Hypoglycaemia

Summary
Introduction
Diagnosis
Investigation
Prevention
Management
Areas Of Uncertainty In Clinical Practice

Summary

reagent stick screening of blood glucose concentrations is not accurate at low levels
most asymptomatic infants can be initially fed an increased volume of milk, and only if hypoglycaemia persist should an IV glucose infusion be started
without a good evidence base for patient management, operational thresholds can be used to guide clinical practice

Introduction

Management of hypoglycaemia is complicated by

an inherent inaccuracy of reagent sticks
being mostly asymptomatic or having symptoms that are non-specific
a lack evidence from randomised clinical trial with long-term outcome data

Diagnosis

Infants with the following clinical features should have their blood glucose checked

CNS excitation
- jitteriness
- high-pitched cry
- seizures
CNS depression
- lethargy
- apnoea
- poor feeding

Since the majority are asymptomatic, infants at risk for hypoglycaemia should also have their blood glucose checked on arrival in the nursery. This includes infants with

reduced glycogen stores or increased glucose demands
- prematurity
- IUGR
- perinatal asphyxia
- hypothermia
- RDS
- sepsis
hyperinsulinaemic states
- infants of diabetic mothers
- Rhesus isoimmunisation
- Beckwith-Weidemann syndrome
  - microcephaly
  - umbilical hernia
  - macroglossia
  - hypoglycaemia
- islet cell hyperplasia
- pancreatic tumour

Investigation

reagent sticks used for screening may overestimate the occurrence of hypoglycaemia. It is important to confirm suspected hypoglycaemia with a true blood glucose estimation on at least one occasion.
the infant of a diabetic mother and those admitted to intensive care should have screening performed promptly after arrival in the nursery. For other at risk infants testing should be performed at three hours of age and continue three hourly until 2 successive readings >2.6mmol/L are obtained.
infants with blood glucose < 2.6 mmol/L should have hourly blood glucose determinations until stable >2.6mmol/L.
premature infants who can be fed early after birth (appropriate for gestational age infants <34 weeks gestation)generally will only require screening before the first two 3 hourly feeds. Other at risk infants require continued screening before every second feed until 24 hours of age.
congenital adrenal hyperplasia can present with hypoglycaemia. Failure to investigate and promptly treat these cases of ambiguous genitalia can be disastrous
if > 10 mg/kg/min of IV glucose is required for normoglycaemia initiate diagnostic steps for hyperinsulinism. When the true blood sugar is < 2.0mmol/L, test urine for ketones and send venous or arterial blood for
- glucose
- insulin
- growth hormone
- cortisol
- free fatty acids

Prevention

If able to take enteral feeds, commence by 1-2 hours of age. Feed frequently either 2 hourly or 3 hourly if risk is low. Use expressed breast milk or full strength formula at 60 mL/kg initially, increase to 90 mL/kg by 24 hours according to tolerance.

If only able to have IV fluid, commence 10% glucose at 60-90mls/kg/24 hours (4-6 mg/kg/min of glucose). If fluid restriction is required increase the concentration of dextrose in the infusion.

Management

Oral Feeds. If a hypoglycaemic infant is able to tolerate enteral feed, this should be given and the blood glucose determined an hour later and before next feed.

IV Glucose. If the infant is unable to tolerate enteral feeds or if there is no response to the above measure:

An IV bolus of 200-300 mg/kg glucose (2-3 ml/kg of 10% glucose)

This is followed by a continuous IV infusion of 10% glucose at 120 mL/kg/d (8 mg/kg/min glucose) to prevent rebound hypoglycaemia. If fluid restriction is necessary, give more concentrated glucose solution (up to 15% with peripheral IV). IV infusion of solutions with >12.5% glucose are best given through a central line in order to avoid complications.

Once the blood glucose normalises, enteral feeds can be reintroduced and the infusion tailed off.

Prescription to make up a 50mL solution of various glucose infusions

Infusion Concentration	Volume of 10%Glucose	Volume of 50%Glucose
12.5%	46.5mL	3.5mL
15.0%	44.0mL	6.0mL
17.5%	40.5mL	9.5mL
20.0%	37.5mL	12.5mL

Glucagon. In infants with adequate glycogen stores (eg. hyperinsulinaemic states) whose hypoglycaemia persists in spite of an IV infusion: An IM statim injection of glucagon 0.3 mg/kg (0.3 u/kg). This may be repeated once only if there is good initial response.

If hypoglycaemia recurs or persists despite IV infusion of 15% dextrose at 120ml/kg/d (12mg/kg/min glucose), an IV glucagon infusion should be considered (1-2 mg/kg/d) while arrangements are made to transfer the infant to a Level 3 centre for continued treatment.

Other Treatments. Corticosteroids (eg Hydrocortisone, 5-10mg/kg/24hours IM/IV) are required rarely in severe hypoglycaemia to raise blood glucose levels. The use of diazoxide and pancreatic surgery is extremely rare, but may need to be considered in profound intractable hypoglycaemia secondary to hyperinsulinism.

The cause of hypoglycaemia (e.g. hypothermia, sepsis) must also be treated.

References

WIlliams AF. Neonatal Hypoglycaemia: Clinical and legal aspects Seminars in Fetal & Neonatal Medicine 2005; 10: 363-368

Koh THHG, Aynsley-Green A, Tarbit M, Eyre JA. Neural dysfunction during hypoglycaemia. Arch Dis Child 1988;63:1353-1358.

Lucas A, Morley R, Cole TJ. Adverse neurodevelopmental outcome of moderate neonatal hypoglycaemia. Br Med J 1988;297:1304-1308.