NEONATAL HYPOGLYCAEMIA

Dorothy Millar ST3

Learning Points

Symptomatic vs. asymptomatic Babies at risk Why its important Management on postnatal wards Rarer causes Summary

Asymptomatic hypoglycaemia Brief period of asymptomatic

hypoglycaemia is universal in babies Term babies mount a brisk response and

can use alternative fuels (brown fat) No evidence this episode is harmful in

these babies

Symptomatic

Symptoms that suggest hypoglycaemia is likely to cause brain damage include Apnoea Seizures Coma

Symptomatic hypoglycaemia in a term baby without risk factors is unusual and requires investigation

About 30% of babies with the above symptoms will have severe neurological abnormalities (severe LD, spastic quadriplegia)

Babies at risk

Low birthweight (<2.5kg) Preterm (<36/40) Macrosomic babies Hypoxia Infants of diabetic mothers Polycythaemia (Poor feeding)

Symptoms of hypoglycaemia Jittery Drowsiness, lethargy Poor feeding Hypothermia Hypotonia Cyanosis Apnoeas Seizures Coma

Causes of hypoglycaemia

Poor feeding Sepsis Hypothermia Transient Polycythaemia Hyperinsulinaemic hypoglycaemia Syndromes Metabolic disease

Management on postnates

Babies at risk: Infants in a cold

environment Preterm <37 or post

term ≥42 weeks IUGR or LBW <2.5kg Infants of diabetic

mothers OR birthweight >4.5kg

Babies who require resus Babies not tolerating

feeds Mum on Beta blockers

(Breast)feed early Keep warm Regular BM’s (not before

4hrs of age) Pre-feed BM’s

Sporadic Neonatal hyperinsulinism

up to 50% with 5% persistent Polycythaemia Macroglossia Macrosomia/

hemihypertrophy Abnormal ear helix Abdominal wall defects

umbilical hernia/ omphalocele) Associated with Wilm’s

tumour 6.5% so need regular screening

Beckwith-Wiedemann syndrome

Endocrine causes

May be multiple or single endocrinopathy

Panhypopituitarism Hypoglycaemia, prolonged jaundice,

hyponatraemia, small genitalia Congenital adrenal hyperplasia

Salt wasting (males), ambiguous genitalia (girls)

Hypothyroidism

Inborn errors of metabolism

Glycogen storage diseases Type 1 – Von Gierke’s Glucose 6 phosphatase deficiency

Galactosaemia Medium chain acyl-CoA dehydrogenase

deficiency (MCAD) No tolerance of fasting (cannot use

alternative fuels Leads to hypoglycaemia - ?SIDS

Aminoacidopathies

Hyperinsulinaemic hypoglycaemia Inappropriate secretion of insulin by

pancreas Insulin drives glucose into sensitive tissues

(skeletal muscle, liver, adipose) Inhibits glucose production (glycolysis and

gluconeogenesis) Suppresses fatty acid release and ketone

synthesis Therefore high risk of brain injury as brain

deprived of both glucose and ketones

Causes of hyperinsulinism

Congenital Secondary to risk factors (maternal DM,

birth asphyxia, IUGR) Associated with syndromes (BW) Rare metabolic syndromes (eg

congenital disorders of glycosylation)

Clinical features

Presents with severe hypoglycaemia in neonatal period

Refractory to feeds; infants need IV Dextrose in high concentration

Macrosomic due to fetal hyperinsulinism This also causes HCOM and hepatomegaly Those due to “risk factors” tend to be

transient However, IUGR + perinatal asphyxia can

have a protracted course

Diagnosis

IV glucose dependence Over 8mg/kg/min ( normal =

4-6mg/kg/min)

Glucose requirement = ml/h x % dextrose

(mg/kg/min) 6 x weight (kg)

Diagnosis (cont.)

Inappropriate serum insulin and c-peptide levels for the glucose level ie a normal insulin level at a low blood

sugar is an inappropriate response May also be a blunted counter-

regulatory response Low cortisol and glucagon levels

Acute Management

Priority is to maintain normoglycaemia Higher threshold of hypoglycaemia (3.5 –

6mmol) Require central access for >12.5% dextrose Oral feeds with extra CHO (eg Maxijul) plus

IV Dextrose IM glucagon in emergency However high doses causes paridoxical

insulin release so also need IV dextrose

Long term management

Diazoxide Blocks ATP channels to prevent depolarisation

of β cell membrane Causes fluid retention (esp in neonates) Often used with chlorthiazide which has

hyperglycaemic properties Octreotide + frequent feeding

Long acting Somatostatin analogue Inhibits release of insulin

Genetic analysis, 18FDOPA-PET scan, Surgery

Summary

Babies can be symptomatic or asymptomatic

Important to recognise babies at risk Untreated can lead to brain injury and long

term consequences Values vary between centres but at NGH is

<2.6 mmol/L Different causes compared with older

children HH is rare but important to treat swiftly