unfamiliar or uncomfortable with basal-plus or basal-bolus insulin (BBI) regimens.8–13
A major challenge to insulin use in the hospital is related to variability in food intake and carbohydrate exposure, with associated concerns for hypoglycemia when patients are not eating regular meals.14–16 Appropriate timing of prandial insulin administration can be complicated by lack of coordination in the timing of food tray delivery with point-of-care (POC) measures of capillary blood glucose (BG) and insulin administration, tasks that are performed by personnel from different departments in the hospital setting. Some patients are unable to ingest prescribed calories because of lack of appetite or dislike of hospital meals. Other patients may skip meals and instead consume snacks and meals brought to the hospital by friends or family members without informing nursing personnel of the need for prandial insulin.14
One of the most frequently encountered scenarios in the care of individuals with diabetes treated with noninsulin or insulin therapy in the hospital is what to do during periods of fasting or inability to take oral nutrition.3,4,15 Scheduled periods of fasting for diagnostic testing or surgical procedures are frequent occurrences in the inpatient setting. Although there is a general awareness of the need for continuation of some form of glucose-lowering therapy during periods of fasting in patients with diabetes, there is uncertainty about how to modify therapy in a way that prevents both hyperglycemia and hypoglycemia.7,15,17 Many patients are admitted through same-day surgery units for short outpatient procedures as well as complicated prolonged procedures that require postoperative hospitalization. Therefore, recommendations for adjustments to a glycemic management regimen often begin at home.15
This chapter will review an approach to adjustments in noninsulin and insulin therapies during periods of fasting and will address the issue of timing of insulin therapy with meals. This section starts with a patient case followed by a discussion of how to modify BBI therapy during a 2-day period of consumption of only clear liquids before a planned surgical procedure. For purposes of this discussion, NPO (nil per os: nothing by mouth) will be used whenever a patient is placed in a fasted state.
Issues to Consider When Writing Consult Notes and Making Recommendations
Patient Case A 64-year-old woman with insulin-treated type 2 diabetes (T2D) is admitted to the hospital for aortic valve replacement. She will be receiving only clear liquids for 2 days before the procedure and will remain NPO after midnight before the procedure. Her admission weight is 76 kg (167 lbs). Her HbA1c 1 month before admission was 8.7%. Her home insulin regimen consists of detemir insulin 40 units at 8 p.m. with fixed doses of 14 units of insulin aspart prior to each meal. She reports home fasting glucose levels of 130–150 mg/dL with daytime values that range between 120 and 260 mg/dL. You are asked to make recommendations regarding her insulin regimen.
Insulin Modifications for Patients on Clear Liquid Diets
Clear liquid diets include the use of fruit juices, sodas (lemon-lime soda and ginger ale), gelatin, popsicles, and broth. Many of these foods are caloric beverages with high sugar content that require doses of nutritional insulin to maintain glycemic control (Table 5.1).
Similar to insulin glargine, detemir is a basal insulin, ideally covering insulin needs in the absence of any food intake.18,19 In the majority of instances, there is no need to reduce the dose of the basal insulin for a clear liquid diet. The patient in this case was on fixed doses of premeal insulin with wide variability in her glycemic control at home, likely representing variability in her caloric consumption at home.
To determine a premeal insulin dose for a clear liquid diet, calculate the prandial insulin dose according to planned carbohydrate intake (Table 5.1).16,20 For example, 4 ounces of apple juice or lemon-lime soda contains ~15 g of carbohydrate. The ratio of insulin-to-carbohydrate intake (insulin-to-carbohydrate ratio [ICR]) could be based on the total daily dose (TDD) of basal insulin using one of several published formulas. Of these, the following formulas are the easiest to use:21
400/TDD basal insulin (5.1)
2.8 × weight (lb)/TDD basal insulin (5.2)
Although these formulas have been accepted and used in many clinical trials, other authors have proposed dosing formulas that call for higher mealtime insulin delivery.20,22–26 Caution is advised in using any formula because of differences in patient populations (type 1 diabetes [T1D] vs. type 2 diabetes [T2D]) and insulin delivery devices (subcutaneous injections vs. insulin pumps) used in these prior studies, with some including lean patients with T1D using insulin pump therapy.26
For the patient in this case, consumption of 12 ounces of ginger ale (32 g), 1 cup of gelatin (19 g), and 1 popsicle (17 g) at a meal provides a total carbohydrate intake of 68 g (Table 5.1). Using the first formula (i.e., 400/TDD detemir), her prandial insulin dose would be based on an ICR of 1 unit for each 10 g of carbohydrate or 7 units of insulin aspart. Using the second formula (2.8 × 167 lbs/ TDD detemir), her ICR would be 1 unit for each 12 g of carbohydrate or 6 units of aspart. Both methods provide a dose of aspart that is roughly equivalent to what would be achieved by reducing the current dose of 14 units by 50%. Correction insulin can be used to provide additional aspart insulin for premeal blood glucose above the desired range, with the majority of correction scales beginning at blood glucose levels >140 mg/dL.20,27
Table 5.2— Guideline for Promoting Appropriate Insulin Administration for Meals on Demand
• Patients are able to order meals within regularly scheduled time intervals
• Nutrition services will call patient for any orders not placed with these intervals
• Personnel distributing meals alert the RN that a meal has been delivered to patient to prompt a BG check and insulin administration
• Prominent note is provided with meal to remind a patient to request a BG check and insulin dose before ingesting a meal
• Avoid administration of meal insulin at intervals of <4 h to avoid insulin stacking
Another option for this patient would be to use a basal-plus-insulin regimen.28,29 This option continues her current dose of detemir insulin once daily in combination with correction insulin before meals. In one study, this type of regimen was found to have a similar efficacy to BBI in hospitalized patients with T2D.29 Correction insulin can be calculated using a formula of 1,700/TDD of insulin, which would calculate to a correction factor of 21 for the patient in this case.21 In the inpatient setting, standardization of correction insulin scales can help prevent errors that occur when too many different algorithms are used.30 Although the calculated correction insulin dose21 for this patient is >40 mg/dL, incremental dosing that is made available on many published correction insulin scales, it would be reasonable to use one of the standardized correction scales to avoid confusion and potential medication errors.30,31 An argument against using a basal-plus regimen for the patient in this case is her requirement for fairly high doses of prandial insulin as an outpatient. This indicates the patient is likely to experience significant hyperglycemia following ingestion of moderate amounts of simple carbohydrates available on a clear liquid diet.
Insulin Regimen Modifications Recommended for Patients Who Become NPO
Once a patient is no longer consuming any caloric foods or liquids, there is no need to provide scheduled nutritional or prandial doses of insulin. Continuation of the basal insulin in combination with correctional insulin for glycemic excursions outside of established goal ranges (i.e., basal plus) is required. Although there is no consensus regarding what percentage of basal insulin to administer to patients who are in the fasting state, there is consensus that insulin-treated patients will require continuation
