Internal Medicine · Year 3 · from Internal Medicine

Case 3: Perioperative Glycemic Management

Patient Presentation

A 56-year-old woman with type 2 diabetes, obesity, and obstructive sleep apnea is scheduled for laparoscopic sleeve gastrectomy. Her diabetes is managed with insulin glargine 40 units at bedtime and insulin lispro sliding scale with meals. She monitors her glucose at home with readings typically 140-200 mg/dL. Her HbA1c is 8.4%.

Vital Signs

  • Blood Pressure: 142/88 mmHg
  • Heart Rate: 82 bpm
  • BMI: 46 kg/m²

Physical Examination

  • General: Obese, well-appearing
  • Cardiovascular: Regular rhythm, no murmurs
  • Pulmonary: Clear but decreased breath sounds at bases
  • Abdomen: Obese, non-tender

Current Medications

  • Insulin glargine 40 units nightly
  • Insulin lispro per sliding scale
  • Lisinopril 20 mg daily
  • CPAP nightly

Laboratory Results

  • HbA1c: 8.4%
  • Fasting glucose: 168 mg/dL
  • Creatinine: 0.9 mg/dL

Clinical Image

Figure 3: Perioperative glucose management algorithm showing target ranges and insulin adjustment strategies.

Image Source: Educational illustration for teaching purposes.

Questions

  1. What is the target blood glucose range in the perioperative period?
  • A) 80-120 mg/dL (tight control)
  • B) 140-180 mg/dL (moderate control)
  • C) 180-250 mg/dL
  • D) No specific target
  1. How should basal insulin be managed on the day of surgery?
  • A) Hold completely
  • B) Give 50-80% of usual dose the night before/morning of surgery
  • C) Give full dose
  • D) Switch to oral medications
  1. What is the management of the prandial (mealtime) insulin?
  • A) Continue as usual
  • B) Hold while NPO
  • C) Increase dose
  • D) Convert to basal insulin
  1. What are the risks of perioperative hyperglycemia?
  1. What additional considerations apply to this patient given her obstructive sleep apnea?

Answers

  1. B) 140-180 mg/dL (moderate control) - Target glucose:
  • ADA recommends 140-180 mg/dL for most hospitalized patients
  • Tighter control (110-140) may be appropriate in select patients if achievable without hypoglycemia
  • Avoid hypoglycemia (<70 mg/dL) - associated with worse outcomes
  • Severe hyperglycemia (>180-200) increases infection risk and impairs wound healing
  1. B) Give 50-80% of usual dose the night before/morning of surgery - Basal insulin management:
  • Insulin glargine: Give 50-80% of usual dose
  • Some give full dose if glucose typically well-controlled; 50% if prone to hypoglycemia
  • For this patient: 20-32 units (50-80% of 40 units) the night before
  • NPH or intermediate insulin: Give 50% of dose
  • Never completely hold basal insulin in type 1 diabetes
  1. B) Hold while NPO - Prandial insulin:
  • Hold rapid-acting/short-acting insulin when patient is NPO
  • Resume with meals postoperatively
  • Use correctional insulin (sliding scale) for hyperglycemia while NPO
  • Insulin infusion may be needed for poorly controlled patients or major surgery
  1. Risks of perioperative hyperglycemia:
  • Increased surgical site infections
  • Impaired wound healing
  • Electrolyte abnormalities
  • Dehydration (osmotic diuresis)
  • Increased length of stay
  • Cardiovascular complications
  • Mortality (especially in cardiac surgery)
  • DKA or HHS risk (especially if insulin-deficient)
  1. OSA considerations:
  • High risk for perioperative respiratory complications
  • Continue CPAP perioperatively
  • Minimize opioid use (increased apnea risk)
  • Consider monitored setting postoperatively
  • Positioning: Avoid supine position
  • Difficulty with intubation anticipated
  • Risk of postoperative oxygen desaturation
  • Bariatric surgery patients with OSA need careful monitoring

Learning Points

  1. RCRI estimates perioperative cardiac risk; functional capacity ≥4 METs often allows proceeding without further testing.
  1. Antiplatelet management: Continue aspirin for most surgeries; hold P2Y12 inhibitors 5-7 days before; never stop DAPT within 1 month of bare metal stent or 6 months of DES.
  1. Bridging anticoagulation is indicated for mechanical heart valves (especially mitral) and high-risk thromboembolism; most AF patients do not require bridging (BRIDGE trial).
  1. Target glucose 140-180 mg/dL perioperatively; give 50-80% of basal insulin; hold prandial insulin when NPO.
  1. Beta-blockers should be continued in patients already taking them; do not initiate on day of surgery.

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