Postnatal alteration in hematocrit and viscosity in normal and polycythemic infants

This study was done to document postnatal alterations in hematocrit and viscosity in the first 18 hours of life in 99 full-term infants, to better understand the age-dependent variations in these measurements that may have a bearing on the diagnosis of neonatal polycythemia. The peripheral venous Hct was highest at 2 hours of age, and dropped to cord blood levels by 18 hours. The whole blood viscosity of peripheral venous samples did not change significantly with age. In infants with peripheral venous Hct greater than or equal to 64%, and therefore considered to have polycythemia, a similar postnatal variation in Hct level was seen. Only 38% of infants with Hct greater than or equal to 64% at 2 hours of age continued to have a high level beyond 12 hours of age. The viscosity level in these infants tended to follow that of the Hct. The mean +/- 2 SD viscosity values obtained from peripheral venous samples was much higher than the upper limits of viscosity used in previous studies in which cord blood viscosity was used as the norm. Cord blood Hct correlated better with peripheral venous Hct than with capillary hematocrit, and provided a noninvasive method for screening. These findings suggest that the postnatal variations in Hct should be taken into consideration in the diagnosis of neonatal polycythemia.     

Elevated calcitonin gene-related peptide in polycythemic newborn infants

In this study, calcitonin gene-related peptide levels were measured in cord and at 16-36 h of extrauterine life in 43 polycythemic newborns; 20 healthy term infants were also studied as controls. Calcitonin gene-related peptide values were significantly higher in polycythemic neonates in comparison with controls both at delivery and at 16-36 h after birth. Five polycythemic (11.6%) infants who develop hypocalcemia had greater elevated calcitonin gene-related peptide concentrations. Our data suggest that calcitonin gene-related peptide may be implicated in the circulatory adaptation to extrauterine life. In polycythemic neonates, calcitonin gene-related peptide is probably increased to compensate for blood hyperviscosity; in some cases, high calcitonin gene-related peptide concentrations may induce hypocalcemia.     

Postnatal development of the sympathoadrenergic system in premature and newborn infants

Autonomic regulatory mechanisms and some metabolic functions are predominantly influenced by the sympathetic nervous system. Premature and mature newborns show a high variability and a low adaptability of the sympathetic nervous system. In order to investigate whether sympathetic systems are completely developed at birth or underly a postnatal maturation process we have determined plasma levels of adrenaline and noradrenaline as well as the density and affinity of alpha- and beta-adrenoceptors on thrombocytes and lymphocytes in pre- and mature newborns and adults. Catecholamines were determined by means of a radioenzymatic method, number and affinity of adrenoceptors by use of the radioactive labelled antagonists 3-H-Yohimbine and 125-I-Cyano-Pindolol. Beta-adrenoceptor responsiveness was assessed by measurement of cyclic AMP in lymphocytes before and after stimulation of beta-adrenoceptors by isoprenaline. A linear relationship occurred between the gestational age and the number of adrenoceptors on lymphocytes, whereas the alpha-adrenoceptors on thrombocytes showed no age dependency. The basal content of cyclic AMP and the accumulation in response to beta-adrenoceptor stimulation by isoprenaline was significantly lower in newborns than in adults. Since noradrenaline and adrenaline plasma levels were not significantly different in newborns and adults it is assumed that the low density of beta-adrenoceptors in premature and mature newborns is due to a postnatal maturation and not to a "down regulation" by circulating catecholamines. Our results suggest that an immaturity of beta-adrenoceptors is involved in the poorly developed adaptive control in newborns.     

Postnatal sensitivity of the peripheral chemoreceptors in newborn infants.

The peripheral chemoreflex was tested in healthy term infants by measuring the ventilatory response to 100% oxygen over 30 seconds. Minute ventilation did not change when studied two to six hours after birth. By contrast, at 2-6 days of age a mean decrease of 9.8% was noted, the difference between the groups being highly significant. There were no significant changes in respiratory rate. It is concluded that the chemoreflex is less active immediately after birth than it is a few days later, possibly due to a resetting of the sensitivity of the peripheral chemoreceptors from the fetal state, with its relatively low arterial oxygen tension to the higher postnatal concentrations.     

Gastrointestinal injury in polycythemic term infants

Necrotizing enterocolitis is uncommon among term infants. In this group, necrotizing enterocolitis has been associated with two risk factors: polycythemia and umbilical catheterization. During a randomized trial of partial plasma exchange transfusion for treatment of polycythemia, an increased risk of gastrointestinal problems was noted. Eight hyperviscous patients treated with partial plasma exchange transfusion, no symptomatically treated patients, and no control infants developed typical necrotizing enterocolitis (blood in the stools, pneumatosis, and systemic signs). The incidence of necrotizing enterocolitis was significantly greater among patients treated with exchange transfusion compared with patients treated symptomatically or control subjects (P less than .001).     

Postnatal hypothermia and cold stress among newborn infants in Nepal monitored by continuous ambulatory recording.

AIMS: To describe the pattern of hypothermia and cold stress after delivery among a normal neonatal population in Nepal; to provide practical advice for improving thermal care in a resource limited maternity hospital. METHODS: The principal government funded maternity hospital in Kathmandu, Nepal, with an annual delivery rate of 15,000 (constituting 40% of all Kathmandu Valley deliveries), severe resource limitations (annual budget Pounds 250,000), and a cold winter climate provided the setting. Thirty five healthy term neonates not requiring special care were enrolled for study within 90 minutes of birth. Continuous ambulatory temperature monitoring, using microthermistor skin probes for forehead and axilla, a flexible rectal probe, and a black ball probe placed next to the infant for ambient temperature, was carried out. All probes were connected to a compact battery powered Squirrel Memory Logger, giving a temperature reading to 0.2 degree C at five minute intervals for 24 hours. Severity and duration of hypothermia, using cutoff values of core temperature less than 36 degrees C, 34 degrees C, and 32 degrees C; and cold stress, using cutoff values of skin-core (forehead-axilla) temperature difference greater than 3 degrees C and 4 degrees C were the main outcome measures. RESULTS: Twenty four hour mean ambient temperatures were generally lower than the WHO recommended level of 25 degrees C (median 22.3 degrees C, range 15.1-27.5 degrees C). Postnatal hypothermia was prolonged, with axillary core temperatures only reaching 36 degrees C after a mean of 6.4 hours (range 0-21.1; SD 4.6). There was persistent and increasing cold stress over the first 24 hours with the core-skin (axillary-forehead) temperature gap exceeding 3 degrees C for more than half of the first 24 hours. CONCLUSIONS: Continuous ambulatory recording identifies weak links in the "warm chain" for neonates. The severity and duration of thermal problems was greater than expected even in a hospital setting where some of the WHO recommendations had already been implemented.     

Postnatal breast development of preterm infants. An index of gonadal function.

Development of breast nodules after birth was examined in 17 preterm infants; nodules developed regularly in girls but not boys. It is concluded that the pituitary-gonadal axis of preterm infants is active in the months after birth and that in preterm infants there is a definite phase of breast growth in early postnatal life.     

Postnatal development of renal function in very low birthweight infants

The postnatal development of renal function was compared in infants with a gestational age of 25-30 weeks, mean 27.8 weeks (GA 28), and in infants with a gestational age of 31-34 weeks, mean 32.5 weeks (GA 32). The infants were comparable with regard to postnatal course, fluid, caloric and salt intake. Observations were made during the 1st, 2nd and 4th-7th (mean 5th) postnatal weeks. From the 1st to the 5th postnatal week the creatinine clearance (CCr ml/min/1.73 m2), increased from 11 to 20 in GA 28 and from 15 to 30 in GA 32. At 2 weeks of age CCr was significantly lower in GA 28 than in GA 32. During the first week of life diuresis was lower in GA 28 than in GA 32 but thereafter was the same in both groups. We interpret this as a sign of dehydration in GA 28. Serum arginine vasopressin (S-AVP) concentrations were high in both groups at all ages. Mean urine osmolality was low (less than 300) regardless of postnatal age and S-AVP. Urinary sodium excretion was high at 1 week of age in both groups and decreased with increasing postnatal age. Na excretion was slightly higher in GA 28 than in GA 32 at 1 but not at 2 and 5 weeks. UK/UNa was below 1 in both groups during the first week of life and increased with postnatal age. Urinary aldosterone excretion was high in both GA 28 and GA 32 at all ages. Serum sodium levels were lower in GA 28 than in GA 32 at all ages.(ABSTRACT TRUNCATED AT 250 WORDS)     

新生儿味觉发育62例分析

目的观察新生儿味觉发育情况及性别差异。方法62个健康新生儿（男女各31名）在出生后90min进行四种味觉测试,味觉溶液浓度为：25％蔗糖（甜味）、5％氯化钠（咸味）、1．43％柠檬酸（酸味）、0．025％盐酸小檗碱。摄像记录新生儿味觉测试中的面部表情。采用卡方检验分析新生儿对味觉的不同面部表情,采用Wilcoxon秩和检验分析味觉性别差异。结果对甜味溶液新生儿的面部表情主要为没有13部动作或13部吸吮动作（P〈0．01）,对咸味溶液新生儿没有特殊表情（P〉0．01）,对酸味溶液的面部表情主要为撅嘴伴皱眉和皱鼻的面中上部表情（P〈0．01）,对苦味溶液的面部表情主要为嘴张开伴皱眉和皱鼻的面中上部表情（P〈0．01）。男性新生儿对甜味和苦味的面部表情较女孩敏感（P〈0．01）,对咸味和酸味男女间没有性别差异（P〉0．05）。结论新生儿能够区分甜、咸、酸、苦四种基本味觉,且男性新生儿对甜味和苦味较女性新生儿敏感。     

Postnatal development of periodic breathing cycle duration in term and preterm infants

Previous studies of the maturation of periodic breathing cycle duration (PCD) with postnatal age in infants have yielded conflicting results. PCD is reported to fall in term infants over the first 6 mo postnatally, whereas in preterm infants PCD is reported either not to change or to fall. Contrary to measured values, use of a theoretical respiratory control model predicts PCD should increase with postnatal age. We re-examined this issue in a longitudinal study of 17 term and 22 preterm infants. PCD decreased exponentially from birth in both groups, reaching a plateau between 4 and 6 mo of age. In preterm infants, PCD fell from a mean of 18.3 s to 9.8 s [95% confidence interval (CI) is +/- 3.2 s]. In term infants, PCD fell from 15.4 s to 10.1 s (95% CI is +/- 3.1 s). The higher PCD at birth in preterm infants, and the similar PCD value at 6 mo in the two groups, suggest a more rapid maturation of PCD in preterm infants. This study confirms that PCD declines after birth. The disagreement between our data and theoretical predictions of PCD may point to important differences between the respiratory controller of the infant and adult.     

Intracranial hemorrhage in preterm- and full-term newborn infants. Frequency and prognosis for development

In a prospective study 306 high-risk infants with a birth-weight between 890 to 4900 gm were examined by means of cerebral ultrasound scanning and about a time of two years the psychomotor development was evaluated. 145 patients (47.4%) were classified as intracerebral haemorrhages. The strongest relation with the event of bleeding was found for the high level of PCO2. With increased severity of the intracranial haemorrhage was associated a worse prognosis of development in the first two years of life. The type I-haemorrhage showed in 72.2%, the types III/IV in yet only 42.9% a development without psychomotor disorders.