Hypoglycaemia

Introduction

Avoidance of hypoglycaemia is a key priority in patients being treated for hyperglycaemia on critical care. Hypoglycaemia is associated with a significantly elevated risk of mortality in critically ill patients and the effect may be related to the severity of the hypoglycaemia.

Hypoglycaemia may be absolute or relative. Patients with pre-existing diabetes with poor control may exhibit cardiovascular, hormonal and neurological changes at low-normal levels. Aggressively targeting a blood glucose in the “normal” range may be harmful in these patients.

Minimising hypoglycaemia in Critical Care consists of three aims:

1. Avoidance
2. Treatment
3. Learning from Hypoglycaemia.

Avoidance of Hypoglycaemia

Monitoring of blood glucose should be 1 hourly when on an insulin infusion. If blood glucose has been stable and between 6 – 10 mmol/L for the last 4 hours, then extend to 2 hourly intervals.

Monitoring frequency should increase to every 30 minutes if blood glucose has dropped below 6.0mmol/L and on an insulin infusion until glucose has been demonstrably stable above 6.0 mmol/L for 2 hours. The insulin infusion should be stopped (as guided by the dynamic calculator) until this is achieved.

For patients on 2 hourly monitoring, any period of instability in either the patients’ glucose control or in their general condition should prompt return to one hourly monitoring until stability is regained.

Blood glucose should be monitored at a minimum of every 4 hours when on a long acting subcutaneous insulin regardless of mode of nutrition

Minimise interruptions to glucose supply. Any patient receiving enteral feed which is interrupted either deliberately (e.g. for procedures) or unintentionally (e.g. due to tube displacement) should be managed according to the following protocol:

Anticipated stop for transfer or procedure

• Stop insulin 1 hour before
• Monitor blood glucose every hour as per standard monitoring protocol

Unanticipated stop (e.g. NG tube displacement or urgent scan)

• Stop Variable Rate Insulin Infusion immediately
• Increase frequency of monitoring to every 30 minutes for 2 hours.

Feed stopped for > 2 hours

• Stop Variable Rate Insulin Infusion
• Consider prescription of 10% glucose infusion at 50 mls/hr

Treatment of Hypoglycaemia

Management of an episode of hypoglycaemia in Critical Care should be according to a treatment protocol that is weighted differently to ward areas. This reflects the patient population being less likely to be conscious and able to report hypoglycaemia symptoms and the likelihood of central venous access making the use of 50% glucose safe and more practical. Management involves the selection of an appropriate glucose preparation, administration, subsequent monitoring and repeated administration as necessary: see algorithm below.

Hypoglycaemic Emergency

Treatment should be initiated as a clinical emergency if blood glucose < 4.0mmol/L – remember "Four is the Floor"

• Stop insulin infusion

• If central access present: administer 50ml of 50% glucose via CVC or PICC line over 10 minutes followed by a 0.9% saline flush.

• If no central access present: administer 250ml of 10% glucose via peripheral cannula over 15 minutes.

• For patients suitable for stepdown to a general ward or with a normally functioning enteral route it is also appropriate to use the ward-based hypoglycaemia algorithm.

• Recheck blood glucose at 15, 30 and 60 minutes or until > 4.0 mmol/L — repeated doses of glucose may be required.

Learning from Hypoglycaemia

It should be recognised that hypoglycaemia is a common and sometimes unavoidable side effect of glucose management in Critical Care. The causes of hypoglycaemia are often multifactorial and steps should be taken to minimise further episodes where possible.

The use of incident reporting for episodes of hypoglycaemia is encouraged to allow learning from these events.

Patients at High Risk of Hypoglycaemia

1. Interruptions in glucose supply – such as NG feeding / tube displacement.
2. Type 1 diabetes or those deemed insulin sensitive.
3. Use of basal insulins especially in those with hepatic or renal impairment
4. Injecting insulin into the arm
5. Mismatch of meal-time insulin to meals
6. Long-acting sulphonylurea agents
7. History of hypoglycaemia unawareness

Algorithm