Metabolic Disturbances, Inborn Errors of Metabolism, Endocrine Disorders and Drug Withdrawal

Chapter 36 Metabolic Disturbances, Inborn Errors of Metabolism, Endocrine Disorders and Drug Withdrawal



Metabolic disturbances



Glucose homeostasis


Following birth there is a fall in glucose concentration. At the same time endocrine changes (decrease in insulin and a surge of catecholamines and release of glucagon) result in an increase in:



image glycogenolysis (breakdown of glycogen stores to provide glucose)


image gluconeogenesis (glucose production from the liver)


image ketogenesis (producing ketones, an alternative fuel)


image lipolysis (release of fatty acids from adipose), bringing about an increase in glucose and other metabolic fuel.


Problems arise in the newborn:



image when there is a lack of glycogen stores to mobilise (preterm and growth-restricted infants), or


image when there is excessive insulin production (infants of diabetic mothers), or


image when infants are sick and have a poor supply of energy and increased requirements.



Hypoglycaemia


The definition of hypoglycaemia is controversial. Currently a cut-off value in the newborn is 2.6 mmol/l. Signs of hypoglycaemia are listed in Box 36.1.



Box 36.1 Signs of hypoglycaemia




• Lethargy


• Poor feeding


• Seizures


• Decreased consciousness level


• Jitteriness (although this is common in the newborn and on its own is not indicative)



Infants at risk of neurological sequelae of hypoglycaemia




image Preterm babies (of less than 37 weeks).


image Growth-restricted babies (less than third centile for gestation).


image Babies of diabetic mothers.


image Sick term babies, e.g. septic or following perinatal hypoxia–ischaemia.


image Babies with inborn errors of metabolism.



Diagnosis, prevention and treatment of hypoglycaemia


Healthy term babies tolerate low blood glucose concentrations by using alternative fuels such as ketone bodies, lactate or fatty acids. Breastfed babies are a group who are particularly likely to have low blood glucose concentrations, probably because of the low energy content of breast milk in the first few postnatal days. Because of their ability to compensate, clinically well, appropriately grown term babies who are feeding do not require monitoring of their glucose concentration. Doing so would result in many infants being inappropriately treated.


Babies at risk of neurological sequelae should be monitored and hypoglycaemia prevented by:



image adequate temperature control – keep the babies warm


image early feeding (within 1 hour of birth) with 100 ml/kg/day if formula feeding


image frequent feeding (3 hourly or less)


image blood glucose check immediately before the second feed and then 4–6 hourly.


As long as there are no symptoms, there is no advantage to checking the blood glucose concentration earlier than this, as it is likely to be low and the appropriate treatment at that stage is to feed the baby. If there are symptoms, the glucose should be checked and treatment given immediately. Breastfed babies are particularly difficult in this situation because it is important to avoid supplemental feeding with formula to promote successful breastfeeding; the risks associated with significant hypoglycaemia in at-risk infants outweigh this consideration.



image If the blood glucose concentration is < 2.6 mmol/l, then feed should be given at an increased volume and decreased frequency (2 hourly or even hourly). This may require supplementary feeding with formula milk in infants who are breastfed, and/or nasogastric tube (NGT) feeding. Breast milk can also be expressed to be given via an NGT.


image If the blood glucose concentration remains low despite these measures and there is an adequate feed volume intake then intravenous treatment with dextrose is required. It is important in this situation that enteral feeding is continued, as feed contains much more energy than 10% glucose and promotes ketone body production and metabolic adaptation.


image If the blood glucose concentration is > 2.6 mmol/l before the second and the third feed, then glucose monitoring can be discontinued but feeding should continue at 3-hourly intervals.


image In infants where enteral feeding is contraindicated for some reason, then intravenous 10% dextrose at least 60 ml/kg/day should commence.



Hyperglycaemia


Hyperglycaemia occurs predominantly in preterm and severely growth-restricted babies. It is also seen in term infants in response to stress, especially following perinatal hypoxia. In general, no treatment is required.



Electrolyte imbalances in the newborn



Postnatal weight loss, fluid and electrolyte changes


All babies lose weight due to a loss of extracellular fluid. Weighing in the first few days is only needed when babies are unwell or if there are concerns about intake and fluid and electrolyte balance.



Sodium


Sodium is normally excreted via the kidney, controlled by the renin–angiotensin system. This control mechanism is functional in the preterm infant but loss of sodium may occur because of renal tubule unresponsiveness. Term breast milk has relatively little sodium (< 1 mmol/kg/day), showing that the normal newborn can preserve sodium via the kidney in order to maintain growth. Normal sodium requirements are 1–2 mmol/kg/day in term infants and 3–4 mmol/kg/day in preterm infants.


The normal serum sodium concentration is 133–146 mmol/l. Changes in serum sodium reflect changes in sodium and water balance. In order to assess changes in sodium concentration it is important to know an infant’s weight.



Hyponatraemia


Hyponatraemia is due to either fluid overload or sodium depletion.



image Hyponatraemia in the presence of weight gain represents fluid overload.


image A low sodium with inappropriate weight loss represents sodium depletion.


The latter may be due to inadequate intake or excessive losses.



Hypernatraemia




image Hypernatraemia in the presence of a loss of weight suggests dehydration.


image When there is weight gain, hypernatraemia is due to fluid and sodium overload.

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Related posts:

  1. The Placenta
  2. Prolonged Pregnancy and Disorders of Uterine Action
  3. Obstetric Emergencies
  4. Problems of Pregnancy

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Jul 11, 2016 | Posted by in MIDWIFERY | Comments Off on Metabolic Disturbances, Inborn Errors of Metabolism, Endocrine Disorders and Drug Withdrawal

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