Assessment of effects of neonatal hypoglycaemia. A study of 41 cases with matched controls

Neonatal Glycaemia and Neurodevelopmental Outcomes: A Systematic Review and Meta-Analysis

BACKGROUND

Hypoglycaemia is the most common metabolic problem in neonates but there is no universally accepted threshold for safe blood glucose concentrations due to uncertainty regarding effects on neurodevelopment.

OBJECTIVE

To systematically assess the association between neonatal hypoglycaemia on neurodevelopment outcomes in childhood and adolescence.

METHODS

We searched MEDLINE, EMBASE, CINAHL, and PsycINFO from inception until February 2018. We included studies that reported one or more prespecified outcomes and compared children exposed to neonatal hypoglycaemia with children not exposed. Studies of neonates with congenital malformations, inherited metabolic disorders and congenital hyperinsulinism were excluded. Two authors independently extracted data using a customized form. We used ROBINS-I to assess risk of bias, GRADE for quality of evidence, and REVMAN for meta-analysis (inverse variance, fixed effects).

RESULTS

1,665 studies were screened, 61 reviewed in full, and 11 included (12 publications). In early childhood, exposure to neonatal hypoglycaemia was not associated with neurodevelopmental impairment (n = 1,657 infants; OR = 1.16, 95% CI = 0.86-1.57) but was associated with visual-motor impairment (n = 508; OR = 3.46, 95% CI = 1.13-10.57) and executive dysfunction (n = 463; OR = 2.50, 95% CI = 1.20-5.22). In mid-childhood, neonatal hypoglycaemia was associated with neurodevelopmental impairment (n = 54; OR = 3.62, 95% CI = 1.05-12.42) and low literacy (n = 1,395; OR = 2.04, 95% CI = 1.20-3.47) and numeracy (n = 1,395; OR = 2.04, 95% CI = 1.21-3.44). No data were available for adolescents.

CONCLUSIONS

Neonatal hypoglycaemia may have important long-lasting adverse effects on neurodevelopment that may become apparent at later ages. Carefully designed randomized trials are required to determine the optimal management of neonates at risk of hypoglycaemia with long-term follow-up at least to school age.

Neurodevelopmental Outcome of Asymptomatic Hypoglycemia Compared With Symptomatic Hypoglycemia and Euglycemia in High-Risk Neonates

AIMS

We assessed the neurodevelopmental outcome at one year of age of children with asymptomatic neonatal hypoglycemia and compared their outcome with that of symptomatic hypoglycemic and euglycemic neonates.

METHOD

Seventy two hypoglycemic (plasma glucose less than 50 mg/dL) neonates, both symptomatic (n = 27) and asymptomatic (n = 45), and 70 weight- and gestation-matched euglycemic neonates of gestational age greater than 32 weeks were enrolled during the first week of life then assessed for neurodevelopmental outcome at corrected age six and 12 months (n = 67 and 62 in hypoglycemia group and 63 and 54 in euglycemia group, with the rest lost to follow-up, and death = 1).

RESULTS

At one year, 8% (five of 62, four in symptomatic and one in asymptomatic group) of hypoglycemic neonates developed cerebral palsy. Mean motor and mental development quotients were significantly lower at corrected ages six and 12 months in any hypoglycemia (P < 0.001) and if blood glucose was less than 40 mg/dL (P < 0.001) when compared with euglycemia. Symptomatic infants had lower motor development quotient (P = 0.004 and 0.003) and mental development quotient (P = 0.001 and 0.001) at corrected ages six and 12 months than asymptomatic infants, and asymptomatic infants had lower motor development quotient (P ≤ 0.001 and 0.004) and mental development quotient (P = 0.001 and 0.004) than the euglycemic group at corrected ages six and 12 months, respectively. Blood glucose of less than 40 mg/dL had high sensitivity (83% for motor development quotient and 81% for mental development quotient) for development quotient scores of less than 85.

CONCLUSION

Hypoglycemia, both symptomatic and asymptomatic, leads to adverse neurodevelopmental outcome when compared with euglycemia, although it was worse in the symptomatic group and at blood glucose less than 40 mg/dL.

Managing "healthy" late preterm infants

BACKGROUND

Late preterm infants are often managed in nursery rooms despite the risks associated with prematurity. The objective of this study was to determine the risks facing late preterm infants admitted to nursery rooms and to establish a management strategy.

METHODS

A total of 210 late preterm infants and 2648 mature infants were assessed. Infants born at 35 and 36 weeks' gestation weighing >or=2000 grams admitted to a nursery room and not requiring medical intervention at birth were of particular interest. The admission rates to the neonatal intensive care unit were evaluated according to the chart review.

RESULTS

Infants born at 35 and 36 weeks' gestation weighing >or=2000 grams had significantly higher admission rates than term infants at birth (Cochran-Mantel-Haenszel test, P < 0.001; common risk ratio, 4.27; 95% confidence interval, 2.41-7.55) and after birth (P < 0.001; common risk ratio, 3.57; 95% confidence interval, 2.40-5.33). More than 80% of admissions from the nursery room to the neonatal intensive care unit after birth were due to apnea or hypoglycemia in neonates born at 35 and 36 weeks' gestation. The admission rates due to apnea increased with decreasing gestational age. The admission rates due to hypoglycemia with no cause other than prematurity accounted for 24.3% of admissions for those born at 35 weeks' gestation and 14.1% of admissions for those born at 36 weeks' gestation; hypoglycemia due to other causes accounted for fewer admissions.

CONCLUSION

The management strategy for late preterm infants should be individualized, based on apnea and hypoglycemia. The respiratory state of late preterm infants should be monitored for at least 2 days, and they should be screened for hypoglycemia on postnatal day 0.

Neurodevelopment after neonatal hypoglycemia: a systematic review and design of an optimal future study

OBJECTIVE

Our goal was to assess the effect of episodes of neonatal hypoglycemia on subsequent neurodevelopment.

METHODS

We searched Medline and Embase for cohort studies on subsequent neurodevelopment after episodes of hypoglycemia in the first week of life. Reference lists of available studies were reviewed, and content experts were contacted for additional studies. Included studies were selected and appraised for methodologic quality by 2 reviewers. Methodologic quality was assessed according to well-accepted criteria for prognostic studies. Eventually, all studies were given an overall quality score: poor, moderate, or high quality. Studies in the latter 2 categories were considered for quantitative data analysis.

RESULTS

Eighteen eligible studies were identified. The overall methodologic quality of the included studies was considered poor in 16 studies and high in 2 studies. Pooling of results of the 2 high-quality studies was deemed inappropriate because of major clinical and methodologic heterogeneity. None of the studies provided a valid estimate of the effect of neonatal hypoglycemia on neurodevelopment. Building on the strengths and weaknesses of existing studies, we developed a proposal for an "optimal" future study design.

CONCLUSIONS

Recommendations for clinical practice cannot be based on valid scientific evidence in this field. To assess the effect of neonatal hypoglycemia on subsequent neurodevelopment, a well-designed prospective study should be undertaken. We submit a design for a study that may answer the still-open questions.

Hypoglycemia in newborn infants: Features associated with adverse outcomes

The purpose of this review article is to document from the literature values of blood/plasma glucose concentration and associated clinical signs and conditions in newborn infants (both term and preterm) that indicate a reasonable clinical probability that hypoglycemia is a proximate cause of acute and/or sustained neurological injury and to review the physiological and pathophysiological responses to hypoglycemia that may influence the ultimate outcome of newborns with low blood glucose. Our overall conclusion is that there is inadequate information in the literature to define any one value of glucose below which irreparable hypoglycemic injury to the central nervous system occurs, at any one time or for any defined period of time, in a population of infants or in any given infant. Clinical signs of prolonged and severe neurological disturbance (coma, seizures), extremely and persistently low plasma/blood glucose concentrations (0 to <1.0 mmol/l [0 to <18-20 mg/dl] for more than 1-2 h), and the absence of other obvious central nervous system (CNS) pathology (hypoxia-ischemia, intracranial hemorrhage, infection, etc.) are important for the diagnosis of injury due to glucose deficiency. Specific conditions, such as persistent hyperinsulinemia with severe hypoglycemic episodes that include seizures, also contribute to the diagnosis of hypoglycemic injury. Such lack of definitive measures of injury specific to glucose deficiency indicates that clinicians should be on the alert for infants at risk of hypoglycemia and for clinical signs and conditions that might herald severe hypoglycemia; they should have a low threshold for investigating and diagnosing 'hypoglycemia' with frequent measurements of plasma/blood glucose concentration; and they should treat low glucose concentrations promptly and maintain them in a safe range. Because there is no conclusive evidence or consensus in the literature that defines an absolute value or duration of 'hypoglycemia' that must occur, with our without related clinical complications, to produce neurological injury, clinicians should consider the information currently available, determine a 'target' plasma or blood glucose concentration that is acceptable, and treat infants with glucose concentrations below this value accordingly. Our intent in this review article is to highlight the studies relevant to this issue and help clinicians formulate a safe and, hopefully, effective strategy for the diagnosis and treatment of hypoglycemia.

Hypoglycemia and the breastfed neonate

Healthy, full-term infants are functionally and metabolically programmed to make the transition from their intrauterine dependent environment to their extrauterine existence without the need for metabolic monitoring or interference with the natural breastfeeding process. Full-term infants are equipped with homeostatic mechanisms that preserve adequate energy substrate to the brain and other vital organs. Thermal stability and early, properly guided, frequent, exclusive breastfeeding are the keys to success. Thus, routine screening for blood glucose concentrations or feeding sugar water is not necessary and potentially counterproductive to the establishment of a healthy mother-infant dyad.

Hypoglycemic brain injury

Hypoglycemia frequently occurs in newborn infants who previously have suffered asphyxia, who are offspring of diabetic mothers, or who are low birthweight for gestational age (IUGR). Many infants who are hypoglycemic do not exhibit clinical manifestations, while others are symptomatic and at risk for the occurrence of permanent brain damage. This review emphasizes the clinical, neuropathologic, and neuro-imaging features of hypoglycemia in newborn infants, especially those who are symptomatic. Neurologic morbidity occurs particularly in those infants who have suffered severe, protracted, or recurrent symptomatic hypoglycemia. Experimental observations emphasize the resistance of the immature brain to the damaging effect of hypoglycemia; such resistance occurs as a consequence of compensatory increases in cerebral blood flow, lower energy requirements, higher endogenous carbohydrate stores, and an ability to incorporate and consume alternative organic substrates to spare glucose for energy production. Hypoglycemia combined with hypoxia-ischemia (asphyxia) is more deleterious to the immature brain than either condition alone.

Controversies regarding definition of neonatal hypoglycemia: suggested operational thresholds

The definition of clinically significant hypoglycemia remains one of the most confused and contentious issues in contemporary neonatology. In this article, some of the reasons for these contentions are discussed. Pragmatic recommendations for operational thresholds, ie, blood glucose levels at which clinical interventions should be considered, are offered in light of current knowledge to aid health care providers in neonatal medicine. Future areas of research to resolve some of these issues are also presented.

Hypoglycemia in the neonate

After a brief history of the development of neonatal hypoglycemia, this review emphasizes the current approach to the anticipation, diagnosis, and management of the neonate with a low plasma glucose concentration. Current techniques for studying the neurophysiological and endocrine-metabolic effects of significant hypoglycemia provide new approaches for establishing relevant definitions of significant hypoglycemia, its prognosis, and pathogenesis. The inadequacy of glucose oxidase strips for screening, the definition of high-risk infants, new definitions for low plasma glucose concentrations, and their treatment are presented as well as the ability of the neonate to respond to significantly low glucose values. New data concerning the hereditary aspects of hyperinsulinemia (Glaser, this issue), hereditary defects in branched-chain amino acid, 3-methylglutaconic aciduria and mitochondrial betaoxidation, and degradation of fatty acids (Ozand, this issue), the role of glucose transporters (Vannucci and Vannucci, this issue), and the newer computed tomography and magnetic resonance imaging techniques (Kinnala, this issue) to study neonatal hypoglycemia are reviewed elsewhere in this issue.

Long-term neurological dysfunction and neonatal hypoglycaemia after diabetic pregnancy

AIM

To determine if children born to mothers with diabetes mellitus during pregnancy, who subsequently developed neonatal hypoglycaemia, experienced long-term neurological dysfunction.

METHODS

Thirteen children with, and 15 without, neonatal hypoglycaemia (blood glucose < 1.5 mmol/l) were randomly selected from a larger cohort and investigated at the age of 8 years. They were also compared with 28 age matched healthy controls.

RESULTS

Children with neonatal hypoglycaemia had significantly more difficulties in a validated screening test for minimal brain dysfunction than controls and were also more often reported to be hyperactive, impulsive, and easily distracted. On psychological assessment, they had a lower total development score than normoglycaemic children born to diabetic mothers, and control children.

CONCLUSIONS

Neonatal hypoglycaemia in diabetic pregnancy was associated with long-term neurological dysfunction related to minimal brain dysfunction/deficits in attention, motor control, and perception.

Neonatal hypoglycemia, part II: pathophysiology and therapy

Contemporary research is elucidating both the molecular mechanisms of hypoglycemia-induced neuronal injury and its corresponding clinical manifestations. Recognizing and screening those neonates at highest risk of hypoglycemia-induced injury is an important skill for all physicians responsible for the care of newborns. Appropriate therapy, consisting of either oral or intravenous glucose, should never be delayed while one is awaiting laboratory confirmation of a "low" glucose level.

Hypoglycaemia of the newborn: a review

It is almost a century since hypoglycaemia (a reduction in the glucose concentration of circulating blood) was first described in children, and over 50 years since the condition was first recognized in infants. Nevertheless, controversy still surrounds the definition, significance, and management of neonatal hypoglycaemia. Technological developments such as bedside glucose monitoring have, paradoxically, exacerbated rather than eased the situation. This article reviews the literature on hypoglycaemia of the newborn, and covers the following: historical aspects; glucose homeostasis and metabolic adaptation at birth; the effect of low blood glucose levels on the central nervous system; the definition of hypoglycaemia; screening; prevention; treatment; research needs; and concludes with recommendations for prevention and management.

Familial hyperinsulinism: successful conservative management

A large family in whom 4 of 13 children were affected with hyperinsulinism of variable severity is described. The oldest affected child required subtotal pancreatectomy to control the hypoglycemia, but the three younger children were managed successfully with prolonged conservative therapy with maintenance oral doses of diazoxide. The three affected school-age children in the family have deficits in the areas of visuomotor integration and short-term memory. The three youngest children have normal intelligence compared with four unaffected siblings; only the oldest child, who has undergone pancreatectomy, has low-average intelligence (IQ80). We conclude that in infants with persistent but asymptomatic hyperinsulinemic hypoglycemia every effort should be made to treat conservatively with antihypoglycemic agents such as diazoxide for as long as possible to allow for spontaneous remission and thereby avoid pancreatectomy.

Adverse neurodevelopmental outcome of moderate neonatal hypoglycaemia

There has been considerable debate over whether asymptomatic neonatal hypoglycaemia results in neurological damage. In a detailed multicentre study of 661 preterm infants hypoglycaemia was found to be common. Moderate hypoglycaemia (plasma glucose concentration less than 2.6 mmol/l) occurred in 433 of the infants and in 104 was found on three to 30 separate days. There was considerable variation among the centres, implying differences in decisions to intervene. The number of days on which moderate hypoglycaemia occurred was strongly related to reduced mental and motor development scores at 18 months (corrected age), even after adjustment for a wide range of factors known to influence development. When hypoglycaemia was recorded on five or more separate days adjusted mental and motor developmental scores at 18 months (corrected age) were significantly reduced by 14 and 13 points respectively, and the incidence of neurodevelopmental impairment (cerebral palsy or developmental delay) was increased by a factor of 3.5 (95% confidence interval 1.3 to 9.4). These data suggest that, contrary to general belief, moderate hypoglycaemia may have serious neurodevelopmental consequences, and reappraisal of current management is urgently required.

Cerebral blood flow and metabolism during hypoglycemia in newborn dogs

Cerebral blood flow (CBF) and cerebral metabolic rates (CMR) were studied in newborn dogs during insulin-induced hypoglycemia. Pups were anesthetized, paralyzed, and artificially ventilated with a mixture of 70% nitrous oxide and 30% oxygen to maintain normoxia and normocarbia. Experimental animals were given regular insulin (0.3 units/gm IV); controls received normal saline. CBF was determined using a modification of the Kety-Schmidt technical employing 133Xe as indicator. Arteriovenous differences for oxygen, glucose, lactate, and beta-hydroxybutyrate (beta-OHB) were also measured, and CMRO2 and CMRsubstrates calculated. Two groups of hypoglycemic dogs were identified; those in which blood glucose levels were greater than 0.5 mM (group 1), and those in which they were less than 0.5 mM (group 2). CBF did not change significantly from control values of 23 +/- 10 ml/min/100 g (mean +/- S.D.) at both levels of hypoglycemia. Similarly, hypoglycemia did not alter CMRO2 significantly from its initial level of 1.05 +/- 0.37 ml O2/min/100 g. Glucose consumption in brain during normoglycemia accounted for 95% of cerebral energy supply with minimal contributions from lactate (4%) and beta-OHB (0.5%). During hypoglycemia, CMRglucose declined by 29 and 52% in groups 1 and 2, respectively, while CMRlactate increased to the extent that this metabolite became the dominant fuel for oxidative metabolism in brain. The cerebral utilization of beta-OHB was unaltered by hypoglycemia. The findings indicate that insulin-induced hypoglycemia in the newborn dog is associated with an increase in cerebral lactate utilization, supplementing glucose as the primary energy fuel and thereby preserving a normal CMRO2. These metabolic responses may contribute to the tolerance of the immature nervous system to the known deleterious effects of hypoglycemia.

Neurological findings at follow-up in neonatal hypoglycaemia

Follow-up examination was carried out in 37 children who had been hypoglycaemic during the neonatal period. Mean age was 3 1/2 years. Five out of 7 children with asymptomatic hypoglycaemia neonatally were completely normal, while minimal brain dysfunction was evident in one, and another child showed pathological EEG. Symptomatic, transient hypoglycaemia seemed to carry a poor prognosis as only one out of 9 individuals was normal. Four patients in this group had convulsions after the neonatal period; two of these had recurrence of hypoglycaemia. One had infantile spasms and was severely mentally retarded with spastic diplegia and epilepsy. One girl was blind due to optic nerve atrophy. Four cases of cerebral palsy were detected in this group. Among 21 cases of secondary hypoglycaemia there were no cases of serious neurological sequelae. It is reasonable to assume that neonatal hypoglycaemia is an important prognostic factor. The deleterious effect on the CNS seems to be related to the duration and severity of the hypoglycaemia.