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 of some portion of basal insulin, often in combination with periodic doses of correctional short- or rapid-acting insulin during a surgical procedure to avoid hyperglycemia.3–5,7 Withholding insulin in patients with T1D or insulin-treated T2D increases risk for diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS) with high risk for perioperative complications.15
To calculate the percentage of basal insulin to be administered to patients during periods of fasting, consider the degree of preoperative glycemic control as determined from measures of HbA1c and results of bedside BG monitoring, patient characteristics, type of diabetes, and analysis of their home regimen (physiologic vs. basal heavy). In one study, patients with T1D were given their full dose of basal insulin (glargine) on a day when they were maintained in a fasting state with a low incidence of hypoglycemia.32 Similar studies with detemir or NPH insulin have not been performed. The pharmacokinetics of NPH insulin with a peak time of action at 6–10 h following administration would support reductions in dose of 25–50% of usual doses.33,34 The pharmacokinetics of detemir can vary from a flat profile at lower doses (<0.3 units/kg/day) to a more pronounced peak action time at higher doses, again supporting recommendations for dose modifications in some patients during periods of fasting.35
One general guideline is to provide 50–75% of the usual basal insulin dose before a surgical procedure.3–5,7,15,17 In one study that employed this recommendation in 585 patients with diabetes admitted to a same-day surgical center, 21% of patients arrived at the center with BG >200 mg/dL and 2% had BG <70 mg/dL.15 This study reveals the wide variability in insulin requirements in patients during periods of fasting. Patients who are under what is considered “tight” glycemic control may require reductions in their doses of basal insulin to avoid hypoglycemia, whereas those who are under fair or poor control may require the full dose to avoid significant hyperglycemia.
Given that the patient in this case was under suboptimal control with BBI as an outpatient, she likely will require the full dose of detemir insulin before surgery. It also is likely that administration of detemir 40 units will not be sufficient to maintain glycemic control during this surgical procedure for which she will receive general anesthesia. General anesthesia is associated with increases in counterregulatory hormones and insulin resistance, often increasing insulin requirements.7,36,37 This differs from regional or spinal anesthesia in which insulin requirements often remain unchanged.7,36,37 The responsibility for glucose monitoring with administration of subcutaneous or intravenous (IV), which is preferred, doses of regular or rapid-acting insulin analogs will fall to the anesthesiologist.15,37,38
Basal-heavy insulin refers to the (usually inappropriate) use of high doses of a single daily injection of basal insulin (glargine, detemir, or NPH) to cover both prandial and basal insulin requirements. Patients on these regimens often receive >0.6 to >1 unit/kg/day of basal insulin each day. Although not recommended by endocrinologists, in reality, this is a fairly common practice. When carbohydrate intake is decreased or eliminated in the NPO state, more aggressive decreases in basal insulin doses of ≥50% are required.
Perioperative Management of Patients Receiving Noninsulin Diabetes Therapy
Evidence is insufficient regarding the best ways to manage patients receiving noninsulin diabetes therapy.7,15,17 It is generally accepted that on the morning before surgery, although patients are consuming a normal diet, all usual diabetes medications should be continued. For patients on a clear liquid diet such as the patient in this case, or those who are receiving dietary preparation for a colonoscopy, we recommend holding sulfonylurea agents because of the risk of hypoglycemia.39 Short-acting insulin secretogogues such as repaglinide and nateglinide can be continued in reduced doses. Other noninsulin therapies usually can be continued until a patient is in the fasted (NPO) state. On the morning of surgery, we recommend holding all oral and injectable noninsulin diabetes medications.15
Suboptimal HbA1c and High-Risk for Postoperative Complications
Although some evidence links preoperative glycemic control with the risk for postoperative complications, available evidence is more suggestive than absolute.40,41 In the patient in this case, there is no need to delay surgery based on her HbA1c. Two days in the hospital preoperatively allows time for insulin adjustments and for the institution of a reasonable level of glycemic control, defined as maintaining BG values between 140 and 180 mg/dL.6,7
For elective procedures (e.g., joint replacement surgery, hernia repair), patients with previous poor diabetes control can be encouraged to improve their metabolic status with the motivating factor being that this will reduce risk for postoperative complications.40,42 The optimal level of “improved control” is not defined, but the authors of this chapter recommend HbA1c values of <8.5%, which correspond to a mean BG of <200 mg/dL, the level at which risk for perioperative complications increases most significantly.43–46
Not all patients will have the ability to achieve this level of glycemic control. In these situations, personal experience and judgment are important. For example, a patient with chronically uncontrolled insulin requiring T2D with HbA1c values >12% resulting from personal chaos and stress may be encouraged to reduce their