Monitoring of early postnatal glucose homeostasis and cerebral function in newborn infants of diabetic mothers. A pilot study

Invasive Neuromonitoring Modalities in the Pediatric Population

Invasive neuromonitoring has become an important part of pediatric neurocritical care, as neuromonitoring devices provide objective data that can guide patient management in real time. New modalities continue to emerge, allowing clinicians to integrate data that reflect different aspects of cerebral function to optimize patient management. Currently, available common invasive neuromonitoring devices that have been studied in the pediatric population include the intracranial pressure monitor, brain tissue oxygenation monitor, jugular venous oximetry, cerebral microdialysis, and thermal diffusion flowmetry. In this review, we describe these neuromonitoring technologies, including their mechanisms of function, indications for use, advantages and disadvantages, and efficacy, in pediatric neurocritical care settings with respect to patient outcomes.

A scoping review of pediatric microdialysis: A missed opportunity for microdialysis in the pediatric neuro-oncology setting

Background

Brain microdialysis is a minimally invasive technique for monitoring analytes, metabolites, drugs, neurotransmitters, and/or cytokines. Studies to date have centered on adults with traumatic brain injury, with a limited number of pediatric studies performed. This scoping review details past use of brain microdialysis in children and identifies potential use for future neuro-oncology trials.

Methods

In December 2020, Cochrane Library: CENTRAL, Embase, PubMed, Scopus, and Web of Science: Core Collection were searched. Two reviewers screened all articles by title and abstract review and then full study texts, using microdialysis in patients less than 18 yo.

Results

Of the 1171 articles screened, 49 were included. The 49 studies included 472 pediatric patients (age range 0–17 years old), in the brain (21), abdominal (16), and musculoskeletal (12) regions. Intracerebral microdialysis was performed in 64 collective patients, with a median age of 11 years old, and predominance in metabolic evaluations.

Conclusion

Historically, pediatric microdialysis was safely performed within the brain in varied neurologic conditions, except neuro-oncology. Adult brain tumor studies using intratumoral/peritumoral microdialysis sampling can inform future pediatric studies to advance diagnosis and treatment options for such aggressive tumors.

Nutrition and management of glycemia in neonates with neonatal encephalopathy treated with hypothermia

Adequate nutrition and glycemic homeostasis are increasingly recognized as potentially neuroprotective for the developing brain. In the context of hypoxia-ischemia, evidence is scarce regarding optimal nutritional support and administration route, as well as the short- and long-term consequences of such interventions. In this review, we summarize current knowledge on disturbances of brain metabolism of glucose and substrates by hypoxia-ischemia, and compound effects of these mechanisms on brain injury characterized by specific patterns on EEG and MRI. Risks and benefits of nutrition delivery via parenteral or enteral routes are examined. Nutrition could mitigate adverse neurodevelopmental outcomes, and the impact of nutritional strategies and specific nutritional interventions are reviewed. Limited literature highlights the need for further studies to understand the changes in energy metabolism during and after hypoxic-ischemic injury, to optimize nutritional regimens and glucose management, and to inform the neuroprotective role of nutrition.

Hyperglycemia and Glucose Variability Are Associated with Worse Brain Function and Seizures in Neonatal Encephalopathy: A Prospective Cohort Study

OBJECTIVES

To investigate how glucose abnormalities correlate with brain function on amplitude-integrated electroencephalography (aEEG) in infants with neonatal encephalopathy.

STUDY DESIGN

Neonates born at full term with encephalopathy were enrolled within 6 hours of birth in a prospective cohort study at a pediatric academic referral hospital. Continuous interstitial glucose monitors and aEEG were placed soon after birth and continued for 3 days. Episodes of hypoglycemia (≤50 mg/dL; ≤2.8 mmol/L) and hyperglycemia (>144 mg/dL; >8.0 mmol/L) were identified. aEEG was classified in 6-hour epochs for 3 domains (background, sleep-wake cycling, electrographic seizures). Generalized estimating equations assessed the relationship of hypo- or hyperglycemia with aEEG findings, adjusting for clinical markers of hypoxia-ischemia (Apgar scores, umbilical artery pH, and base deficit).

RESULTS

Forty-five infants (gestational age 39.5 ± 1.4 weeks) were included (24 males). During aEEG monitoring, 16 episodes of hypoglycemia were detected (9 infants, median duration 77.5, maximum 220 minutes) and 18 episodes of hyperglycemia (13 infants, median duration 237.5, maximum 3125 minutes). Epochs of hypoglycemia were not associated with aEEG changes. Compared with epochs of normoglycemia, epochs of hyperglycemia were associated with worse aEEG background scores (B 1.120, 95% CI 0.501-1.738, P < .001), less sleep-wake cycling (B 0.587, 95% CI 0.417-0.757, P < .001) and more electrographic seizures (B 0.433, 95% CI 0.185-0.681, P = .001), after adjusting for hypoxia-ischemia severity.

CONCLUSIONS

In neonates with encephalopathy, epochs of hyperglycemia were temporally associated with worse global brain function and seizures, even after we adjusted for hypoxia-ischemia severity. Whether hyperglycemia causes neuronal injury or is simply a marker of severe brain injury requires further study.

Defining neonatal hypoglycaemia: a continuing debate

Hypoglycaemia is one of the most frequent metabolic problems in neonatal medicine, and maintaining glucose homeostasis is one of the important physiological events during fetal-to-neonatal transition. Although frequently observed transient low blood glucose concentrations in the majority of healthy newborns are the reflections of normal metabolic adaptation processes during this transition, there has been a genuine concern that prolonged or recurrent low blood glucose levels may result in acute systemic effects and long-term neurological and developmental consequences. Hence, it is not surprising that neonatal hypoglycaemia remains one of the most important issues in our day-to-day practice and that we also become obsessed with the numbers and values that we believe are a 'cut-off' for its definition. The aim of this article is to critically appraise some of the available evidence either to support or refute the most widely accepted definition of 'neonatal hypoglycaemia' (blood glucose concentration: <2.6 mmol/l or 47 mg/dl), to highlight our knowledge gaps in defining neonatal hypoglycaemia, and to address the important concept of using an 'operational threshold', rather than focusing too much on a single blood glucose cut-off value, which is often applied to all newborn infants.

15-year follow-up of recurrent "hypoglycemia" in preterm infants

BACKGROUND

Observational study of 543 infants who weighed <1850 g, published in 1988 reported seriously impaired motor and cognitive development at 18 months in those with recurrent, asymptomatic hypoglycemia (plasma glucose level ≤2.5 mmol/L on ≥3 days). No study has yet replicated this observation.

AIM

To quantify disability in a similar cohort of children followed up throughout childhood.

POPULATION

All children born at <32 weeks' gestation in the north of England in 1990-1991 and had laboratory blood glucose levels measured daily for the first 10 days of life.

RESULTS

Forty-seven index children of the 566 who survived to 2 years had a blood glucose level of ≤2.5 mmol/L on ≥3 days. All of these children and hypoglycemia-free controls, matched for hospital of care, gestation, and birth weight, were assessed at age 2. No differences in developmental progress or physical disability were detected. The families were seen again when the children were 15 years old, and 38 of the index children (81%) and matched controls agreed to detailed psychometric assessment. Findings in the 2 groups were nearly identical (mean full-scale IQ: 80.7 vs 81.2). Findings in the 21 children with a level of ≤2.5 mmol/L on ≥4 days, 7 children with a level this low on 5 days, and 11 children with a level of <2.0 mmol/L on 3 different days did not alter these conclusions.

CONCLUSIONS

This study found no evidence to support the belief that recurrent low blood glucose levels (≤2.5 mmol/L) in the first 10 days of life usually pose a hazard to preterm infants.

Cot-side electroencephalography monitoring is not clinically useful in the detection of mild neonatal hypoglycemia

OBJECTIVES

To determine whether there is a relationship between electroencephalography patterns and hypoglycemia, by using simultaneous cot-side amplitude integrated electroencephalography (aEEG) and continuous interstitial glucose monitoring, and whether non-glucose cerebral fuels modified these patterns.

STUDY DESIGN

Eligible babies were ≥ 32 weeks gestation, at risk for hypoglycemia, and admitted to the neonatal intensive care unit. Electrodes were placed in C3-P3, C4-P4 O1-O2 montages. A continuous interstitial glucose sensor was placed subcutaneously, and blood glucose was measured by using the glucose oxidase method. Non-glucose cerebral fuels were measured at study entry, exit, and during recognized hypoglycemia.

RESULTS

A total of 101 babies were enrolled, with a median weight of 2179 g and gestation of 35 weeks. Twenty-four of the babies had aEEG recordings, and glucose concentrations were low (< 2.6 mM). There were 103 episodes of low glucose concentrations lasting 5 to 475 minutes, but no observable changes in aEEG variables. Plasma concentrations of lactate, beta-hydroxybutyrate, and glycerol were low and did not alter during hypoglycemia.

CONCLUSIONS

Cot-side aEEG was not useful for the detection of neurological changes during mild hypoglycemia. Plasma concentrations of non-glucose cerebral fuels were low and unlikely to provide substantial neuroprotection.

Carbon dioxide and glucose affect electrocortical background in extremely preterm infants

OBJECTIVES

To investigate if Paco(2) and plasma glucose levels affect electrocortical activity.

METHODS

Ours was an observational study of 32 infants with a gestational age of 22 to 27 weeks. We performed simultaneous single-channel electroencephalogram (EEG) and repeated blood gas/plasma glucose analyses during the first 3 days (n = 247 blood samples with corresponding EEG). Interburst intervals (IBIs) and EEG power were averaged at the time of each blood sample.

RESULTS

There was a linear relationship between Paco(2) and IBI; increasing Paco(2) was associated with longer IBIs. One day after birth, a 1-kPa increase in Paco(2) was associated with a 16% increase in IBI in infants who survived the first week without severe brain injury. EEG power was highest at a Paco(2) value of 5.1 kPa and was attenuated both at higher and lower Paco(2) values. Corrected for carbon dioxide effects, plasma glucose was also associated with IBI. Lowest IBI appeared at a plasma glucose level of 4.0 mmol/L, and there was a U-shaped relationship between plasma glucose level and EEG with increasing discontinuity at glucose concentrations above and below 4.0 mmol/L.

CONCLUSIONS

Both carbon dioxide and plasma glucose level influenced EEG activity in extremely preterm infants, and values considered to be within normal physiologic ranges were associated with the best EEG background. Increasing EEG discontinuity occurred at carbon dioxide levels frequently applied in lung-protection strategies; in addition, moderate hyperglycemia was associated with measurable EEG changes. The long-term effects of changes in carbon dioxide and glucose on brain function are not known.

Continuous electroencephalography monitoring of the preterm infant

Continuous electroencephalography (EEG) monitoring provides clinically relevant information in preterm infants. Acute changes during development of intraventricular hemorrhage and white matter injury are associated with EEG and amplitude-integrated EEG (aEEG) deterioration. The early EEG background is also correlated with outcome in preterm infants, although other problems associated with prematurity may influence the long-term prognosis. The limitations of EEG monitoring should be well-understood by users and the continuous EEG monitor should be used as a complement to the standard EEG.

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.

Cerebral function monitoring: a new scoring system for the evaluation of brain maturation in neonates

OBJECTIVE

Cerebral function monitoring (CFM), using compressed single-channel amplitude-integrated electroencephalogram recorded from 2 biparietal electrodes, has been shown previously to be a simple bedside tool for monitoring neonatal central nervous system (CNS) status. As the pattern of the CFM changes with gestational age, the technique can be used to assess brain maturation in premature infants. We have developed a new scoring system for the interpretation of neonatal CFM recordings. The objective of this study was to evaluate CFM tracings at increasing gestational and postnatal ages to develop a scoring system to quantify CFM pattern changes.

METHODS

Term and preterm neonates were studied with CFM at 12 to 24 hours of life, 48 to 72 hours of life, and then weekly or biweekly until hospital discharge. Each study comprised 8 to 24 hours of continuous CFM recording. CFM recordings were evaluated using the scoring system for record continuity, presence of cyclic changes in electrical activity, degree of voltage amplitude depression, and bandwidth. Each variable was scored for each recording. All variables were summed to yield a total score (minimum 0, maximum 13). Total scores were correlated with gestational and postconceptional ages.

RESULTS

Thirty infants were studied with gestational ages at birth that ranged from 24 to 39 weeks and birth weights that varied between 450 and 3850 g. A total of 146 CFM tracings were analyzed. With advancing gestational and postconceptional age, scores for each variable as well as total scores progressively increased with CNS maturation. The highest scores were attained at 35 to 36 weeks' postconceptional age, which corresponded to previously reported subjective observations performed by visual description of CFM patterns. Of the 4 component variables that we analyzed, the most sensitive indicators of CNS maturity were 1) the presence of a cycling pattern, 2) the continuity of the record pattern, and 3) the CFM recording bandwidth.

CONCLUSIONS

Our proposed scoring system may be a valuable tool to quantify changes during CFM more objectively, reflecting variations in CNS activity in newborn infants and allowing for better statistical comparisons between amplitude-integrated electroencephalogram tracings from different patients as well as from the same patient at different points of time.