The goal of this multi-center, pragmatic, randomized controlled trial is to assess the effectiveness of continuous glucose monitoring (CGM) compared with conventional monitoring in enhancing surgical outcomes for diabetic patients. The main questions it aims to answer are:

• To assess the effectiveness of CGM compared with conventional monitoring in reducing the comprehensive complication index (CCI) for patients with diabetes or impaired glucose tolerance (IGT) within 30 days after surgery.
• To analyze the impact of different age groups, types of surgery, preoperative levels of HbA1c, and preoperative 24h glycemic variations on the improvement of surgical outcomes under the CGM model.

Participants will receive CGM prescribed by the attending physician for at least 6 hours before surgery. Glucose monitoring should be continued until the 7th day after surgery or discharge.

The investigators will compare conventional monitoring group to see if CGM could reduce the CCIs for patients with diabetes or impaired glucose tolerance within 30 days after surgery.

Abstract: Postoperative complications are important factors in reducing surgical quality and increasing healthcare costs. The CCI is an internationally recognized index to quantify postoperative complications. Patients with diabetes mellitus (DM) or IGT are more prone to developing dysglycemia during the perioperative period, which in turn leads to various types of complications and increased mortality, as evidenced by a significant increase in CCI. Our previous study confirmed that strict glucose management in the perioperative period can help reduce the incidence of postoperative complications such as surgical site infections (SSIs), but this strategy has not been replicated in the perioperative period due to the disadvantages of heavy and complex operations and the possible increased risk of concomitant hypoglycemia. CGM, with its advantages of portability, accuracy, real-time, and information-richness, has been used for precise glucose management in chronic diseases. A small number of prospective randomized controlled studies have previously demonstrated the existence of an improved effect of CGM on intraoperative glycemic management in major surgery. However, there are no real-world studies with large sample sizes to clarify the efficacy and safety of CGM in reducing CCI in patients with DM or IGT. This is where our research comes in. In this real-world study, we aim to clarify the role of perioperative CGM in improving both prognosis and efficacy of surgery.

This is an investigator-initiated, multi-center, pragmatic,1:1ratio randomized, parallel-group, controlled trial which consisted of a 1 to 3-day screening period, and a 7-day(at least 3-day) intervention period, with a final evaluation at day 30. A total of approximately 10168 patients (≥ 18 years of age) with DM or IGT undergoing elective surgeries (including major thoracoabdominal surgery [excluding cardiac surgery], open orthopedic surgery, or neurosurgery) will be enrolled. Patients fulfilling all of the inclusion criteria and none of the exclusion criteria will be randomized into two groups (CGM group versus C group) according to the 1:1 ratio after offering informed content.

Glucose monitoring models:

1. CGM group: A CGM prescription will be issued by the attending physician at least 6 hours before surgery. The primary nurse in charge will educate the participant and their family members on the proper wearing and connection of the CGM device. The calibration frequency and interval of preoperative and postoperative glucose monitoring devices will be determined based on institutional diagnostic and treatment guidelines and the requirements of the monitoring device used. Intraoperative glucose calibration will be performed immediately upon admission, immediately after surgical incision, every 2 hours after surgical incision, and at the completion of wound closure.
2. C group: Perioperative glucose monitoring will be conducted based on institutional diagnostic and treatment guidelines.
3. Glucose/blood glucose monitoring will be continued for both groups of patients until postoperative day 7 or discharge.

Perioperative glucose management:

1. Preoperatively: For elective surgery, preoperative fasting blood glucose/glucose ≤10 mmol/L and HbA1c≤7.0%. For emergency surgery, the decision whether the participant's current blood glucose level is acceptable for surgical treatment is based on institutional practice and the experience of the physician in charge.
2. Intraoperatively: Blood glucose level will be set at 4.5-10mmol/L. Participants in both groups will be given glucose to elevate blood glucose when blood glucose was found to be≤4.5 mmol/L, or insulin when blood glucose was found to be ≥10 mmol/L. Drug dosages and administration methods will follow the medical practice of the institution and the anaesthesiologist in charge. In the CGM group, if mean amplitude of glycemic excursions (MAGE) ≥3.9 mmol/L or largest amplitude of glycemic excursions (LAGE)≥4.4 mmol/L was found in the last 2 h, the dose or rate of glucose/insulin administration will be adjusted as appropriate.
3. Postoperatively: The target of blood glucose management in the early postoperative period is 4.5-7.8 mmol/L. According to the institutional practice and the supervising physician's experience, participants in both groups will be treated with glucose to elevate blood glucose when blood glucose was found to be ≤4.5 mmol/L, and will be treated with insulin to lower blood glucose when blood glucose was found to be ≥7.8 mmol/L.In the CGM group, if excessive blood glucose variability was found, including coefficient of variation (CV)≥36%, LAGE≥4.4 mmol/L, postprandial glucose excursions of three dinners (PPGE)≥2.2mmol/L, standard deviation of blood glucose (SDBG)≥2.0 mmol/L or time in range (TIR)≤70%, an endocrinologist will aid in adjusting the blood glucose management programme.

The primary objective is to observe the improvement of CGM on the surgical outcomes of participants with DM or IGT, including a reduction in the CCI, overall postoperative infection rate, major adverse cardiovascular events (MACE) rate, and shortened postoperative hospital stay within 30 days after surgery.

The study consists of 9 visits including the day of screening and randomization,1,2,3,4,5,6,7 and 30-day follow-up postoperatively.

Demographic information, symptoms and signs, laboratory test, auxiliary examinations, CCIs will be recorded during the program. The trial is anticipated to last from April 2024 to December 2025 with 10168 subjects recruited from 50 centers in China. All the related investigative organization and individuals will obey the Declaration of Helsinki and Chinese Good Clinical Practice standard. A Data and Safety Monitoring Board (DSMB) will regularly monitor safety during the study. The trial has been approved by the ethics committee of Beijing Tsinghua Chang Gung Hospital and corresponding branch centers.

Inclusion Criteria:

1. Patients aged above 18 years;
2. Patients with diabetes mellitus or impaired glucose tolerance;
3. Expected major thoracic and abdominal surgery (except cardiac surgery; including endoscopic surgery and robotic surgery), open orthopedic surgery, neurosurgery;
4. Volunteered for this study and written informed consent.

Exclusion Criteria:

1. The patient refused;
2. The time between wearing CGM sensor and surgical skin incision cannot meet 6 hours or more;
3. Expected monitoring time less than 72 hours in CGM group;
4. Patients had comorbidities that affected the evaluation of endpoints;
5. The attending physician thought that the patient had inappropriate indications for enrollment;
6. Participants were involved in other studies that interfered with the evaluation of the results of this study.

The data are not publicly available due to containing information that could compromise the privacy of research participants. The data that support the findings of this study are available on request from the corresponding author.