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MKSAP quiz: Perioperative glucose control

This month's quiz asks readers to choose management for a 59-year-old man undergoing elective hip arthroplasty who has a recent hemoglobin A1c of 7.9% and a blood glucose concentration of 230 mg/dL (12.8 mmol/L) three hours before surgery.


A 59-year-old man is evaluated in the hospital on the morning of elective hip arthroplasty. He has type 2 diabetes mellitus. He has no other medical problems. His only outpatient medication is metformin twice daily; his morning dose was withheld.

Physical examination findings, including vital signs, are normal.

Three days ago, his hemoglobin A1c was 7.9%. Three hours before surgery, his blood glucose concentration is 230 mg/dL (12.8 mmol/L).

Which of the following is the most appropriate management?

A. Delay surgery until preoperative hemoglobin A1c is less than 7%
B. Proceed with surgery as planned
C. Target blood glucose concentration to 80 to 100 mg/dL within 1 to 4 hours of surgery
D. Target blood glucose concentration to 100 to 180 mg/dL within 1 to 4 hours of surgery

Reveal the Answer

MKSAP Answer and Critique

The correct answer is D. Target blood glucose concentration to 100 to 180 mg/dL within 1 to 4 hours of surgery. This item is available to MKSAP subscribers as item 1 in Extension Set 4 of the General Internal Medicine 2 section. More information about MKSAP is online.

In this patient with type 2 diabetes mellitus, the most appropriate management is to target blood glucose concentration to 100 to 180 mg/dL (5.6-10 mmol/L) within 1 to 4 hours of surgery using fast-acting insulin (Option D). Hyperglycemia in the perioperative period is associated with increased risk of multiple adverse outcomes, including wound infection, pneumonia, and cardiovascular events. However, hypoglycemia (blood glucose concentration <70 mg/dL [3.9 mmol/L]) is also associated with substantial harm. Blood glucose levels of 100 to 180 mg/dL (5.6-10 mmol/L) immediately before surgery are associated with the best outcomes in balancing control of hyperglycemia with the risk of hypoglycemia. Most oral diabetes medications are withheld before surgery, and fast-acting insulin is the quickest and most reliable method of achieving the desired blood glucose range. Hypoglycemia, if present, should be treated with glucose tablets or gel if other oral intake is not advisable before surgery. In addition, if possible, elective surgery for patients with diabetes should be scheduled in the morning to limit duration of fasting. This patient with preoperative hyperglycemia of 230 mg/dL (12.8 mmol/L) should receive fast-acting insulin to achieve blood glucose levels of 100 to 180 mg/dL (5.6-10 mmol/L) before surgery.

Delaying surgery until this patient's preoperative hemoglobin A1c is less than 7% (Option A) is unnecessary. Perioperative blood glucose levels have been shown to affect surgical outcomes more than hemoglobin A1c. For elective surgery, it is reasonable to defer surgery in patients who have a hemoglobin A1c above 8% if there is a significant likelihood diabetes control can be improved in the short term. This patient's hemoglobin A1c is 7.9% and delaying surgery is not indicated.

Proceeding with surgery as planned (Option B) is not the best option, as improved glycemic control in the immediate preoperative period is associated with improved outcomes.

Tight glucose control aiming to maintain blood glucose in the normal range of 80 to 100 mg/dL (5.6-10 mmol/L) (Option C) may be associated with increased harm due to hypoglycemia and does not favorably affect surgical outcomes. Likewise, tight control of inpatient glucose concentration between 80 to 110 mg/dL (5.6-10 mmol/L) may increase mortality and is not consistently associated with improved outcomes.

Key Point

  • For patients with diabetes mellitus undergoing elective surgery, a hemoglobin A1c level of less than 8% and a preoperative blood glucose concentration of 100 to 180 mg/dL (5.6-10 mmol/L) within 1 to 4 hours of surgery should be targeted.