Care with interstitial (percutaneous) continuous glucose monitoring (CGM) devices
When a patient needs to have their blood glucose levels monitored intraoperatively, it is recommended that anaesthetists primarily rely on capillary blood samples (such as finger prick) or laboratory blood analysis (such as blood gas machine).
ANZCA has recently received a report via webAIRS in which a patient’s continuous glucose monitoring (CGM) device, situated on their upper arm while they were under anaesthesia, recorded false low readings. This was discovered after an initial intervention when the patient’s capillary glucose levels from their ear lobe was subsequently checked. While the reason for the inaccurate readings is unclear, these devices can be displaced or disrupted by pressure such as a tourniquet or blood pressure cuff being placed on top of them.
Regarding the CGM devices themselves:
- Ensure no pressure – for example, tourniquet or blood pressure cuff – is placed over a CGM device intraoperatively.
- Consider whether any intraoperative equipment – for example, diathermy – may be used that could potentially cause electrical interference with a digital CGM device or its signal.
- Rapid changes in glucose levels may not be detected as the response time for changes in blood glucose levels to be reflected by the interstitial monitoring device can be five to 15 minutes.
- Verify any readings prior to administering insulin or glucose.
References:
- Perez-Guzman MC, et al. Continuous Glucose Monitoring in the Operating Room and Cardiac Intensive Care Unit. Diabetes Care. 2021 Mar;44(3):e50-e52. doi: 10.2337/dc20-2386
- American Diabetes Association Professional Practice Committee for Diabetes. 16. Diabetes Care in the Hospital: Standards of Care in Diabetes-2026. Diabetes Care. 2026 Jan 1;49(Supplement_1): S339-S355. doi: 10.2337/dc26-S016.
