Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 55-year-old man with a history of coronary artery disease and diabetes mellitus will undergo elective coronary artery bypass graft surgery. His last hemoglobin A1c value was 7.8%, and his plasma glucose level 2 hours prior to scheduled surgery was 238 mg/dL (13.2 mmol/L). Hemoglobin is 11.9 g/dL (119 g/L).

His current medications include glipizide, metformin, and pioglitazone. He has no allergies.

Prior to surgery, hair is clipped from his anterior chest in the area of the anticipated surgical incision. He is scheduled to receive preoperative cefazolin with a second dose if the surgery duration is longer than 4 hours.

The addition of which of the following interventions will most likely contribute to a decreased risk of surgical site infection for this patient?

A) Blood transfusion
B) Maintenance of operative hypothermia
C) Mupirocin nasal ointment at the time of anesthesia
D) Perioperative intravenous insulin therapy

MKSAP Answer and Critique

The correct answer is D) Perioperative intravenous insulin therapy. This item is available to MKSAP 15 subscribers as item 44 in the Infectious Diseases section. More information about MKSAP 15 is available online.

Prospective randomized studies have found that tight glucose control during the perioperative period in diabetic patients undergoing cardiac surgery was associated with reduced infection risk. Aggressive glucose control in the perioperative period can be achieved using a continuous intravenous insulin infusion. In these studies, serum glucose was maintained at a level of less than 200 mg/dL (11.1 mmol/L).

Evidence suggests that preoperative or postoperative anemia is associated with increased mortality and hospital length of stay. Patients who require transfusions before surgery have an increased risk of infectious complications. This patient does not require a preoperative blood transfusion, and if one were required, it might actually increase, not decrease, his risk for infection.

A randomized trial in patients undergoing urgent or cardiac surgery who were hypothermic or normothermic showed no difference in the rate of surgical site infections (SSIs). Most experts now advocate for maintenance of perioperative normothermia to reduce the risk of SSIs, and there is no evidence suggesting that maintaining hypothermia decreases SSI rates.

The use of nasal mupirocin for the prevention of SSIs is controversial and is not supported by prospective randomized studies. However, in a subgroup analysis of patients with proven staphylococcal nasal carriage, treatment with mupirocin ointment significantly reduced SSI rates compared with rates in noncarriers. Protocols describe the use of ointment in the nares for 5 days prior to surgery. It is unlikely that application of mupirocin just before surgery would have much effect on SSIs, even in staphylococcal nasal carriers. No analysis has determined if identification and treatment of nasal carriers is cost-effective.

Key Point

• Perioperative glucose control with insulin infusion reduces the risk of surgical site infections for patients with diabetes who are undergoing cardiac surgery.

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