Postnatal weight loss in preterm neonates less than 1,500 g is due to isotonic dehydration of the extracellular volume

Actual electrolyte intake during the first week of life and morbidity in very-low-birthweight infants

AIM

To describe sodium and potassium intake, their sources and plasma concentrations, and the association between intake and morbidity in very-low-birthweight (VLBW, <1500 g) infants during the first week of life.

METHODS

This retrospective cohort study comprised 951 VLBW infants born at <32 weeks. Infants were divided into three groups according to gestational age: 23-26 (n = 275), 27-29 (n = 433) and 30-31 (n = 243) weeks. Data on fluid management and laboratory findings were acquired from an electronic patient information system.

RESULTS

The median sodium intake was highest in the 23-26 week group, peaking at 6.4 mmol/kg/day. A significant proportion of sodium derived from intravascular flushes; it reached 27% on day 1 in the 23-26 week group. High cumulative sodium intake in the first postnatal week was associated with weight gain from birth to day 8 in the 23-26 week group. High intake of sodium associated with an increased risk of surgically ligated patent ductus arteriosus (PDA), bronchopulmonary dysplasia and intraventricular haemorrhage, whereas low intake of potassium associated with an increased risk of PDA.

CONCLUSION

Sodium intake in the most premature infants exceeded recommendations during the first postnatal week. Saline flushes accounted for a significant proportion of the sodium load.

Time-Varying Clearance in Milrinone Pharmacokinetics from Premature Neonates to Adolescents

BACKGROUND AND OBJECTIVES

Milrinone is an inotrope and vasodilator used for prophylaxis or treatment of low cardiac output syndrome after weaning from cardiopulmonary bypass (CPB). It is renally eliminated and has an acceptable therapeutic range of 100-300 μg/L, but weight-based dosing alone is associated with poor target attainment. We aimed to develop a population pharmacokinetic model for milrinone from premature neonates to adolescents, and to evaluate how age, renal function and recovery from CPB may impact dose selection.

METHODS

Fifty paediatric patients (aged 4 days to 16 years) were studied after undergoing cardiac surgery supported by CPB. Data from 29 premature neonates (23-28 weeks' postmenstrual age) treated for prophylaxis of low systemic blood flow were available for a pooled pharmacokinetic analysis. Population parameters were estimated using non-linear mixed effects modelling (NONMEM 7.5.1).

RESULTS

There were 369 milrinone measurements available for analysis. A one-compartment model with zero-order input and first-order elimination was used to describe milrinone disposition. Population parameters were clearance 17.8 L/70 kg [95% CI 15.8-19.9] and volume 20.4 L/h/70 kg [95% CI 17.8-22.1]. Covariates included size, postmenstrual age and renal function for clearance, and size and postnatal age for volume. Milrinone clearance is reduced by 39.5% [95% CI 24.0-53.7] immediately after bypass, and recovers to baseline clearance with a half-time of 12.0 h [95% CI 9.7-15.2]. Milrinone volume was 2.07 [95% CI 1.87-2.27] times greater at birth than the population standard and decreased over the first days of life with a half-time of 0.977 days [95% CI 0.833-1.12].

CONCLUSION

Milrinone is predominately renally eliminated and so renal function is an important covariate describing variability in clearance. Increasing clearance over time likely reflects increasing cardiac output and renal perfusion due to milrinone and return to baseline following CPB.

Higher versus lower sodium intake for preterm infants

BACKGROUND

Infants born preterm are at increased risk of early hypernatraemia (above-normal blood sodium levels) and late hyponatraemia (below-normal blood sodium levels). There are concerns that imbalances of sodium intake may impact neonatal morbidities, growth and developmental outcomes.

OBJECTIVES

To determine the effects of higher versus lower sodium supplementation in preterm infants.

SEARCH METHODS

We searched CENTRAL in February 2023; and MEDLINE, Embase and trials registries in March and April 2022. We checked reference lists of included studies and systematic reviews where subject matter related to the intervention or population examined in this review. We compared early (< 7 days following birth), late (≥ 7 days following birth), and early and late sodium supplementation, separately.

SELECTION CRITERIA

We included randomised, quasi-randomised or cluster-randomised controlled trials that compared nutritional supplementation that included higher versus lower sodium supplementation in parenteral or enteral intake, or both. Eligible participants were preterm infants born before 37 weeks' gestational age or with a birth weight less than 2500 grams, or both. We excluded studies that had prespecified differential water intakes between groups.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed eligibility and risk of bias, and extracted data. We used the GRADE approach to assess the certainty of evidence.

MAIN RESULTS

We included nine studies in total. However, we were unable to extract data from one study (20 infants); some studies contributed to more than one comparison. Eight studies (241 infants) were available for quantitative meta-analysis. Four studies (103 infants) compared early higher versus lower sodium intake, and four studies (138 infants) compared late higher versus lower sodium intake. Two studies (103 infants) compared intermediate sodium supplementation (≥ 3 mmol/kg/day to < 5 mmol/kg/day) versus no supplementation, and two studies (52 infants) compared higher sodium supplementation (≥ 5 mmol/kg/day) versus no supplementation. We assessed only two studies (63 infants) as low risk of bias. Early (less than seven days following birth) higher versus lower sodium intake Early higher versus lower sodium intake may not affect mortality (risk ratio (RR) 1.02, 95% confidence interval (CI) 0.38 to 2.72; I2 = 0%; 3 studies, 83 infants; low-certainty evidence). Neurodevelopmental follow-up was not reported. Early higher versus lower sodium intake may lead to a similar incidence of hyponatraemia < 130 mmol/L (RR 0.68, 95% CI 0.40 to 1.13; I2 = 0%; 3 studies, 83 infants; low-certainty evidence) but an increased incidence of hypernatraemia ≥ 150 mmol/L (RR 1.62, 95% CI 1.00 to 2.65; I2 = 0%; 4 studies, 103 infants; risk difference (RD) 0.17, 95% CI 0.01 to 0.34; number needed to treat for an additional harmful outcome 6, 95% CI 3 to 100; low-certainty evidence). Postnatal growth failure was not reported. The evidence is uncertain for an effect on necrotising enterocolitis (RR 4.60, 95% CI 0.23 to 90.84; 1 study, 46 infants; very low-certainty evidence). Chronic lung disease at 36 weeks was not reported. Late (seven days or more following birth) higher versus lower sodium intake Late higher versus lower sodium intake may not affect mortality (RR 0.13, 95% CI 0.01 to 2.20; 1 study, 49 infants; very low-certainty evidence). Neurodevelopmental follow-up was not reported. Late higher versus lower sodium intake may reduce the incidence of hyponatraemia < 130 mmol/L (RR 0.13, 95% CI 0.03 to 0.50; I2 = 0%; 2 studies, 69 infants; RD -0.42, 95% CI -0.59 to -0.24; number needed to treat for an additional beneficial outcome 2, 95% CI 2 to 4; low-certainty evidence). The evidence is uncertain for an effect on hypernatraemia ≥ 150 mmol/L (RR 7.88, 95% CI 0.43 to 144.81; I2 = 0%; 2 studies, 69 infants; very low-certainty evidence). A single small study reported that later higher versus lower sodium intake may reduce the incidence of postnatal growth failure (RR 0.25, 95% CI 0.09 to 0.69; 1 study; 29 infants; low-certainty evidence). The evidence is uncertain for an effect on necrotising enterocolitis (RR 0.07, 95% CI 0.00 to 1.25; 1 study, 49 infants; very low-certainty evidence) and chronic lung disease (RR 2.03, 95% CI 0.80 to 5.20; 1 study, 49 infants; very low-certainty evidence). Early and late (day 1 to 28 after birth) higher versus lower sodium intake for preterm infants Early and late higher versus lower sodium intake may not have an effect on hypernatraemia ≥ 150 mmol/L (RR 2.50, 95% CI 0.63 to 10.00; 1 study, 20 infants; very low-certainty evidence). No other outcomes were reported.

AUTHORS' CONCLUSIONS

Early (< 7 days following birth) higher sodium supplementation may result in an increased incidence of hypernatraemia and may result in a similar incidence of hyponatraemia compared to lower supplementation. We are uncertain if there are any effects on mortality or neonatal morbidity. Growth and longer-term development outcomes were largely unreported in trials of early sodium supplementation. Late (≥ 7 days following birth) higher sodium supplementation may reduce the incidence of hyponatraemia. We are uncertain if late higher intake affects the incidence of hypernatraemia compared to lower supplementation. Late higher sodium intake may reduce postnatal growth failure. We are uncertain if late higher sodium intake affects mortality, other neonatal morbidities or longer-term development. We are uncertain if early and late higher versus lower sodium supplementation affects outcomes.

Increasing Sodium Variability in the First 96 Hours after Birth is Associated with Adverse In-Hospital Outcomes of Preterm Newborns

Background

Neonatal intraventricular hemorrhage prevention bundles for preterm infants commonly defer daily weighing for the first 72 h, with reweighing occurring on day 4. Clinicians rely on maintaining stable sodium values as a proxy of fluid status to inform fluid management decisions over the first 96 h after birth. Yet, there exists a paucity of research evaluating whether serum sodium or osmolality are appropriate proxies for weight loss and whether increasing variability in sodium or osmolality during this early transitional period is associated with adverse in-hospital outcomes.

Objectives

To evaluate whether serum sodium or osmolality change in the first 96 h after birth was associated with percent weight change from birth weight, and to assess potential associations between serum sodium and osmolality variability with in-hospital outcomes.

Methods

This retrospective, cross-sectional study included neonates born at ≤30 gestational weeks or ≤1250 g. We evaluated associations between serum sodium coefficient of variation (CoV), osmolality CoV, and maximal weight loss percentage in the first 96 h after birth with in-hospital neonatal outcomes.

Results

Among 205 infants, serum sodium and osmolality were poorly correlated with percent weight change in individual 24-h increments (R2 = 0.01-0.14). For every 1% increase in sodium CoV, there was an associated 2-fold increased odds of surgical necrotizing enterocolitis and 2-fold increased odds of in-hospital mortality (odds ratio, 2.07; 95% CI: 1.02, 4.54; odds ratio, 1.95; 95% CI: 1.10, 3.64, respectively). Sodium CoV was more strongly associated with outcomes than absolute sodium maximal change.

Conclusions

In the first 96 h, serum sodium and osmolality are poor proxies for assessing percent weight change. Increasing variability of serum sodium is associated with later development of surgical necrotizing enterocolitis and all-cause in-hospital mortality. Prospective research is needed to evaluate whether reducing sodium variability in the first 96 h after birth, as assessed by CoV, improves newborn health outcomes.

Development of an imputation model to recalibrate birth weights measured in the early neonatal period to time at delivery and assessment of its impact on size-for-gestational age and low birthweight prevalence estimates: a secondary analysis of a pregnancy cohort in rural Nepal

OBJECTIVES

In low-income countries, birth weights for home deliveries are often measured at the nadir when babies may lose up of 10% of their birth weight, biasing estimates of small-for-gestational age (SGA) and low birth weight (LBW). We aimed to develop an imputation model that predicts the 'true' birth weight at time of delivery.

DESIGN

We developed and applied a model that recalibrates weights measured in the early neonatal period to time=0 at delivery and uses those recalibrated birth weights to impute missing birth weights.

SETTING

This is a secondary analysis of pregnancy cohort data from two studies in Sarlahi district, Nepal.

PARTICIPANTS

The participants are 457 babies with daily weights measured in the first 10 days of life from a subsample of a larger clinical trial on chlorhexidine (CHX) neonatal skin cleansing and 31 116 babies followed through the neonatal period to test the impact of neonatal massage oil type (Nepal Oil Massage Study (NOMS)).

OUTCOME MEASURES

We developed an empirical Bayes model of early neonatal weight change using CHX trial longitudinal data and applied it to the NOMS dataset to recalibrate and then impute birth weight at delivery. The outcomes are size-for-gestational age and LBW.

RESULTS

When using the imputed birth weights, the proportion of SGA is reduced from 49% (95% CI: 48% to 49%) to 44% (95% CI: 43% to 44%). Low birth weight is reduced from 30% (95% CI: 30% to 31%) to 27% (95% CI: 26% to 27%). The proportion of babies born large-for-gestational age increased from 4% (95% CI: 4% to 4%) to 5% (95% CI: 5% to 5%).

CONCLUSIONS

Using weights measured around the nadir overestimates the prevalence of SGA and LBW. Studies in low-income settings with high levels of home births should consider a similar recalibration and imputation model to generate more accurate population estimates of small and vulnerable newborns.

Clinical factors within a week of birth influencing sodium level difference between an arterial blood gas analyzer and an autoanalyzer in VLBWIs: A retrospective study

Neonatologists often experience sodium ion level difference between an arterial blood gas analyzer (direct method) and an autoanalyzer (indirect method) in critically ill neonates. We hypothesize that clinical factors besides albumin and protein in the blood that cause laboratory errors might be associated with sodium ion level difference between the 2 methods in very-low-birth-weight infants during early life after birth. Among very-low-birth-weight infants who were admitted to Jeonbuk National Hospital Neonatal Intensive Care Units from October 2013 to December 2016, 106 neonates were included in this study. Arterial blood sample was collected within an hour after birth. Blood gas analyzer and biochemistry autoanalyzer were performed simultaneously. Seventy-six (71.7%) were found to have sodium ion difference exceeding 4 mmol/L between 2 methods. The mean difference of sodium ion level was 5.9 ± 6.1 mmol/L, exceeding 4 mmol/L. Based on sodium ion level difference, patients were divided into >4 and ≤4 mmol/L groups. The sodium level difference >4 mmol/L group showed significantly (P < .05) higher sodium level by biochemistry autoanalyzer, lower albumin, lower protein, and higher maximum percent of physiological weight than the sodium level difference ≤4 mmol/L group. After adjusting for factors showing significant difference between the 2 groups, protein at birth (odds ratio: 0.835, 95% confidence interval: 0.760-0.918, P < .001) and percent of maximum weight loss (odds ratio: 1.137, 95% confidence interval: 1.021-1.265, P = .019) were factor showing significant associations with sodium level difference >4 mmol/L between 2 methods. Thus, difference in sodium level between blood gas analyzer and biochemistry autoanalyzer in early stages of life could reflect maximum physiology weight loss. Based on this study, if the study to predict the body's composition of extracellular and intracellular fluid is proceeded, it will help neonatologist make clinical decisions at early life of preterm infants.

The Role of Nutrition in the Prevention and Management of Bronchopulmonary Dysplasia: A Literature Review and Clinical Approach

Bronchopulmonary dysplasia (BPD) remains the most common severe complication of preterm birth, and nutrition plays a crucial role in lung growth and repair. A practical nutritional approach for infants at risk of BPD or with established BPD is provided based on a comprehensive literature review. Ideally, infants with BPD should receive a fluid intake of not more than 135-150 mL/kg/day and an energy intake of 120-150 kcal/kg/day. Providing high energy in low volume remains a challenge and is the main cause of growth restriction in these infants. They need a nutritional strategy that encompasses early aggressive parenteral nutrition and the initiation of concentrated feedings of energy and nutrients. The order of priority is fortified mother's own milk, followed by fortified donor milk and preterm enriched formulas. Functional nutrient supplements with a potential protective role against BPD are revisited, despite the limited evidence of their efficacy. Specialized nutritional strategies may be necessary to overcome difficulties common in BPD infants, such as gastroesophageal reflux and poorly coordinated feeding. Planning nutrition support after discharge requires a multidisciplinary approach to deal with multiple potential problems. Regular monitoring based on anthropometry and biochemical markers is needed to guide the nutritional intervention.

High Early Parenteral Lipid in Very Preterm Infants: A Randomized-Controlled Trial

OBJECTIVE

To determine whether high early parenteral soybean oil lipid intake in very low birth weight (VLBW) infants in the first week after birth decreases the proportion of weight loss and subsequently the incidence of extrauterine growth restriction (EUGR).

STUDY DESIGN

This was a randomized controlled trial of appropriate for gestational- ge VLBW infants. Lipid intake in the control group started at 0.5-1 g/kg per day and increased daily by 0.5-1 g/kg per day till reaching 3 g/kg per day. The intervention group was started on 2 g/kg per day that increased to 3 g/kg per day the following day.

RESULTS

Of the 176 infants assessed for eligibility, 83 were included in the trial. Infants in the intervention group were started on lipid sooner (13.8 ± 7.8 vs 17.5 ± 7.8 hour; P = .03) and had higher cumulative lipid intake in the first 7 days of age (13.5 ± 4.2 vs 10.9 ± 3.5 g/kg per day; P = .03). Infants in the intervention group had a lower percentage of weight loss (10.4 vs 12.7%; P = .02). The mean triglyceride level was higher in the intervention group (1.91 ± 0.79 vs 1.49 ± 0.54 mmol/L; P = .01), however, hypertriglyceridemia was similar between the 2 groups. The incidence of EUGR was lower in the intervention group (38.6% vs 67.6%; P = .01). Head circumference z score was higher in the intervention group (-1.09 ± 0.96 vs -1.59 ± 0.98; P = .04).

CONCLUSIONS

In VLBW infants, provision of a high early dose of parenteral lipid in the first week of age results in less weight loss and lower incidence of EUGR.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT03594474.

Hidden sources like saline flushes make a significant contribution to the fluid intake of very low birthweight infants during the first postnatal week

AIM

We examined actual fluid intake, and routes of administration, in very low birthweight (VLBW) infants during the first week of life in a neonatal intensive care unit.

METHODS

This retrospective cohort study comprised 953 infants born at <32 weeks and 1500 g and treated at Helsinki University Children's Hospital from 2005 to 2013. All parenterally and enterally administered fluids, and their sources, were obtained from our patient information system. Infants were divided into three groups according to their gestational age: 23-26, 27-29 and 30-31 weeks.

RESULTS

Fluid intake exceeded European guidelines during the first 3 days. On days 1-7, total fluid intake was highest in the most premature group (P < .001) and the median total fluid intake in this group peaked at 177 mL/kg/d (IQR 154-209) on day three. Intravascular flushes provided a considerable source of fluids, with the median intake in the most preterm group peaking at 26.4 mL/kg/d, which represented 15.6% of total fluid intake.

CONCLUSION

During the first 3 days of life, our VLBW infants had a higher total fluid intake than the European guidelines. A considerable percentage came from hidden sources, such as saline flushes, which should be taken into account when prescribing fluids.

Population pharmacokinetics and pharmacodynamics of dobutamine in neonates on the first days of life

AIMS

To describe the pharmacokinetics (PK) and concentration-related effects of dobutamine in critically ill neonates in the first days of life, using nonlinear mixed effects modelling.

METHODS

Dosing, plasma concentration and haemodynamic monitoring data from a dose-escalation study were analysed with a simultaneous population PK and pharmacodynamic model. Neonates receiving continuous infusion of dobutamine 5-20 μg kg-1 min-1 were included. Left ventricular ejection fraction (LVEF) and cardiac output of right and left ventricle (RVO, LVO) were measured on echocardiography; heart rate (HR), mean arterial pressure (MAP), peripheral arterial oxygen saturation and cerebral regional oxygen saturation were recorded from patient monitors.

RESULTS

Twenty-eight neonates with median (range) gestational age of 30.4 (22.7-41.0) weeks and birth weight (BW) of 1618 (465-4380) g were included. PK data were adequately described by 1-compartmental linear structural model. Dobutamine clearance (CL) was described by allometric scaling on BW with sigmoidal maturation function of postmenstrual age (PMA). The final population PK model parameter mean typical value (standard error) estimates, standardised to median BW of 1618 g, were 41.2 (44.5) L h-1 for CL and 5.29 (0.821) L for volume of distribution, which shared a common between subject variability of 29% (17.2%). The relationship between dobutamine concentration and RVO/LVEF was described by linear model, between concentration and LVO/HR/MAP/cerebral fractional tissue oxygen extraction by sigmoidal Emax model.

CONCLUSION

In the postnatal transitional period, PK of dobutamine was described by a 1-compartmental linear model, CL related to BW and PMA. A concentration-response relationship with haemodynamic variables has been established.

Updates on Assessment and Monitoring of the Postnatal Growth of Preterm Infants

Assessing and monitoring the physical growth of preterm infants is fundamental to NICU care. The goals of nutritional care are to approximate the growth and body composition of the healthy fetus and to support optimal brain development while minimizing future cardiometabolic risk. Both poor and excessive growth predict adverse long-term health outcomes. Growth curves are clinical tools used to assess the preterm infant's growth status. Several growth curves for preterm infants were developed in the past decade. To use them effectively, clinicians need to understand how each growth curve was developed; the underlying reference population; intended use; and strengths and limitations. Intrauterine growth curves are references that use size at birth to represent healthy fetal growth. These curves serve 2 purposes-to assign size classifications at birth and to monitor postnatal growth. The INTERGROWTH-21 ^st preterm postnatal growth standards were developed to compare the postnatal growth of preterm infants to that of healthy preterm infants rather than the fetus. Individualized weight growth curves account for the water weight loss that frequently occurs after birth. In addition, body mass index (BMI) curves are now available. In this review, we discuss the main characteristics of growth curves used for preterm infants as well as the use of percentiles, z scores, and their change over time to evaluate size and growth status. We also review the differences in body composition between preterm infants at term-equivalent age and term-born infants and the potential role of monitoring proportionality of growth using BMI curves.

Population Pharmacokinetics and Dosing of Milrinone After Patent Ductus Arteriosus Ligation in Preterm Infants

OBJECTIVES

The postoperative course of patent ductus arteriosus ligation is often complicated by postligation cardiac syndrome, occurring in 10-45% of operated infants. Milrinone might prevent profound hemodynamic instability and improve the recovery of cardiac function in this setting. The present study aimed to describe the population pharmacokinetics of milrinone in premature neonates at risk of postligation cardiac syndrome and give dosing recommendations.

DESIGN

A prospective single group open-label pharmacokinetics study.

SETTINGS

Two tertiary care neonatal ICUs: Tallinn Children's Hospital and Tartu University Hospital, Estonia.

PATIENTS

Ten neonates with postmenstrual age of 24.6-30.1 weeks and postnatal age of 5-27 days undergoing patent ductus arteriosus ligation and at risk of postligation cardiac syndrome, based on echocardiographic assessment of left ventricular output of less than 200 mL/kg/min 1 hour after the surgery.

INTERVENTIONS

Milrinone at a dose of 0.73 μg/kg/min for 3 hours followed by 0.16 μg/kg/min for 21 hours. Four blood samples from each patient for milrinone plasma concentration measurements were collected.

MEASUREMENTS AND MAIN RESULTS

Concentration-time data of milrinone were analyzed with nonlinear mixed-effects modeling software (NONMEM Version 7.3 [ICON Development Solutions, Ellicott City, MD]). Probability of target attainment simulations gave a dosing schedule that maximally attains concentration targets of 150-250 μg/L. Milrinone pharmacokinetics was described by a one-compartmental linear model with allometric scaling to bodyweight and an age maturation function of glomerular filtration rate. Parameter estimates for a patient with the median weight were 0.350 (L/hr) for clearance and 0.329 (L) for volume of distribution. The best probability of target attainment was achieved with a loading dose of 0.50 μg/kg/min for 3 hours followed by 0.15 μg/kg/min (postmenstrual age < 27 wk) or 0.20 μg/kg/min (postmenstrual age ≥ 27 wk).

CONCLUSIONS

Population pharmacokinetic modeling and simulations suggest a slow loading dose followed by maintenance infusion to reach therapeutic milrinone plasma concentrations within the timeframe of the postligation cardiac syndrome.

Z-score differences based on cross-sectional growth charts do not reflect the growth rate of very low birth weight infants

Objective

To test whether the assessment of growth in very low birth weight infants during the hospital stay using z-score differences (Z_diff) is confounded by gestational age (GA), birth weight percentiles (BW%ile), and length of the observation period (LOP). We hypothesize that Z_diff calculated from growth charts based on birth weight data introduces a systematic statistical error leading to falsely classified growth as restricted in infants growing similarly to the 50^th percentile.

Methods

This observational study included 6,926 VLBW infants from the German Neonatal Network (2009 to 2015). Inclusion criterion was discharge between 37 and 41 weeks postmenstrual age. For each infant, Z_diff, weight gain velocity, and reference growth rate (50^th percentile Fenton) from birth to discharge were calculated. To account for gestational age dependent growth rates, assessment of growth was standardized calculating the weight gain ratio (WGR) = weight gain velocity/reference growth rate. The primary outcome is the variation of the Z_diff-to-WGR relationship.

Results

Z_diff and WGR showed a weak agreement with a Z_diff of -0.74 (-1.03, -0.37) at the reference growth rate of the 50^th percentile (WGR = 1). A significant proportion (n = 1,585; 23%) of infants with negative Z_diff had weight gain velocity above the 50^th percentile’s growth rate. Z_diff to WGR relation was significantly affected by the interaction of GA x BW%ile x LOP.

Conclusion

This study supports the hypothesis that Z_diff, which are calculated using birth weights, are confounded by skewed reference data and can lead to misinterpretation of growth rates. New concepts like individualized growth trajectories may have the potential to overcome this limitation.

Preterm newborn's postnatal growth patterns: how to evaluate them

OBJECTIVES

There are several factors that influence the postnatal growth of preterm infants. It is crucial to define how to evaluate the growth rate of each preterm child and its individual trajectory, the type of growth curve, either with parameters of prescriptive curves for healthy preterm infants with no morbidities or, in the case of preterm infants and their "bundle of vulnerabilities", growth curves that may represent how they are actually growing, with the aim of directing appropriate nutritional care to each gestational age range.

DATA SOURCES

The main studies with growth curves for growth monitoring and the appropriate nutritional adjustments that prioritized the individual trajectory of postnatal growth rate were reviewed. PubMed and Google Scholar were searched.

DATA SYNTHESIS

The use of longitudinal neonatal data with different gestational ages and considering high and medium-risk pregnancies will probably be essential to evaluate the optimal growth pattern.

CONCLUSIONS

Prioritizing and knowing the individual growth trajectory of each preterm child is an alternative for preterm infants with less than 33 weeks of gestational age. For larger preterm infants born at gestational age >33 weeks, the Intergrowth 21st curves are adequate.

Prevalence of electrolyte disturbances in perinatal asphyxia: a prospective study

BACKGROUND

Birth asphyxia is defined as the presence of hypoxia, hypercapnia, and acidosis leading the newborn to systemic disturbances probably electrolyte disturbance also. Knowledge of these electrolyte disturbances is very valuable as it can be an important parameter affecting perinatal morbidity, mortality and ongoing management.

METHODS

Serum sodium, potassium and ionized calcium of asphyxiated term newborn were sent within one hour of birth as per the inclusion criteria. Statistical comparison of mean values of different electrolytes between different groups of perinatal asphyxia was performed by ANOVA test for parametric data and significant data were further analyzed using post hoc test. Bivariate analysis was done to determine the correlations between Apgar score at 5 min and serum electrolytes. Pearson test was used to calculate the correlation coefficient. Box plot was used to show the median and quartile between serum electrolytes and Apgar score at 5 min.

RESULT

The mean values of sodium for mild, moderate and severe asphyxia were 135.52, 130.7 and 127.15 meq/l respectively. The values of potassium for mild, moderate and severe asphyxia were 4.96, 5.93 and 6.78 meq/l respectively. Similarly, the mean values of ionized calcium for mild, moderate and severe asphyxia were 1.07, 1.12 and 0.99 mmol/l respectively. The values of sodium and potassium among different severity of asphyxia were significantly different (p-value< 0.001). Significant positive correlation was found between serum sodium and Apgar score at 5 min. Significant negative correlation was present between serum potassium and Apgar score at 5 min.

CONCLUSION

The degree of hyponatremia and hyperkalemia was directly proportional to the severity of birth asphyxia. So these electrolyte disturbances should always be kept in mind while managing cases of perinatal asphyxia and should be managed accordingly.

Postnatal Weight Gain Patterns in Preterm Very-Low-Birth-Weight Infants Born in a Tertiary Care Center in South India

BACKGROUND

Extrauterine growth retardation is a common problem in preterm, very-low-birth-weight (VLBW) babies, as well as paucity of growth charts that follow their postnatal growth.

AIM

To evaluate and plot postnatal weight gain patterns of preterm VLBW babies of <34 weeks' gestation born at a tertiary care neonatal unit in South India.

METHODS

Weight gain patterns of all preterm (27 to < 34 weeks' gestation) and VLBW (<1500 g) neonates were used for plotting the centile curves by retrospective review of electronic medical records. The growth velocity was calculated from birth and from the time baby regained their birth weight.

RESULTS

Mean growth rate (±SD) of these babies was 16.2 ± 2.4 g/kg/day and average time to regain birth weight was 14.2 days (range 12.0-17.6).

CONCLUSION

The recommended growth velocity of 10-15 g/kg/day can be achieved using unfortified expressed breast milk, though at higher feeding volumes of 200 ml/kg/day. These centile curves can be useful for monitoring postnatal growth.

Individualized Postnatal Growth Trajectories for Preterm Infants

BACKGROUND

Growth of preterm infants is monitored using fetal charts despite individual trajectories being downshifted postnatally by adaptational processes. The study aims to compare different approaches to create individualized postnatal trajectories.

METHODS

Three approaches to achieve growth similar to healthy term infants at 42+0/7 weeks postmenstrual age (PMA) on World Health Organization growth standards (WHOGS) (target weight) were tested by comparing trajectories obtained by: 1) following birth percentiles (Birth-Weight-Percentile Approach); 2) following percentiles achieved at day of life 21 (Postnatal-Percentile Approach); 3) using day-specific fetal median growth velocities starting at day of life 21 (Fetal-Median-Growth Approach [FMGA]). The primary outcome was delta weight (ΔW), defined as difference between target weight (WHOGS) at 42+0/7 weeks and weight predicted by trajectories. The secondary outcome was ΔW vs %fat mass in a cohort of 20 disease-free surviving very low-birth-weight infants.

RESULTS

Birth-Weight-Percentile and Postnatal-Percentile Approach showed high ΔW; FMGA alone reduced ΔW. Introducing a factor to FMGA to reflect the transition to extrauterine conditions (Growth-Velocity Approach [GVA]) minimized ΔW. GVA merged with target and best normalized for body composition related to ΔW.

CONCLUSIONS

GVA provides an evidence-based approach for individualized growth trajectories. GVA is based on physiologic data and that healthy preterm infants adjust their postnatal trajectory below their birth percentile. GVA may reflect a biologic principle because it matches consistently with WHOGS at 42+0/7 weeks for all preterm infants from 24 to 34 weeks. This concept could become a bedside tool to aid clinicians in monitoring growth, guiding nutrition, and minimizing chronic adult disease risks as a consequence of unguided, inappropriate growth.

Population Pharmacokinetic Characteristics of Amikacin in Suspected Cases of Neonatal Sepsis in a Low-Resource African Setting: A Prospective Nonrandomized Single-Site Study

BACKGROUND

Amikacin exhibits marked pharmacokinetic (PK) variability and is commonly used in combination with other drugs in the treatment of neonatal sepsis. There is a paucity of amikacin PK information in neonates from low-resource settings.

OBJECTIVES

To determine the PK parameters of amikacin, and explore the influence of selected covariates, including coadministration with aminophylline, on amikacin disposition in neonates of African origin.

METHODS

Neonates with suspected sepsis admitted to an intensive care unit in Accra, Ghana, and treated with amikacin (15 mg/kg loading followed by 7.5 mg/kg every 12 hours), were recruited. Serum amikacin concentration was measured at specified times after treatment initiation and analyzed using a population PK modeling approach.

RESULTS

A total of 419 serum concentrations were available for 247 neonates. Mean (SD) trough amikacin concentration (from samples collected 30 minutes before the fourth dose) among term (n = 25), and preterm (<37 weeks' gestation n = 36) neonates were 6.2 (3.4) and 9.2 (5.7) µg/mL, respectively (P = 0.02). A 1-compartment model best fitted amikacin disposition, and birth weight was the most important predictor of amikacin clearance (CL) and distribution (V). The population CL and V of amikacin were related as CL (L/h) = 0.153 (birth weight/2.5)^1.31, V (L) = 2.94 (birth weight/2.5)^1.18. There was a high between-subject variability (58.9% and 50.7%) in CL and V, respectively. CL and V were 0.058 L/h/kg and 1.15 L/kg, respectively, for a mean birth weight of 2.1 kg, and the mean half-life (based on 1-compartment model), was 13.7 hours.

CONCLUSIONS

The V and half-life of amikacin in this cohort varied from that reported in non-African populations, and the high trough and low peak amikacin concentrations in both term and preterm neonates suggest strategies to optimize amikacin dosing are required in this population.

Postnatal Transitional Weight Loss and Adverse Outcomes in Extremely Premature Neonates

The early postnatal weight loss (EPWL) is highly variable in the extremely low birth weight infants (birth weight <1000 g, ELBW). It is reported to be unassociated with adverse outcomes within a range of 3-21% of birth weight. Its wide range might have contributed to this lack of association. The aim of our paper is to study the effects of maximum EPWL, graded as low, medium and large on clinical outcomes in ELBW infants. In a retrospective cohort observational study EPWL was measured as maximum weight loss from birth weight (MWL) in ELBW infants and grouped as low (5-12%) moderate (18.1-12%) and high (18-25%). The clinical course and complications of infants were compared between the groups. Gestational age (GA) was highest and surfactant administration, peak inspiratory pressure requirement, fluid intake, urinary output, oxygen dependent days and the number of oxygen dependent infants at age 28 days were lower in the low MWL compared to the high MWL group. However, all these significant P-values declined after controlling for GA. Diabetes mellitus and pregnancy associated hypertension were not noted in mothers in high MWL group, whereas 38% of mothers in low MWL group suffered from the latter (P=0.05). Maximum postnatal transitional weight loss, assessed in the range of low, moderate and high, is not associated with adverse outcomes independent of gestational age in ELBW infants. Maternal hypertension decreases EPWL in them.

Physiological adjustment to postnatal growth trajectories in healthy preterm infants

BACKGROUND

International guidelines suggest that growth of preterm infants should match intrauterine rates. However, the trajectory for extrauterine growth may deviate from the birth percentile due to an irreversible, physiological loss of extracellular fluid during postnatal adaptation to extrauterine conditions. To which "new" physiological growth trajectory preterm infants should adjust to after completed postnatal adaptation is unknown. This study analyzes the postnatal growth trajectories of healthy preterm infants using prospective criteria defining minimal support, as a model for physiological adaptation.

METHODS

International, multi-center, longitudinal, observational study at five neonatal intensive care units (NICUs). Daily weights until day of life (DoL) 21 of infants with undisturbed postnatal adaptation were analyzed (gestational ages: (i) 25-29 wk, (ii) 30-34 wk).

RESULTS

981 out of 3,703 admitted infants included. Maximum weight loss was 11% (i) and 7% (ii) by DoL 5, birth weight regained by DoL 15 (i) and 13 (ii). Infants transitioned to growth trajectories parallel to Fenton chart percentiles, 0.8 z-scores below their birth percentiles. The new trajectory after completed postnatal adaptation could be predicted for DoL 21 with R(2) = 0.96.

CONCLUSION

This study provides a robust estimate for physiological growth trajectories of infants after undisturbed postnatal adaptation. In the future, the concept of a target postnatal trajectory during NICU care may be useful.

Do early postnatal body weight changes contribute to neonatal morbidities in the extremely low birth weight infants

BACKGROUND

The implications of early postnatal body weight changes (Δbw) in the morbidities related to body fluid metabolism in sick preterm infants in not well investigated. The extremely low birth weight infants (ELBW, birth weight <1000 g) have the highest incidence of such morbidities among all neonates.

AIM

To determine the relationships between Δbw and neonatal morbidities associated with body fluid metabolism in the ELBW infants.

METHODS

In an observational study, the associations between daily weight changes from birth weight (DΔ bw) and oxygen dependence on postnatal day 28 (BPD28), patent ductus arteriosus (PDA), intraventricular-periventricular hemorrhage (IVH), antenatal steroid (ANS) and gestational age (GA) were evaluated. Maximum weight loss (MΔ bw) was correlated with GA, BPD28 and BPD36 (oxygen dependence on postmenstrual 36 weeks). Pearson's correlation co-efficient and multivariate logistic regressions were performed for analysis.

RESULTS

DΔ bw correlated inversely with GA on days 1-8 of life (p <  0.01 for all, 0.06 for DOL 2). DΔ bw was associated with a lower risk of BPD28 on days 6 (OR 0.87, 95% CI 0.76-1), 10 (OR 0.86, 95% CI 0.76-0.98) and 11 (OR 0.87, 95% CI 0.77-0.99); with PDA on days 8-11 (OR ranging between 0.89 to 0.92 for the 4 days, 95% CI 0.83 to 0.99) and with IVH on day 5 (OR 0.93, 95% CI 0.86-1) after controlling for GA. DΔ bw was not identified as risk factor for the tested morbidities. ANS decreased DΔ bw on days 4 (OR 0.88, 95% CI 0.78-1) and 10 (OR 0.9, 95% CI 0.84-1). MΔbw correlated directly with BPD28 (r = 0.3, p = 0.004), which declined after controlling for GA (r = 0.2, p = 0.2).

CONCLUSIONS

DΔ bw is protective for PDA, BPD28 and IVH, independent of gestational age, whereas, the effects of MΔ bw on BPD are governed by maturation in ELBW infants. ANS decreases DΔbw, which correlates inversely with GA during the first week of life.

Are Developmental Trajectories of Cortical Folding Comparable Between Cross-sectional Datasets of Fetuses and Preterm Newborns?

Magnetic resonance imaging has proved to be suitable and efficient for in vivo investigation of the early process of brain gyrification in fetuses and preterm newborns but the question remains as to whether cortical-related measurements derived from both cases are comparable or not. Indeed, the developmental folding trajectories drawn up from both populations have not been compared so far, neither from cross-sectional nor from longitudinal datasets. The present study aimed to compare features of cortical folding between healthy fetuses and early imaged preterm newborns on a cross-sectional basis, over a developmental period critical for the folding process (21-36 weeks of gestational age [GA]). A particular attention was carried out to reduce the methodological biases between the 2 populations. To provide an accurate group comparison, several global parameters characterizing the cortical morphometry were derived. In both groups, those metrics provided good proxies for the dramatic brain growth and cortical folding over this developmental period. Except for the cortical volume and the rate of sulci appearance, they depicted different trajectories in both groups suggesting that the transition from into ex utero has a visible impact on cortical morphology that is at least dependent on the GA at birth in preterm newborns.

The interplay between drugs and the kidney in premature neonates

The kidney plays a central role in the clearance of drugs. However, renal drug handling entails more than glomerular filtration and includes tubular excretion and reabsorption, and intracellular metabolization by cellular enzyme systems, such as the Cytochrome P450 isoenzymes. All these processes show maturation from birth onwards, which is one of the reasons why drug dosing in children is not simply similar to dosing in small adults. As kidney development normally finishes around the 36th week of gestation, being born prematurely will result in even more immature renal drug handling. Environmental effects, such as extra-uterine growth restriction, sepsis, asphyxia, or drug treatments like caffeine, aminoglycosides, or non-steroidal anti-inflammatory drugs, may further hamper drug handling in the kidney. Dosing in preterm neonates is therefore dependent on many factors that need to be taken into account. Drug treatment may significantly hamper postnatal kidney development in preterm neonates, just like renal immaturity has an impact on drug handling. The restricted kidney development results in a lower number of nephrons that may have several long-term sequelae, such as hypertension, albuminuria, and renal failure. This review focuses on the interplay between drugs and the kidney in premature neonates.

Fluid restriction and prophylactic indomethacin in extremely low birth weight infants

Although survival of extremely low birth weight (ELBW) infants dramatically improved over last decades, bronchopulmonary dysplasia (BPD) rate has not changed. The use of indomethacin prophylaxis in ELBW infants results in improved short-term outcomes with no effect on long-term outcomes. The addition of fluid restriction to the indomethacin prophylaxis policy could result in a reduction of BPD and improve long-term survival without neurosensory impairment at 18 months corrected age. To determine the effect of a policy of fluid restriction compared with a policy of no fluid restriction on morbidity and mortality in ELBW infants receiving indomethacin prophylaxis. The standard search strategy for the Cochrane Neonatal Review Group was used. This included search of OVID MEDLINE-National Library of Medicine, EMBASE, and the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 8, 2011). Additional search included conference proceedings, references in articles, and unpublished data. All randomized or quasi-randomized trials that compared fluid restriction and indomethacin prophylaxis vs. indomethacin prophylaxis alone in ELBW infants were included. Standard methods of the Cochrane Neonatal Review Group were planned to assess the methodological quality of the trials. Review Manager 5 software was planned to be used for statistical analysis. We found no randomized controlled trials to investigate the possible interaction between fluid restriction and indomethacin prophylaxis vs. indomethacin prophylaxis alone in ELBW infants. A well-designed randomized trial is needed to address this question.

Is intrauterine growth appropriate to monitor postnatal growth of preterm neonates?

When using the useful 2013 Fenton Chart, data should be interpreted with caution taking into account two aspects: the physiologic loss of body water after birth for the weight curves, and the questionable accuracy of the birth length curves considering the heterogeneity and reliability of the methods used in the original measurements.

Nutrition and bronchopulmonary dysplasia

We aimed to assess the current knowledge on the nutritional management of preterm infants at risk of developing bronchopulmonary dysplasia (BPD) or with BPD. We considered the evidence supporting the actual fluid and energy intake, proteins, lipids, and electrolytes requirement, and need for other nutrients in preterm infant at risk of developing BPD or with BPD. We concluded that, although many areas remain to be investigated, early nutrition support and careful adjustment of parenteral nutrition and appropriate enteral feeding selection may enhance the growth and contribute a better neurodevelopment in these patients.

Fluid and electrolyte management of very low birth weight infants

Recent advances in medical knowledge and technology have markedly improved the survival rates of very low birth weight infants. Optimizing the neuro-developmental outcomes of these survivors has become an important priority in neonatal care, which includes appropriate management for achieving fluid and electrolyte balance. This review focuses on the principles of providing maintenance fluid to these infants, including careful assessment to avoid excessive fluid administration that may increase the risk of such neonatal morbidities as necrotizing enterocolitis, patent ductus arteriosus, and bronchopulmonary dysplasia (BPD). The review also describes the principles of fluid and electrolyte management of infants with BPD, which includes the strategy of providing adequate nutrition to promote normal growth.

Fluid restriction and prophylactic indomethacin versus prophylactic indomethacin alone for prevention of morbidity and mortality in extremely low birth weight infants

BACKGROUND

Although survival of extremely low birth weight (ELBW) infants has dramatically improved over the last decades, the rate of bronchopulmonary dysplasia (BPD) has not changed. The use of indomethacin prophylaxis in ELBW infants results in improved short-term outcomes with no effect on long-term outcomes. The addition of fluid restriction to the indomethacin prophylaxis policy could result in a reduction of BPD and improve long-term survival without neurosensory impairment at eighteen months corrected age.

OBJECTIVES

To determine the effect of a policy of fluid restriction compared with a policy of no fluid restriction on morbidity and mortality in ELBW infants receiving indomethacin prophylaxis.

SEARCH STRATEGY

We used the standard search strategy for the Cochrane Neonatal Review Group (CNRG). This included searches of the Cochrane Central Register of Controlled Trials (CENTRAL) ( The Cochrane Library 2010, Issue 1), MEDLINE (1966 to December 2010), and EMBASE (1980 to December 2010). Additional searches included conference proceedings, references in articles and unpublished data.

SELECTION CRITERIA

We planned to include all randomized or quasi-randomized trials that compared fluid restriction and indomethacin prophylaxis versus indomethacin prophylaxis alone in ELBW infants.

DATA COLLECTION AND ANALYSIS

If we had identified any eligible studies, we would have assessed the methodological quality of the trials using the standard methods of the CNRG. We planned to use Review Manager 5 software for statistical analysis.

MAIN RESULTS

We did not identify any eligible trials.

AUTHORS' CONCLUSIONS

We found no randomized controlled trials to investigate the possible interaction between fluid restriction and indomethacin prophylaxis versus indomethacin prophylaxis alone in ELBW infants. A well-designed randomized trial is needed to address this question.

Clinical determinants and utility of early postnatal maximum weight loss in fluid management of extremely low birth weight infants

BACKGROUND

The early postnatal physiological body weight loss process is poorly understood in preterm infants. It is complicated by clinical conditions which adversely affect the body fluid balance during 1st two weeks of life. A lack of physiological weight loss potentially could result in significant morbidities. Body weight is utilized in determining daily fluid volume intakes. Extremely low birth weight infants (birth weight<1000 g, ELBW) have the highest morbidity and mortality among all neonates.

AIM/OBJECTIVE

The objective was to evaluate the early postnatal weight changes and its clinical determinants in ELBW infants. We examined the maximum weight loss from birth weight (MWL) in ELBW infants and tested its association with clinical variables which could potentially implicate the body fluid balance during the first two weeks of life.

STUDY DESIGN

Prospectively entered data in the computerized radiology, biochemical and hematological records, and daily case notes were retrospectively extracted during a 3-year study period. The infants' and maternal demographic, clinical course and outcome variables relevant to body fluid balance during the first two weeks of life were correlated with MWL. Pearson's correlation coefficient and Pearson's partial correlation tests were utilized for data analysis.

RESULTS

Data are presented as mean+/-SD. MWL in the entire cohort (n=102) was 14.2+/-5.4%. Day of life of MWL was 5.5+/-2.1 and that of birth weight regained 14.5+/-4.2 days. MWL correlated negatively with gestational age, antenatal steroid receipt (ANS) and pregnancy associated hypertension and positively with total days on oxygen, fluid intake, urinary output and the day of life when birth weight was regained. All these correlations were lost after controlling for GA except for the day of life when birth weight was regained. MWL did not correlate with RDS or its severity, hypotension, PIE, IVH, PDA and length of stay. Over 91% infants had MWL within 3.1-25%. Male, Caucasian and ELBW infants unexposed to ANS tended to have weight loss in excess of 25%.

CONCLUSION

MWL is governed by maturation and is not affected by concurrent clinical factors including fluid intakes during the 1st two weeks of life in ELBW infants. MWL within the estimated range of 14.5+4.2% of birth weight does not promote morbidities. Male, Caucasian and ELBW infants unexposed to ANS are susceptible to excessively high weight losses in early postnatal period.

Hypernatraemia in preterm infants born at less than 27 weeks gestation

AIMS

To study the incidence of hypernatraemia (plasma sodium >145 mmol/L), identify predisposing factors to and associated complications of hypernatraemia in preterm infants born less than 27 weeks gestation in the first 5 days of life.

METHODS

Preterm infants less than 27 week gestation over an 18-month period were studied by retrospective analysis of patient records. Data were collected on gestation, birthweight, sex, antenatal steroid use, phototherapy, incubator humidity, time of transfer to incubator, plasma sodium, urea and creatinine. Actual fluid and sodium intake was calculated for the first 5 days of life. Data were collected on chronic lung disease, patent ductus arteriosus, intraventricular haemorrhage, necrotising enterocolitis and death.

RESULTS

In this study 46 (69.7%) of 66 infants studied developed hypernatraemia (>145 mmol/L), occurring most frequently between 24 and 48 h of age. The median gestation of hypernatraemic babies was significantly lower. There was no significant difference in median birthweight, or factors associated with increased insensible water loss between the hypernatraemic and the non-hypernatraemic groups. Fluid intake was significantly higher on days 2, 3 and 4 in the hypernatraemic group. There was no difference in sodium intake between the two groups. More hypernatraemic babies compared with controls developed chronic lung disease, patent ductus arteriosus, significant intraventricular haemorrhage, necrotising enterocolitis and died, but was not significant.

CONCLUSION

Hypernatraemia occurs commonly in preterm infants less than 27 weeks gestation and was not associated with significant morbidity. The more immature infants developed hypernatraemia and all cases resolved after increasing fluid intake.

Emergence of physiological rhythmicity in term and preterm neonates in a neonatal intensive care unit

BACKGROUND

Biological rhythmicity, particularly circadian rhythmicity, is considered to be a key mechanism in the maintenance of physiological function. Very little is known, however, about biological rhythmicity pattern in preterm and term neonates in neonatal intensive care units (NICU). In this study, we investigated whether term and preterm neonates admitted to NICU exhibit biological rhythmicity during the neonatal period.

METHODS

Twenty-four-hour continuous recording of four physiological variables (heart rate: HR recorded by electrocardiogram; pulse rate: PR recorded by pulse oxymetry; respiratory rate: RR; and oxygen saturation of pulse oxymetry: SpO2) was conducted on 187 neonates in NICU during 0-21 days of postnatal age (PNA). Rhythmicity was analyzed by spectral analysis (SPSS procedure Spectra). The Fisher test was performed to test the statistical significance of the cycles. The cycle with the largest peak of the periodogram intensities was determined as dominant cycle and confirmed by Fourier analysis. The amplitudes and amplitude indexes for each dominant cycle were calculated.

RESULTS

Circadian cycles were observed among 23.8% neonates in HR, 20% in PR, 27.8% in RR and 16% in SpO2 in 0-3 days of PNA. Percentages of circadian cycles were the highest (40%) at < 28 wks of gestational age (GA), decreasing with GA, and the lowest (14.3%) at > or = 37 wks GA within 3 days of PNA in PR and were decreased in the later PNA. An increase of the amplitude with GA was observed in PR, and significant group differences were present in all periods. Amplitudes and amplitude indexes were positively correlated with postconceptional age (PCA) in PR (p < 0.001). Among clinical parameters, oxygen administration showed significant association (p < 0.05) with circadian rhythms of PR in the first 3 days of life.

CONCLUSION

Whereas circadian rhythmicity in neonates may result from maternal influence, the increase of amplitude indexes in PR with PCA may be related to physiological maturity. Further studies are needed to elucidate the effect of oxygenation on physiological rhythmicity in neonates.

Association between fluid intake and weight loss during the first ten days of life and risk of bronchopulmonary dysplasia in extremely low birth weight infants

OBJECTIVE

To demonstrate the association between fluid intake and weight loss during the first 10 days of life and the risk of bronchopulmonary dysplasia (BPD) in extremely low birth weight (ELBW) infants.

STUDY DESIGN

A retrospective analysis of data from a cohort of ELBW infants enrolled in the Neonatal Research; 1,382 infants with birth weight between 401 and 1,000 g were randomized. The daily fluid intake and weight loss during the first 10 days of life were compared between the infants who survived without BPD and those who either died or developed BPD. Demographic and clinical neonatal variables were also compared. Multivariate logistic regression was used to analyze the effect of fluid intake and weight loss on death or BPD, controlling for demographic and clinical factors that are significantly associated with BPD by univariate analysis.

RESULTS

585 infants survived without BPD and 797 infants either died or developed BPD. Univariate analysis showed that the daily fluid intakes were higher (day 2-10) and weight loss less (day 6-9) in the group of infants who either died or developed BPD. In addition, lower birth weight, lower gestational age, male gender, lower 1 and 5-minute Apgar Scores, higher oxygen requirement at 24 hours of age, longer duration of assisted ventilation, use of postnatal steroids for BPD and presence of severe intraventricular hemorrhage, proven necrotizing enterocolitis, patent ductus arteriosus, and late onset sepsis, were associated with higher incidence of death or BPD. The adjusted risk of higher fluid intake and less weight loss during the first 10 days of life remained significantly related to death or BPD.

CONCLUSION

In this cohort of ELBW infants treated during the post surfactant era, higher fluid intake and less weight loss during the first 10 days of life were associated with an increased risk of BPD. The finding suggests that careful attention to fluid balance might be an important means to reduce the incidence of BPD.

Clinical implications of postnatal alterations in body water distribution

Substantial alterations take place in the quantity and distribution of body water compartments after birth. Clinical management must be tailored to the pace of postnatal adaptation, and the neonatal physician must be aware of these alterations in order to promote both normal physiological change and growth.

Nutrient requirements for preterm infant formulas

Achieving appropriate growth and nutrient accretion of preterm and low birth weight (LBW) infants is often difficult during hospitalization because of metabolic and gastrointestinal immaturity and other complicating medical conditions. Advances in the care of preterm-LBW infants, including improved nutrition, have reduced mortality rates for these infants from 9.6 to 6.2% from 1983 to 1997. The Food and Drug Administration (FDA) has responsibility for ensuring the safety and nutritional quality of infant formulas based on current scientific knowledge. Consequently, under FDA contract, an ad hoc Expert Panel was convened by the Life Sciences Research Office of the American Society for Nutritional Sciences to make recommendations for the nutrient content of formulas for preterm-LBW infants based on current scientific knowledge and expert opinion. Recommendations were developed from different criteria than that used for recommendations for term infant formula. To ensure nutrient adequacy, the Panel considered intrauterine accretion rate, organ development, factorial estimates of requirements, nutrient interactions and supplemental feeding studies. Consideration was also given to long-term developmental outcome. Some recommendations were based on current use in domestic preterm formula. Included were recommendations for nutrients not required in formula for term infants such as lactose and arginine. Recommendations, examples, and sample calculations were based on a 1000 g preterm infant consuming 120 kcal/kg and 150 mL/d of an 810 kcal/L formula. A summary of recommendations for energy and 45 nutrient components of enteral formulas for preterm-LBW infants are presented. Recommendations for five nutrient:nutrient ratios are also presented. In addition, critical areas for future research on the nutritional requirements specific for preterm-LBW infants are identified.

Postnatal weight loss and contraction of the extracellular compartment is triggered by atrial natriuretic peptide

Following birth there is a contraction in the extracellular compartment, marked clinically by natriuresis, diuresis and weight loss. It is uncertain how these postnatal phenomena, which suggest an interrelationship with cardiopulmonary adaptation, are brought about. The aim of this study was to evaluate the temporal relationship between alterations in circulating atrial natriuretic peptide (ANP), respiratory status, sodium excretion and extracellular fluid volume (ECFV) in preterm babies, in the first days after birth. Eighteen male infants below 34 weeks gestational age were studied longitudinally, measuring urine output, sodium balance, arterial-alveolar oxygen ratio and circulating ANP. Daily changes in ECFV were assessed by endogenous chloride balance, following baseline measurement of bromide space. There was a clear period of improvement in respiratory function in 15 babies and in these there was a highly significant elevation in circulating ANP, either immediately prior to, or during, the period of improvement. In three infants there was no definable period of respiratory improvement. In four babies, two of whom had very mild respiratory distress, there was an immediate decline in ECFV after birth, in contrast to the remaining 14 infants, in whom there was an initial increase. This study demonstrates that there is a temporal relationship between improvement in respiratory function and an acute elevation in circulating ANP. Babies with respiratory distress syndrome are at risk of initial expansion of the extracellular compartment after birth. This is likely to increase morbidity. These observations are of relevance with regard to the clinical management of newborns with respiratory distress syndrome.

Body water content of extremely preterm infants at birth

BACKGROUND

Preterm birth is often associated with impaired growth. Small for gestational age status confers additional risk.

AIM

To determine the body water content of appropriately grown (AGA) and small for gestational age (SGA) preterm infants in order to provide a baseline for longitudinal studies of growth after preterm birth.

METHODS

All infants born at the Hammersmith and Queen Charlotte's Hospitals between 25 and 30 weeks gestational age were eligible for entry into the study. Informed parental consent was obtained as soon after delivery as possible, after which the extracellular fluid content was determined by bromide dilution and total body water by H(2)(18)O dilution.

RESULTS

Forty two preterm infants were studied. SGA infants had a significantly higher body water content than AGA infants (906 (833-954) and 844 (637-958) ml/kg respectively; median (range); p = 0.019). There were no differences in extracellular and intracellular fluid volumes, nor in the ratio of extracellular to intracellular fluid. Estimates of relative adiposity suggest a body fat content of about 7% in AGA infants, assuming negligible fat content in SGA infants and lean body tissue hydration to be equivalent in the two groups.

CONCLUSIONS

Novel values for the body water composition of the SGA preterm infant at 25-30 weeks gestation are presented. The data do not support the view that SGA infants have extracellular dehydration, nor is their regulation of body water impaired.

Randomised controlled trial of postnatal sodium supplementation on body composition in 25 to 30 week gestational age infants

AIMS

To compare the effects of early and delayed sodium supplementation on body composition and body water compartments during the first two weeks of postnatal life.

METHODS

Preterm infants of 25-30 weeks' gestation were stratified and randomly assigned according to gender and gestational age, to receive a sodium intake of 4 mmol/kg/day beginning either on the second day after birth or when weight loss of 6% of birthweight had been achieved. Daily sodium intake, total fluid intake, energy intake, urine volume, and urinary sodium excretion were recorded. Total body water was measured by H(2)(18)O dilution on days 1, 7, and 14, and extracellular fluid volume by sodium bromide dilution on days 1 and 14.

RESULTS

Twenty four infants received early, and 22 delayed, sodium supplementation. There were no significant differences between the groups in body water compartments on day 1. In the delayed group, but not the early group, there was a significant loss of total body water during the first week (delayed -44 ml/kg, p=0. 048; early 6 ml/kg, p=0.970). By day 14 the delayed, but not the early group, also had a significant reduction in extracellular fluid volume (delayed -53 ml/kg, p=0.01; early -37 ml/kg, p=0.2). These changes resulted in a significant alteration in body composition at the end of the first week (total body weight: delayed 791 ml/kg; early 849 ml/kg, p=0.013). By day 14 there were once again no significant differences in body composition between the two groups.

CONCLUSIONS

Body composition after preterm birth is influenced by the timing of introduction of routine sodium supplements. Early sodium supplementation can delay the physiological loss of body water that is part of normal postnatal adaptation. This is likely to be of particular relevance to babies with respiratory distress syndrome. A tailored approach to clinical management, delaying the introduction of routine sodium supplements until there has been postnatal loss of body water, is recommended.

Influence of respiratory distress syndrome on body composition after preterm birth

AIM

To observe changes in body composition during the first week after birth, in preterm neonates with and without respiratory distress syndrome (RDS), so as to be able to provide optimal fluid and energy intake.

METHODS

Twenty four babies with RDS and 19 healthy preterm babies, with gestational ages ranging from 26-36 weeks, were studied daily for the first week after birth. Total body water (TBW) was measured using bioelectrical impedance analysis. The babies were weighed daily and a record made of fluid and energy intake. Body solids were calculated as the difference between body weight and TBW.

RESULTS

There was a highly significant reduction in body weight by the end of the week, with the RDS babies losing more than the healthy babies (RDS 7.6%; non-RDS 3.7%). There was no significant difference in the amount of TBW at birth in the babies with and without RDS (RDS 85.1%; non-RDS 85.5%) and both groups lost the same amount of body water (RDS 10.9%; non-RDS 9.9%) by the end of the first week. The amount of total body water lost was unrelated to the volume of fluid administered. There was a loss of body solids during the first day in the RDS group, but, overall, there was a highly significant increase in both groups between birth and day 7, which was greater in the healthy babies (RDS 13.0%; non-RDS 42.7%).

CONCLUSIONS

Loss of body water after birth occurs to the same extent in healthy preterm neonates and in babies with RDS and is unrelated to the volume of fluid administered. Given adequate nutritional support, an increase in body solids can accompany early postnatal weight loss and begins almost immediately after birth, in both healthy preterm babies and babies with RDS.

Postnatal changes in water content and proton magnetic resonance relaxation times in newborn rabbit tissues

In the present study, using proton nuclear magnetic resonance relaxation (H1 NMR) measurements, an attempt was made to quantitate water fractions with different mobility in the skin, skeletal muscle, and liver tissues obtained from New Zealand white rabbit pups. Serial studies were carried out at the postnatal age of 0-1, 24, 48, and 72 h in pups nursed with their mothers and suckling ad libitum (group I) and in those pups separated from their mothers and completely withheld from suckling (group II). Tissue water content (desiccation method) and T1 and T2 relaxation times (H1 NMR method) were measured. Free, loosely bound, and tightly bound water fractions were calculated by applying multicomponent fits of the T2 relaxation curves. It was demonstrated that skin water content and T1 and T2 relaxation times decreased with age (p < 0.01), the decrease in T2 proved to be more pronounced in group II than in group I (p < 0.05). Muscle and liver water, and T1 and T2 relaxation times did not change with age in the suckling pups. In response to with-holding fluid intake muscle water remained constant, liver water increased paradoxically (p < 0.05). T1 relaxation time showed no consistent change in either tissues, whereas T2 relaxation time decreased significantly (muscle, p < 0.01) or tended to decrease (liver, p < 0.06). Using biexponential analysis fast and slow components of T2 relaxation curve could be distinguished that corresponded to the bound and free water fractions. Bound water accounted for 42-47%, 50-57%, and 34-40% of total tissue water in the skin, skeletal muscle, and liver, respectively, regardless of age and fluid intake. Triexponential fits of the T2 relaxation curve made possible the further partition of tissue water into tightly bound (fast component), loosely bound (middle component), and free (slow component) water fractions. In all tissues studied, loosely bound fraction predominated (skin, 48-64%; muscle, 54-65%; liver, 45-63%), followed by the free (skin, 26-45%; muscle, 23-32%; liver, 20-25%) and the tightly bound water fraction (skin, 6-14%; muscle, 10-16%; liver, 14-33%). Postnatal age and fluid intake had no apparent influence on this pattern of distribution. It is concluded that the majority of neonatal tissue water is motion-constrained. The free, the loosely bound, and the tightly bound water fractions appear to be interrelated and dependent on age, fluid intake, the tissues studied, and their hydration.

Measurement of transepidermal water loss in Tanzanian cot-nursed neonates and its relation to postnatal weight loss

In healthy cot-nursed Tanzanian neonates (n = 92, gestation 26-42 weeks) measurements of trans-epidermal water loss (TEWL) and weight change were performed during the first 24 h after birth at an average ambient humidity of 70% and an environmental temperature of 32 degrees C. Urine production on day 1 (ml/kg per 24 h) was documented for a subgroup of 13 preterm and 8 term infants. In a limited group of preterm infants (n = 5) TEWL measurements, weight and 24 h urine volume measurements were repeated daily for 7 days. Maximum weight loss was determined in 7 preterm (gestational age 30-36 weeks) and 6 term infants. TEWL was estimated by measuring the evaporation rate at three sites of the body using the water vapour pressure gradient method. On day 1, TEWL was highest in the most preterm infants, whereas TEWL and urine production were higher in large for gestational age infants as compared to appropriate for gestational age (AGA) infants of the same gestational age (31-36 weeks). For the whole group, weight loss on day 1 was correlated with TEWL (r = 0.49, p < 0.05). At follow-up TEWL in preterm infants remained almost constant during the first 4 days and decreased after the fourth day, at which time weight gain commenced. Preterm AGA infants (gestational age 24-37 weeks) showed a mean postnatal weight loss of 4.4% of the birth weight, while in term infants this loss was only 2.6%. A reduced postnatal weight loss as compared to Caucasian infants may be explained by a lower water loss during the first days after birth, through both skin evaporation and urine excretion.

Regulation of extracellular fluid volume in neonates

This review summarises mechanisms of control of extracellular fluid volume in the neonatal period. 'Normal' body fluid distribution and methods of its measurement are discussed as well as regulatory mechanisms with particular emphasis on hormonal and renal aspects.

Relationship between nutrition, weight change, and fluid compartments in preterm infants during the first week of life

This study was conducted to investigate the redistribution of fluid compartments and to examine the factors contributing to the variability of early weight loss in premature infants. Fourteen preterm infants (mean +/- SD: birth weight, 1473 +/- 342 gm; gestational age, 30.7 +/- 2.4 weeks) were studied at 1 and 7 days of age. Total body water was measured by deuterium oxide dilution, extracellular volume by bromide dilution, and intracellular volume by the difference between total body water and extracellular volume. There were significant changes in body fluid distribution per concurrent weight from birth to age 1 week. Extracellular volume decreased by 11%, and intracellular volume increased by 8.5% with no change in total body water. Infants were then grouped according to postnatal weight loss (group 1 (n = 7) > 10% and group 2 (n = 7) < 5% of birth weight). In group 1 there was a significant loss of both weight (mean +/- SD: 15.6% +/- 3.7%) and extracellular volume (15.9% +/- 9% of birth weight), with no change in intracellular volume. In group 2 there was no significant weight loss (1.4% +/- 1.8%), but a significant loss of extracellular volume (13.0% +/- 5.4% of birth weight) and a significant increase in intracellular volume. Other differences between the groups were a lower energy intake in group 1 than in group 2 (mean +/- SD: 177 +/- 46 vs 269 +/- 45 kilojoules/kg per day; p < 0.005) and a higher physiologic stability index in group 1 (p < 0.05). We conclude that significant postnatal weight loss as a result of the contraction of the extracellular compartment occurs only in less stable infants whose energy intake is inadequate. With adequate energy intake, weight loss is minimal because of the expansion of the intracellular compartment, which may be related to the onset of growth.

Body composition, nutrition, and fluid balance during the first two weeks of life in preterm neonates weighing less than 1500 grams

To determine whether body weight during the first 2 weeks of life in preterm infants weighing less than 1500 gm reflects nutritional status or fluid balance, we studied total body water (TBW) (deuterium oxide dilution), extracellular volume (sucrose dilution), and plasma volume (Evans blue dilution), together with intake-output studies of nitrogen, fluid, and sodium on day 1 (median age 0.3 day), at a weight loss of 7.8% of birth weight (median age 3.4 days), and after birth weight was regained (median age 8.9 days) in eight clinically stable preterm infants (birth weight 810 to 1310 gm, gestational age 26 to 30 weeks) receiving ventilatory support. During the initial weight loss we found no evidence of catabolism. Body solids (weight--TBW) remained unchanged, there was nitrogen retention, and energy intake was sufficient to meet energy expenditure by day 2. However, we found evidence of fluid loss: TBW (mean +/- SD, -95 +/- 99 ml), extracellular volume (-98 +/- 63 ml), and interstitial volume (-102 +/- 75 ml) decreased significantly, indicating negative fluid and sodium balances. Blood volume and plasma volume remained unchanged. With the regaining of birth weight there was no increase in body solids despite a high degree of nitrogen retention, but there was a positive fluid balance although no significant increase in any body fluid compartment was found. We conclude that the observed postnatal weight changes reflect changes in interstitial volume.