once every 300 minutes (5 hours) in the 6-month-old term infant. Ten percent of the OA were accompanied by TEB. Of these, 10% were accompanied by a PtcO2 decrease of > 10 mm Hg. OA with TEB followed a nonmonotonic curve, the highest percentage of infants showing this pattern at the age of highest risk for SIDS. Minor differences among study groups were confined to less movements with OA in subsequent siblings and an earlier peak incidence of OA with TEB in prematures, compared to normal term infants. OA were seen in all study groups, were self-limited, and apparently were devoid of pathological consequences.

Respiration during the first six months of life in normal infants: IV. Gender differences.

Respiratory rates and breathing pauses of various durations were examined in 19 normal infants, 12 male and 7 female, during the first 6 months of life. Twelve-hour all-night polygraphic recordings were obtained during the first week of life and at 1, 2, 3, 4 and 6 months. A computer program and visual analysis were used to score sleep state and calculate respiratory rates and apnea densities. In the newborn period there were no gender differences. Males breathed faster and exhibited fewer breathing pauses between 2 and 5 sec from one month of age on. The close correlation between respiratory rate and short breathing pauses suggests that the latter are an integral part of normal respiratory regulation. These findings can be explained by gender-related differences in metabolic rate or maturation of the central nervous system.

Prediction of neurodevelopmental outcome in infants with and without bronchopulmonary dysplasia.

In a group of 236 very low birth weight (VLBW) surviving infants, 60 had developed bronchopulmonary dysplasia (BPD) in the nursery. When compared with the 176 infants without BPD, infants with BPD were smaller, more immature, with lower one- and five-minute Apgar scores. Infants with BPD had a greater incidence of cardio-pulmonary and central nervous system (CNS) complications in the nursery. On follow-up, 25 (42%) of these infants were abnormal developmentally compared to 7% of infants without BPD (p less than .001). When comparisons were made within the group of infants with BPD, very few differences were found in maternal or infant risk factors between the normal and abnormal infants. The infants with BPD who had poor outcome more often had seizures and severe intraventricular hemorrhage (IVH). The infants with BPD who had good outcome were more often small for gestational age (SGA) and resuscitated with intubation at birth. They had apnea in the nursery more frequently than did abnormal infants with BPD. We conclude that VLBW infants with BPD are at greater risk for poor neurodevelopmental outcome than those without BPD. The risk for the infant with BPD relates to CNS complications rather than to chronic lung disease.

Intrauterine growth curves of weight, length, and head circumference for a predominantly Hispanic infant population.

The purpose of this study was to develop intrauterine growth curves in a predominantly Hispanic population of low socioeconomic status near sea level and to compare them with published intrauterine growth curves. Infants born at Los Angeles County-University of Southern California Medical Center provided the study population. Gestational age was determined by maternal history and confirmed by Ballard clinical assessment in 6,100 infants. Growth curves were developed for weight, length, and head circumference from 24 through 44 weeks gestation. The intrauterine curves were similar to those developed from white non-Hispanic births in California and from white middle class infants born in Portland, OR. The Los Angeles curves differed from other curves developed in Denver, CO, where the infants were significantly smaller from the 34th week of gestation. The authors found no adverse effects on intrauterine growth by race or socioeconomic status. The curves presented in this paper are more appropriate than the Denver curves for white populations born near sea level regardless of socioeconomic status.

Care of very low birth weight infants by neonatal nurse clinicians.

In 1980, the medical facility at the authors' hospital developed a program to train neonatal critical care nurses for primary care provider roles in the intensive care nursery. The neonatal nurse clinician (NNC) program consists of a didactic portion that emphasizes physiology and pathophysiology of sick newborns, and an internship that focuses on the medical needs of very low birth weight (VLBW) neonates. At the completion of the internship, the NNC is assigned to be the primary care provider for infants with birth weights less than or equal to 1,250 g. This report discusses the NNC training program and the five-year experience with the NNC caring for VLBW infants.

Factors differentiating postponed neonatal death from survival in low birth weight infants.

Although survival of low birth weight infants during the neonatal period has improved, an increasing percentage of infants succumb after 28 days but before discharge from the nursery. In a retrospective study we compared 11 postponed neonatal deaths (PND) with survivors matched for birth weight, gestational age, gender, race, inborn or outborn status, and year of birth in an attempt to identify possible differentiating factors early in the clinical course. Evaluation of antenatal, intrauterine, and early nursery events could not differentiate the two groups. By day 14, however, significantly more PND required assisted ventilation because of poor respiratory effort and total parenteral nutrition because of poor gastrointestinal motility. Metabolic differences were noted at this time in the serum bilirubin, phosphorus, and chloride levels. At autopsy all infants had evidence of CNS injury, and moderate chronic lung disease, and in addition nine infants had bronchopneumonia. The major differences between the PNDs and survivors may primarily involve neurologic control of respiration and gastrointestinal motility. Early recognition of PND may have important medical, ethical, and financial implications for newborn intensive care.

Nursery survival for infants of birth weight 500-1500 grams during 1982-1995.

OBJECTIVE: To evaluate nursery survival of very low birth weight infants (VLBW) over time, born in the same large inner-city hospital with a predominantly Hispanic population. METHODS: All liveborn VLBW infants weighing 500-1500 g at birth were included in four time periods of 2 years' duration during 1982 to 1995. Demographics were collected for the obstetric population. Clinical data were collected including maternal and infant perinatal factors. All infants were assigned a cause of death and infants dying with lethal anomalies were then excluded from further evaluations. RESULTS: Overall survival improved progressively (p = 0.0001) with dramatic improvement in survival of infants 500-750 g birth weight (BW) in period 4 (1994-1995). The number of lethal anomalies did not increase but accounted for a larger portion of deaths in period 4. Decreases in other causes of death over time reflected changes in perinatal care. Although the mothers were high-risk, none of the maternal factors evaluated showed any consistent effect on infant survival. Improved labor and delivery care was associated with improvement in Apgar scores, a decrease in intracranial hemorrhage/intraventricular hemorrhage as a cause of death and an improvement in survival between the first two periods. In spite of the increase in Cesarean sections for infants of 500-750 g BW and their improved survival in period 4, no clear advantage for Cesarean section could be demonstrated. The marked improvement seen in period 4 was associated with three changes in care: increased use of maternal steroids, administration of surfactant, and the use of newer ventilatory methods including high-frequency oscillatory ventilation. Although female gender has been reported to confer a protective influence for survival, this was not found in the final period. Black mothers comprised only about 2.5% of the total obstetric population but delivered approximately 10% of the VLBW infants. Despite the increased incidence of small for gestational age (SGA) among black infants, there were no differences in survival between blacks and Hispanics. Mean birth weight and gestational age in both survivors and nonsurvivors decreased significantly over the four time periods. In period 4, 50% survival occurred at a birth weight of 600-700 g and a gestational age of 23 weeks. CONCLUSION: Nursery survival improved throughout the period of the study from 1982 to 1995 but especially during period 4 (1994-1995). Improved survival was associated with changes in both maternal and infant care. In infants of BW 500-750 g, gestational age rather than birth weight was more closely associated with survival.

Maternal factors associated with delivery of infants with birthweight less than 2000 grams in a low socioeconomic population.

Women of low socioeconomic status (SES) are known to have a higher incidence of low birthweight (LBW) infants who are a major source of neonatal mortality and morbidity. SES, however, does not define a homogeneous population. If prenatal programs could be oriented specifically toward women of higher risk within the low SES population, they should be more effective. Within our uniformly low SES population, we compared mothers who had given birth to infants weighing less than 2000 g with mothers of infants weighing over 3000 g in order to identify factors associated with a LBW birth. We found medical factors, including hypertension and infection during pregnancy, demographic factors, including race, marital status, and lack of prenatal care, and lifestyle factors, including drug and alcohol abuse, to be more common among women giving birth to infants weighing less than 2000 g. These factors can be used to develop more effective intervention programs for low SES populations.