Interactive diabetes case 12: Perioperative management of a 67-year-old patient with type 2 diabetes who undergoes coronary artery bypass surgery

CASE — You are asked to see in consultation a 67-year-old man with type 2 diabetes who is admitted to the hospital for coronary artery bypass surgery. During a routine examination at age 53 years, the patient was found to have diabetes with a fasting blood glucose of 237 mg/dL (13.2 mmol/L). The patient weighed 210 pounds, had a body mass index (BMI) of 33 kg/m², and was put on a "diabetic diet." He lost 10 pounds over three months and fasting blood glucose levels improved to approximately 150 mg/dL (8.3 mmol/L).

He gained 15 pounds in the next year, and the fasting blood glucose rose again to 170 to 190 mg/dL (9.4 to 10.6 mmol/L). He was treated with glipizide 5 mg twice daily. The dose of glipizide was increased one year later to 20 mg twice daily. Nine years ago, metformin 500 mg twice daily was added; the dose was increased to 1000 mg twice a day six years ago. In the last two years, all glycated hemoglobin (A1C) values have been in the range of 8.5 to 9.1 percent.

The patient has hypertension and hyperlipidemia. Additional medications are lisinopril 10 mg a day, metoprolol 50 mg twice a day, isosorbide mononitrate 60 mg a day, atorvastatin 40 mg a day, and aspirin 81 mg a day.

On admission to the hospital, the patient's weight is 222 pounds and his BMI is 34.8 kg/m². The blood pressure is 145/85 mmHg right arm supine, 140/90 mmHg right arm upright. The heart rate is 60 bpm regular. Examination reveals bilateral background retinopathy and lesions consistent with previous photocoagulation therapy. The dorsalis pedis and posterior tibial pulses are absent bilaterally. Light touch sensation is markedly reduced to the distal calf level bilaterally, vibration sense is absent at the great toes and reduced at the medial malleoli and tibial tubercles, and the deep tendon reflexes are absent at the ankles. A random blood glucose level at admission is 193 mg/dL (10.7 mmol/L).

You see the patient in the cardiac surgical intensive care unit (ICU) the day after a four-vessel coronary artery bypass procedure. The blood glucose values in the operating room were variable, from 183 to 297 mg/dL (10.2 to 16.5 mmol/L). The glucose value was 187 mg/dL (10.4 mmol/L) on his arrival in the ICU, with a current downward trend. What do you recommend?

●You conclude that the glucose values are below 200 mg/dL (11.1 mmol/L), are improving, and are likely to improve. You recommend an insulin sliding scale with aspart, a rapidly acting insulin, with insulin administered every four to six hours if the glucose level exceeds 200 mg/dL (11.1 mmol/L). (See "Interactive diabetes case 12: Perioperative management of a 67-year-old patient with type 2 diabetes who undergoes coronary artery bypass surgery – A1".)

●You recommend a continuous insulin infusion using the protocol that is available in the ICU. You set the target glucose at 100 to 140 mg/dL (5.6 to 7.8 mmol/L). (See "Interactive diabetes case 12: Perioperative management of a 67-year-old patient with type 2 diabetes who undergoes coronary artery bypass surgery – A2".)

●You recommend a continuous insulin infusion using the protocol that is available in the ICU. You set the target glucose at 140 to 180 mg/dL (7.8 to 10 mmol/L). (See "Interactive diabetes case 12: Perioperative management of a 67-year-old patient with type 2 diabetes who undergoes coronary artery bypass surgery – A3".)

●You conclude that the patient's diabetes was not optimally managed based on the A1C values before admission and that the patient will need a basal subcutaneous insulin regimen at the time of discharge from the hospital. You decide to initiate this in the ICU to facilitate determination of the patient's dose requirement before discharge. You order NPH insulin 10 units at 10 PM. (See "Interactive diabetes case 12: Perioperative management of a 67-year-old patient with type 2 diabetes who undergoes coronary artery bypass surgery – A4".)