How to manage blood glucose levels in a patient with type 2 diabetes (T2D) and suspected appendicitis who is being kept Nil Per Os (NPO) for surgery, with current metabolic acidosis and risk of hypoglycemia or hyperglycemia?

Management of Blood Glucose in NPO Type 2 Diabetic Patient with Suspected Appendicitis

For a T2D patient being kept NPO for emergency appendicitis surgery with metabolic acidosis, immediately initiate continuous IV insulin infusion at 1-2 units/hour with concurrent IV glucose at 4 g/hour, targeting blood glucose 5-10 mmol/L (90-180 mg/dL), while monitoring glucose hourly and potassium every 4 hours. 1, 2

Immediate Preoperative Management

Critical Safety Protocol

• Never administer IV insulin without concurrent IV glucose infusion - this is the most critical safety measure to prevent severe hypoglycemia in the NPO state 1, 3
• The American College of Anaesthesiologists specifically recommends IV glucose at 4 g/hour when continuous IV insulin is required 1
• Preoperative glucose infusion is NOT necessary if the patient is not receiving insulin, but becomes mandatory once insulin therapy starts 2, 1

Insulin Initiation

• Use ultra-rapid short-acting insulin analogues via continuous IV infusion, starting at 1-2 units/hour 1
• Target blood glucose <10 mmol/L (180 mg/dL) to reduce morbidity and mortality 2, 4
• The acceptable range is 5-10 mmol/L (90-180 mg/dL) during the perioperative period 2, 1

Monitoring Requirements

• Measure blood glucose every 1-2 hours during stable periods 1
• Increase to hourly monitoring after each insulin rate adjustment 1
• Monitor potassium every 4 hours during insulin therapy, targeting 4-4.5 mmol/L, as hypokalaemia occurs in approximately 50% of patients during treatment of hyperglycemic crises 2, 1

Addressing the Metabolic Acidosis

Ketoacidosis Risk Assessment

• Type 2 diabetics can develop euglycemic ketoacidosis, particularly in the perioperative setting - this is a critical pitfall that is often missed 5
• The presence of metabolic acidosis in a T2D patient being kept NPO raises concern for ketoacidosis, even without marked hyperglycemia 5
• Check β-hydroxybutyrate levels if metabolic acidosis is present, as levels >5 mmol/L indicate significant ketosis 5

Continuous Insulin Infusion Protocol

• Continuous insulin infusion is the preferred regimen for patients with hyperglycemic crises and severe stress hyperglycemia 2
• For moderate-to-severe ketoacidosis, continuous insulin infusion is mandatory 2
• The insulin infusion should not be stopped even if glucose normalizes, as insulin deficiency leads to worsening ketoacidosis 2

Medication Management Before Surgery

Oral Antidiabetic Agents

• Hold all non-insulin medications on the morning of surgery 2
• Metformin must be discontinued from the evening before surgery (not just the morning of) to reduce risk of lactic acidosis 2, 6
• SGLT2 inhibitors must be discontinued 3-4 days before surgery to prevent euglycemic diabetic ketoacidosis 2, 1

Previous Insulin Regimens

• If the patient was on insulin at home, inject the usual dose the evening before surgery 2
• Insulin pumps should be maintained until the patient arrives in the surgical unit 2

Intraoperative Management

Anesthetic Considerations

• Propofol is preferred over halogenated agents for maintenance of anesthesia to minimize hyperglycemic stress 4
• Optimize pain control, as poorly controlled pain is an independent risk factor for hyperglycemia 4
• Avoid dexamethasone doses >4 mg for antiemetic prophylaxis, as higher doses significantly increase hyperglycemia risk 4

Glucose Monitoring During Surgery

• Measure blood glucose every 1-2 hours during surgery 4
• Maintain targets of 5-10 mmol/L (90-180 mg/dL) 4
• Adjust insulin infusion rate based on glucose trends 1

Postoperative Transition Planning

Timing of Transition

• Once the patient is stable and able to eat, transition from IV to subcutaneous insulin can begin 2
• Administer basal subcutaneous insulin 2-4 hours before stopping IV insulin to prevent rebound hyperglycemia and ketoacidosis 1
• Estimate the total daily subcutaneous insulin dose from the average hourly IV insulin rate over the preceding 12 hours (multiply hourly rate by 24) 2

Subcutaneous Insulin Regimen

• Use a basal-bolus approach rather than sliding scale insulin alone 2, 7
• Distribute the total daily dose as approximately 50% basal insulin and 50% prandial insulin 2
• For a patient receiving an average of 1.5 units/hour IV, the estimated daily subcutaneous dose would be 36 units (18 units basal, 18 units divided among meals) 2

Common Pitfalls to Avoid

• Never pursue glucose targets <5.5 mmol/L (100 mg/dL) perioperatively - this increases hypoglycemia risk without mortality benefit 1
• Never rely on sliding scale insulin alone - this is strongly discouraged and leads to persistent hyperglycemia 2, 7
• Do not assume T2D patients cannot develop ketoacidosis - euglycemic ketoacidosis can occur postoperatively in T2D 5
• Do not stop insulin infusion when glucose normalizes if ketoacidosis is present - continue insulin with increased glucose infusion 2
• Do not forget to check and replace potassium during insulin therapy - hypokalaemia is common and associated with increased mortality 2

Special Considerations for Emergency Surgery

• Schedule diabetic patients first in the morning when possible to minimize prolonged fasting 1
• For emergency cases like appendicitis, the stress response and surgical urgency increase hyperglycemia risk 2
• Stress hyperglycemia occurs in 30-80% of surgical patients, with prevalence varying by procedure type 2
• Blood glucose <10 mmol/L before intervention decreases risk of death, infection, and duration of stay 2