Neonatal Hypoglycemia - Current Concepts

Hypoglycaemia is a common problem in the neonatal period, and it frequently reflects difficulties in adapting to extra uterine life. Strategies to facilitate this physiological adaptation should be enhanced. (Sem fetal neo del 2005) Incidence is variable depending on the definition criteria used in different studies, but according to Cornblath (Cornblath et al 1993, 2000 as cited by Fernández Loranzo et al 2011) it varies from 5-7% in term newborns and from 3.2 to 14.7% in preterm infants. Respective to weight, it occurs in 8% of Large for Gestational Age (LGA) and up to 15% of Small for Gestational Age (SGA) infants. There is still no universal consensus on how to define hypoglycaemia. Establishing a universal cut-off glucose value is difficult and considerations must be made regarding the measuring device used, type of sample (blood, serum or plasma), moment of measurement after birth, duration and degree of hypoglycaemia and characteristics of the newborn. Based on the World Health Organization (WHO) recommendations (WHO 1997 as cited by Fernández Lorenzo et al 2011) thresholds would be: Sick newborn, (signs of illness): <2.5mmol/L or 45 mg/dL Healthy term / preterm (feeding well): < 1.1 mmol/L or < 19.8 mg/dL Most expert authors support the cut-off value of 36mg/dL for asymptomatic healthy newborns, rather than the WHO suggested threshold, and some authors even suggest that values down to 1.7mmol/L should be accepted in an otherwise healthy term infant (Fugelseth 2001). In a recent review on neonatal hypoglycaemia, operational thresholds of less than 40mg/dL (2.2mmol/L) during the first 24 hours and less than 50mg/dL (2.8mmol/L) thereafter are suggested (Chan 2011). Other definitions have been suggested such as using an epidemiological concept: considering hypoglycaemia when glucose levels are 2 standard deviations below the mean value for infants of the same age (which would be around 20-30mg/dL). However, this value does not seem like the optimal threshold, so this definition is rarely used in clinical practice or for study purposes. Experts agree that the neurological disabilities associated to neonatal hypoglycaemia depend on gestational and chronological age and associated risk factors such as HypoxicIschemic Encephalopathy (HIE) and that they frequently result after situations of persistent and severe hypoglycaemia (Fernández Lorenzo et al 2011). What is more, the vast majority of healthy term newborns with isolated glucose levels under the target of 45 mg/dL will have a normal neurological prognosis. (Hay et al 2009) Recent consensus workshop (Straussman & Levitsky 2010) results reveal that there has been little progress in establishing a clear numerical definition for hypoglycaemia, but