Continuous glucose monitoring (CGM): Inpatient (Guidelines)

There have been significant advances in diabetes care in recent years, including the development of technological solutions. More patients are now using CGMs for testing blood glucose.

• There needs to be an agreed plan with the DNS before using CGM. Contact: nhsh.dsninpatientreferral@nhs.scot.
• If a sensor is being used in hospital, at least two CBG tests should also be performed in a 24 hour period.
• For insulin pump patients, see specific guidance on the use of CGMs.

Alarms

If the patient with diabetes is capable of using their CGM, they should be encouraged to do so as they do out of hospital. Alarms are useful to trigger a capillary glucose reading and consideration of intervention by ward nursing staff.

Placement

Avoid placing CGM sensors on the abdomen in the prone individual, as increased pressure whilst lying on it may reduce sensor accuracy.

• Libre sensors are only licensed to be worn on the subcutaneous tissue on the back of the arm.
• Dexcom can be worn on back of arm or abdomen.

As per manufacturer guidance, ensure CGM devices are not inserted into an area of generalised oedema or cellulitis.

Supply

Patients are encouraged to maintain their own supply of sensors whilst in hospital as they are GP funded.

For any person with diabetes admitted to hospital, particularly type 1 diabetes and insulin-treated type 2 diabetes, check whether they use any wearable technology. If admitted unconscious, check for CGM (usually worn on the arm or abdomen) which should be removed and routine point-of-care CBG testing done at the recommended frequency.

Removing sensor prior to MRI/CT

Cardiac arrest

• CGM devices should ideally be removed for external DC cardioversion (but do NOT delay CPR).
• Do not use CGM glucose to guide treatment of hypoglycaemia in cardiac arrest.

Patients should be familiar with removing their own sensor as below:

1. Wash hands with soap and water (put gloves on if doing it for the patient).
2. Gently peel up the adhesive edge of the sensor.
3. Slowly peel the sensor away from the skin in a single motion.
4. Use warm soapy water, adhesive removal, or alcohol to help take it off.
5. Sensor can be put in clinical waste (some Dexcoms come in 2 parts; a sensor and a transmitter. The transmitter is designed to last for 90 days, so please keep in a safe place).

JBDS-IP define an acceptable difference as being within ±20% difference between CGM and CBG glucose levels.

Reasons for ensuring capillary glucose checks are performed in hospital include that these are quality assured, and that point of-care glucose results may be linked to safety systems and to the diabetes team.

If the discrepancy is significant, more frequent CBG monitoring is advised for next few hours (depending on clinical need)

• For CGM devices that can be calibrated (e.g. Dexcom G6 and Decom 1+) consider calibration with point-of-care glucose using a blood glucose meter, and use if accurate.
• If the discrepancy persists, remove the sensor, and replace.
• As above, ensure CGM devices are not inserted into an area of generalized oedema or cellulitis as this could cause inaccuracies

Readings can be affected by acute illness, systemic shock, and some medications (notably paracetamol, aspirin and vitamin C), though this should NOT stop you prescribing these medications.