Neonatal hypoglycemia

Reduced blood glucose (hypoglycemia) is one of the more common metabolic emergencies during the neonatal period, which in a small minority of cases results in permanent brain damage. It remains unclear how low blood glucose concentration must fall for such devastating effect. This gray area of understanding is illuminated somewhat by the results of a literature-based research conducted at UCLA School of Medicine in Los Angeles.

Using a MEDLINE search under the heading "neonatal hypoglycemia", the authors of this study identified all English-language studies on the subject dating back over four decades. From this massive database they selected 16 studies for detailed analysis. 

The criterion for selection of these 16 studies was that they include case histories of well-documented brain damage attributed to hypoglycemia during the first hours and days of life. In total, analysis of the 16 studies revealed 89 such cases. 

In all 89 cases plasma glucose was less than 32 mg/dL (1.8 mmol/L) and in more than 95 % of cases, plasma glucose was less than 25 mg/dL (1.4 mmol/L). The diagnosis of hypoglycemia was made more than 10 hours after birth in 95 % of cases. 

Within the 16 selected studies were seven studies in which there were case histories of neonatal hypoglycemia, both with and without attendant permanent brain damage. From these seven studies the authors identified all 159 cases in which plasma glucose was less then 25 mg/dL. Of these 159, just 33 (21 %) suffered permanent brain damage.

The authors conclude that the data they have collated from studies stretching back 40 years suggests that plasma glucose of 25 mg/dL (1.4 mmol/L) might be an operational lower threshold for possible permanent brain damage; their evidence suggests that around 20 % of infants with this degree of hypoglycemia in the immediate postnatal period suffer permanent brain damage.