Perioperative Diabetes Control
1. Elective outpatient setting:
- HbA1c < 8% — widely accepted threshold (some say <7% ideal, but <8% acceptable for elective surgery) Each 1% increase in HbA1c above ~7% is associated with incrementally higher rates of surgical site infections, anastomotic complications, and longer length of stay.
- Cardiovascular — CAD, hypertension, lipids
- Renal — eGFR/CrCl (affects drug dosing, contrast risk)
- Autonomic neuropathy — gastroparesis (affects fasting), bladder dysfunction
- Peripheral neuropathy — foot examination, wound healing risk
- Retinopathy — if diabetic eye disease, avoid certain positioning (want to avoid increased IOP)
- Infection — screen for occult infection before elective cases
2. Perioperative
Perioperative BGL target: 6–10 mmol/L (avoid hypoglycaemia — BGL < 4 is dangerous perioperatively)
2.1. Medications
- SGLT2 inhibitors (empagliflozin, dapagliflozin) — withhold 3-4 days pre-op (risk of euglycemic DKA)
- GLP-1 agonists (semaglutide, dulaglutide) — withhold on day of surgery (delayed gastric emptying, risk of aspiration)
- Metformin — withhold on day of surgery (risk of lactic acidosis, especially with renal impairment or contrast)
- Sulfonylureas (glibenclamide) — withhold (hypo risk while fasting)
- Insulin: Long-acting (glargine, detemir) — reduce dose, typically 50-75% of usual (not full dose for either T1 or T2) Short-acting/prandial — withhold on day of surgery T1DM specifically — you want basal insulin coverage, but can reduce by ~20-25% to avoid overnight hypoglycemia while fasting
2.2. HHS vs DKA
- DKA — acidosis (pH <7.3), high anion gap, ketones positive
- HHS — no acidosis (pH normal), normal anion gap, ketones negative
- Glucose: HHS is much higher (>30 mmol/L), DKA is elevated but often <30