Comparison of heart rate responses during cortical and subcortical arousals in term and preterm infants

The aim of this study was to determine whether prematurity affects heart rate responses during spontaneous arousals. Polygraphic recordings were performed during undisturbed daytime naps in 35 preterm infants (gestational age at birth 32+/-2 weeks) and 35 term infants. Arousals were scored according to the recommendations of the International Paediatric Work Group on Arousals and categorized either as cortical arousals (CA) or subcortical arousals (SCA). Heart rate (HR) and respiratory frequency (RF) were measured during arousal and during the 10-s and 30-s period before and after arousal. Changes in HR and RF were expressed as the percentage of modification normalized for the 30-s period preceding arousal. Altogether, 122 arousals in preterm infants (66 CA, 56 SCA) and 105 arousals in term infants (57 CA, 48 SCA) were scored. Mean duration of the arousal period was 9+/-4 s and 8+/-3 s, respectively. In term infants, a significant increase in HR during arousal could be shown (11.3+/-8.2%; p<0.001), whereas this increase was significantly greater during CA compared to SCA (13.7+/-6.2% versus 8.4+/-9.4%; p<0.001). In contrast, HR decreased during arousal in preterm neonates (-3.9+/-19.3%; p<0.05). These findings suggest that cardiovascular control seems to be maturationally delayed in preterm infants, which may contribute to their increased risk for Sudden Infant Death Syndrome (SIDS).     

Cerebral hemodynamics during arousals in preterm infants

The aim of the study was to evaluate potential changes of cerebral blood volume (CBV) related to arousals in preterm infants. As arousals are known to change different physiological parameters, it was postulated that this could also hold true for CBV. Polygraphic recordings were performed in 38 preterm infants (18 female, 20 male). The infants' gestational age at birth was 32.0+/-2.3 weeks, postconceptional age was 35.1+/-1.2 weeks and postnatal age at study entry was 24.3+/-2.9 days, birth weight was 1793+/-527 g and actual weight at study entry was 2011+/-324 g [mean (+/- standard deviation)]. CBV was measured using near infrared spectroscopy. Arousals were scored due to the guidelines of the "International Paediatric Work Group on Arousals" and categorized as either cortical (CA) or subcortical arousals (SCA). Altogether, 122 arousals (66 CA, 56 SCA) were scored. According to sleep stage, 77 arousals were analyzed in active sleep, 23 in quiet sleep and 22 in intermediate sleep. Mean duration of arousals was 8.8+/-0.3 s. CBV, cerebral vascular oxygenation and the balance between oxygen delivery and oxygen consumption remained constant during arousals in preterm infants. This was demonstrated for both CA and SCA and was independent of sleep stage, suggesting that the impact of arousals in stable preterm infants is too small to alter cerebral vascular autoregulation.     

Erythrocyte cupric/zinc superoxide dismutase exhibits reduced activity in preterm and low-birthweight infants at birth

In a comparative study in term, preterm and low-birthweight infants, the mean activity and standard error of the mean for copper/zinc superoxide dismutase (Cu/Zn SOD) in cord erythrocytes from five term small for gestational age infants was 0.94 ±0.10 SOD units (mg protein)⁻¹. This value was significantly lower than the activity (2.34 ± 0.24) in nine term, appropriate for gestational age (AGA) babies ( p < 0.005). In 15 preterm (AGA) infants, the activity at birth (1.05±0.07SOD units (mg protein)⁻) was also significantly lower ( p < 0.001) relative to term AGA babies. An increased level of activity (1.59 ± 0.09) was detected in the red cells of eight preterm AGA infants on their expected date of delivery compared with (0.87 ± 0.06) at birth ( p < 0.001). However, the activity (1.59 ± 0.09) was still lower than that detected in term AGA babies (2.34 ±0.24; p < 0.02). Similar findings were obtained when enzymatic activity was expressed in units per millilitre of packed erythrocytes. The low activity of Cu/Zn SOD in preterm and low-birthweight babies may render them susceptible to diseases associated with membrane lipid peroxidation.     

Does bladder voiding during sleep and wakefulness change the behavioural state of infants?

AIM: To evaluate whether bladder voiding in healthy infants is accompanied by body movements or any changes in heart rate (HR), respiratory frequency (RF) or electroencephalogram (EEG) frequency during sleep and during wakefulness. METHODS: Polygraphic recordings were performed on 33 healthy infants (17 female) born at term. The infants' age at study entry was 41+/-10 d, and actual body weight was 4876+/-403 g (mean+/-SD). Bladder voiding was recorded by an adapted enuresis detector connected to the polygraphic computer unit. RESULTS: Awakening was observed in 12 (36%) infants 77+/-9 s before bladder voiding. Twenty-one infants (64%) continued sleeping during bladder voiding. In sleeping infants, bladder voiding occurred during non-REM sleep only, and was accompanied by a cortical arousal. During wakefulness, RF was lower, and HR and EEG frequency were higher, but stayed constant during bladder voiding. CONCLUSION: Our observations demonstrate that bladder voiding in healthy infants during sleep is accompanied by body movements and changes in HR and EEG frequency, indicating cortical arousals, whereas during wakefulness these changes cannot be observed.     

Longitudinal measurements of bone status in preterm infants

BACKGROUND: Quantitative ultrasound measurement of the speed of sound (SOS) through bone has been investigated as a means of assessing bone status in preterm infants. Few studies report longitudinal measurements. OBJECTIVE: To assess longitudinal changes in bone SOS in preterm infants. METHODS: Sixty preterm infants with gestational ages of < 33 weeks and with birth weight appropriate for gestational age (AGA), and 48 healthy, term AGA infants were enrolled. SOS measurements of the tibia were made within the first week of life in the preterm infants, and within the first 72 hours of life in the term infants. During their hospital stay, weekly measurements of tibial SOS were made in 29 of the preterm infants, who were divided into three gestational age groups: Group 1: 24-26 weeks (n = 8), Group 2: 27-29 weeks (n = 9), and Group 3: 30-32 weeks (n = 12). RESULTS: The median SOS value for the 60 newborn preterm infants was significantly lower than that for the 48 newborn term infants (2,924 versus 3,036 m/sec, p < 0.001). At each time point, SOS values for each of the preterm infant gestational age groups were significantly lower than the term newborn infant SOS values. SOS values decreased significantly over time for the entire cohort of 29 preterm infants (p < 0.001), and for Groups 1 (p = 0.015) and 2 (p = 0.003). At several time points, there was a significant negative correlation between serum alkaline phosphatase levels and SOS values, and a significant positive correlation between serum phosphorus levels and SOS values. CONCLUSION: SOS measurements of the tibia decline during hospitalization in preterm infants, suggesting a progressive loss of bone strength. Longitudinal measurements of bone SOS in combination with serum alkaline phosphatase and serum phosphorus levels may identify infants at risk of developing osteopenia of prematurity.     

Plasma levels of asymmetric dimethylarginine in premature neonates: its possible involvement in developmental programming of chronic diseases

Aim: The endothel dysfunction in early life may play a role in developmental programming of cardiovascular morbidity. The changes of dimethylarginines' plasma levels during the first month among preterm infants and their determinants had been investigated in our study.
Methods: Twenty preterm infants of healthy mothers were studied. Mean (±SD) birth weight and gestational age were 919.5 ± 235.5 g and 26.7 ± 1.6 weeks, respectively. Blood samples were taken by venipuncture at the 3rd, 7th, 14th, 21st and 28th days. Plasma concentrations of L-arginine, asymmetric and symmetric dimethylarginine (SDMA) were measured by liquid chromatography-mass spectrometry method, evaluated by multivariate linear regression analysis.
Results: L-arginine (p < 0.001) and asymmetric dimethylarginine (ADMA) levels (p < 0.001) were positively associated with postnatal age. ADMA levels were negatively correlated with gestational age (p = 0.007), dopamine-need on the 3rd day of life (p = 0.015) and late infection (p = 0.038). The higher birth weight was associated with higher L-arginine (p = 0.052) and ADMA (p = 0.002) concentrations. The dopamine-need on the 7th day of life had a significant effect on postnatal elevation of SDMA levels (p = 0.035).
Conclusion: The progressive increase of ADMA levels described by our study among preterm infants suggests that early endothel dysfunction may take part in developmental programming of chronic adult diseases.     

Intestinal permeability in relation to birth weight and gestational and postnatal age

OBJECTIVE: To determine the relation between intestinal permeability and birth weight, gestational age, postnatal age, and perinatal risk factors in neonates. STUDY DESIGN: Intestinal permeability was measured by the sugar absorption test within two days of birth and three to six days later in preterm and healthy term infants. In the sugar absorption test, the urinary lactulose/mannitol ratio is measured after oral ingestion of a solution (375 mosm) of lactulose and mannitol. RESULTS: A first sugar absorption test was performed in 116 preterm (26-36 weeks gestation) and 16 term infants. A second test was performed in 102 preterm and nine term infants. In the preterm infants, the lactulose/mannitol ratio was not related to gestational age (r = -0.09, p = 0.32) or birth weight (r = 0.07, p = 0.43). The median lactulose/mannitol ratio was higher if measured less than two days after birth than when measured three to six days later (0.427 and 0.182 respectively, p<0.001). The lactulose/mannitol ratio was higher in preterm infants than term infants if measured within the first 2 days of life (0.404 and 0.170 respectively, p < 0.001), but not different three to six days later (0.182 and 0.123 respectively, p = 0.08). In multiple regression analysis of perinatal risk factors, only umbilical arterial pH correlated with the lactulose/mannitol ratio in preterm infants less than 2 days of age (T = -1.98, p = 0.05). CONCLUSIONS: In preterm infants (26-36 weeks gestation), intestinal permeability is not related to gestational age or birth weight but is higher during the first 2 days of life than three to six days later. It is higher in preterm infants than in healthy term infants only if measured within two days of birth. This suggests rapid postnatal adaptation of the small intestine in preterm infants.     

Ontogeny of sleep and awake states in relation to breathing in preterm infants.

This review will focus on the development of behavioural states and breathing during early developmental stages prior to term gestation. Although these behavioural states are immature during early development, their cyclicity is clearly seen. Preterm infants characteristically have a large proportion of indeterminate sleep and small amount of wakefulness. Whereas oxygenation is relatively stable during active and quiet sleep in ventilated preterm infants, indeterminate sleep and arousals are associated with hypoxaemic episodes. Arousals have also been linked to apnoea in spontaneously breathing infants. Since well-defined sleep cycles are beneficial for the oxygenation of preterm infants, we should explore ways to promote their natural sleep while they are exposed to neonatal intensive care. Care practices such as clustering procedures, kangaroo care and optimal positioning have been shown to improve the integrity of sleep. Optimizing the sleep cycling might improve the long-term outcome of preterm infants. More studies in this area are clearly needed.     

VASOACTIVE INTESTINAL PEPTIDE (VIP) IN PRETERM AND TERM NEONATES

ABSTRACT. There is a little information on vasoactive intestinal peptide (VIP) in the neonatal period. We have measured plasma concentrations of this biologically important peptide in 159 preterm infants and 98 term neonates. Preterm neonates during the first four days of life had plasma VIP concentrations which were five times greater than the levels in 12 healthy adult controls (9.6±0.7 pmol/1, mean ± S. E. M., compared with 1.95±0.5 pmol/l, p <0.001), and these elevated concentrations persisted throughout the neonatal period. In contrast term infants on the sixth day of life, had plasma VIP concentrations only half those seen in preterm infants at the same post natal age ( p <0.001). Bottle-fed term infants had higher VIP levels than those who were breast fed (5.6±0.4 vs. 4.3±0.4, p <0.05). Plasma VIP concentrations did not change following a feed in any of the groups of neonates studied. The high plasma levels of VIP described may indicate a reduced neuropepitide clearance mechanism in neonates or alternatively, suggest a hitherto unrecognised role for this peptide hormone in the neonatal period.     

Neonatal opiate abstinence syndrome in term and preterm infants

Data on 178 term and 34 preterm infants born to methadone-maintained mothers were analyzed to assess the effects of neonatal opiate abstinence in infants of varying gestational ages. More mothers in the term group (79%) than in the preterm group (53%) had abused other drugs during pregnancy (p less than 0.001). Mean (+/- SD) gestational age was 39.5 weeks +/- 1.4 for term infants and 34.3 weeks +/- 2.6 for preterm infants. On the basis of a semiobjective symptom scoring scale, term infants had more severe abstinence symptoms and more prominent central nervous system manifestations than preterm infants. The severity of abstinence symptoms correlated with maternal methadone dosage in both term and preterm infants. Maternal multiple drug abuse (e.g., heroin, cocaine) did not influence severity of abstinence symptoms in either group. More term infants (145/178) than preterm infants (20/34) required treatment for these symptoms (p less than 0.005). In 13 of 178 term infants, compared with 1 of 34 preterm infants, abstinence-related seizures developed. Peak severity occurred 1 to 2 days earlier in term than in preterm infants. A less severe abstinence syndrome in preterm infants may be due to (1) developmental immaturity of either dendritic ramifications, specific opiate receptors, or neurotransmitter function, or (2) reduced total drug exposure during the intrauterine period.     

Early alteration of structural and functional brain development in premature infants born with intrauterine growth restriction

Placental insufficiency with fetal intrauterine growth restriction (IUGR) is an important cause of perinatal mortality and morbidity and is subsequently associated with significant neurodevelopmental impairment in cognitive function, attention capacity, and school performance. The underlying biologic cause for this association is unclear. Twenty-eight preterm infants (gestational age 32.5 +/- 1.9 wk) were studied by early and term magnetic resonance imaging (MRI). An advanced quantitative volumetric three-dimensional MRI technique was used to measure brain tissue volumes in 14 premature infants with placental insufficiency, defined by abnormal antenatal Doppler measurements and mean birth weights <10(th) percentile (1246 +/- 299 g) (IUGR) and in 14 preterm infants matched for gestational age with normal mean birth weights 1843 +/- 246 g (control). Functional outcome was measured at term in all infants by a specialized assessment scale of preterm infant behavior. Premature infants with IUGR had a significant reduction in intracranial volume (mean +/- SD: 253.7 +/- 29.9 versus 300.5 +/- 43.5 mL, p < 0.01) and in cerebral cortical gray matter (mean +/- SD: 77.2 +/- 16.3 versus 106.8 +/- 24.6 mL, p < 0.01) when measured within the first 2 wk of life compared with control premature infants. These findings persisted at term with intracranial volume (mean +/- SD: 429.3 +/- 47.9 versus 475.9 +/- 53.4 mL, p < 0.05) and cerebral cortical gray matter (mean +/- SD: 149.3 +/- 29.2 versus 189 +/- 34.2 mL, p < 0.01). Behavioral assessment at term showed a significantly less mature score in the subsystem of attention-interaction availability in IUGR infants (p < 0.01). Cerebral cortical gray matter volume at term correlated with attention-interaction capacity measured at term (r = 0.45, p < 0.05). These results suggest that placental insufficiency with IUGR have specific structural and functional consequences on cerebral cortical brain development. These findings may provide insight into the structural-functional correlate for the developmental deficits associated with IUGR.     

Acute cardiovascular responses in preterm infants at 34–39 weeks of gestational age

Background

Premature infants demonstrate immature physiological control mechanisms; however their acute cardiovascular control has not yet been widely studied.

Aim

The aim of this study was to analyze heart rate (HR) and blood pressure (BP) control in preterm infants.

Subjects

Twenty preterm infants with a mean gestational age of 31 ± 2.4 (26–34) weeks at birth were evaluated at a gestational age of 36 ± 1.5 (34–39) weeks. Results were compared to twenty, healthy, full-term, control infants studied at the age of 12 ± 3 weeks.

Outcome measures

HR and BP responses to 45° head-up tilt and side motion tests during non-rapid eye movement sleep were analyzed. In addition, HR responses to spontaneous arousals from non-rapid eye movement sleep were evaluated.

Results

Preterm infants showed significantly smaller initial HR and BP responses compared with controls in head-up tilt (HR p = 0.0005, systolic BP p = 0.02, diastolic BP p = 0.01) and side motion tests (HR p = 0.002, systolic BP p < 0.0001, diastolic BP p < 0.0001). Furthermore, in tilt tests, preterm infants presented with greater intersubject variability in BP responses than controls (systolic BP p = 0.009, diastolic BP p = 0005). Preterm HR responses to spontaneous arousals were similar to controls.

Conclusions

This study indicates immature vestibulo-mediated cardiovascular control in preterm infants compared with term infants. This is seen as attenuated BP responses to side motion test and more labile acute BP control to postural challenge.     

Bone turnover in preterm infants

Total parenteral nutrition is associated with osteopenia in preterm infants. Insufficient calcium and phosphate are likely causes: aluminum contamination is another possible contributing factor as this adversely affects bone formation and mineralization. The study was designed to evaluate changes in biochemical markers of bone turnover in 22 preterm infants receiving total parenteral nutrition in comparison with 19 term infants. We collected urine and serum samples from 22 preterm infants, mean gestational age 29 wk, within 48 h and again at 3 wk of life. We also collected urine samples from 19 term infants, mean gestational age 39 wk, during the first day of life. Bone resorption was assessed by the measurement of urinary pyridinium cross-links by HPLC and ELISA and the N-telopeptide of type I collagen by ELISA. Bone formation was assessed in premature infants by the measurement of serum osteocalcin. The N-telopeptide of type I collagen was higher in the preterm infants compared with term at baseline (p < 0.01). There was no difference between the pyridinium cross-links in the preterm and term infants. All the biochemical markers of bone turnover increased significantly in the preterm infants during the first 3 wk of life, e.g. N-telopeptide was a 153% change from baseline (p < 0.001). Aluminum in the total parenteral nutrition solutions did not cause a decrease in bone formation at the level administered (3-6 microg, 0.1-0.2 micromol x kg(-1) x d(-1)).     

EFFECT OF INTRAVENOUS L-ALANINE ADMINISTRATION ON PLASMA GLUCOSE, INSULIN AND GLUCAGON, BLOOD PYRUVATE, LACTATE AND BETA-HYDROXYBUTYRATE CONCENTRATIONS IN NEWBORN INFANTS Study in Term and Preterm Newborn Infants

ABSTRACT. Ten term and eleven preterm newborn infants with appropriate weights for their gestational age were infused for one minute with L-alanine (150 mg/kg) at the age of 29 to 76 hours (mean 48 hours) and circulating levels of glucose, lactate, pyruvate, d -betahydroxybutyrate ( d -BOHB), insulin and glucagon were monitored. Plasma glucose concentrations increased from 2.7±0.16 (mean±S.E.M.) to 3.7±0.2 mmol/1 after 50 min (p±0.01) in term infants. In preterm infants, after an initial decrease of the glucose level from 3.1±0.16 to 2.6±0.16 mmol/1 (p±0.05), it returned to the baseline level at 50 min: 3.0±0.2 mmol/1. The blood concentration of d -BOHB decreased in term infants from 192±37 to 112±6 μM/1 (p±0.01) after 40 min. In preterms, its decrease was not significant (p±0.05). Plasma glucagon levels rose from 53±5 to 70±8 pmol/1 after ten minutes (p±0.01) in term infants and from 61±6 to 75±9 after 20 min (p±0.01) in preterm infants. There were no significant changes in plasma insulin concentrations in either group. Forty minutes after l -alanine infusion, I/G ratios were lower in preterm infants (1.26±0.14) than in term infants (1.71±0.25) (p±0.01). There was no relationship between the glycemic responses to l -alanine and the basal levels of d -BOHB.
The data suggest that the glycemic effect of l -alanine infusion and circulating glucagon depends upon a specific stage in maturation. The antiketogenic effect of l -alanine infusion is observed in term infants as in adults.     

Arterial oxygen saturation in preterm infants at discharge from the hospital and six weeks later.

To obtain normal data on arterial oxygen saturation (SaO2) in preterm infants and to study early developmental changes in SaO2, we obtained overnight tape recordings of SaO2 and breathing movements in 160 preterm infants at their discharge from three special care baby units (mean gestational age at birth 33 weeks; at time of study, 37 weeks). One hundred ten infants (69%) underwent a second recording 6 weeks later. Median baseline SaO2 during regular breathing was 99.5% (range 88.7% to 100%) at discharge, and 100% (range 95.3% to 100%) at follow-up (p less than 0.001). The number of episodes of desaturation, defined as a fall in SaO2 to less than or equal to 80% for at least 4 seconds, corrected to the mean duration of recording (12.2 hours), decreased from a median of 3 (0 to 355) to 0 (0 to 17) (p less than 0.001). The median duration of each episode of desaturation remained unchanged (5.2 (4.0 to 22.7) vs 5.5 (4.2 to 24.0) seconds). At discharge, a small minority of infants had a clinically unrecognized low baseline SaO2 (lowest, 88.7%; 5th percentile, 95.7%) or a high number of desaturation episodes (the highest was six times the 95th percentile value). At follow-up, all outlying values had normalized. Follow-up recordings made between 42 and 47 weeks of gestational age (n = 53) were compared with similar recordings from 67 term infants at the same gestational age. The preterm infants had a significantly higher baseline SaO2 and no more desaturation than the infants born at term. Knowledge of normal ranges of oxygenation and their changes with age may be of value in identifying clinically undetected hypoxemia in preterm infants at discharge from the hospital. The potential influence of such hypoxemia on clinical outcome remains to be determined.     

Arousal from sleep pathways are affected by the prone sleeping position and preterm birth: Preterm birth,prone sleeping and arousal from sleep

Objectives

Preterm infants exhibit depressed arousability from sleep when compared with term infants. As the final cortical element of the arousal process may be the most critical for survival, we hypothesized that the increased vulnerability of preterm infants to the Sudden Infant Death Syndrome (SIDS) could be explained by depressed cortical arousal (CA) responses. We evaluated the effects of preterm birth on stimulus-induced arousal processes in both the prone and supine sleeping positions.

Study design

10 healthy preterm infants were studied with daytime polysomnography, in both supine and prone sleeping positions, at 36 weeks gestational age, 2–4 weeks, 2–3 months and 5–6 months post-term corrected age. Sub-cortical activations and cortical arousals (CA) were expressed as proportions of total arousal responses. Preterm data were compared with data from 13 healthy term infants studied at the same corrected ages.

Results

In preterm infants increased CAs were observed in the prone position at all ages studied. Compared to term infants, preterm infants had significantly fewer CAs in QS when prone at 2–3 months of age and more CAs when prone at 2–4 weeks in AS. There were no differences in either sleep state when infants slept supine.

Conclusions

Prone sleeping promoted CA responses in healthy preterm infants throughout the first six months of post-term age. We have previously suggested that in term infants enhanced CA represents a critical protection against a potentially harmful situation; we speculate that for preterm-born infants the need for this protection is greater than in term infants.     

Anti-oxidant enzymes and related elements in term and preterm newborns

Background:  Although oxidative stress-related diseases mostly affect neonates with extremely low birthweight, healthy preterm newborns might also be at risk of oxidative damages. The aim of the present study was to verify this possibility.
Methods:  Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), erythrocyte glutathione peroxidase (GSHPx) and superoxide dismutase (SOD), plasma and erythrocyte concentrations of selenium, zinc and copper were measured until 100 days of life in 30 preterm infants with mean ± SD birthweight and gestational age of 1605 ± 122 g and 34.5 ± 0.5 weeks. The control group included 30 term infants with birthweight 3123 158 g and gestational age 39.6 0.7 weeks.
Results:  Throughout the study period urinary 8-OHdG, taken as a marker of oxidative stress, was significantly higher in the preterm than in the term group. Up until 20 days of life, GSHPx activity was significantly lower in the preterm than in the term infants but this was not associated with any apparent selenium deficiency. Conversely, up until 100 days, preterm infants had significantly reduced SOD levels that appeared to reflect a shortage of the elements needed for this enzyme's activity, notably copper, the plasma concentrations of which were constantly and significantly below the control values.
Conclusion:  The nutritional status of the elements related to the anti-oxidant enzymes, especially zinc and copper, should be carefully assessed in preterm infants, even if their birthweight is not extremely low.     

Low thymic size in preterm infants in the neonatal intensive care unit,a possible marker of infection? A prospective study from birth to 1 year of age

Aim: To study the growth of the thymus in preterm infants. Methods: Ultrasonographic thymic size (Ti) was studied in 80 preterm infants (gestational age 24–36 weeks) from birth to discharge from the neonatal intensive care unit (NICU). Thirty‐three of these infants were followed to 1 year of age. Results: At birth, the median Ti was 5.2 compared with 11.8 in term infants. At discharge, the median Ti was 10.0 and not significantly different from Ti in term infants at birth (p = 0.22). The size of the thymus was significantly associated with postmenstrual age and weight (both p < 0.01). Infections during admission were negatively associated with the size of the thymus (p < 0.01). During the first 3 months after discharge, preterm infants had a significantly higher frequency of infections than did term infants (p = 0.002); hereafter, the preterm infants had significantly fewer infections than term infants (p = 0.002). The median Ti in preterm infants and term infants at 1 year of age was 21.1 and 17.3, respectively. This difference was not statistically significant (p = 0.41). Conclusions: Growth of thymus was not compromised by preterm birth. Ti is negatively associated with the frequency of infections in preterm neonates submitted to NICU.     

Mean platelet volume and platelet distribution width in the neonate

Normal values for mean platelet volume (MPV) and platelet distribution width (PDW) have not been firmly established for term and preterm neonates. Cord blood samples from 143 healthy newborns (78 full term and 65 premature) were analyzed with the Coulter counter. Platelet count and MPV were significantly greater (p less than 0.05 and p less than 0.001, respectively) in term versus preterm infants, while PDW was significantly less in term infants (p less than 0.001). Platelet count and MPV correlated with gestational age, and platelet count also correlated with birth weight. There was a significant (p less than 0.001) negative correlation of PDW with gestational age and birth weight. These data represent normal reference ranges for neonates and demonstrate significant variation with gestational age.     

A developmental study on types and frequency distribution of short apneas (3 to 15 seconds) in term and preterm infants

We measured the frequency distribution and the ventilatory correlates of the various types of apneas 3 to 15 s long during sleep in eight term infants (birth weight 3.65 +/- 0.16 kg; gestational age 39.5 +/- 0.3 wk) and eight preterm infants (birth weight 2.07 +/- 0.18 kg; gestational age 34.3 +/- 0.4 wk). Each infant was studied on five to seven occasions from birth to 56 wk of postconceptual age using a modified flow-through system. Sixty-six paired epochs of quiet sleep (1163 min) and rapid eye movement sleep (829 min) were analyzed in term infants and 85 paired epochs of quiet sleep (1553 min) and rapid eye movement sleep (1328 min) in preterm infants. Of the 783 apneas recorded in term infants 82% were central, 1.5% obstructive, 0.5% mixed, and 16% were of the breath-holding type; the corresponding figures for the 4086 apneas recorded in preterm infants were 93, 0.5, 1.0, and 5.5%. This distribution was similar in the two sleep states but term infants had a higher percentage of breath-holding apneas than preterm infants (p less than 0.01). In preterm infants the rate of central apneas decreased with postnatal age (p less than 0.01); in term infants the rate did not change significantly. The duration of apneas showed a modal distribution for central apneas at about 8 s for both groups during the 1st month of life (p less than 0.05). The findings suggest: 1) apneas in the newborn and early infancy are primarily central and are more frequent in preterm than in term infants.(ABSTRACT TRUNCATED AT 250 WORDS)