Selected principles of perinatal-neonatal glucose metabolism

Association Between Hypoglycemia and the Occurrence of Early Onset Sepsis in Premature Infants

BACKGROUND

We examined the association between hypoglycemia and the occurrence of early onset sepsis (EOS) in premature infants admitted to the neonatal intensive care unit (NICU).

METHODS

We included infants discharged from 358 NICUs between 1997 and 2020 with gestational age <34 weeks, ≥1 culture collected in the first 3 days of life, and ≥1 serum glucose value recorded on the day of or day prior to culture collection. We used multivariable logistic regression and inverse probability weighting (IPW) and constructed models for three definitions of hypoglycemia: American Academy of Pediatrics (AAP), Pediatric Endocrine Society, and a definition based on neurodevelopmental studies. We performed subgroup analysis in EOS episodes caused by Gram-negative and Gram-positive organisms.

RESULTS

Of the 62,178 infants and 64,559 cultures that met study inclusion criteria, 739 (1%) cultures were positive. The median (25th, 75th percentile) glucose value was 75 mg/dL (50, 106) on the day of or day prior to a positive culture versus 70 mg/dL (50, 95) on the day of or day prior to a negative culture. We found that hypoglycemia was not associated with the occurrence of EOS for all organisms and Gram-positive organisms, whereas there was a small but significant association between the lower AAP glucose cutoff value and EOS due to Gram-negative organisms (logistic regression: risk difference [RD] 0.24% [95% CI, 0.01-0.47]; IPW: RD 0.22% [95% CI, 0.00-0.43]).

CONCLUSIONS

Hypoglycemia may be an early marker of EOS, particularly in episodes caused by Gram-negative organisms and when using a stricter definition of hypoglycemia.

[Prospective study on influence of perinatal factors on the development of early neonatal hypoglycemia in late-preterm and term infants]

INTRODUCTION AND OBJECTIVE

Neonatal hypoglycemia offers multiple controversies. The study aims to assess the main factors involved in the development of early hypoglycemia in term and late preterm infants, and the implication of different environmental circumstances.

METHODS

A prospective cohort study, in infants born between 34 0/7 weeks and 36 6/7 weeks of gestation. Three capillary blood glucose determinations were performed during the eight first hours after birth.

SAMPLE SIZE

207; 59 neonates developed hypoglycemia.

RESULTS

Prenatal risk factors include gestational diabetes with poor glycemic control, twin pregnancy and gestational age. The presence of meconium amniotic fluid and planned cesarean delivery are associated with a higher probability of hypoglycemia. After birth, skin to skin contact, breastfeeding, soft lightening, and normothermia are described as protective factors. The predictive model that combines the type of lightening, body temperature and the excess of bases level, correctly classifies 98% of the severe hypoglycemia cases, with a high Nagelkerke R2 value (0.645) and specificity of 99.5%.

CONCLUSIONS

Postnatal environmental factors seem to be directly related to early hypoglycemia development, so it is essential to support the maternal-child union and breastfeeding. Our results allow better identification of neonates who are not subsidiary to performing blood glucose determinations because they have little risk of developing it.

Pregnancies in Diabetes and Obesity: The Capacity-Load Model of Placental Adaptation

Excess nutritional supply to the growing fetus, resulting from maternal diabetes and obesity, is associated with increased risks of fetal maldevelopment and adverse metabolic conditions in postnatal life. The placenta, interposed between mother and fetus, serves as the gateway between the two circulations and is usually considered to mediate maternal exposures to the fetus through a direct supply line. In this Perspective, however, we argue that the placenta is not an innocent bystander and mounts responses to fetal "signals of distress" to sustain its own adequate function and protect the fetus. We describe several types of protection that the placenta can offer the fetus against maternal metabolic perturbations and offer a theoretical model of how the placenta responds to the intrauterine environment in maternal diabetes and obesity to stabilize the fetal environment. Our approach supports growing calls for early screening and control of pregnancy metabolism to minimize harmful fetal outcomes.

Hyperglycaemia in the Newborn Infant. Physiology Verses Pathology

Hyperglycemia is common in newborns requiring intensive care, particularly in preterm infants, in sepsis and following perinatal hypoxia. The clinical significance, and optimal intervention strategy varies with context, but hyperglycaemia is associated with increased mortality and morbidity. The limited evidence for optimal clinical targets mean controversy remains regarding thresholds for intervention, and management strategies. The first consideration in the management of hyperglycaemia must be to ascertain potentially treatable causes. Calculation of the glucose infusion rate (GIR) to insure this is not excessive, is critical but the use of insulin is often helpful in the extremely preterm infant, but is associated with an increased risk of hypoglycaemia. The use of continuous glucose monitoring (CGM) has recently been demonstrated to be helpful in targeting glucose control, and reducing the risk from hypoglycaemia in the preterm infant. Its use in other at risk infants remains to be explored, and further studies are needed to provide a better understanding of the optimal glucose targets for different clinical conditions. In the future the combination of CGM and advances in computer algorithms, to provide intelligent closed loop systems, could allow a safer and more personalized approached to management.

IGF1, serum glucose, and retinopathy of prematurity in extremely preterm infants

BACKGROUND

Hyperglycemia, insulin insensitivity, and low IGF1 levels in extremely preterm infants are associated with an increased risk of retinopathy of prematurity (ROP), but the interactions are incompletely understood.

METHODS

In 117 extremely preterm infants, serum glucose levels and parenteral glucose intake were recoded daily in the first postnatal week. Serum IGF1 levels were measured weekly. Mice with oxygen-induced retinopathy alone versus oxygen-induced retinopathy plus streptozotocin-induced hyperglycemia/hypoinsulinemia were assessed for glucose, insulin, IGF1, IGFBP1, and IGFBP3 in blood and liver. Recombinant human IGF1 was injected to assess the effect on glucose and retinopathy.

RESULTS

The highest mean plasma glucose tertile of infants positively correlated with parenteral glucose intake [r₍₃₉₎ = 0.67, P < 0.0001]. IGF1 plasma levels were lower in the high tertile compared with those in low and intermediate tertiles at day 28 (P = 0.038 and P = 0.03). In high versus lower glucose tertiles, ROP was more prevalent (34 of 39 versus 19 of 39) and more severe (ROP stage 3 or higher; 71% versus 32%). In oxygen-induced retinopathy, hyperglycemia/hypoinsulinemia decreased liver IGF1 expression (P < 0.0001); rh-IGF1 treatment improved normal vascular regrowth (P = 0.027) and reduced neovascularization (P < 0.0001).

CONCLUSION

In extremely preterm infants, high early postnatal plasma glucose levels and signs of insulin insensitivity were associated with lower IGF1 levels and increased ROP severity. In a hyperglycemia retinopathy mouse model, decreased insulin signaling suppressed liver IGF1 production, lowered serum IGF1 levels, and increased neovascularization. IGF1 supplementation improved retinal revascularization and decreased pathological neovascularization. The data support IGF1 as a potential treatment for prevention of ROP.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02760472 (Donna Mega).

FUNDING

This study has been supported by the Swedish Medical Research Council (14940, 4732, 20144-01-3, and 21144-01-3), a Swedish government grant (ALFGB2770), Lund medical faculty grants (ALFL, 11615 and 11601), the Skåne Council Foundation for Research and Development, the Linnéa and Josef Carlsson Foundation, the Knut and Alice Wallenberg Foundation, the NIH/National Eye Institute (EY022275, EY017017, EY017017-13S1, and P01 HD18655), European Commission FP7 project 305485 PREVENT-ROP, Deutsche Forschungsgemeinschaft (CA-1940/1-1), and Stiftelsen De Blindas Vänner.

In extremely preterm infants, high early postnatal plasma glucose levels and signs of insulin insensitivity were associated with lower IGF1 levels and increased retinopathy of prematurity severity.

Placental Regulation of Energy Homeostasis During Human Pregnancy

Successful pregnancies rely on sufficient energy and nutrient supply, which require the mother to metabolically adapt to support fetal needs. The placenta has a critical role in this process, as this specialized organ produces hormones and peptides that regulate fetal and maternal metabolism. The ability for the mother to metabolically adapt to support the fetus depends on maternal prepregnancy health. Two-thirds of pregnancies in the United States involve obese or overweight women at the time of conception. This poses significant risks for the infant and mother by disrupting metabolic changes that would normally occur during pregnancy. Despite well characterized functions of placental hormones, there is scarce knowledge surrounding placental endocrine regulation of maternal metabolic trends in pathological pregnancies. In this review, we discuss current efforts to close this gap of knowledge and highlight areas where more research is needed. As the intrauterine environment predetermines the health and wellbeing of the offspring in later life, adequate metabolic control is essential for a successful pregnancy outcome. Understanding how placental hormones contribute to aberrant metabolic adaptations in pathological pregnancies may unveil disease mechanisms and provide methods for better identification and treatment. Studies discussed in this review were identified through PubMed searches between the years of 1966 to the present. We investigated studies of normal pregnancy and metabolic disorders in pregnancy that focused on energy requirements during pregnancy, endocrine regulation of glucose metabolism and insulin resistance, cholesterol and lipid metabolism, and placental hormone regulation.

Hyperglycaemia as a risk factor for the development of retinopathy of prematurity: A cohort study

BACKGROUND

Retinopathy of prematurity (ROP) is a preventable cause of childhood blindness. Without treatment, over 45% of eyes can develop permanent visual loss. Hyperglycaemia has recently been described as a risk factor for the development of retinopathy of prematurity (ROP), a proliferative vascular disease of the retina that primarily affects premature infants. The characteristic neoproliferative growth of blood vessels in the retina is very well under stood with the clinical and experimental experiences with Diabetic retinopathy. The purpose of this study was to evaluate a possible relation between glucose levels in VLBW (Very Low Birth Weight) infants and development of ROP.

METHOD

All at risk infants of a Neonatal Intensive Care Unit (NICU) of a tertiary care centre in western India were included in the study. The blood sugar values of the neonates were recorded at multiple times during their first week of life. On completion of 31 weeks of gestational age or 04 weeks of birth age, the neonates were subjected to ROP screening as per standard protocols.

RESULT

A total of 103 neonates were included in the study and were subjected to ROP screening. A total of 32 neonates developed ROP at the end of the study. It was found with statistical significance that the neonates with higher average blood glucose values in the initial period of life had higher incidence of ROP at the time of screening with a Relative Risk of 2.506 (CI = 1.287, 4.882).

CONCLUSION

A high average blood glucose level in neonates during the first week of life is an indicator for developing ROP at a later date. These neonates should be kept under close follow up in order to facilitate timely detection and prompt intervention.

Targeting glucose control in preterm infants: pilot studies of continuous glucose monitoring

OBJECTIVE

Hyperglycaemia is common in very preterm infants and is associated with adverse outcomes. Preventing hyperglycaemia without increasing the risk of hypoglycaemia is difficult. Real time tracking with continuous glucose monitors (CGM) may improve glucose control. We assessed the feasibility and safety of CGM to target glucose control in preterm infants, to inform a randomised controlled trial (RCT).

DESIGN

We performed a single centre study in very preterm infants during the first week of life. Accuracy was assessed by comparison of CGM with blood glucose levels (n=20 infants). In a separate pilot study of efficacy (n=20), real-time CGM combined with a paper guideline to target glucose control (2.6-10 mmol/L) was compared with standard neonatal care (masked CGM). Questionnaires were used to assess staff acceptability.

RESULTS

No concerns were raised about infection or skin integrity at sensor site. The sensor performed well compared with point-of-care blood glucose measurements, mean bias of -0.27 (95% CI -0.35 to -0.19). Per cent time in target range (sensor glucose 2.6-10 mmol/L) was greater with CGM than POC (77% vs 59%, respectively) and per cent time sensor glucose >10 mmol/L was less with CGM than POC (24% vs 40%, respectively). The CGM also detected clinically unsuspected episodes of hypoglycaemia. Staff reported that the use of the CGM positively improved clinical care.

CONCLUSIONS

This study suggests that CGM has sufficient accuracy and utility in preterm infants to warrant formal testing in a RCT.

Continuous Glucose Monitoring Linked to an Artificial Intelligence Risk Index: Early Footprints of Intraventricular Hemorrhage in Preterm Neonates

OBJECTIVE

To develop and validate a new risk score for intraventricular hemorrhage (IVH) in preterm neonates based on continuous glucose monitoring (CGM).

STUDY DESIGN

We retrospectively analyzed CGM traces obtained from 50 very preterm neonates, grouped into two sub-cohorts started on CGM within 12 and 48 h of birth, respectively. A CGM linked to an Artificial Intelligence Risk (CLAIR) index was developed to quantify glucose variability during the first 72 h of life in neonates with and without IVH. Brain-US was performed at least twice a day for the first 5 days of birth. An integrated remote monitoring platform was developed to capture major clinical events in real time and gather data for the risk index. The new score performance was further compared with other measures of glucose variability (coefficient of variation [CV] and standard deviation [SD]) and with a clinical risk index for babies II (CRIB-II) as a predictor of IVH event. The two cohorts were analyzed separately for internal validation of the method.

RESULTS

The primary cohort consisted of 26 neonates (gestational age 30 [28, 31] weeks; BW1275 g[1090, 1750]). Controls (n = 23) exhibited higher CLAIR index than cases (P = 0.004). A cut-off of 0.69 for the new CLAIR index allowed a 100% sensitivity and an 83% specificity for IVH prediction. The CLAIR index was the sole significant predictor for IVH (P = 0.003) when compared with clinical variables, CV, SD, and CRIB-II. In a subgroup analysis in very low-birth-weight infants, the CLAIR index was the sole variable significantly associated with IVH (P = 0.009). Analysis on the secondary cohort (five cases and 16 controls) confirmed a higher CLAIR index in the controls (P = 0.008), in the absence of a difference for CV, SD, and CRIB-II between the two groups.

CONCLUSION

CGM, combined with the AI-algorithm, provides a high-sensitivity index for risk detection of IVH that reflects the glycemic impairment preceding IVH.

Clinical impact of improved point-of-care glucose monitoring in neonatal intensive care using Nova StatStrip: Evidence for improved accuracy, better sensitivity, and reduced test utilization

OBJECTIVES

Studies have demonstrated improved analytical performance of the Nova StatStrip glucose meter, but limited data is available on its clinical performance in critically ill neonates in the neonatal intensive care unit (NICU).

DESIGN AND METHODS

A retrospective charge review was conducted on 651 neonates admitted to the NICU over 2 years. Demographics, sample collection information, and clinical details were recorded. Glucose measurements were performed at the bedside using either the Nova StraStrip or LifeScan SureStep Flexx meters as well as corresponding measurements of laboratory venous plasma glucose. Performance was analyzed by receiver operator characteristic (ROC) curves for detecting hypoglycemia and critical glucose levels.

RESULTS

Linear regression analysis comparing StatStrip and laboratory venous plasma glucose samples demonstrated significantly tighter agreement (r(2)=0.7994) and accuracy (mean bias=0.13mmol/L) than SureStep (r(2)=0.6845 and mean bias=0.53mmol/L). StatStrip also showed improved sensitivity for detecting critical low glucose values ≤3.0mmol/L (80.9 vs 68.9%, p<0.05). ROC curve analysis further demonstrated excellent performance of StatStrip at this cutoff with an AUC of 0.98. Overall, neonates were also tested significantly less frequently with the StatStrip meter by 24% compared to SureStep.

CONCLUSIONS

Implementation of StatStrip led to better agreement with venous plasma glucose, improved detection of critical low glucose results, and more efficient test utilization. This study demonstrates the importance of accurate and sensitive glucose monitoring in the NICU.

The potential risks and benefits of insulin treatment in hyperglycaemic preterm neonates

Preterm hyperglycaemia in the first 2 weeks of life is common under 29 weeks gestation and is associated with increased mortality and morbidity. While the definition of hyperglycaemia is reasonably consistent (>8 mmol/L) the treatment threshold varies widely in clinical practice. Insulin therapy is the most common approach despite international guidance urging caution because of hypoglycaemia. Significant hypoglycaemia is unusual outside studies targeting normoglycaemia. Insulin treatment also forms part of a nutritional strategy aiming to optimise early protein and energy intake so minimising the risk of preterm postnatal growth failure. Early parenteral amino acids also improve blood glucose control. There is some evidence of improved postnatal head growth with this approach but longer term neurodevelopmental studies are required. Glucose reduction is the alternative approach. This compromises early nutritional intake but avoids the potential for long-term cardiovascular and metabolic complications linked with high postnatal nutritional intakes and theoretically, insulin treatment.

Clinically stable very low birthweight infants are at risk for recurrent tissue glucose fluctuations even after fully established enteral nutrition

OBJECTIVE

In previous cases, we have observed occasional hypoglycaemic episodes in preterm infants after initial intensive care. In this prospective study, we determined the frequency and severity of abnormal tissue glucose (TG) in clinically stable preterm infants on full enteral nutrition.

METHODS

Preterm infants born at <1000 g (n=23; G1) and birth weight 1000-1500 g (n=18; G2) were studied at a postmenstrual age of 32±2 weeks (G1) and 33±2 weeks (G2). Infants were fed two or three hourly, according to a standard bolus-nutrition protocol, and continuous subcutaneous glucose measurements were performed for 72 h. Normal glucose values were assumed at ≥2.5 mmol/L (45 mg/dL) and ≤8.3 mmol/L (150 mg/dL). Frequency, severity and duration of glucose values beyond normal values were determined.

RESULTS

We observed asymptomatic low TG values in 39% of infants in G1 and in 44% in G2. High TG values were detected in 83% in G1 and 61% in G2. Infants in G1 experienced prolonged and more severe low TG episodes, and also more frequent and severe high TG episodes. In G1 and G2, 87% and 67% of the infants, respectively, showed glucose fluctuations characterised by rapid glucose increase followed by a rapid glucose drop after feeds. In more mature infants, glucose fluctuations were less pronounced and less dependent on enteral feeds.

CONCLUSIONS

Clinically stable well-developing preterm infants beyond their initial period of intensive care show interstitial glucose instabilities exceeding values as low as 2.5 mmol/L and as high as 8.3 mmol/L. This novel observation may play an important role for the susceptibility of these high-risk infants for the development of the metabolic syndrome.

TRIAL REGISTRATION NUMBER

German trial registration number DRKS00004590.

Brain mass estimation by head circumference and body mass methods in neonatal glycaemic modelling and control

INTRODUCTION

Hyperglycaemia is a common complication of stress and prematurity in extremely low-birth-weight infants. Model-based insulin therapy protocols have the ability to safely improve glycaemic control for this group. Estimating non-insulin-mediated brain glucose uptake by the central nervous system in these models is typically done using population-based body weight models, which may not be ideal.

METHOD

A head circumference-based model that separately treats small-for-gestational-age (SGA) and appropriate-for-gestational-age (AGA) infants is compared to a body weight model in a retrospective analysis of 48 patients with a median birth weight of 750g and median gestational age of 25 weeks. Estimated brain mass, model-based insulin sensitivity (SI) profiles, and projected glycaemic control outcomes are investigated. SGA infants (5) are also analyzed as a separate cohort.

RESULTS

Across the entire cohort, estimated brain mass deviated by a median 10% between models, with a per-patient median difference in SI of 3.5%. For the SGA group, brain mass deviation was 42%, and per-patient SI deviation 13.7%. In virtual trials, 87-93% of recommended insulin rates were equal or slightly reduced (Δ<0.16mU/h) under the head circumference method, while glycaemic control outcomes showed little change.

CONCLUSION

The results suggest that body weight methods are not as accurate as head circumference methods. Head circumference-based estimates may offer improved modelling accuracy and a small reduction in insulin administration, particularly for SGA infants.

The golden hour: improving the stabilization of the very low birth-weight infant

A term borrowed from emergency and cardiovascular medicine, the phrase "Golden Hour" refers to the first hour of an infant's life following delivery. The impact of implementation of a Golden Hour Protocol in a level III neonatal intensive care unit (NICU) for infants delivered at less than 28 weeks gestation was examined, with a focus on admission temperature, admission glucose, and time to the initiation of an intravenous glucose and amino acid administration. As part of a quality initiative project, data were collected before and after the implementation of the Golden Hour Protocol for infants born at less than 28 weeks gestational age from May 2008 through December 2011. Desired outcomes were admission axillary temperature within a range of 36.5°C to 37.4°C, admission glucose more than 50 mg/dL, and the initiation of a glucose and amino acid infusion within 1 hour of birth. Key components of the Golden Hour included the use of a protocolized script, which clearly defined the roles of the delivery room personnel, placing the infant in a polyethylene bag to prevent heat loss, the application of the isolette skin temperature probe within 10 minutes of age, and insertion of umbilical catheters before moving the infant from the resuscitation area to the NICU. Data were collected on 225 infants born less than 28 weeks gestation: 106 in the preprotocol group and 119 in the postprotocol group. Differences between the 2 groups were not statistically significant for birth weight and gestational age. There was a statistically significant difference in the number of infants with an admission temperature in-range (36.5°C-37.4°C) between the preprotocol and postprotocol infants (28.3% vs 49.6%; P = .002). There was a statistically significant difference in the incidence of admission glucose greater than 50 mg/dL between the pre- and postprotocol groups (55.7% vs 72%; P = .012). There was a highly statistically significant difference in the number of post-Golden Hour Protocol infants who received an intravenous administration of glucose and amino acids within 1 hour of life compared with the preprotocol group (61.3% vs 7%; P = 0.001). Our results suggest that the implementation of the Golden Hour Protocol can significantly improve the stabilization of infants delivered less than 28 weeks gestation.

Hyperglycemia increases the risk of death in extremely preterm baboons

BACKGROUND

Transient neonatal hyperglycemia (HG) has been reported in up to 80% of extremely preterm human infants. We hypothesize that severe HG is associated with increased morbidity and mortality in preterm baboons.

METHODS

Sixty-six baboons born at 67% of gestation were studied. HG was defined as serum glucose level ≥150 mg/dl during the first week of life. Animals were stratified into two groups: severe HG (≥8 events) and nonsevere HG (<8 events).

RESULTS

HG developed in 65 of the 66 (98%) baboons that were included. A total of 3,386 glucose measurements were obtained. The mean serum glucose level was 159 ± 69 mg/dl for the severe HG group and 130 ± 48 mg/dl for the nonsevere HG group during the first week of life. No differences were found in gender, birth weight, sepsis, patent ductus arteriosus, or oxygenation/ventilation indexes between groups. Severe HG was associated with early death even after controlling for sepsis, postnatal steroid exposure, and catecholamine utilization.

CONCLUSION

HG is common in preterm baboons and is not associated with short-term morbidity. Severe HG occurring in the first week of life is associated with early death in preterm baboons.

Identification of a novel Pfkfb1 mRNA variant in rat fetal liver

The bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2) catalyzes the synthesis and degradation of fructose-2,6-bisphosphate, a key metabolite in the glucose homeostasis. Four genes, Pfkfb1-4, have been characterized in mammals that code for several isoforms generated by alternative splicing through the control of several promoters and 5' non-coding exons. Here, we characterize in fetal rat liver new mRNA variants which are transcribed from a new Pfkfb1 gene promoter. The long variant codes to a new isoform (FL-PFK-2) that would be of relevant function to modulate the transition of fetal to adult liver metabolism.

In utero fuel homeostasis: Lessons for a clinician

Fetus exists in a complex, dynamic, and yet intriguing symbiosis with its mother as far as fuel metabolism is concerned. Though the dependence on maternal fuel is nearly complete to cater for its high requirement, the fetus is capable of some metabolism of its own. The first half of gestation is a period of maternal anabolism and storage whereas the second half results in exponential fetal growth where maternal stores are mobilized. Glucose is the primary substrate for energy production in the fetus though capable of utilizing alternate sources like lactate, ketoacids, amino acids, fatty acids, and glycogen as fuel under special circumstances. Key transporters like glucose transporters (GLUT) are responsible for preferential transfers, which are in turn regulated by complex interaction of maternal and fetal hormones. Amino acids are preferentially utilized for growth and essential fatty acids for development of brain and retina. Insulin, insulin like growth factors, glucagon, catecholamines, and letpin are the hormones implicated in this fascinating process. Hormonal regulation of metabolic substrate utilization and anabolism in the fetus is secondary to the supply of nutrient substrates. The knowledge of fuel homeostasis is crucial for a clinician caring for pregnant women and neonates to manage disorders of metabolism (diabetes), growth (intrauterine growth restriction), and transitional adaptation (hypoglycemia).

Pilot study of a model-based approach to blood glucose control in very-low-birthweight neonates

Background

Hyperglycemia often occurs in premature, very low birthweight infants (VLBW) due to immaturity of endogenous regulatory systems and the stress of their condition. Hyperglycemia in neonates has been linked to increased morbidities and mortality and occurs at increasing rates with decreasing birthweight. In this cohort, the emerging use of insulin to manage hyperglycemia has carried a significant risk of hypoglycemia. The efficacy of blood glucose control using a computer metabolic system model to determine insulin infusion rates was assessed in very-low-birth-weight infants.

Methods

Initial short-term 24-hour trials were performed on 8 VLBW infants with hyperglycemia followed by long-term trials of several days performed on 22 infants. Median birthweight was 745 g and 760 g for short-term and long-term trial infants, and median gestational age at birth was 25.6 and 25.4 weeks respectively. Blood glucose control is compared to 21 retrospective patients from the same unit who received insulin infusions determined by sliding scales and clinician intuition. This study was approved by the Upper South A Regional Ethics Committee, New Zealand (ClinicalTrials.gov registration NCT01419873).

Results

Reduction in hyperglycemia towards the target glucose band was achieved safely in all cases during the short-term trials with no hypoglycemic episodes. Lower median blood glucose concentration was achieved during clinical implementation at 6.6 mmol/L (IQR: 5.5 – 8.2 mmol/L, 1,003 measurements), compared to 8.0 mmol/L achieved in similar infants previously (p < 0.01). No significant difference in incidence of hypoglycemia during long-term trials was observed (0.25% vs 0.25%, p = 0.51). Percentage of blood glucose within the 4.0 – 8.0 mmol/L range was increased by 41% compared to the retrospective cohort (68.4% vs 48.4%, p < 0.01).

Conclusions

A computer model that accurately captures the dynamics of neonatal metabolism can provide safe and effective blood glucose control without increasing hypoglycemia.

Trial Registration

ClinicalTrials.gov registration NCT01419873

Energy metabolism in the newborn farm animal with emphasis on the calf: endocrine changes and responses to milk-born and systemic hormones

Neonatal mammals need adaption to changes in nutrient supply because energy intake shifts from continuous parenteral supply of nutrients (mainly glucose, lactate, and amino acids) via the placenta to discontinuous colostrum and milk intake with lactose and fat as main energy sources. Besides ingested lactose, endogenous glucose production is essential in the neonate to assure sufficient glucose availability. Fetal endogenous glucose production is low, but endocrine changes (especially the prenatal rise of glucocorticoid production) promote maturation of metabolic pathways that enable marked glycogen synthesis before and enhanced gluconeogenesis after birth to establish an adequate glucose status during postnatal maturation. In preterm born farm animals gluconeogenic activity is low, mainly because of a low glucocorticoid and thyroid status. In full-term neonates, endogenous glucose production increases with age. Colostral bioactive components (such as growth factors, hormones, bioactive peptides, and cytokines) do not have a direct effect on endogenous glucose production. However, colostrum feeding stimulates intestinal growth and development, an effect at least in part mediated by bioactive substances. Increased nutrient and glucose absorption thus allows increased glucose supply and hepatic glycogen storage, which improves the glucose status. The improved energetic status of colostrum-fed neonates is reflected by an accelerated maturation of the somatotropic axis, leading especially to enhanced production of IGF-I in the neonate. Secretion and production of hormones involved in the regulation of glucose and fat metabolism in neonates depend on the developmental stage and the response to feeding. In addition, many such hormones have actions in the neonate that differ from adult animals. Endocrine action to support endogenous energy supply in neonates is probably not fully established, and therefore, needs postnatal maturation. Therefore, our knowledge on energy metabolism in the neonate needs to be extended to better understand the function and the failure and to assess endocrine responses during the neonatal period.

Modeling the glucose regulatory system in extreme preterm infants

BACKGROUND

Premature infants represent a significant proportion of the neonatal intensive care population. Blood glucose homeostasis in this group is often disturbed by immaturity of endogenous regulatory systems and the stress of their condition. Hypo- and hyperglycemia are frequently reported in very low birth weight infants, and more mature infants often experience low levels of glycemia. A model capturing the unique fundamental dynamics of the neonatal glucose regulatory system could be used to develop better blood glucose control methods.

METHODS

A metabolic system model is adapted from adult critical care to the unique physiological case of the neonate. Integral-based fitting methods were used to identify time-varying insulin sensitivity and non-insulin mediated glucose uptake profiles. The clinically important predictive ability of the model was assessed by assuming insulin sensitivity was constant over prediction intervals of 1, 2 and 4h forward and comparing model-simulated versus actual clinical glucose values for all recorded interventions. The clinical data included 1091 glucose measurements over 3567 total patient hours, along with all associated insulin and nutritional infusion data, for N=25 total cases. Ethics approval was obtained from the Upper South A Regional Ethics Committee for this study.

RESULTS

The identified model had a median absolute percentage error of 2.4% [IQR: 0.9-4.8%] between model-fitted and clinical glucose values. Median absolute prediction errors at 1-, 2- and 4-h intervals were 5.2% [IQR: 2.5-10.3%], 9.4% [IQR: 4.5-18.4%] and 13.6% [IQR: 6.3-27.6%] respectively.

CONCLUSIONS

The model accurately captures and predicts the fundamental dynamic behaviors of the neonatal metabolism well enough for effective clinical decision support in glycemic control. The adaptation from adult to a neonatal case is based on the data from the literature. Low prediction errors and very low fitting errors indicate that the fundamental dynamics of glucose metabolism in both premature neonates and critical care adults can be described by similar mathematical models.

Development of blood glucose control for extremely premature infants

Extremely premature neonates often experience hyperglycaemia, which has been linked to increased mortality and worsened outcomes. Insulin therapy can assist in controlling blood glucose levels and promoting needed growth. This study presents the development of a model-based stochastic targeted controller designed to adapt insulin infusion rates to match the unique and changing metabolic state and control parameters of the neonate. Long-term usage of targeted BG control requires successfully forecasting variations in neonatal metabolic state, accounting for differences in clinical practices between units, and demonstrating robustness to errors that can occur in everyday clinical usage. Simulation studies were used to evaluate controller ability to target several common BG ranges and evaluate controller sensitivity to missed BG measurements and delays in control interventions on a virtual patient cohort of 25 infants developed from retrospective data. Initial clinical pilot trials indicated model performance matched expected performance from simulations. Stochastic targeted glucose control developed using validated patient-specific virtual trials can yield effective protocols for this cohort. Long-term trials show fundamental success, however clinical interface design appears as a critical factor to ensuring good compliance and thus good control.

Fluid, electrolytes, and nutrition: minutes matter

Historically, in very low-birth-weight infant care, nutritional support was delayed during the first postnatal days because of fear of toxicity and harm with immature metabolic systems and intestinal function. Recent evidence demonstrates that early nutritional support is not only safe but likely necessary to optimize infant growth and neurodevelopment. In fact, nutrition management is a critical factor in very low-birth-weight infant golden hour support. Contemporary studies in protein and lipid intravenous support and early feeds as minimal enteral nutrition exhibit safety and some efficacy. We will present analysis of this evidence and development of potential better practices on the basis of these data as well as a review of golden hour fluid and glucose management. In addition, we provide several outcomes following our adoption of potentially better golden hour nutrition practices.

Physiological and clinical role of insulin in the neonate

In the newborn infant, insulin secretion has to adjust in response to the switch from a regulated and continuous placental supply of glucose in utero to the delivery of intermittent oral feeds postnatally. Changes in insulin secretion must reflect its primary role for maintaining glucose homeostasis, but also its roles in promoting growth and anabolism and in the newborn disorders of insulin secretion or sensitivity, which present with hyperglycemia and impaired growth. Recent elucidation of the genetic basis of neonatal diabetes has helped to provide valuable insights into the molecular mechanisms of β-cell function and the potential for treatment of some patients with oral hypoglycemic agents, although the majority require prolonged subcutaneous insulin treatment, which may prove challenging. The recent development of insulin pump therapy has significantly improved the clinical management of these infants. Although they do not have neonatal diabetes, the preterm or very-low-birthweight infant, subjected to the combined effects of insulin resistance owing to the impact of intensive care, and relative insulin deficiency related to prematurity, may have long periods of hyperglycemia and impaired growth, which have been associated with adverse clinical outcomes. Although these infants often require insulin treatment, the optimal management of glucose control and use of insulin has not been determined and remains controversial.

Blood glucose prediction using stochastic modeling in neonatal intensive care

Hyperglycemia is a common metabolic problem in premature, low-birth-weight infants. Blood glucose homeostasis in this group is often disturbed by immaturity of endogenous regulatory systems and the stress of their condition in intensive care. A dynamic model capturing the fundamental dynamics of the glucose regulatory system provides a measure of insulin sensitivity (S(I)). Forecasting the most probable future S(I) can significantly enhance real-time glucose control by providing a clinically validated/proven level of confidence on the outcome of an intervention, and thus, increased safety against hypoglycemia. A 2-D kernel model of S(I) is fitted to 3567 h of identified, time-varying S(I) from retrospective clinical data of 25 neonatal patients with birth gestational age 23 to 28.9 weeks. Conditional probability estimates are used to determine S(I) probability intervals. A lag-2 stochastic model and adjustments of the variance estimator are used to explore the bias-variance tradeoff in the hour-to-hour variation of S(I). The model captured 62.6% and 93.4% of in-sample S(I) predictions within the (25th-75th) and (5th-95th) probability forecast intervals. This overconservative result is also present on the cross-validation cohorts and in the lag-2 model. Adjustments to the variance estimator found a reduction to 10%-50% of the original value provided optimal coverage with 54.7% and 90.9% in the (25th-75th) and (5th-95th) intervals. A stochastic model of S(I) provided conservative forecasts, which can add a layer of safety to real-time control. Adjusting the variance estimator provides a more accurate, cohort-specific stochastic model of S(I) dynamics in the neonate.

Blood glucose controller for neonatal intensive care: virtual trials development and first clinical trials

BACKGROUND

Premature neonates often experience hyperglycemia, which has been linked to worsened outcomes. Insulin therapy can assist in controlling blood glucose (BG) levels. However, a reliable, robust control protocol is required to avoid hypoglycemia and to ensure that clinically important nutrition goals are met.

METHODS

This study presents an adaptive, model-based predictive controller designed to incorporate the unique metabolic state of the neonate. Controller performance was tested and refined in virtual trials on a 25-patient retrospective cohort. The effects of measurement frequency and BG sensor error were evaluated. A stochastic model of insulin sensitivity was used in control to provide a guaranteed maximum 4% risk of BG < 72 mg/dl to protect against hypoglycemia as well as account for patient variability over 1-3 h intervals when determining the intervention. The resulting controller is demonstrated in two 24 h clinical neonatal pilot trials at Christchurch Women's Hospital.

RESULTS

Time in the 72-126 mg/dl BG band was increased by 103-161% compared to retrospective clinical control for virtual trials of the controller, with fewer hypoglycemic measurements. Controllers were robust to BG sensor errors. The model-based controller maintained glycemia to a tight target control range and accounted for interpatient variability in patient glycemic response despite using more insulin than the retrospective case, illustrating a further measure of controller robustness. Pilot clinical trials demonstrated initial safety and efficacy of the control method.

CONCLUSIONS

A controller was developed that made optimum use of the very limited available BG measurements in the neonatal intensive care unit and provided robustness against BG sensor error and longer BG measurement intervals. It used more insulin than typical sliding scale approaches or retrospective hospital control. The potential advantages of a model-based approach demonstrated in simulation were applied to initial clinical trials.

Stress and pain relief in the care of the surgical neonate

In recent years, there has been a major change in our thinking about the way neonates experience stress. This understanding has led to advances in anesthetic technique and the pre- and postoperative care of the surgical neonate. Stress can develop before birth due to placental insufficiency. This can lead to preterm delivery, and the preterm infant is much more vulnerable to stressful stimulus. Stress is detrimental to the neonate in the short term and can also have adverse effects on the future wellbeing of the child. Limiting stress is not just about good pain control. The nursing environment is vitally important. Much can be achieved with good attention to detail in this respect. The effects of stress and the ways they can be minimized are discussed.

Early insulin therapy in very-low-birth-weight infants

BACKGROUND

Studies involving adults and children being treated in intensive care units indicate that insulin therapy and glucose control may influence survival. Hyperglycemia in very-low-birth-weight infants is also associated with morbidity and mortality. This international randomized, controlled trial aimed to determine whether early insulin replacement reduced hyperglycemia and affected outcomes in such neonates.

METHODS

In this multicenter trial, we assigned 195 infants to continuous infusion of insulin at a dose of 0.05 U per kilogram of body weight per hour with 20% dextrose support and 194 to standard neonatal care on days 1 to 7. The efficacy of glucose control was assessed by continuous glucose monitoring. The primary outcome was mortality at the expected date of delivery. The study was discontinued early because of concerns about futility with regard to the primary outcome and potential harm.

RESULTS

As compared with infants in the control group, infants in the early-insulin group had lower mean (+/-SD) glucose levels (6.2+/-1.4 vs. 6.7+/-2.2 mmol per liter [112+/-25 vs. 121+/-40 mg per deciliter], P=0.007). Fewer infants in the early-insulin group had hyperglycemia for more than 10% of the first week of life (21% vs. 33%, P=0.008). The early-insulin group had significantly more carbohydrate infused (51+/-13 vs. 43+/-10 kcal per kilogram per day, P<0.001) and less weight loss in the first week (standard-deviation score for change in weight, -0.55+/-0.52 vs. -0.70+/-0.47; P=0.006). More infants in the early-insulin group had episodes of hypoglycemia (defined as a blood glucose level of <2.6 mmol per liter [47 mg per deciliter] for >1 hour) (29% in the early-insulin group vs. 17% in the control group, P=0.005), and the increase in hypoglycemia was significant in infants with birth weights of more than 1 kg. There were no differences in the intention-to-treat analyses for the primary outcome (mortality at the expected date of delivery) and the secondary outcome (morbidity). In the intention-to-treat analysis, mortality at 28 days was higher in the early-insulin group than in the control group (P=0.04).

CONCLUSIONS

Early insulin therapy offers little clinical benefit in very-low-birth-weight infants. It reduces hyperglycemia but may increase hypoglycemia (Current Controlled Trials number, ISRCTN78428828.)

Permanent neonatal diabetes caused by a homozygous nonsense mutation in the glucokinase gene

Glucokinase deficiency is an unfrequent cause of permanent neonatal diabetes (PND), as only seven patients have been reported, either homozygous for a missense or frameshift mutation or compound heterozygous for both of them. We report here the first known case caused by a homozygous nonsense mutation (Y61X) in the glucokinase gene (GCK) that introduces a premature stop codon, generating a truncated protein that is predicted to be completely inactive as it lacks both the glucose- and the adenosine triphosphate-binding sites. The proband, born to consanguineous parents, was a full-term, intra-uterine growth-retarded male newborn who presented with a glycaemia of 129 mg/dL (7.16 mmol/L) on his second day of life, increasing thereafter up to 288 mg/dL (15.98 mmol/L) and 530 mg/dL (29.41 mmol/L) over the next 24 h, in the face of low serum insulin (<3 muIU/mL; <20.83 pmol/L). He was put on insulin on the third day of life. Insulin has never been discontinued since then. The patient was tested negative for anti-insulin and islet cell antibodies at age 5 months. His father had non-progressive, impaired fasting glucose for several years. The mother was found to be mildly hyperglycaemic only when her glucose was checked after the child was diagnosed. In conclusion, biallelic GCK loss should be considered as a potential cause of PND in children born to consanguineous parents, even if they are not known to be diabetic at the time of PND presentation.

Hyperglycemia in extremely low birth weight infants in a predominantly Hispanic population and related morbidities

OBJECTIVE

This study describes the incidence, correlates and subsequent morbidities of hyperglycemia, a highly prevalent condition in extremely low birth weight (ELBW) infants.

STUDY DESIGN

A retrospective chart review of 169 infants with birth weight (BW)<1000 g was conducted. Hyperglycemia was defined as plasma glucose level > or =150 mg/dl during the first 2 weeks of life. Data were analyzed by logistic regression, multivariate analysis and Fisher exact test.

RESULTS

Overall, 88% of the study sample developed hyperglycemia in the first 2 weeks of life. Both gestational age (GA) (odds ratio (OR) 0.11, 95% confidence interval (CI)=0.01-0.89) and chorioamnionitis (OR 0.10, 95% CI=0.01-0.64) were inversely associated with hyperglycemia, whereas BW, sepsis and postnatal steroid exposure were not. After adjusting for GA, BW and postnatal steroids, hyperglycemia was associated with a statistically significant increase in retinopathy of prematurity (ROP) (OR 4.6, 95% CI 1.12-18.9). No association was found with bronchopulmonary dysplasia, intraventricular hemorrhage, death or prolonged hospital stay.

CONCLUSION

Lower GA was identified as the main factor associated with hyperglycemia in ELBW infants during the first 2 weeks of life. Hyperglycemia was associated with an increased incidence of ROP; further studies need to determine if this association is causal.

Effects of colostrum feeding and glucocorticoid administration on insulin-dependent glucose metabolism in neonatal calves

Colostrum feeding and glucocorticoid administration affect glucose metabolism and insulin release in calves. We have tested the hypothesis that dexamethasone as well as colostrum feeding influence insulin-dependent glucose metabolism in neonatal calves using the euglycemic-hyperinsulinemic clamp technique. Newborn calves were fed either colostrum or a milk-based formula (n=14 per group) and in each feeding group, half of the calves were treated with dexamethasone (30 microg/[kg body weight per day]). Preprandial blood samples were taken on days 1, 2, and 4. On day 5, insulin was infused for 3h and plasma glucose concentrations were kept at 5 mmol/L+/-10%. Clamps were combined with [(13)C]-bicarbonate and [6,6-(2)H]-glucose infusions for 5.5h (i.e., from -150 to 180 min, relative to insulin infusion) to determine glucose turnover, glucose appearance rate (Ra), endogenous glucose production (eGP), and gluconeogenesis before and at the end of the clamp. After the clamp liver biopsies were taken to measure mRNA levels of phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC). Dexamethasone increased plasma glucose, insulin, and glucagon concentrations in the pre-clamp period thus necessitating a reduction in the rate of glucose infusion to maintain euglycemia during the clamp. Glucose turnover and Ra increased during the clamp and were lower at the end of the clamp in dexamethasone-treated calves. Dexamethasone treatment did not affect basal gluconeogenesis or eGP. At the end of the clamp, dexamethasone reduced eGP and PC mRNA levels, whereas mitochondrial PEPCK mRNA levels increased. In conclusion, insulin increased glucose turnover and dexamethasone impaired insulin-dependent glucose metabolism, and this was independent of different feeding.

Hyperglycaemia as a possible marker of invasive fungal infection in preterm neonates

AIM

The incidence of invasive fungal infection in preterm newborns is rising steadily. Early recognition and treatment are imperative, but diagnosis is difficult as data from microbiological investigations are often poor, and clinical and laboratory signs do not help in differentiating bacterial from fungal infections. We evaluated whether glucose intolerance could represent a possible surrogate marker predictor of invasive fungal infection in preterm neonates.

METHODS

We performed a case-control study on neonates with birthweight less than 1250 g admitted to our tertiary-level unit during the years 1998-2004 (n = 383), comparing those with invasive fungal infection (n = 45, group A) to matched controls with late-onset sepsis caused by bacterial agents (n = 46, group B). We investigated in both groups the occurrence of hyperglycaemia (serum glycaemia > 215 mg/dl, i.e. 12 mmol/l) in the first month of life, and its temporal relationship with the episodes of sepsis.

RESULTS

Hyperglycaemia occurred significantly more often in group A (21/45, 46.6%) than in group B neonates (11/46, 23.9%) (OR 1.95, 95% CI 1.235-4.432, p = 0.008). Moreover, in 19 of 21 (90.4%) neonates with hyperglycaemia in group A, the carbohydrate intolerance episode typically occurred 72 h prior to the onset of invasive fungal infection; in contrast, no temporal relationship was found in neonates with bacterial sepsis (p = 0.002). Correction of hyperglycaemia was successfully achieved in all neonates of both groups, with no significant differences in the number of days of insulin treatment needed to normalize glycaemia (p = 0.15).

CONCLUSIONS

Hyperglycaemia is significantly more frequent in neonates who subsequently develop fungal rather than bacterial late-onset sepsis, with a typical 3-d interval. We suggest that a preterm neonate whose birthweight is less than 1250 g in its first month of life should be carefully evaluated for systemic fungal infection whenever signs of carbohydrate intolerance occur.

Stimulation of gluconeogenesis by intravenous lipids in preterm infants: response depends on fatty acid profile

In preterm infants, both hypo- and hyperglycemia are a frequent problem. Intravenous lipids can affect glucose metabolism by stimulation of gluconeogenesis by providing glycerol, which is a gluconeogenic precursor, and/or free fatty acids (FFA), which are stimulants of the rate of gluconeogenesis. In 25 preterm infants, glucose production and gluconeogenesis were measured using stable isotope techniques during a 6-h infusion of glucose only, glucose plus glycerol, or glucose plus an intravenous lipid emulsion. Two lipid emulsions differing in FFA composition were used: Intralipid ( approximately 60% polyunsaturated FFA) and Clinoleic (approximately 60% monounsaturated FFA). The rate of glucose infusion was 22 micromol x kg(-1) x min(-1) in all groups. During the study infusion, the FFA concentrations were higher in both lipid groups vs. the glycerol group (P < 0.001). Compared with baseline, the glucose production rate increased in the Intralipid group, whereas it decreased in the other groups (P = 0.002) due to a significant increase in gluconeogenesis in the Intralipid group (P = 0.016). The plasma glucose concentration was significantly higher during Intralipid infusion vs. the other groups (P = 0.046). Our conclusion was that Intralipid enhanced glucose production by increasing gluconeogenesis in preterm infants. This can be ascribed to the stimulatory effect of FFA in addition to any effect of glycerol alone. The lack of stimulation of gluconeogenesis in the Clinoleic vs. the Intralipid group suggests that different classes of fatty acids exert different effects on glucose kinetics in preterm infants.

Neonatal epileptic encephalopathy caused by mutations in the PNPO gene encoding pyridox(am)ine 5′-phosphate oxidase

In the mouse, neurotransmitter metabolism can be regulated by modulation of the synthesis of pyridoxal 5'-phosphate and failure to maintain pyridoxal phosphate (PLP) levels results in epilepsy. This study of five patients with neonatal epileptic encephalopathy suggests that the same is true in man. Cerebrospinal fluid and urine analyses indicated reduced activity of aromatic L-amino acid decarboxylase and other PLP-dependent enzymes. Seizures ceased with the administration of PLP, having been resistant to treatment with pyridoxine, suggesting a defect of pyridox(am)ine 5'-phosphate oxidase (PNPO). Sequencing of the PNPO gene identified homozygous missense, splice site and stop codon mutations. Expression studies in Chinese hamster ovary cells showed that the splice site (IVS3-1g>a) and stop codon (X262Q) mutations were null activity mutations and that the missense mutation (R229W) markedly reduced pyridox(am)ine phosphate oxidase activity. Maintenance of optimal PLP levels in the brain may be important in many neurological disorders in which neurotransmitter metabolism is disturbed (either as a primary or as a secondary phenomenon).