Assessing the Impact of Intraoperative Diathermy on Accuracy and Functioning of Glucose Monitoring Systems

Background and rationale:

The incidence of type 1 diabetes is rising and technology is an increasingly important part of monitoring and responding to glucose levels. Contemporary monitoring of glucose levels using continuous glucose monitoring (CGM) systems provide users with information about their glucose levels in real time without finger-prick capillary glucose testing. Crucially, these new systems provide information about the trend in blood glucose levels and is now standard in type 1 diabetes. Use of CGM systems is also needed for patients who use "closed loop" systems which adjust insulin at, typically, 5-minute intervals in response to glucose levels. Use of these strategies in glucose level monitoring and management improves long-term outcomes for persons living with diabetes and is now standard of care in type 1 diabetes. Their importance during inpatient admissions and surgery is increasingly recognised but data is limited.

During surgery, diathermy is often used to control bleeding by using high-frequency electrical energy to seal small blood vessels. Available literature supports the hypothesis that CGM systems may not be affected by diathermy, but there is limited information on the actual impact of diathermy on the accuracy of CGM systems. At present, CGM systems warranties are invalidated by diathermy use. Consequently, patients undergoing surgery require a period of blood glucose testing to monitor and respond to glucose levels which are often rendered unstable in the period around surgery. This exposes patients to potentially unnecessary interventions and, for those patients who are needle-phobic or have learning difficulties, the need to renew repeated finger-prick capillary blood testing around surgery may be a significant barrier to effective and optimal glucose monitoring and control. In addition, there may be a delay in responding to hypoglycaemia and hyperglycaemia, due to the time between measurements.

This study aims to assess the impact of intraoperative diathermy use on the accuracy and functioning of CGM systems. Demonstrating that glucose monitoring systems could be effectively used during surgery would:

• Prevent/reduce the need for the anaesthetic team to access the patients' fingers/toes and venous/arterial lines for blood glucose testing during surgery.
• Provide easy, convenient and accurate glucose monitoring to the anaesthetic team, with data transmitted from monitoring systems which can remain underneath surgical coverings.
• Provide prompt, real-time information on glucose trends during surgery, leading to better control of glucose levels including earlier recognition of low and high glucose levels (hypoglycaemia and hyperglycaemia, respectively).