Diabetes mellitus and perioperative glucose
Stem
A 47-year-old woman, 91 kg, with type 1 diabetes for 30 years is scheduled for an elective lumbar laminectomy and fusion expected to last five hours. She uses glargine 30 units nightly and lispro with meals. Her A1c is 7.6%. She reports early satiety, lightheadedness on standing and two nocturnal hypoglycemic episodes this month. Fingerstick glucose on arrival is 212 mg/dL.
Question
How will you manage her diabetes and glucose from the night before surgery through recovery?
Ideal answer
HeadlineType 1 never goes without insulin. 212 does not cancel her; ketoacidosis would, so I check for an anion gap.
- Type, control and end organs: I ask about hypoglycemia, autonomic neuropathy, gastroparesis, renal disease and silent ischemia; she has the first three.
- About 75–80% of her glargine the night before, less given her nocturnal lows, lispro held while fasting.1
- Intravenous insulin infusion, hourly glucose, dextrose available, for a long case with fluid shifts and glucose above 180,1 aiming for ADA's 100–180 mg/dL.2
- Rapid-sequence induction, early arterial line, for gastroparesis and orthostasis. Prayer sign: stiff-joint syndrome limits atlanto-occipital extension.
- Subcutaneous basal insulin before the infusion stops in recovery, or a type 1 patient is in ketoacidosis within hours.
Watch for: hypoglycemia masked by anesthesia; under 70 in an unconscious patient shows no signs.
Breaking down the answer
- Basal continues, bolus stops — a type 1 patient without basal insulin is in ketoacidosis within hours regardless of glucose. Half the morning NPH, and rapid-acting insulin held with the missed meal;1 less still with nocturnal hypoglycemia.
- Oral agents — metformin is traditionally held the day of surgery for lactic acidosis risk,1 though SAMBA continues it unless renal function is a concern;3 sulfonylureas stop: fasting hypoglycemia.3 SGLT2 inhibitors stop at least 3 days before (4 for ertugliflozin): euglycemic ketoacidosis.4
- The number that cancels — the derangement cancels, not the number: SAMBA does not cancel ambulatory cases for hyperglycemia alone,5 while inpatient guidance suggests considering postponement above about 250 mg/dL.1
- A1c — alone it does not cancel surgery;5 above 8% it prompts optimization only if control can be improved quickly, for example before elective joint or spine surgery.2
- Infusion for long or major cases — subcutaneous absorption is unreliable with vasoconstriction and hypothermia; cardiac surgery, transplant, or cases over about 4 hours with large fluid shifts and glucose above 180.1
- Targets differ by setting — tighter control raises hypoglycemia without improving outcomes: 140–180 in the critically ill;1 SAMBA 2024 accepts 180–250 for ambulatory surgery, with subcutaneous insulin.5
- GLP-1 receptor agonists — most continue them, with a liquid diet for 24 hours beforehand; gastric ultrasound or rapid sequence if symptomatic or dose-escalating.6
Follow-up question
At the end of the five-hour case, the volatile is off, the train-of-four is full, and she does not wake up. What do you do?
Follow-up answer
HeadlineGlucose before anything else: hypoglycemia is the fastest reversible cause, and the anesthetic hid every sign. I tell the room what I am looking for.
Below 70 mg/dL I give 25 g dextrose (50 mL of D50), stop the insulin infusion, and recheck in 15 minutes. If it is high, I look for hyperosmolar coma: sodium, osmolality, anion gap; with a gap, the DKA protocol, fluids first, then insulin at 0.1 units/kg/h once potassium is above 3.5 mmol/L, replacing potassium as it falls.7 If normal, the rest of the delayed-emergence differential: residual drug, hypothermia, hypercarbia, stroke.
Pitfalls that cost points
- Blurring preoperative, intraoperative and postoperative, or skipping the airway, stomach, kidneys and silent ischemia that diabetes hides.
- Quoting a single cancellation cutoff without asking about ketones, hydration and urgency.
- Chasing a 190 with a large subcutaneous dose: delayed absorption crashes her glucose in PACU.
- Missing the SGLT2 inhibitor: a patient still on one with an anion gap gets a beta-hydroxybutyrate before I proceed.
Rapid-fire
Q: Why does hyperglycemia matter intraoperatively? A: It impairs neutrophil function and wound healing, worsens outcome after cardiac and neurologic injury, and causes osmotic diuresis with volume depletion.
Q: Why does stress hyperglycemia occur in non-diabetics? A: Catecholamines, cortisol and glucagon raise hepatic glucose output and cause insulin resistance; I treat it to the same target above 180.
Q: Do you avoid lactated Ringer's? A: No; lactate raises glucose trivially and the evidence of harm is weak. I avoid dextrose-containing maintenance fluids unless insulin is running.
Q: A glucose of 420 with an anion gap on arrival for an urgent case? A: DKA protocol, fluids first, then insulin once potassium is above 3.5 mmol/L;7 I delay the incision until the gap is closing unless the surgery is the source of the ketoacidosis.
Q: What does autonomic neuropathy predict? A: Resting tachycardia, orthostasis and lost heart-rate variability predict induction instability and silent ischemia.
Q: Why does hypoglycemia present differently under anesthesia? A: Sweating, tachycardia and tremor are blunted by anesthesia and beta-blockade, so the first sign is often delayed emergence or a seizure.
Numbers to know
| Item | Value |
|---|---|
| Intraoperative glucose target | ADA 100–180 mg/dL;2 SAMBA ambulatory 180–250 mg/dL5 |
| Hypoglycemia threshold and treatment | <70 mg/dL; 25 g dextrose IV, recheck in 15 min |
| Basal insulin the night before | 75–80% of usual dose1 |
| SGLT2 inhibitor hold | ≥3 days before surgery; ertugliflozin ≥4 days4 |
| Metformin | Hold day of surgery or continue if renal function normal (SAMBA)3 |
| Insulin infusion start | 1–2 units/h regular insulin; 0.1 units/kg/h in DKA7 |
| Postpone elective surgery | DKA or HHS; not for A1c or hyperglycemia alone in ambulatory cases5 |
Links
- dka, Preoperative cardiac evaluation for non-cardiac surgery, Chronic kidney disease and the dialysis patient, Delayed emergence, aspiration
- ADA Standards of Care, diabetes care in the hospital; SAMBA consensus on perioperative glucose management
Sources
- 1.Diabetic Perioperative Management · StatPearls (NCBI Bookshelf), 2024 · ncbi.nlm.nih.gov
- 2.MKSAP quiz: Perioperative glucose control · American College of Physicians, 2024 · diabetes.acponline.orgADA-aligned target 100–180 mg/dL within 1–4 h of surgery; deferring for A1c >8% reasonable only if quickly improvable.
- 3.Updated guidelines for perioperative blood glucose management in ambulatory surgery patients with diabetes · NYSORA, 2024 · nysora.comSummary of SAMBA 2024: long-acting insulin reduced 20–25%; metformin generally continued; IV insulin for >300 mg/dL.
- 4.FDA Approves Safety Labeling Changes to SGLT2 Inhibitors · Drug Topics (FDA labeling change, March 2020), 2020 · drugtopics.com
- 5.Society for Ambulatory Anesthesia Updated Consensus Statement on Perioperative Blood Glucose Management in Adult Patients With Diabetes Mellitus Undergoing Ambulatory Surgery (APSF literature summary) · SAMBA / APSF, 2024 · apsf.orgRajan et al., Anesth Analg 2024;139:459-477. Liberal intraoperative target 180–250 mg/dL; A1c not used to postpone; no cancellation for hyperglycemia absent DKA/HHS.
- 6.New Multi-society Clinical Practice Guidance Released (GLP-1 receptor agonists) · ASA / AGA / ASMBS / ISPCOP / SAGES, 2024 · asahq.org
- 7.Hyperglycemic crises in adults: a look at the 2024 consensus report · Cleveland Clinic Journal of Medicine, 2025 · ccjm.org
Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.