What is the recommended peri‑operative management of oral antidiabetic agents for a patient with type 2 diabetes undergoing surgery or procedural anesthesia?

Perioperative Management of Oral Antidiabetic Agents

Hold all oral antidiabetic agents on the morning of surgery, with metformin stopped on the day of surgery and SGLT2 inhibitors discontinued 3–4 days preoperatively to prevent euglycemic ketoacidosis. 1, 2

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Preoperative Medication Management

Metformin

• Stop metformin on the day of surgery to reduce the risk of lactic acidosis, particularly in the setting of perioperative fasting, potential tissue hypoperfusion, and renal impairment 1, 2, 3, 4
• Metformin should remain discontinued for 48 hours postoperatively or until renal function is confirmed stable and oral intake is re-established 3, 4
• The risk of lactic acidosis is substantially elevated during acute illness, hypoperfusion states, and when combined with contrast administration 1

SGLT2 Inhibitors

• Discontinue SGLT2 inhibitors 3–4 days before surgery to prevent euglycemic diabetic ketoacidosis, a potentially life-threatening complication 1, 2
• This class of medications can cause ketoacidosis even with normal or near-normal glucose levels, making early discontinuation critical 1, 2

Other Oral Hypoglycemic Agents

• Hold all other oral hypoglycemic agents (sulfonylureas, DPP-4 inhibitors, thiazolidinediones, meglitinides) on the morning of surgery 1, 2, 3
• Continuing these agents during the perioperative fasting period creates severe hypoglycemia risk, which increases morbidity, mortality, ICU length of stay, and overall hospital duration 3
• Sulfonylureas and meglitinides pose the highest hypoglycemia risk due to their insulin-secretagogue mechanism 3, 5

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Alternative Approach: Continuation of Oral Agents in Ambulatory Surgery

• For ambulatory surgery with minimal fasting time, continuing oral hypoglycemic agents may result in better perioperative glucose control (mean 138 mg/dL vs 156 mg/dL when discontinued, P<0.001) 6
• This approach is only appropriate when the patient will miss a single meal and can resume oral intake within 2–3 hours postoperatively 7
• If surgery is scheduled so the patient leaves recovery before 10:00 AM, provide breakfast immediately and allow the patient to take morning medications at that time 7
• If discharge occurs between 10:00 AM and noon, the patient should take their usual medication on arrival at the hospital with a glucose infusion (G 10% 40 mL/h) until the next meal 7

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Insulin Management on Day of Surgery

Type 1 Diabetes

• All type 1 diabetic patients require insulin even during preoperative fasting to meet basal physiological demands and prevent ketoacidosis 5, 8
• Administer 50% of the usual NPH dose or 75–80% of the usual long-acting analog dose (glargine, detemir, degludec) on the morning of surgery 1, 2
• Never completely withhold basal insulin in type 1 diabetes, as this can precipitate diabetic ketoacidosis within hours 5, 8

Type 2 Diabetes on Insulin

• Give 50% of the usual NPH dose or 75–80% of the usual long-acting analog dose on the morning of surgery 1, 2
• Hold all rapid-acting and short-acting insulin doses until the patient resumes eating 1, 2
• Type 2 diabetic patients on multiple injectable agents are susceptible to hyperglycemic hyperosmolar state (HHS) if insulin is completely withheld 5

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Intraoperative Glucose Monitoring and Management

• Monitor blood glucose every 2–4 hours while the patient is NPO, targeting a range of 100–180 mg/dL (5.6–10.0 mmol/L) 1, 2
• Administer short- or rapid-acting insulin as needed to maintain target glucose range 1, 2
• If blood glucose exceeds 16.5 mmol/L (297 mg/dL) on the day of surgery, postpone elective procedures and administer corrective insulin 2
• The goal is to avoid hypoglycemia (which can cause neurological damage) and extreme hyperglycemia (which impairs wound healing, increases infection susceptibility, and worsens ischemic damage to myocardium and brain) 8, 4

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Postoperative Resumption of Oral Agents

• Resume oral feeding as soon as possible after surgery to facilitate return to normal glucose control 1, 2
• Restart oral hypoglycemic agents when blood glucose is 90–180 mg/dL and the patient is tolerating oral intake 1, 2
• Continue blood glucose monitoring until the patient is stable and eating regularly 1, 2
• If blood glucose exceeds 180 mg/dL postoperatively, administer corrective subcutaneous insulin boluses until glucose decreases to 90–180 mg/dL 7
• If blood glucose exceeds 300 mg/dL (16.5 mmol/L), hospitalization may be required for IV insulin therapy 1

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Preoperative Glycemic Targets

• Target HbA1c <8% for elective surgery whenever possible 1, 2
• For emergency extractions or urgent procedures in patients with uncontrolled diabetes, proceed with prophylactic antibiotics when fasting glucose exceeds 250 mg/dL 1
• Patients with HbA1c ≥10–12% with symptomatic or catabolic features may require immediate basal-bolus insulin therapy rather than oral agents alone 1

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Special Considerations

Fasting Guidelines

• Allow clear liquids until 2 hours before anesthesia induction for all diabetic patients, including water, clear juices without pulp, black coffee, and tea without milk 2
• Allow light meals (such as toast) until 6 hours before anesthesia 2
• Standard fasting guidelines apply to most diabetic patients, as those with uncomplicated type 2 diabetes have normal gastric emptying 2

Preoperative Carbohydrate Loading

• Consider administering 400 mL of 12.5% carbohydrate drink 2–3 hours before anesthesia to reduce insulin resistance and preserve lean body mass, though evidence in diabetic patients is weaker 2
• Carbohydrate loading can be given to diabetic patients along with their usual diabetic medication 2

Scheduling Considerations

• Schedule diabetic patients early on the surgical list to minimize disruption to their medication and meal routine 1
• Priority should be given to diabetic patients to reduce the number of missed meals and simplify perioperative management 7

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Common Pitfalls to Avoid

• Do not continue metformin perioperatively, as the risk of lactic acidosis in the setting of surgery, fasting, and potential renal impairment is substantial 3, 4
• Do not delay discontinuation of SGLT2 inhibitors; these must be stopped 3–4 days before surgery to prevent euglycemic ketoacidosis 1, 2
• Do not withhold all insulin in type 1 diabetic patients, even during fasting, as this will precipitate diabetic ketoacidosis 5, 8
• Do not restart oral agents before confirming adequate oral intake and stable glucose levels, as premature resumption increases hypoglycemia risk 1, 2
• Do not use oral agents as the sole management strategy in patients with severe hyperglycemia (glucose >300 mg/dL or HbA1c >10%), as these patients require insulin therapy 1, 5