The goal of this observational study is to investigate if diathermy (a surgical tool that uses electrical energy to control bleeding) has any affect on the accuracy and functioning of continuous glucose monitoring systems in adults and young people with Type 1 Diabetes. The main questions this study aims to answer is -

- Does the accuracy of continuous glucose monitoring systems change after use of diathermy?

Participants will:

• Have their height and weight checked.
• Provide information about their medical history including type of diabetes, other medical conditions and any current medications they take.
• Have paired glucose meter and sensor glucose measurements taken every 15-75 minutes from up to 4 hours before surgery until up to 4 hours after the end of surgery.
• Have two blood samples taken to measure glucose levels, The first one will be before the use of diathermy and the second will be after the use of diathermy.

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).

Study design:

This is a single-centre, prospective, single-arm, observational, non-inferiority study of adults and young people with diabetes using CGM systems. 126 participants will be recruited. Sample size was calculated using simulation.

Participants will undergo paired glucometer and sensor glucose measurements every 15-75 minutes from up to 4 hours before the planned time of surgery until up to 4 hours after the completion of surgery, for not more than 24 hours. They will also have two venous blood samples taken for glucose concentration analysis.

Patient recruitment:

Participants will be recruited from patients due to have an elective surgical procedure at Nottingham University Hospital NHS Trust. The initial approach may be from a member of the patient's usual care team with consent to share contact details with the study team. In addition, the Trust's Theatre Management system (Nervecentre) will be reviewed to identify patients with type 1 diabetes who are due to attend for surgery.

Data management and analysis:

Data will be collected by members of the research team using study specific case report forms (CRFs). An ANOVA mixed effects model will be used with participant as a random effect and pre/post diathermy as a fixed effect. An equivalence F-test with an ARD equivalence value of 0.05 will be performed to determine effect of diathermy on ARD.

Quality assurance plan:

Monitoring of study data shall include confirmation of informed consent; source data verification; data storage and data transfer procedures; local quality control checks and procedures, back-up and disaster recovery of any local databases and validation of data manipulation. Entries on CRFs will be verified by inspection against the source data. A 10% sample of CRFs will be checked on a regular basis for verification of all entries made. In addition, the subsequent capture of the data on the study database will be checked. Where corrections are required, these will carry a full audit trail and justification. Study data and evidence of monitoring and systems audits will be made available for inspection by the REC as required.

Reporting adverse effects:

Intraoperative glucose monitoring is currently undertaken using blood glucose meters. The same monitoring will be continued through this study and this study involves no deviation from standard care. Sensor glucose measurements are passively recorded from the participant's receiving device and eligible participants would already be routinely using sensors as part of their diabetes care.

Equipment failure issues, where a sensor or blood glucose measurement is not able to be obtained, will be recorded on the CRF. Adverse events as a result of participation within this study are not expected but will be recorded on an Adverse Event Form if any occurs. Clinical deterioration and surgical complications, not related to the study, will be considered expected in terms of classification.

Inclusion Criteria:

• Diagnosis of type 1 diabetes mellitus.
• Planned admission for elective surgery at Nottingham University Hospitals NHS Trust.
• Currently routinely using a prescribed Abbott Libre-2, Abbott Libre-3, Dexcom G6 or Dexcom G7 glucose monitoring system to monitor glucose concentrations.
• Aged 4 years or older on the day of surgery.
• Ability to give informed consent / ability of parent/carer to give informed consent (as appropriate).

Exclusion Criteria:

• Use of paracetamol above maximum dose within 7 days before the scheduled date of surgery (in adults with body weight under 51kg - maximum of 60mg/kg per day, in adults with body weight 51kg and above - maximum of 4g per day, in children - maximum dose as per their age as stated in the British National Formulary for Children)
• Any use of hydroxyurea within 7 days before the scheduled date of surgery
• Use of more than 500mg per day of ascorbic acid / vitamin C within 7 days before the scheduled date of surgery
• Currently taking medications as part of a clinical trial.

Patients aged 4 or older with type 1 diabetes mellitus scheduled to undergo elective surgery at Nottingham Universities Hospitals NHS Trust.