Situation: A 60-year-old man is admitted the day before an elective open abdominal operation under general anesthesia. He has type 2 diabetes mellitus and hypertension. He has no history of delayed gastric emptying, no gastrointestinal symptoms, and no known drug allergies. On the evening before surgery, the nurse reviews his medication history. Which finding should the nurse report to the surgeon and the anesthesia provider?

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are held before surgery because of the risk of euglycemic ketoacidosis: 3 days for most drugs in the class, but 4 days for ertugliflozin. A last dose 3 days before surgery is one day short and must be reported. The other findings follow the usual rules for metformin, angiotensin receptor blockers, and beta blockers.

Perioperative medication safety: SGLT2 inhibitor hold time

The correct finding to report is option 4. This patient took his last dose of ertugliflozin only 3 days before surgery, but ertugliflozin requires a longer preoperative hold than most other SGLT2 inhibitors. The concern is not hypoglycemia or hyperglycemia; it is euglycemic diabetic ketoacidosis (EDKA), a dangerous metabolic state in which ketoacidosis develops even though blood glucose looks near-normal or only mildly elevated.

SGLT2 inhibitors promote urinary glucose loss and shift metabolism toward ketogenesis, so surgical fasting and stress can trigger ketoacidosis without marked hyperglycemia. Because the blood glucose may appear unremarkable, EDKA is easy to miss on routine postoperative checks. The perioperative risk is highest when the drug effect is still active during the fasting and stress of surgery.

The hold duration differs within the class. Most SGLT2 inhibitors—such as canagliflozin, dapagliflozin, and empagliflozin—are generally stopped 3 days before elective surgery. However, ertugliflozin requires a 4-day preoperative hold. A last dose taken 3 days before surgery is therefore one day short and must be reported to the surgeon and anesthesia provider so the team can adjust monitoring or consider rescheduling.

Medication	Preoperative hold	Rationale
Ertugliflozin	4 days	Longer hold needed to reduce EDKA risk; last dose 3 days before surgery is insufficient
Most other SGLT2 inhibitors	3 days	Standard class hold before elective surgery
Metformin	Withhold on day of surgery; last dose with dinner the night before is acceptable	Risk of lactic acidosis with renal hypoperfusion; short half-life allows evening dose
Losartan (ARB)	Often held morning of surgery; last dose yesterday morning is acceptable	Risk of intraoperative hypotension; no need for multi-day hold
Metoprolol (beta blocker)	Continue on day of surgery with a sip of water	Abrupt withdrawal risks rebound tachycardia and hypertension

Watch out! EDKA can present with normal or only mildly elevated glucose, so relying on blood glucose alone will miss the diagnosis. Postoperative monitoring must include beta-hydroxybutyrate, anion gap, and bicarbonate when SGLT2 inhibitor exposure is recent or uncertain.

Key point! The hold time is drug-specific. Do not apply a uniform “3 days for all SGLT2 inhibitors” rule; ertugliflozin is the exception with a 4-day requirement.

The other options reflect standard perioperative practice and do not require reporting. Metformin taken with dinner the night before surgery is acceptable because it is held only on the day of surgery; its short half-life and the concern for lactic acidosis under intraoperative hypoperfusion do not require a longer preoperative washout. Losartan, an angiotensin receptor blocker, is often held the morning of surgery to reduce intraoperative hypotension, but a last dose the previous morning is not a safety concern. Metoprolol should be continued perioperatively, including on the morning of surgery with a sip of water, because abrupt beta blocker withdrawal can cause rebound tachycardia, hypertension, and myocardial ischemia.

The underlying mechanism of SGLT2 inhibitor-associated EDKA involves persistent urinary glucose excretion, which lowers plasma glucose and reduces insulin secretion. At the same time, the drug promotes a shift toward ketogenesis. When surgery adds fasting, dehydration, and stress hormones, the combination can produce ketoacidosis even at normal glucose levels ^[1][2]. The risk can persist beyond the nominal hold period in some patients, which is why clinical vigilance and ketone monitoring remain important even when the drug was stopped several days earlier ^[3]. A structured perioperative checklist for SGLT2 inhibitors emphasizes verifying the specific drug, the exact last dose date, and the planned monitoring for ketones and acid-base status ^[4].