<p>Glucose or dextrose is a vital source of nutrient energy and is required continuously by the fetus. Neonatal needs are met with either intermittent oral feeds or continuous IV fluids. There has been a controversy regarding definition of hypoglycemia. There is lack of concrete evidence of association between low blood glucose levels and long term neurologic sequelae. Operational thresholds i.e. what levels to treat, have been evolved. The important steps in preventing and treating hypoglycemia are to identify neonates at risk of developing hypoglycemia, to recognize symptoms of hypoglycemia, introducing early feeds and to initiate IV fluid therapy, where ever needed.</p></sec><sec id="sec002"><title>Neonates at risk of hypoglycemia

Any baby who has poor energy reserves or has high catabolic state due to sickness is at high risk of hypoglycemia. Hypothermia is one of the most important risk factor especially in small and compromised infants. Low Birth Weight (LBW) especially less than 2.0 kg, more so very low birth weight infants less than 1500gm, preterm infants less than 35 wk, Small for Gestation Age (SGA) or Large for Gestation Age (LGA) infants are at higher risk. Other predisposing factors include infants of diabetic mother, perinatal asphyxia, poor feeding, neonatal sepsis, Respirotary Distort Syndrome (RDS), Polycythemia, and shock.

Definition of hypoglycemia

Screening blood glucose level of 40 mg/dl or plasma glucose less than 50mg/dl in a newborn without or with symptoms which resolve with glucose administration is defined as hypoglycemia. Whole blood sugar is about 10–15% less than plasma sugar. Dextrostix method assesses the whole blood sugar, is a screening method and should be verified by plasma sugar where the dextrostix level is below 40.

Technique of dextrostix estimation of blood sugar

Equipment needed for performing a dextrostix is soap to wash hands, alcohol for skin preparation, test strips/glucometer and 23 gauge needle or lancets. Heel is the commonly used site for performing dextrostix. Make sure heel is not cold. Warm by rubbing, if required. Prepare the site with 70% isopropyl alcohol/spirit, using a scrubbing/circular motion. Do NOT use povidine/betadine, as specimen contamination may elevate some results. Allow spirit to dry. Failure to allow spirit to dry may contaminate the specimen and give fallacious results or destroy RBCs. Make a needle stick puncture on the postero-lateral aspect of heel. Avoid the middle portion of heel and avoid making deep punctures.

Allow a drop of blood to form and to fall on the strip. Do not rub the strip against the skin. Follow the instruction on the dextrostix bottle or glucometer. A blood sugar/dextrostix value of less than 40 mg/dl is defined as hypoglycemia. False positive readings with dextrostix are obtained with low hematocrit values (<35%) and contamination with isopropyl alcohol. False negative values are observed with high hematocrit values (>55%), when glucose values are more than 200mg/dl or there is a delay in lab analysis. The glucose level can fall by 14–18 mg/dl per hour in a blood sample that awaits analysis.

Symptoms of hypoglycemia

The symptoms of hypoglycemia are very nonspecific and can mimic any illness. The common symptoms are not looking well, lethargic, weak cry, poor feeding, temperature instability like hypothermia, poor respiratory effort, apnea or cyanosis and neurologic symptoms like: excessive jitteriness, convulsions or hypotonia. The diagnosis of hypoglycemia as the cause of above mentioned symptoms can be confirmed by the Whipple's Triad: (i) Presence of symptoms known or likely to be caused byhypoglycemia (ii) A low glucose measured at the time of the symptoms (iii) Relief of symptoms when the glucose is raised to normal. If the signs are not alleviated by IV glucose, then consider other diagnostic possibilities for the symptoms.

Management of hypoglycemia

At risk asymptomatic infants who weigh more than 1500gm or > 32 wk at birth should be initiated on early breast feeds and should be given 2 hrly feeds. At risk newborn who can't suckle at breast should be fed expressed breast milk or any other available milk with spoon/paladai or gavage feeds. If blood sugar level is low i.e. between 20 – 40mg/dl give additional feed and repeat blood sugar after ½ hour. If sugar level still remains low or is below 20 mg/dl start IV glucose. All symptomatic Infants should be started on IV fluids and underlying causes like shock, respiratory distress, sepsis, polycythemia should be appropriately managed.

How much dextrose to give

To raise the blood sugar value to normal range, give 200 mg/kg of dextrose i.e. 2 ml/kg of 10% dextrose as bolus slowly over 3–5 minutes and start maintenance fluids with a dextrose infusion rate DIR of 6–8 mg/kg/min. Repeat blood sugar estimation/dextrostix after 15–30 minutes, if still low, repeat bolus and increase (DIR) by 1–2 mg/kg/min or the maintenance fluids by 10–20 ml/kg/day. For example in a low birth weight baby on first day of life give 80ml/kg/day i.e. 80 x wt of the baby e.g. 1.8 kg i.e. 144 ml/day. Divide by 24 to obtain fluid per hour (144/24 = 6 ml/hr). Take a measured volume set, fill 1/4th or 6 hrs fluid i.e. 24 ml and deliver at a rate of 6 micro drops/min (number ofdrops per minute is equal to rate of fluid/hour). It is important to provide continuous infusion of glucose. The dextrose infusion rate can be calculated by the following formula:

How often to monitor blood glucose in hypoglycemia

The schedule for screening newborn infants at risk of hypoglycemia is arbitrary. In high-risk infants, screening for hypoglycemia should be done at 2, 6, 12, 24, 48 and 72 hr of age, prior to feeding. In asymptomatic babies measure blood glucose within 2 hr of birth, preferably before feeds. Frequency & duration depends on clinical features and glucose value, initial frequency may be 2 hrly, and later 4 hrly and finally 8–12 hrly. Monitoring is usually done for 72 hr after birth in at risk newborns or till glucose levels remain normal for 48–72 hr. Symptomatic babies may require more frequent monitoring. Maintain the same DIR till the blood glucose is stable for at least 6–8 hr. IV infusion of glucose should not be stopped abruptly, it may cause rebound hypoglycemia. Once the blood glucose have been stable for 12–24 hr and enteral feeds have been initiated and increased as the baby tolerates, the DIR should be decreased by not greater than 1–2 mg/kg/min every 2 hours with adequate monitoring. Dextrose Infusion Rate (DIR) Calculator. (From Klaus M. H. Fanaroff A.A. (Eds), Care of the High-risk Neonate, 2nd ed. Philadelphia: Saunders, 1979, p. 430.

Resistant or Persistent hypoglycemia

Requirement of a dextrose infusion rate or more than 12 mg/kg/min suggests resistant hypoglycemia. Any hypoglycemia persisting beyond one week despite adequate management suggests persistent hypoglycemia. One should rule out hyperinsulinemic state or inborn errors of metabolism. Increase the DIR to 12–15 mg/kg/min, keeping in mind that more than 12.5% dextrose should not be given through a peripheral vein and a central venous catheterization is required required. In resistant or persistent hypoglycemia the following drugs should be considered:

Hydrocortisone: 5–10 mg/kg/day in two divided doses intravenously

Glucagon: 100 μg/kg/dose (max 300μg) subcutaneous or intramuscular to a maximum of 3 doses in babies with adequate glycogen stores. Do not use glucagon in small-for-gestational age infants.

Diazoxide: 2–5 mg/kg/dose every 8 hr orally

Octreotide: Synthetic somatostatin in a dose of 2–10 μg/kg/day subcutaneously q 8–12 hr

Early and frequent breast feeds in ‘at risk’ neonates would prevent hypoglycemia in most situations. Special care should be taken in high risk neonates where adequate nutrition is delivered either through direct breast feeding or by gavage/cup or spoon feeds. Those neonates who are not able to accept enough nutrition enterally should be supplemented with continuous infusion of dextrose. In hypoglycemic neonates, the aim is to achieve normoglycemia. Avoid large or repeated boluses to prevent hyperglycemia and once blood sugars get stabilized, monitor for another 12–24 hr. Gradually build up enteral feeds and taper IV dextrose. Never stop dextrose infusion abruptly as it may cause rebound hypoglycemia. Frequent monitoring in high risk neonates, early feeds and prevention & early management of risk factors which predispose to hypoglycemia will reduce the possible risk of adverse neurodevelopmental outcome.

Simplified Approach to Case of Hypoglycemia