Glycemic Considerations for Tests and Procedures

Background

Achieving glycemic control is imperative for patients with diabetes undergoing tests and procedures, many of which require dietary restrictions. For these patients, mismanagement of diabetes medications during fasting periods can have dangerous consequences including hypo- or hyperglycemia. This chapter will review glycemic management and guidelines for patients with type 1 diabetes (T1D) and type 2 diabetes (T2D) undergoing tests and procedures in both the inpatient and outpatient settings.

General Approach to Glycemic Management While NPO

The glycemic management of patients who are nil per os (NPO or “nothing by mouth”) should begin with plasma blood glucose checks every 4–6 hours. Basal insulin should still be administered, but with a 20%–40% reduction. Patients with T1D require daily basal insulin to avoid diabetic ketoacidosis, a life-threatening complication of hyperglycemia. Basal insulin products are intermediate or long-acting which include insulin glargine, insulin detemir, and insulin degludec. While bolus premeal insulin should be held to avoid potential hypoglycemic episodes, correctional bolus insulin should be made available in the instance of hyperglycemia. Bolus insulin for before meals or as a correctional is rapid-acting and included insulin aspart, insulin lispro, and insulin glulisine.

An Overview of Inpatient Diabetes

INPATIENT GLYCEMIC TARGETS

Persistent hyperglycemia is associated with a range of adverse outcomes in hospitalized patients. According to the American Diabetes Association, all patients with diabetes or hyperglycemia (blood glucose ≥140 mg/dL or 7.8 mmol/L) should have a hemoglobin A1c (HbA1c) test upon admission if one was not performed within 3 months preceding admission. Injectable insulin, not oral or noninsulin subcutaneous (SQ) agents, should be prescribed in patients with pre-existing diagnoses or those with a HbA1c ≥6.5%, allowing for dosage adjustments based on blood glucose fluctuations. Once insulin therapy has been initiated, an inpatient glycemic target of 140–180 mg/dL or 7.8–10 mmol/L should be maintained. Tighter glycemic control, maintaining a target of 110–140 mg/dL or 6.1–7.8 mmol/L, is recommended only for critically ill postsurgical patients and those undergoing cardiac surgery, taking care to avoid hypoglycemia. Tight glycemic control in patients outside of these categories has been linked to increased mortality and should be avoided. Bedside glucose monitoring should occur before meals and at bedtime in patients who are eating, and every 4–6 hours in NPO patients.

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