Blood glucose testing in fasted neonates - anaesthesia

Risk factors

Neonatal hypoglycaemia risk factors are extensive. They include, but are not limited to:

• Prematurity

• Prolonged fasting

• Stressed infants e.g. sepsis

• Iatrogenic – including sudden cessation of glucose infusion or TPN

Symptoms and Signs

Symptoms are a poor predictor of blood glucose levels. Half of hypoglycaemic infants are asymptomatic, and half of infants with symptoms are not hypoglycaemic.
Anaesthetised patients are unable to demonstrate any symptoms, but the following may be seen in the pre-operative area if fasting has been prolonged

Signs of neuroglycopaenia:

• Abnormal cry

• Lethargy, apathy, floppiness (hypotonia)

• Poor feeding

• Jitteriness

• Apnoea

• Convulsions

Other signs occur occasionally due to catecholamine response - unusual in neonates except those with hyperinsulinaemia:

• Pallor

• Sweating

• Tachycardia

Testing

All neonates (term or pre-term) 44 weeks post-menstrual age or younger should have a blood glucose tested in theatre after induction, and before the start of surgery. The anaesthetist is responsible for knowing the post-menstrual age and asking for a glucose test. The Accu-Chek (purple theatre glucometer) or a blood gas sample is acceptable.

In SaferSleep, please document

• Post-menstrual age

• Glucose reading

• Device used to check glucose (Accu-Chek or blood gas sample)

In neonates, the Accu-Chek glucometer is accurate for glucose levels >3.0mM. A reading <3.0mM will likely indicate a need for treatment, but a blood gas sample should be taken if a precise reading is required.

If the child has had a glucose tested in the last 2 hours and the operation is brief, then testing is not required but the most recent result should be documented in the anaesthetic SaferSleep record.

Note that the Accu-Chek and lancer requires a trained user with authorised access to operate the machine.

Blood Sampling

When using the Accu-Chek device, the ideal sample is a drop of blood taken from an IV line upon insertion.

The alternative is to obtain a capillary sample using a lancet. In neonates, the recommended process is to sample from the lateral or medial heel using the Quickheel Preemie Lancet. Sampling from a finger or middle of heel is not recommended due to the risk of injury to underlying bone.

Management

Active treatment for hypoglycaemia is indicated for blood glucose levels <3.0. Although the absolute threshold for neonatal hypoglycaemia is 2.6mM, any Accu-Chek glucometer reading <3mM is not accurate, and the blood glucose level could continue to fall if surgery or fasting is prolonged.

For a blood glucose level between 3 and 4mM, a glucose infusion might be indicated if there is any risk of delays for the patient returning to feeding after surgery.

A neonate with blood glucose over 4mM may warrant a glucose infusion if prolonged surgery or a delay to feeding is anticipated

Consider a paediatrician review if there is a confirmed reading <2mM or persistent hypoglycaemia despite treatment

Glucose Containing Solutions

There are a wide range of glucose solutions available in theatres.

Options include, but are not limited to

• 1000ml bag of Plasmalyte 148 + 5% glucose – appropriate for maintenance fluids

• 50ml syringe of Plasmalyte 148 + 10% glucose – this is made by drawing up 40mls of Plasmalyte 148 with a 10ml ampoule of 50% glucose. Appropriate for maintenance fluids at a low rate (e.g. 50% maintenance). Bolus 2.5ml/kg for treatment of mild hypoglycaemia

• 10ml ampoules of 50% glucose. Undiluted, this solution is highly osmotic and corrosive to peripheral veins. Give 0.5ml/kg only in an emergency via a central line.