Association of hypoglycaemia with symptoms in the newborn

The current etiologic profile and neurodevelopmental outcome of seizures in term newborn infants

OBJECTIVES

The objectives of this study were to delineate the etiologic profile and neurodevelopmental outcome of neonatal seizures in the current era of neonatal intensive care and to identify predictors of neurodevelopmental outcome in survivors.

METHODS

Eighty-nine term infants with clinical neonatal seizures underwent neurologic examination, electroencephalography (EEG), neuroimaging, and extensive diagnostic tests in the newborn period. After discharge, all infants underwent regular neurologic evaluations and, at 12 to 18 months, formal neurodevelopmental testing. We tested the prognostic value of seizure etiology, neurologic examination, EEG, and neuroimaging.

RESULTS

Etiology was found in 77 infants. Global cerebral hypoxia-ischemia, focal cerebral hypoxia-ischemia, and intracranial hemorrhage were most common. Neonatal mortality was 7%; 28% of the survivors had poor long-term outcome. Association between seizure etiology and outcome was strong, with cerebral dysgenesis and global hypoxia-ischemia associated with poor outcome. Normal neonatal period/early infancy neurologic examination was associated with uniformly favorable outcome at 12 to 18 months; abnormal examination lacked specificity. Normal/mildly abnormal neonatal EEG had favorable outcome, particularly if neonatal neuroimaging was normal. Moderate/severely abnormal EEG, and multifocal/diffuse cortical or primarily deep gray matter lesions, had a worse outcome.

CONCLUSIONS

Mortality associated with neonatal seizures has declined although long-term neurodevelopmental morbidity remains unchanged. Seizure etiology and background EEG patterns remain powerful prognostic factors. Diagnostic advances have changed the etiologic distribution for neonatal seizures and improved accuracy of outcome prediction. Global cerebral hypoxia-ischemia, the most common etiology, is responsible for the large majority of infants with poor long-term outcome.

Hypoglycemia in small for gestational age babies

The main objectives of the study were to find the incidence and risk factors associated with development of hypoglycemia in small for gestational age (SGA) babies, to compare haemoglucotest strips (Boehringer Mannheim) with the standard laboratory method (glucose-hexokinase) for estimation of blood glucose, and to measure the insulin and cortisol responses of SGA babies. This was a prospective longitudinal study. The sample included SGA babies and over a period of six months, 127 consecutively born small for gestational age babies were investigated prospectively for development of hypoglycemia in first 48 hrs of life. Plasma samples were taken during episodes of hypoglycemia for insulin and cortisol estimation and compared with non-hypoglycemic controls. The overall incidence of hypoglycemia was 25.2% in SGA babies and 98% of the episodes occurred within first 24 hrs. Compared to non-hypoglycemics, mothers of hypoglycemic babies had higher incidence of receiving i.v. fluids (5% dextrose) during labour. The hypoglycemic babies were more likely to be sick and oral feeds had been initiated by one hour of life in only 37% of them compared to 63% of non-hypoglycemic babies. Plasma insulin/glucose ratio was significantly higher in hypoglycemic than non-hypoglycemic babies, whereas the cortisol levels were similar. Small for gestational age babies are highly prone to develop hypoglycemia in first 24 hrs of life.

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.

Body size and neonatal hypoglycemia in intrauterine growth retardation

The relationship between blood glucose and body physique of 233 (42 hypo-and 191 normologycemic) intrauterine growth-retarded neonates was analyzed using different body measurements and indices of body proportions. Classification by combination of weight and length deficit for fetal age revealed that the disproportionately retarded infants (deficit in weight for age > 30%; deficit in length for age less than equal to 15%) were particularly prone to hypoglycemia. The lowest incidence of hypoglycemia was observed in the group with severe proportionate retardation (weight deficit for age > 30%; length deficit for age > 15%). Among the indices of body proportions ponderal index (W/L3), and percentage deviation from the expected weight for length turned out to be a sensitive predictor of the risk of hypoglycemia. The majority of hypoglycemia neonates were underweight for length and a considerable number of normoglycemic infants were overweight for length. These findings point to the significance of soft tissue wasting rather than low birth weight for gestational age itself, in the development and diagnosis of neonatal hypoglycemia. The significance of anthropometry in the classification of different types of intrauterine growth impairment, as well as in predicting specific hazards after birth is discussed.

Etiology of convulsions in neonatal and infantile period

1) Etiology of convulsions starting prior to two years of age was discussed in 418 cases. Neonatal seizures before 30 days old appeared in 86 cases (53 boys and 33 girls). Three hundred and thirty-two patients (172 boys and 160 girls) had convulsions in infancy. Twelve patients (9 boys and 3 girls) suffered from convulsions both in neonatal and infantile period. 2)Etiology of convulsions was prenatal in 67 cases (16%), natal in 49 cases (12%), postnatal in 158 cases (38%) and unknown in 144 cases (34%). Prenatal factors consisted of cerebral malformation (23 cases, 6%), associated physical minor anomaly such as cataracta or finger abomaly (11 cases, 3%), abnormal pernatal history (8 cases, 2%), congenital heart disease 3) cases, 1%), tuberose scleorsis (7 cases, 2%) and positive family history (13 cases, 3%). Postnatal causes included hypocalcemia or hypoglycemia (7 cases, 2%), brain tumors (3 cases, 1%), breath-holding spells (21 cases, 5%), febrile convulsion (44 cases, 11%), bathing (3 cases, 1%), afebrile colds (3 cases, 1%), purulent meningitis (17 cases, 4%), DPT immunization (10 cases 2%), vaccination (7 cases, 2%) and acute hemiplegia (10 cases, 2%). The group of unknown etiology were as fns (38 cases, 9%), epilepsy associated with interictal signs (23 cases, 6%), benign infantile convulsions (57 cases, 14%), neonatal convulsion of unknown etiology (12 cases, 3%) and miscellaneous categories (4%). 3) Pregnancy was abnormal in 53% of cases with cerebral malformation. Asphyxia at birth was noted in 43% of patients with tuberose sclerosis and in 35% of congenital cerebral abomaly. 4) Pneumoencephalographic examinations revealed midline anomaly in 50% of cerebral malformation. It was abnormal in all cases with tuberose sclerosis, head injury and epilepsy with interseizure neurological signs. 5) There were no correlations between the seizure pattern and the etiology in neonatal convulsion. In infancy, focal-unilateral convulsions and infantile spasms were frequently associated with organic damages. Generalized seizures were seen in organic lesions as well as functional ones although approximately half of the cases were febrile convulsion, benign infantile convulsion or breath-holding spell. 6) EEG features of cerebral malformation were asymmetrical or multifocal dischages in neonatal period and hypsarhythmia or focal-unilateral spike discharges in infancy. Tuberose sclerosis showed hypsarhythmia in infancy. In birth injury or cerebral anoxia, EEG mostly revealed focal-unilateral abnormality or suppression-burst activity in newborns and hypsarhythmia or focal features in infants. 7) The occurrence rate of neonatal seizures in autopsy cases with intracranial pathology was demonstrated. EEG with intravenous diazepam was useful to know pathophysiology of infantile spasms.

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

41 infants who had experienced neonatal hypoglycaemia (blood glucose less than 20 mg/100 ml) were reviewed at a mean age of 51 months and compared to a group of matched controls. Symptomatic and asymptomatic infants were represented in the hypoglycaemic group in a similar ratio to that found during a previous study of the incidence of hypoglycaemia in a special care unit. Evidence of cerebral damage was found in 6 of the children who had been hypoglycaemic (14·6%) and in 5 of the controls (12·2%). This difference is not significant. The mean IQ and locomotor scores of the two groups were identical, and there was no difference in the incidence of behaviour disorders or convulsions. It is concluded that, while it is important to identify and treat cases of `true' symptomatic hypoglycaemia, the large majority of infants tolerate low blood glucose levels without sequelae. The prognosis for infants with asymptomatic hypoglycaemia is particularly good, none of the 12 infants in this series showing any evidence of cerebral damage.