MKSAP quiz: Insulin in the ICU

This month's quiz asks readers to evaluate a 67-year-old woman who is transferred to the cardiothoracic ICU after undergoing repair of an abdominal aortic aneurysm. She has a 12-year history of type 2 diabetes mellitus.

A 67-year-old woman is transferred to the cardiothoracic ICU after undergoing repair of an abdominal aortic aneurysm. She has a 12-year history of type 2 diabetes mellitus. Her blood glucose level on arrival at the ICU is 289 mg/dL (16.0 mmol/L). Although no longer on a cardiopulmonary bypass pump, she remains intubated and on vasopressors.

Which of the following is the best treatment to control her blood glucose level during her ICU stay?

A. Insulin glargine, once daily
B. Intravenous insulin infusion
C. Neutral protamine Hagedorn insulin, twice daily
D. Regular insulin administered on a sliding scale

Reveal the Answer

MKSAP Answer and Critique

The correct answer is B. Intravenous insulin infusion. This item is available to MKSAP 18 subscribers as item 9 of extension set 4 in the Endocrinology and Metabolism section. More information about MKSAP 18 is available online.

This patient should receive intravenous insulin infusions during her ICU stay. The intensive control of glucose levels in hospitalized patients during critical illness has garnered substantial attention over the past decade. Several randomized clinical trials have shown a benefit to patient morbidity and mortality with stringent glycemic control. The precise target remains controversial, but the bulk of the data suggests that treating to achieve glucose levels between 140 and 180 mg/dL (7.8 and 10.0 mmol/L) may be optimal. In the ICU setting, this is best and most safely achieved using intravenous insulin. Intravenous insulin infusions should be administered based on validated written or computerized protocols that allow for predefined adjustments in the infusion rate, accounting for glycemic fluctuations and insulin dose. Intravenous delivery of insulin allows for more rapid titration and does not rely on subcutaneous absorption, which may be diminished or delayed in patients with cardiogenic shock or other critical illnesses associated with poor peripheral circulation.

If it appears that ongoing insulin is required once this patient is ready for transfer to a general ward (and is eating), she should be transitioned to an injectable regimen involving long- or intermediate-acting and rapid-acting insulins. Oral agents can be restarted before discharge as long as no contraindications, such as impaired kidney function, are present.

Insulin glargine, the dosage of which is typically adjusted every 2 to 3 days until optimal glycemic control is achieved, cannot quickly guarantee adequate control during the 1 to 2 days that this patient is likely to be in the ICU. For similar reasons, using neutral protamine Hagedorn (NPH) insulin twice daily is unlikely to be the best treatment.

Although the dosage of regular insulin can be adjusted more frequently when administered on a sliding scale, this approach to glycemic control is considered inadequate because insulin is provided only when hyperglycemia becomes established. This method is not proactive enough to result in acceptable glycemic control during an ICU stay. The American Diabetes Association strongly discourages the use of only a sliding-scale insulin regimen in the hospital setting.

Key Point

  • Intensive glycemic control is best achieved in the ICU with an intravenous insulin infusion.