Academic journal article Bulletin of the World Health Organization

Hypoglycaemia of the Newborn: A Review

Academic journal article Bulletin of the World Health Organization

Hypoglycaemia of the Newborn: A Review

Article excerpt

1. Historical background

The term "hypoglycaemia" refers to a reduction in the glucose concentration of circulating blood. It is almost 100 years since hypoglycaemia was first described in children and over 50 years since it was recognized in newborn and older infants (1). In view of the numerous advances that have subsequently occurred in the care of newborn infants, it is surprising that so much controversy still surrounds the definition, significance, and management of neonatal hypoglycaemia. Paradoxically, technological developments (bedside glucose monitoring) have exacerbated rather than eased the problem by facilitating screening for an ill-characterized clinical entity.

1.1. Patterns of hypoglycaemia

The vulnerability to hypoglycaemia of premature infants and of infants born to diabetic mothers was recognized early in the history of neonatal medicine (2-5). The transient nature of hypoglycaemia and the apparent infrequency of clinical manifestations led many to assume that low blood glucose concentrations among newborn infants were innocuous and "physiological", in contrast to hypoglycaemia caused by metabolic and endocrine disease. However, in 1959, Cornblath et al. (6) described eight, 2-day-old infants born to mothers with pre-eclamptic toxaemia whose symptoms (apnoea, cyanosis, coma and convulsions) were associated with reduced blood glucose concentrations (1-24 mg.[dl.sup.-1]).(a) Infusion of intravenous glucose produced a clinical response in the infants and the course of their hypoglycaemia was self-limited but quite refractory. The outcome for this small group of infants was poor; five were normal when followed-up at 2 weeks to 11 months of age but one died and two had persistent neurological abnormalities. Subsequently further neurological sequelae associated with symptomatic hypoglycaemia (i.e. that associated with clinical signs(b) which resolve at increased blood glucose concentration) in the newborn were described.

Concern arose that hypoglycaemia without associated clinical signs (asymptomatic hypoglycaemia) might also lead to neurodevelopmental sequelae. This resulted in an attempt to define hypoglycaemia statistically as a blood glucose concentration greater than 2 SD below the mean for populations of well full-term and low-birth-weight infants. This, and the introduction in the early 1970s of reagent strip glucose assays (e.g. Dextrostix[TM]) for cotside screening of newborns at risk, led to clinical classifications of neonatal hypoglycaemia (7, 8). Gutberlet & Cornblath estimated the prevalence of hypoglycaemia (defined as serum glucose concentration [is less than] 30 mg per 100 ml(a)) as 4.4 per 1000 total inborn live births (15.5 per 1000 low-birth-weight infants) (8). Lubchenco & Bard reported much higher levels: 11.4% of all nursery admissions and 20.3% of premature or low-birth-weight infants had blood sugar concentrations [is less than] 30 mg per 100 ml if screened before feeding at 6 hours of age (9).

Estimating the exact frequency of asymptomatic hypoglycaemia clearly needs, as a prerequisite, a quantitative definition of the condition. This is dealt with in Section 4 but it is worth noting that transitional hypoglycaemia is a common problem in both industrialized and less developed countries, although few formal studies have been carried out in the latter. However, Anderson et al. observed that 38% of uncomplicated term infants born in Kathmandu, Nepal, had a blood glucose concentration of [is less than] 2.6 mmol.[l.sup.1] during the first 50 hours of life (10). An approach aimed first at the prevention of hypoglycaemia, second at its reliable detection in neonates at risk, and third at appropriate treatment that will not be deleterious to breastfeeding is thus of global importance.

1.2. Symptomatic and asymptomatic hypoglycaemia

Despite clinical characterization of neonatal hypoglycaemia on the basis of blood glucose concentration, there was controversy as to whether hypoglycaemia, particularly in the absence of clinical signs, caused or was merely associated with neurodevelopmental sequelae. …

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