What are the key principles for managing diabetes mellitus in a perioperative area?

Perioperative Management of Diabetes Mellitus: PowerPoint Lecture Guide

Target Glycemic Range

Maintain blood glucose between 90-180 mg/dL (5-10 mmol/L) throughout the perioperative period to reduce morbidity and mortality while avoiding hypoglycemia. 1, 2

• Hyperglycemia >180 mg/dL increases infection risk, mortality, and length of stay 1
• Tight glycemic control (80-120 mg/dL) increases severe hypoglycemia and possibly mortality without improving outcomes 1
• The broader target of 90-180 mg/dL represents the optimal balance between preventing complications and avoiding dangerous hypoglycemia 1, 2

---

Preoperative Optimization

Risk Assessment and Timing

• Schedule diabetic patients first in the morning to minimize fasting time 1
• Target A1C <8% for elective surgeries whenever possible 1
• Perform cardiac risk assessment for patients with known coronary disease, autonomic neuropathy, or renal failure 1, 3

Medication Management (Day of Surgery)

• Hold metformin on the day of surgery 1
• Discontinue SGLT2 inhibitors 3-4 days before surgery to prevent euglycemic DKA 1
• Hold all other oral hypoglycemic agents the morning of surgery 1, 3
• Give 50% of NPH dose or 75-80% of long-acting insulin analog (based on diabetes type and clinical judgment) 1
• Remove personal insulin pumps and immediately start IV insulin infusion at surgery start 1

MCQ #1 (Medium Difficulty): A 58-year-old Type 2 diabetic on metformin and empagliflozin is scheduled for elective cholecystectomy on Monday. When should the SGLT2 inhibitor be stopped?

• A) Morning of surgery
• B) 24 hours before surgery
• C) 3-4 days before surgery ✓
• D) 1 week before surgery

---

Intraoperative Management

Insulin Administration

For any patient requiring insulin perioperatively, use continuous IV insulin infusion with short-acting analogs (regular insulin or rapid-acting), always combined with IV glucose (4 g/hour) and electrolyte monitoring. 1, 2

• IV insulin is preferred over subcutaneous for predictable absorption and rapid titration 1, 2
• All Type 1 diabetics and insulin-dependent Type 2 diabetics require IV insulin for all surgical procedures to prevent ketoacidosis 2
• Never give insulin without concurrent glucose administration to prevent hypoglycemia 1

Monitoring Protocol

• Check blood glucose every 1-2 hours intraoperatively 1
• Monitor potassium every 4 hours (insulin causes hypokalemia) 1
• Use arterial or venous blood samples, NOT capillary glucose meters 1
• Capillary meters overestimate glucose, especially with vasoconstriction; a reading of 70 mg/dL (3.8 mmol/L) should be treated as hypoglycemia and verified by laboratory measurement 1

MCQ #2 (Difficult): During laparoscopic surgery, a diabetic patient's capillary glucose reads 75 mg/dL. What is the most appropriate next step?

• A) Continue current insulin infusion rate
• B) Reduce insulin infusion by 50%
• C) Treat as hypoglycemia and verify with arterial/venous sample ✓
• D) Increase glucose infusion only

---

Management of Severe Hyperglycemia

Crisis Recognition

If glucose exceeds 300 mg/dL intraoperatively, immediately check for ketosis and measure serum electrolytes. 2, 4

• For ketosis absent: give 6 units rapid-acting insulin IV bolus, increase IV insulin infusion rate, ensure adequate hydration 2
• For ketosis present or suspected DKA: requires ICU-level care with continuous IV insulin, aggressive fluid resuscitation, and electrolyte replacement 1, 4
• Check serum sodium, potassium, chloride, bicarbonate urgently to assess for hyperosmolar state 4

MCQ #3 (Difficult): A 45-year-old Type 1 diabetic develops intraoperative glucose of 320 mg/dL. Ketones are negative. What is the immediate management?

• A) Give 10 units subcutaneous insulin
• B) Give 6 units IV insulin bolus, increase infusion rate, ensure hydration ✓
• C) Stop surgery and transfer to ICU
• D) Continue current insulin rate and recheck in 2 hours

---

Hypoglycemia Management

Treat any glucose <60 mg/dL immediately, even without symptoms, as surgical anesthesia masks hypoglycemia awareness. 4

• Conscious patients: give 15-20g oral glucose 4
• Unconscious or NPO patients: give IV glucose immediately, then switch to oral when able 4
• Recheck glucose every 15 minutes until >70 mg/dL and stable 4
• Never ignore altered mental status—check glucose immediately 4

---

Fluid and Electrolyte Management

• Use 0.9% normal saline as primary IV fluid 4
• All IV solutions (including Ringer's lactate) may be used perioperatively 1
• Ensure adequate hydration to prevent dehydration-related hyperglycemia 4
• Monitor for insulin-induced hypokalemia with regular potassium checks 1

MCQ #4 (Medium Difficulty): Which IV fluid is contraindicated in diabetic patients during surgery?

• A) 0.9% normal saline
• B) Ringer's lactate
• C) 5% dextrose in water
• D) None—all may be used ✓

---

Postoperative Transition

Immediate Postoperative Period (0-24 hours)

• Check capillary glucose immediately post-op, then every 1-2 hours if on insulin 4
• Continue IV insulin until patient is eating AND subcutaneous insulin has been administered 2
• Do not abruptly stop IV insulin—causes rebound hyperglycemia 4

Transition to Subcutaneous Insulin

Calculate total 24-hour IV insulin dose and give half as long-acting basal insulin subcutaneously, then discontinue IV insulin 2-4 hours later. 2

• Start basal insulin 12-24 hours before stopping IV insulin 5
• Add rapid-acting insulin with meals (basal-bolus regimen) 1, 4, 5
• Basal-bolus regimens are superior to sliding-scale insulin alone for preventing complications 1, 5

MCQ #5 (Difficult): A patient received 48 units of IV insulin over 24 hours postoperatively. When transitioning to subcutaneous insulin, what is the appropriate basal insulin dose?

• A) 12 units
• B) 24 units ✓
• C) 36 units
• D) 48 units

---

Anesthetic Considerations

Antiemetic Strategy

• Minimize nausea/vomiting to enable rapid resumption of oral intake 1
• Use propofol over volatile anesthetics, avoid N₂O, avoid neostigmine reversal, favor regional anesthesia 1
• Limit dexamethasone to lower doses (<8 mg) as 8-10 mg increases hyperglycemia risk 1

Positioning and Nerve Protection

• Take extra precautions to prevent peripheral nerve damage during positioning 3
• Diabetic patients have increased vulnerability to pressure and stretch injuries from pre-existing neuropathy and vascular disease 3

---

Key Pitfalls to Avoid

1. Never use capillary glucose meters as sole monitoring—they overestimate values 1
2. Never give insulin without concurrent glucose infusion 1
3. Never stop IV insulin abruptly—overlap with subcutaneous insulin 2, 4
4. Never ignore glucose >300 mg/dL—check for ketosis immediately 2, 4
5. Never continue metformin on day of surgery 1
6. Never continue SGLT2 inhibitors within 3-4 days of surgery 1

MCQ #6 (Medium Difficulty): Which statement about perioperative glucose monitoring is correct?

• A) Capillary glucose meters are adequate for all patients
• B) Arterial/venous samples should be used, as capillary meters overestimate glucose ✓
• C) Glucose monitoring every 4 hours is sufficient
• D) Laboratory confirmation is only needed if glucose <40 mg/dL

---

Take-Home Messages

✓ Target glucose 90-180 mg/dL perioperatively—tighter control increases hypoglycemia without benefit 1, 2

✓ Use IV insulin infusion with concurrent glucose for all insulin-requiring patients during surgery 1, 2

✓ Monitor glucose every 1-2 hours with arterial/venous samples, not capillary meters 1

✓ Stop SGLT2 inhibitors 3-4 days before surgery and metformin on day of surgery 1

✓ Treat glucose >300 mg/dL as a crisis—check ketones and electrolytes immediately 2, 4

✓ Transition to subcutaneous insulin by giving half the 24-hour IV dose as basal insulin before stopping IV infusion 2

✓ Schedule diabetic patients first in morning to minimize fasting time 1