Control of the blood sugar level in the neonatal period.

Hypoglycaemia, as judged by adult standards, has been recorded by the majority of those responsible for approximately 50 papers on the subject of blood sugar levels in newborn infants. Most of these studies may be criticized for one or other of the following reasons. Levels vary not only between individual babies but from day to day in the same infants; this fluctuation is most marked in the first hours of life so that the range of 'normal' from birth on each day thereafter must be found and cannot be determined for the newborn period by considering the values in infants of different ages. The blood sugar has been determined after fasting periods which have been not only of varying length but also shorter than would be acceptable even in a routine laboratory investigation. The chemical method or the way in which it has been employed has been at times unsatisfactory. Among the well-known investigations are those of Kohler (1932), McKittrick (1940), Norval, Kennedy and Berkson (1949), Reis, De Costa and Allweiss (1950), Pedersen (1952), Creery and Parkinson (1953) and Komrower (1954). Of these the last three publications were concerned only with the first neonatal day, Norval's paper failed to appreciate the changes that might occur in the first hours while Reis et al. in an otherwise comprehensive study made no reference to the accuracy of their method. Of those who followed serial levels, Kohler regarded five and a half hours as a satisfactory fasting period, McKittrick accepted a miniimum of three and a half, Norval four hours and Reis et al. did not mention it. Previous workers have agreed, however, that individual babies show quite wide fluctuations while there is great variation on any one day in a group accepted as normal. Sugar levels tend to fall for some hours before becoming stabilized and the lowest figures are recorded on the second and third days when a gradual rise is usual. None of the serial studies so far, however, has taken a fast which would be acceptable at any other age, the reason probably being an unwillingness to interfere with the infant's feeding routine. Economy in blood is essential in small babies and this has led to single specimens only being analysed. Very little contamination or deterioration of reagents introduces quite wide errors and duplicate specimens are therefore more reliable. It is true also that the scrupulous conditions applied to testing a method's accuracy may not always be employed in later use. Wooton and King (1953) have shown how scattered the results on a known glucose solution may be when analysed in different laboratories while Lehmann and Silk (1952) have pointed out the difficulties in colour development and stability when duplicate analyses were made by the method of Folin and Wu or its modifications. King and Garner (1947) have also had difficulty with their modifications of this method while the familiar Folin and Wu tube is a confession of the method's instability. Many of the investigators of neonatal sugar levels have relied, however, on single determinations by this method.