Metabolic Effects Associated with NPO Status
Prolonged fasting is associated with reductions in insulin sensitivity in patients with and without diabetes.48,49 In the absence of diabetes, fasting is associated with a decline in insulin levels and an increase in glucagon, with associated increases in circulating free fatty acids that further impair insulin sensitivity.49 Although it is beyond the scope of this chapter, the reader is referred to several recent publications that explore the continued administration of carbohydrates in preparation for surgical procedures as a way to avoid potentially harmful increases in counterregulatory hormones.49–52
For prolonged procedures, the IV administration of glucose- or dextrose- containing IV fluids may help to limit perioperative changes in insulin sensitivity. Administration of glucose-containing IV fluids contributes to elevated BG. One liter of D5%-containing IV fluid has 50 g of glucose or ~200 calories. If this is infused at a rate of 100 cc/h, this provides 5 g of glucose or 20 calories/h. This calculates to ~1.2 mg/kg/min for an individual who wieghts 70 kg. Although this amount may seem trivial, personal experience indicates that in some cases, this is sufficient to contribute to mild elevations in BG that prompt administration of additional insulin. No published studies have investigated the effect of these low glucose infusion rates on hyperglycemia in hospitalized patients. In one study, glucose infusion rates of ≤4 mg/kg/min were not associated with hyperglycemia in patients without diabetes receiving total parenteral nutrition.53
Preventing Hypoglycemia When NPO Status Is Imposed Abruptly
Some patients may be abruptly placed in the fasting state after full doses of a weight-based BBI regimen has been administered, placing patients at increased risk for hypoglycemia.39 We generally recommend that infusions of D5% or D10% be initiated with more frequent glucose monitoring as a way to reduce this risk.54
Patients Who Experience Hypoglycemia while NPO for a Procedure
Little data have addressed the issue of patients who experience hypoglycemia while NPO.7 Studies that discuss the benefit of preoperative carbohydrate loading can provide a guide to the safety of ingesting carbohydrate-containing liquids in the event of a hypoglycemic event.55,56 Our recommendation to patients is to consume 4 ounces of a caloric clear liquid beverage in the event of a hypoglycemic event during the fasting period (Table 5.1).15 If hypoglycemia persists, this can be repeated as necessary. Patients need to inform personnel in the same-day surgical suite that that this occurred.
Timing of Insulin and Meals
Patient Case The patient in this case eventually will resume eating regular meals within 24–36 h of a surgical procedure. Although food intake may begin while she is in a surgical intensive care unit, she eventually will be transferred to a nursing unit where they will need to coordinate insulin dosing and meal administration.
Hospitalized patients with diabetes depend on hospital personnel to monitor blood glucose levels, administer diabetes medications, and deliver meals in a timely and coordinated manner.14,16,57 This is a challenge to personnel providing care to inpatients with diabetes in the best of circumstances. This has become even more difficult following the introduction of “meals on demand” or “room service” as part of routine care in many hospitals.16
Hospitals have responded to the introduction of meals on demand in one of several ways. Some have tried unsuccessfully to disallow this practice in insulin-treated patients, resulting in patient and therefore administrative dissatisfaction. Others have implemented guidelines to help minimize the chaos that leads to poor coordination of the components of administering meal-related insulin (Table 5.2).57 One institution introduced a procedure that included posting of signs on the doors of patients scheduled to receive nutritional insulin with the following statement: “Before you eat, please call your nurse for your premeal medication.” Meal servers remove the sign at the time of meal tray delivery and give this to the patient who then calls the nurse to bring their insulin. This resulted in a significant improvement in the percentage of patients receiving meal insulin in a timely manner.58
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
The most important component of promoting the glycemic success (i.e., avoiding hypoglycemia and hyperglycemia) is the need to establish communication among the patient, nurse, and nutrition services. This can be achieved by providing education to nursing and nutrition services personnel regarding the pharmacokinetics of insulin preparations as this relates to meal ingestion.16 Engaging patients, dietary, and nursing personnel in ensuring timely administration of premeal insulin can facilitate the coordination of activities that promote patient safety in the hospital setting.
Carbohydrate Counting in the Hospital
Even patients with a good appetite who are eating regular meals pose a challenge to diabetes management in the hospital. The decisions as to how and when to cover carbohydrate content of patient meals usually fall under the direction of hospital personnel rather than the patient, even for patients who self-managed their diabetes before admission.1,3–5 Some hospitals use carbohydrate-controlled diets for all patients with diabetes, which provide a fixed amount of carbohydrate with each meal allowing for more accurate prandial insulin administration.
As outlined previously, many hospitals have introduced programs that allow patients more flexibility in the timing and content of their meals. One justification for this approach is an improvement in patient satisfaction with their care while hospitalized, which has increased their popularity among hospital administrators who are concerned with hospital rankings. As a way to adjust to this variability in the timing of meal delivery for individual patients, some hospitals have adopted the practice of administrating prandial insulin based on carbohydrate intake. This practice requires extensive training and education of nutrition and nursing personnel.
These meal-on-demand practices, in association with insulin dosing based on carbohydrate counting and insulin sensitivity, can allow for more accurate prandial insulin coverage. To date, only one relatively small study had formally examined this issue and has found that a fixed meal dosing strategy provided similar glucose control as flexible meal dosing.20 There were no group differences in mean carbohydrate intake per meal consumed, frequency of hypoglycemia, or overall patient satisfaction. In this study, an inpatient diabetes team provided all diabetes treatment with expertise in glycemic management, a service that is not available in most hospitals. This raises questions about the safety of this practice in hospitals where these teams may not be available.
Timing of Prandial Insulin Administration
There are varying opinions as to the optimal timing of insulin administration in the hospital setting. Some clinicians prefer that insulin be given about 15 min before the meal, which is similar to recommendations for the outpatient setting for rapid-acting insulin administration. Others feel that it is safer to administer prandial doses of insulin following a meal, particularly when there is uncertainty regarding how much food a patient will consume.