Preoperative Carbohydrate Loading in Diabetes Mellitus

Preoperative carbohydrate loading has been widely recognized as a core component of Enhanced Recovery After Surgery (ERAS) protocols. In non-diabetic patients, drinking a carbohydrate solution two hours before anesthesia improves perioperative metabolic status, reduces insulin resistance, and enhances postoperative recovery without increasing the risk of aspiration or other complications. However, its safety and effectiveness in patients with type 2 diabetes mellitus (T2DM) remain controversial due to concerns about delayed gastric emptying and hyperglycemia.

Recent studies have shown that preoperative carbohydrate drinks in patients with well-controlled T2DM do not significantly delay gastric emptying and cause only transient increases in blood glucose levels, typically returning to baseline within 180 minutes. These findings suggest that carbohydrate loading may be safe for this population, provided their diabetes is well managed and they have no symptoms of gastroparesis. Despite this, current guidelines remain cautious, and further evidence is needed to strengthen clinical recommendations, particularly in Asian populations.

This randomized, open-label, parallel-group clinical trial is being conducted at Nhan Dan Gia Dinh Hospital, Ho Chi Minh City, Vietnam. The study enrolls adult patients (aged 18-65 years) with well-controlled T2DM (HbA1c <7%, fasting glucose 6.5-10 mmol/L) scheduled for elective surgery under general anesthesia. Participants are randomly assigned in a 1:1 ratio to receive either 200 mL of 25% carbohydrate solution two hours before anesthesia (intervention group) or to continue standard fasting for at least six hours before surgery (control group). Randomization is performed using computer-generated allocation.

Capillary blood glucose levels are measured at baseline and at 1, 2, and 4 hours after ingestion. Bedside gastric ultrasonography is used to estimate gastric volume before anesthesia, and residual volume greater than 1.5 mL/kg is considered gastric retention. Patients with capillary glucose >10 mmol/L persisting beyond 180 minutes will receive intravenous insulin infusion according to the hospital protocol.

The primary endpoint is capillary blood glucose level at four hours after carbohydrate ingestion. Secondary outcomes include total insulin administered to treat hyperglycemia and the proportion of participants with gastric retention before anesthesia. Safety outcomes include incidence of aspiration, diabetic ketoacidosis, and other adverse events.

The hypothesis is that preoperative carbohydrate loading in well-controlled T2DM increases blood glucose by no more than 2 mmol/L compared with fasting and does not increase gastric residual volume or aspiration risk. If confirmed, these findings will provide new evidence supporting the safe integration of carbohydrate loading into ERAS protocols for diabetic patients, helping to improve comfort, reduce perioperative stress, and optimize recovery after surgery.

Inclusion criteria

• Adults aged 18-65 years scheduled for elective surgery under general anesthesia.
• Diagnosed with type 2 diabetes mellitus with well-controlled glycemia (HbA1c < 7% within the last 3 months).
• Fasting plasma glucose between 6.5 and 10 mmol/L on the day before surgery.
• ASA physical status II-III.
• Capable of oral intake and able to provide written informed consent.
• No contraindication to carbohydrate ingestion or ultrasonographic gastric assessment.

Exclusion criteria

• History or clinical evidence of gastroparesis, gastroesophageal reflux disease (GERD), or hiatal hernia.
• Conditions increasing aspiration risk: obesity (BMI > 30 kg/m²), pregnancy, or emergency surgery.
• Severe systemic comorbidities (renal failure, hepatic failure, heart failure, or COPD exacerbation).
• Use of medications affecting gastric motility (opioids, prokinetics, anticholinergics) within 24 hours.
• Known hypersensitivity or intolerance to carbohydrate drink components.
• Refusal or inability to participate.