Atrial natriuretic peptide and renin-aldosterone relationship in healthy newborn infants

Preoperative factors as a predictor for early postoperative outcomes after repair of congenital transposition of the great arteries

Transposition of the great arteries (TGA) requires early surgical repair during the neonatal period. Several preoperative factors have been identified for the postoperative poor outcome after arterial switch operation (ASO). However, the data remain uncertain an association. Therefore, we investigated the preoperative factors which affect the early postoperative outcomes. Between March 2005 and May 2012, a retrospective study was performed which included 126 infants with an ASO for TGA. Preoperative data included the vasoactive inotropic score (VIS) and baseline hemodynamics. Early postoperative outcomes included the duration of mechanical ventilation, the length of stay in the intensive care unit and hospital, and early mortality. Multivariate linear regression and receiver operating characteristics analysis were performed. The duration of mechanical ventilation was significantly correlated with the preoperative mechanical ventilator support and VIS, and CPB time. On multivariate linear regression analysis, a higher preoperative VIS, preoperative B-type natriuretic peptide (BNP) level, and the CPB time were identified as independent risk factors for delayed mechanical ventilation. Preoperative VIS (OR 1.154, 95 % CI 1.024-1.300) and the CPB time (OR 1.034, 95 % CI 1.009-1.060) were independent parameters predicting early mortality. A preoperative VIS of 12.5 had the best combined sensitivity (83.3 %) and specificity (85.3 %) and an AUC of 0.852 (95 % CI 0.642-1.061) predicted early mortality. Our results suggest that preoperative VIS and BNP can predict the need for prolonged postoperative mechanical ventilation. Moreover, preoperative VIS may be used as a simple and feasible indicator for predicting early mortality.

The effects of delivery route and anesthesia type on early postnatal weight loss in newborns: the role of vasoactive hormones

OBJECTIVE

To investigate the effects of delivery route and maternal anesthesia type and the roles of vasoactive hormones on early postnatal weight loss in term newborns.

METHODS

Ninety-four term infants delivered vaginally (group 1, n=31), cesarean section (C/S) with general anesthesia (GA) (group 2, n=29), and C/S with epidural anesthesia (EA) (group 3, n=34) were included in this study. All infants were weighed at birth and on the second day of life and intravenous (IV) fluid infused to the mothers for the last 6 h prior to delivery was recorded. Serum electrolytes, osmolality, N-terminal proANP (NT-proANP), brain natriuretic peptide (BNP), aldosterone and plasma antidiuretic hormone (ADH) concentrations were measured at cord blood and on the second day of life.

RESULTS

Our research showed that postnatal weight loss of infants was higher in C/S than vaginal deliveries (5.7% vs. 1.3%) (p < 0.0001) and in EA group than GA group (6.8% vs. 4.3%) (p < 0.0001). Postnatal weight losses were correlated with IV fluid volume infused to the mothers for the last 6 h prior to delivery (R = 0.814, p = 0.000) and with serum NT-proANP (R = 0.418, p = 0.000), BNP (R = 0.454, p = 0.000), and ADH (R = 0.509, p = 0.000) but not with aldosterone concentrations (p > 0.05).

CONCLUSION

Large amounts of IV fluid given to the mothers who were applied EA prior to the delivery affect their offsprings' postnatal weight loss via certain vasoactive hormones.

Predictors of delayed first voiding in newborn

AIM

Delay>24 h of age in neonates' first voiding attracts attention, although the phenomenon is usually benign. Earlier studies indicate that stress increases the infant's arginine vasopressin (AVP) and aldosterone secretion during birth. Our aim was to seek predictors of delayed first voiding and indirect evidence of AVP effect behind this phenomenon.

METHODS

The study population comprised 20 normal-term newborns whose first voiding was delayed>24 h of age (cases), and 19 age-matched control infants who voided for the first time at <24 h of age (controls). The first urine was collected and osmolality (U-Osm) and sodium content (U-Na) measured.

RESULTS

The median of U-osm in cases was 432.50 (284-519) and in controls 337.50 (169-497) mOsm/L (p=0.005), and U-Na 21.50 (9-241) and 40.00 (13-226) mmol/L (p=0.001), respectively. Cases were more frequently born to primiparous mothers than controls (70% vs. 21%, p=0.004). Duration of labour was longer in cases than controls, first stage 10.5 h (3.92-20.50 h) versus 5.7 h (1.17-16.00 h) (p=0.045) and second stage 0.42 h (0.08-1.25 h) versus 0.17 h (0.08-0.92 h) (p=0.015). All seven (35%) abnormal cardiotocographies were recorded with cases (p=0.008).

CONCLUSIONS

Delayed voiding appears to be related to a prolonged and stressful birth. Laboratory findings in the first urine suggest increased AVP and aldosterone secretion in such cases.

Urodilatin excretion and its correlation with sodium excretion in healthy full-term newborn infants

BACKGROUND

Urodilatin (URO) is a member of the natriuretic family, cleaved by the kidney, which acts as a paracrine hormone in the regulation of natriuresis and diuresis. In newborn infants the excretion of urodilatin and its biological effects have not been explored.

METHODS

We measured urinary URO excretion, by direct RIA (radioimmunoassay), as well as its correlation to neonatal body weight loss, and sodium homeostasis in 30 full-term newborn infants on the 4th day of life.

RESULTS

The URO excretion, estimated as URO:creatinine ratio, was significantly correlated to sodium excretion.

CONCLUSION

These data show that in full-term newborn infants the mechanisms that control synthesis, excretion and signal transduction of URO are developed and that URO contributes to natriuresis regulation.

Clinical value of NT-ProBNP and BNP in pediatric cardiology

BACKGROUND

Although less common than in adults, heart disease is a significant cause for morbidity and death in infants and children. Congenital structural cardiac anomalies and acquired heart diseases may result in heart failure.

METHODS AND RESULTS

Available data suggest that the natriuretic peptide system has a similar role in health and disease in the pediatric age group as in adults. In healthy infants and children, levels of B-type natriuretic peptide (BNP) and the N-terminal segment of its pro-hormone (NT-proBNP) are elevated in the first few days after birth. Thereafter, their levels decrease and remain relatively constant throughout childhood. Infants and children with heart disease that causes significant pressure or volume overload of the right or the left ventricle have elevated BNP and NT-proBNP levels. In children with congestive heart failure, BNP and NT-proBNP levels correlate with functional capacity. Both peptides can differentiate cardiac from pulmonary causes in infants with respiratory distress. Limited data suggest that these peptides may also serve as markers in cyanotic, obstructive, and inflammatory heart diseases.

CONCLUSION

The present data suggest that both NT-proBNP and BNP are markers for heart disease in infants and children. Their use may improve clinical practice in pediatric cardiology.

Reference values of NT-proBNP serum concentrations in the umbilical cord blood and in healthy neonates and children

BACKGROUND

N-terminal brain natriuretic peptide (NT-proBNP) is a neurohormonal substance secreted mainly by the cardiac myocytes of the left ventricle and to a less degree of the left atrium. The releasing mechanism is induced by an increased wall stress on the base of volume or pressure load of the ventricle. The physiologic actions of BNP are prohibition of the sympathetic activity, vasodilatation, natriuresis, diureses and inhibition of the renin-angiotensin system. Because of its high sensitivity and specifity in relation to the left ventricular incompetence, BNP as well as NTproBNP are well accepted markers of ventricular dysfunction. It was the aim of the study to establish reference values of NT-proBNP serum concentrations throughout childhood, in particular in the newborn age group.

METHODS

In a cross sectional study, serum NT-proBNP concentrations were measured by an ElectroChemiLuminescenceImmunoAssay ("ECLIA" Roche) in the umbilical cord blood of 62 healthy full-term neonates and in 222 healthy probands from birth up to the age of 18 years.

RESULTS

The concentration of NT-proBNP in the cord blood samples ranged from 281 to 2595 pg/ml (mean: 818 pg/ml). There was a significant increase in the first days of life followed by a rapid decrease during the first year and a further gradual decrease throughout infancy; beyond the 10(th) year of age normal adult values were approached.

CONCLUSIONS

The knowledge of the normal range of plasma NT-proBNP levels in healthy subjects during childhood serves as a non-invasive marker for differentiation of pathologic conditions such as acute myocarditis, hypertrophic or dilated cardiomyopathy, tachyarrhythmias and pulmonary hypertension.

Plasma aldosterone levels in the 1st week of life in infants of less than 30 weeks gestation

Plasma aldosterone levels were measured in 50 infants of less than 30 weeks gestation at 24 h (D1) and 7 days (D7). The relationship between the plasma aldosterone level and a number of clinical and biochemical variables was explored. Plasma aldosterone levels ranged from 1000 to 30000 pmol/l and were inversely correlated with the severity of illness (D1 or D7), serum sodium (D7) and 24 h sodium intake (D1). No correlation with the serum potassium level was noted.

CONCLUSION

Plasma aldosterone levels in this extremely premature cohort were significantly greater than those reported in more mature infants. Important determinants were severity of illness and sodium homeostasis.

Normal values of B type natriuretic peptide in infants, children, and adolescents

OBJECTIVE

To determine normal values of plasma B type natriuretic peptide from infancy to adolescence using a commercially available rapid assay.

SETTING

Tertiary referral centre.

DESIGN

The study was cross sectional. Plasma BNP concentration was measured in 195 healthy infants, children, and adolescents from birth to 17.6 years using the triage BNP assay (a fluorescence immunoassay).

RESULTS

During the first week of life, the mean (SD) plasma concentration of BNP in newborn infants decreased significantly from 231.6 (197.5) to 48.4 (49.1) pg/ml (p = 0.001). In all subjects older than two weeks plasma BNP concentration was less than 32.7 pg/ml. There was no significant difference in mean plasma BNP measured in boys and girls younger than 10 years (8.3 (6.9) v 8.5 (7.5) pg/ml). In contrast, plasma concentration of BNP in girls aged 10 years or older was significantly higher than in boys of the same age group (12.1 (9.6) v 5.1 (3.5) pg/ml, p < 0.001). Plasma BNP concentrations were higher in pubertal than in prepubertal girls (14.4 (9.7) v 7.1 (6.6) pg/ml, p < 0.001) and were correlated with the Tanner stage (r = 0.41, p = 0.001).

CONCLUSIONS

Plasma BNP concentrations in newborn infants are relatively high, vary greatly, and decrease rapidly during the first week of life. In children older than 2 weeks, the mean plasma concentration of BNP is lower than in adults. There is a sex related difference in the second decade of life, with higher BNP concentrations in girls. BNP concentrations in girls are related to pubertal stage.

Hyponatraemic hypertensive syndrome in two extremely low birthweight infants

Two cases of hyponatraemic hypertensive syndrome occurring in extremely low birthweight infants are presented. Both infants experienced unilateral renal ischaemia resulting in hyponatraemia and hypertension. A proposed pathophysiological mechanism, namely unilateral renal ischaemia leading to a pressure-natriuresis in the contralateral kidney, is presented. This is associated with an increase in plasma renin and aldosterone, with a paradoxical increase in urinary sodium loss. Immature renal tubular function and relative aldosterone resistance could place the extremely low birthweight infant at increased risk for the condition. The paucity of reports suggests that the condition might be under-recognized.

Serial plasma concentrations of atrial natriuretic peptide, plasma renin activity, aldosterone, and antidiuretic hormone in neonates on extracorporeal membrane oxygenation

To obtain information on water and salt regulating hormones and volume homeostasis during neonatal extracorporeal membrane oxygenation (ECMO), serial determinations of atrial natriuretic peptide (ANP), plasma renin activity (PRA), aldosterone (Aldo), antidiuretic hormone (ADH), colloid-osmotic pressure (COP), osmolality (Osmol), and central venous pressure (CVP) before, during, and after neonatal ECMO in 10 neonates with meconium aspiration syndrome (MAS) were carried out. Mean gestational ages and birth weights were 41(+3) weeks (39(+6) - 42(+4)) and 4,063 gm (3,500-4700), respectively; mean age at start and duration of ECMO 29.3 (14-69) and 152.6 hr (92-267), respectively. Plasma ANP (mean +/- SD) was 67.8+/-69.1 pmol/L before, decreased to 33.3+/-22.1 (not significant) pmol/L during, and significantly increased to 274.6+/-131.8 pmol/L after ECMO (p < 0.05). ANP correlated positively with CVP (r = 0.63; p < 0.001). Pre-ECMO PRA, Aldo, and ADH were comparable to those described earlier in normal neonates, decreased during (p < 0.001 for Aldo; p < 0.05 for PRA and ADH) and either remained elevated (PRA, p < 0.001; Aldo, p < 0.05) or decreased (ADH) after ECMO. COP and Osmol remained unchanged. Neonatal ECMO for MAS is characterized by circulatory and osmotic equilibrium. It is suggested that circulating volume contracts during and expands after neonatal ECMO for MAS.

The effect of hypoxia from birth on the regulation of aldosterone in the 7-day-old rat: plasma hormones, steroidogenesis in vitro, and steroidogenic enzyme messenger ribonucleic acid

Adaptation to hypoxia in the neonate requires an appropriate adrenocortical response. The purpose of this study was to examine the adaptation of the aldosterone pathway in rat pups exposed to hypoxia in vivo from birth to 7 days of age. Neonatal rats (with their lactating dams) were exposed to normoxia (21% O2) or hypoxia (12% O2) continuously for 7 days from birth. Trunk blood was collected, and entire adrenal glands were processed from 7-day-old rats to study the activity of the steroidogenic pathway in dispersed cells and isolated mitochondria, for measurement of expression of the steroidogenic enzyme messenger RNAs (mRNAs) by RT-competitive PCR and in situ hybridization histochemistry, for measurement of zona glomerulosa width by immunohistofluorescent staining for P450c11AS protein, and for measurement of mitochondrial number and distribution by transmission electron microscopy. Exposure to hypoxia for 7 days from birth resulted in a marked increase in plasma ACTH, corticosterone, and aldosterone with no change in PRA. Aldosteronogenesis and P450c11AS activity were both augmented in dispersed cells; this effect was lost in isolated mitochondria (from entire adrenal glands) using a permeable substrate for P450c11AS. There was no significant effect of hypoxia on expression of the steroidogenic enzyme mRNAs measured by RT-competitive PCR or in situ hybridization histochemistry. Finally, hypoxia had no effect on mitochondrial number or stereology as assessed by transmission electron microscopy or on zona glomerulosa width as assessed by staining for P450c11AS protein. We conclude that, as opposed to that in adults, hypoxia in the neonate results in an augmentation of aldosteronogenesis. This effect is not accounted for by a change in steroidogenic enzyme mRNA expression, zona glomerulosa width (i.e. hyperplasia), or mitochondrial number or distribution. This functional augmentation of aldosteronogenesis may be due to a change in mitochondrial permeability to steroid substrates and/or the effect of cytosolic factors that control mitochondrial steroidogenesis.

Immunoreactive renin concentrations in healthy children from birth to adolescence

We establish normative data for immunoreactive renin concentration in serum of healthy children. In a retrospective study, surplus sera of 281 healthy children, aged 0-18 years, were collected from the laboratory. The determinations were performed with a commercially available two-site immunoradiometric assay. Functional sensitivity was 4.0 mU/l, inter-assay and intra-assay variance were 7.0-18.3% and 3.8-7.5%, respectively. In umbilical cord and during the first 4 days of life, renin concentrations (geometric mean) were significantly higher (P < 0.05) than in older infants and children [umbilical cord: 155.2 mU/l; newborn infants (2-4 days of life): 90.9; newborn infants (5-7 days of life): 32.5; 2 weeks-3 months: 40.8; 4 months-1 year: 54.5; 1-3 years: 46.3; 3-5 years: 48.5; 5-7 years: 51.6; 7-11 years: 38.5; 11-15 years: 37.7; 15-18 years: 31.9]. Newborn infants delivered by Caesarian section had significantly lower renin concentrations in umbilical cord than those delivered vaginally (P < 0.02). Considering the methodological advantages and disadvantages of plasma renin activity and renin concentration assays, renin measurement was at least as valuable and accurate as plasma renin activity determination.

Altered regulation of natriuretic peptides in the rat heart by prenatal exposure to morphine

1. Both endogenous and exogenous opioids modulate blood pressure and cardiac function by stimulating cardiac synthesis of atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP). Since morphine crosses the placental barrier, it could alter the ANF-BNP system in the fetal heart. The aim of this study was to characterize cardiac natriuretic peptides in normal rat development and in rats prenatally exposed to morphine. 2. Female rats received either saline or morphine (10 or 20 mg kg-1 day-1) via osmotic minipumps during gestation. The effects of this treatment were investigated in offspring at 1, 4 and 22 days of age. 3. During maturation, atrial ANF and ANF mRNA increased by 3-fold from birth to 3 weeks of age, but BNP and BNP mRNA tended to decrease. In the ventricles, both ANF and BNP content decreased at 3 weeks after birth, from 25.11 +/- 3.6 to 0.81 +/- 0.1 ng (mg protein)-1 (P < 0.001), and from 3.36 +/- 0.33 to 0.19 +/- 0.01 ng (mg protein)-1 (P < 0.001), respectively. However, whereas ventricular ANF mRNA decreased, BNP mRNA levels did not change during maturation. Prenatal exposure to morphine significantly increased ANF content in the left atria of 22-day-old rats, and in the right atria of 1-, 4- and 22-day-old rats compared with age-matched saline controls. In contrast, prenatal exposure to 20 mg kg-1 day-1 morphine significantly inhibited BNP and BNP mRNA in the ventricles at all ages studied. 4. These observations suggest that alterations in mRNA synthesis or stability and/or post-translational processing of ANF and BNP occur in the heart during maturation, and that prenatal exposure to morphine alters cardiac production, and possibly release, of both peptides.

Transient elevation of aldosterone levels in perinatal asphyxia

We measured plasma aldosterone levels in cord blood and peripheral blood collected 18-24 h after birth in 19 asphyxiated and 19 normal term newborn infants. The asphyxiated newborn infants had significantly higher aldosterone levels in cord blood than the normal newborn infants. At 18-24 h after birth there was no difference between the groups with respect to aldosterone levels. There was a positive significant correlation between aldosterone levels and PCO2 in cord blood by multiple linear regression analysis. There is a transient elevation of aldosterone levels in perinatal asphyxia.

Early changes in plasma brain and atrial natriuretic peptides in premature infants: correlation with pulmonary arterial pressure

To define the change in plasma natriuretic peptides in newborns, we prospectively studied 10 premature infants. They were followed sequentially during the first week of extrauterine life by two-dimensional and pulsed Doppler echocardiography, and studied for atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). We estimated mean pulmonary arterial pressure (MPAP) and measured blood pressure on days 1, 2, 3, 5, 7, respectively. Plasma ANP levels were 81.7 +/- 11.4 pg/ml on day 1 and 67.9 +/- 6.0 pg/ml on day 7, respectively. Between day 2 and day 7, there was a fall in MPAP, i.e. from 37 +/- 4 mmHg to 22 +/- 2 mmHg (P < 0.01), which was associated with a significant decrease in plasma BNP (41.8 +/- 10.1 pg/ml on day 2 vs. 10.4 +/- 0.9 pg/ml on day 7, P < 0.01). There was a positive correlation between MPAP and plasma BNP level (r = 0.643, P < 0.0001), but there was no correlation between MPAP and plasma ANP level. These data suggest that the pattern of secretion of BNP is different from that of ANP and that BNP levels reflect the changes of pulmonary arterial pressure in the neonatal period in premature infants.

Splicing mutation in CYP21 associated with delayed presentation of salt-wasting congenital adrenal hyperplasia

Patients with salt-wasting congenital adrenal hyperplasia (SW-CAH) most commonly carry an A-G transition at nucleotide 656 (nt 656 A-->G), causing abnormal splicing of exons 2 and 3 in CYP21, the gene encoding active steroid 21-hydroxylase. Affected infants are severely deficient in cortisol and aldosterone, and usually come to medical attention during the neonatal period. We report on 2 affected boys, homozygous for the nt 656 mutation, who thrived in early infancy, but suffered salt-wasting crises unusually late in infancy, at 3.5 and 5.5 months, respectively. Laboratory studies at presentation showed hyponatremia, hyperkalemia, dehydration, and acidosis; serum aldosterone was low in spite of markedly elevated plasma renin activity. Basal 17-hydroxyprogesterone levels were only moderately elevated, yet the stimulated levels were more typical of severe, classic CAH due to 21-hydroxylase deficiency. Genomic DNA from the patients was analyzed. Southern blot showed no major deletions or rearrangements. CYP21-specific amplification by polymerase chain reaction, coupled with allele-specific hybridization using wild-type and mutant probes at each of 9 sites for recognized disease-causing mutations, revealed a single, homozygous mutation in each patient: nt 656 A-->G. These results were confirmed by sequence analysis. We conclude that the common nt 656 A-->G mutation is sometimes associated with delayed phenotypic expression of SW-CAH. We speculate that variable splicing of the mutant CYP21 may modify the clinical manifestations of this disease.

Effects of the mode of delivery on ANP and renin-aldosterone system in the fetus and the neonate

Plasma ANP and aldosterone levels, plasma renin activity (PRA), haematocrit, systolic and diastolic blood pressure (BP), were evaluated in 15 full-term infants delivered by elective Caesarean section (CS group) and in 15 full-term infants delivered vaginally (vaginal group). The mode of delivery did not influence the cord blood levels of ANP and their increase at the 24th hour of life. Instead, PRA was lower and plasma aldosterone levels were higher in the CS group than in the vaginal group. Also haematocrit and BP were influenced by mode of delivery. The haematocrit values were lower in the CS group than in the vaginal group at birth as well at the 24th hour of life. The values of systolic and diastolic BP were the same in both groups, at birth, but at the 24th hour of life increases were observed only in the vaginal group. On the fourth day of life weight loss was the same in both groups. Our findings suggest that the mode of delivery has more influence on neonatal BP adaptation than on neonatal volume homeostasis.