What is the primary goal and management strategy for blood glucose control in diabetic patients undergoing surgery?

Perioperative Glucose Management in Diabetic Patients

When insulin is required perioperatively, administer IV glucose at 4 g/hour (equivalent to approximately 100 mL/hour of D10W) concurrently with continuous IV insulin infusion to maintain target blood glucose of 5-10 mmol/L (90-180 mg/dL) while preventing hypoglycemia. 1

Primary Management Strategy

The fundamental principle is that insulin therapy, when needed, must always be accompanied by IV glucose administration to avoid hypoglycemia while maintaining glycemic control. 1

Specific IV Glucose Protocol

• Administer IV glucose at 4 g/hour when continuous IV insulin is required 1
• This translates to approximately 100 mL/hour of 10% dextrose solution 1
• Add electrolytes (particularly potassium 10-20 mEq/L) to the glucose infusion in patients with normal renal function to prevent insulin-induced hypokalemia 1, 2
• All IV solutions may be used perioperatively, including Ringer's lactate 1

Target Blood Glucose Range

Maintain blood glucose between 5-10 mmol/L (90-180 mg/dL) throughout the perioperative period. 1, 3 This broader target is recommended because:

• Tight glycemic control (targeting 80-120 mg/dL or 4.4-6.7 mmol/L) significantly increases severe hypoglycemia risk and potentially mortality 1
• Hyperglycemia >10 mmol/L (180 mg/dL) increases morbidity, particularly infections, and mortality 1
• The moderate range of 7.7-10 mmol/L (140-180 mg/dL) represents the best compromise for reducing morbidity/mortality without increasing hypoglycemia 1

Insulin Administration Protocol

When insulin is required:

• Use ultra-rapid short-acting insulin analogues via continuous IV infusion (IVES) 1
• Typical starting rate: 1-2 units/hour, adjusted based on frequent glucose monitoring 1, 2
• Never administer IV insulin without concurrent IV glucose - this is a critical safety measure 1

Monitoring Requirements

• Measure blood glucose every 1-2 hours during stable periods 1, 3
• Increase to hourly monitoring after each insulin rate adjustment 1
• Check every 15-30 minutes during hypoglycemic episodes 1
• Monitor potassium every 4 hours during insulin therapy (target 4-4.5 mmol/L) 1
• Use arterial or venous blood samples rather than capillary measurements, as capillary readings overestimate glucose levels, especially during vasoconstriction 1

Critical Preoperative Considerations

Patient Scheduling and Fasting

• Schedule diabetic patients first in the morning to minimize prolonged fasting 1
• Prolonged fasting increases perioperative glycemic instability 1
• Preoperative glucose infusion is NOT necessary if the patient is not receiving insulin 1

Medication Management

For patients NOT requiring insulin:

• Non-insulin medications are held on the morning of surgery 1
• Metformin is held from the evening before surgery 1
• SGLT2 inhibitors must be discontinued 3-4 days before surgery to prevent euglycemic diabetic ketoacidosis 3

For insulin-dependent patients:

• Administer usual insulin dose the evening before surgery 1
• Reduce basal insulin by 25% the evening before surgery to achieve better perioperative control with lower hypoglycemia risk 3
• Maintain insulin pumps until patient arrives in the surgical unit, then transition to IV insulin 1

Common Pitfalls to Avoid

• Never pursue glucose targets <100 mg/dL (5.5 mmol/L) perioperatively - this increases hypoglycemia without benefit 3
• Never administer IV insulin without concurrent glucose infusion - this causes severe hypoglycemia 1
• Never continue SGLT2 inhibitors within 3-4 days of surgery - risk of euglycemic DKA 3
• Never rely solely on capillary glucose measurements during vasoconstriction or suspected hypoglycemia - values of 0.7 g/L (3.8 mmol/L) on capillary readers should be considered hypoglycemia and verified by laboratory measurement 1
• Never use correction-only insulin without basal insulin in general surgery patients - this is associated with worse outcomes 3

Special Considerations

Type 1 Diabetes

• Insulin deficiency leads to ketoacidosis within hours in Type 1 diabetic patients 1
• Continuous insulin replacement is mandatory at all times, regardless of nutritional status 4
• When transitioning from IV to subcutaneous insulin, administer basal insulin 2-4 hours before stopping IV insulin to prevent rebound hyperglycemia and ketoacidosis 3

Gastroparesis Risk

• Diabetic gastroparesis creates aspiration risk at induction 1
• Use rapid sequence induction technique when gastroparesis is present 1

Glucocorticoid Administration

• Glucocorticoids induce hyperglycemia in 56-86% of hospitalized patients 3
• Require substantial increases in prandial and correction insulin (40-60% or more) in addition to basal insulin 3
• Use 4 mg dexamethasone (rather than 8-10 mg) for antiemetic prophylaxis to minimize hyperglycemia risk 1