Tube Feeding and Blood Glucose Levels

August 2007

Optimizing Enteral Feeding for Patients With Diabetes
By Theresa A. Fessler, MS, RD, CNSD
Today's Dietitian
Vol. 9 No. 8 P. 52

A patient complains that she cannot tolerate her enteral feeding because of nausea and vomiting. A stroke patient's wife tells you that she increased her husband's amount of tube feeding well beyond his requirement because he continues to lose weight. After further questioning, you find that these patients have glucose levels ranging from 200 to 300 milligrams per deciliter. What should you do?

Management of enteral nutrition (EN) is more challenging because of the metabolic and physical complications of diabetes mellitus (DM). With continuing advancements in DM care, there is always more to learn. Beyond basic nutritional assessments, RDs can positively impact patient care by detecting glucose problems, careful monitoring, educating patients, and choosing appropriate EN formulas, feeding routes, and feeding schedules.

Identifying the Problem
Awareness of DM risk factors, diagnostic criteria, and symptoms is helpful to ensure that patients on EN receive optimal care. DM risk is higher for those aged 45 or older or with a body mass index greater than 25 kilograms per square meter, as well as several other factors.1 DM can be diagnosed by a random glucose greater than 200 milligrams per deciliter with symptoms, postprandial glucose greater than 200 milligrams per deciliter, or a fasting (eight-hour) glucose greater than 126 milligrams per deciliter.1 While type 1 DM is usually quickly recognized due to acute symptoms and hyperglycemia, type 2 DM may go unnoticed for years. For those who work in long-term or home care settings, DM identification is more intuitive. Patient complaints of the classic symptoms—polyuria, polydipsia, and unintended weight loss—especially if they are taking goal amounts of EN, are possible signs of DM.

Hyperglycemia can occur as a complication of other disorders, such as cystic fibrosis and pancreatitis.1 In chronic pancreatitis, both insulin- and glucagon-producing cells are destroyed, and patients are prone to both hyperglycemia and hypoglycemia.2 Chronic use of steroid medications and immunosuppressants can predispose patients to hyperglycemia, and stress-induced diabetes can occur during acute critical illness.3

Importance of Glucose Control
Hyperglycemia over the long term leads to microvascular, macrovascular, and neurologic complications. Retinopathy, nephropathy, neuropathy, peripheral vascular disease, and atherosclerosis can develop. The most common consequences of DM neuropathy are foot ulcers and amputations.1 In critical care, hyperglycemia can increase catabolism and impair immune function and wound healing. Strict glucose control can decrease the incidence of infectious complications.3 Intensive insulin therapy as compared with conventional treatment has resulted in decreased morbidity and mortality in surgical intensive care units (ICU) and decreased morbidity in medical ICU patients.4,5

Medications
Medication for glucose control depends on many factors, such as the degree of insulin resistance, presence of infection and other disease states, other medications, gastrointestinal (GI) tolerance of EN, calorie levels, and feeding schedule. For critically ill patients who are on continuous EN in ICU settings, an insulin drip is recommended, with the goal of 80 to 110 milligrams per deciliter.3-5 For other hospitalized patients on EN, a long- or intermediate-acting insulin, along with regular or rapid-acting insulin on a scheduled and/or as needed "sliding scale," is commonly used. Dosages are adjusted depending on whether the EN is given nocturnally or diurnally and whether it is given as boluses (several smaller feedings) or continuously (all day and night). Familiarity with the different types of insulin and their duration of effect is helpful in identifying potential problems with glucose control.6

Some type 2 DM patients do not need medication, while others use oral hypoglycemic medications alone or in combination with insulin. Many different classes and brands of DM medications are available. Pharmacists should be consulted for information about the ability to crush and administer these via feeding tubes. Oral DM medications are often discontinued at the time of hospital admission to prevent hypoglycemia and other complications. In the hospital, EN feedings are skipped for procedures, tests, or GI intolerance. Metformin is contraindicated in patients with renal insufficiency and can increase the risk for lactic acidosis in those with congestive heart failure (CHF) and other conditions. Thiazolidinediones can be unsafe in patients with CHF, and they also have a delay in producing a glucose-lowering effect.1,6,7

Care Planning
Goals are for nutritional maintenance or repletion, avoidance of excessive calories, and glucose control. The daily EN schedule should be the same or as similar as possible. Glucose levels should be checked before, during, and after EN feedings until stabilized. Nurses and RDs are often the first to become aware of blood glucose fluctuations; changes in weight, activity, and EN tolerance; or if patients have changed their EN schedule. The RD should notify physicians or, in the case of home care, advise patients or caregivers to do this so medications can be adjusted. Glycosylated hemoglobin (Hb A1C) should be tested twice per year for stable patients and four times per year for those whose glucose control has not been stable or whose EN or medications have changed.1 The goal for Hb A1C is less than 7% or better.1

EN for obese patients should be limited in calories to allow for gradual weight loss and glucose control. A 1-calorie-per-milliliter high-protein product is useful in these situations. The amount of EN formula will likely be restricted so much that the adequacy of other macronutrients and micronutrients is compromised. Protein supplements and liquid or crushed multivitamin tablets can be mixed with water and administered via the feeding tube. Supplements should be followed by water flushes to avoid tube clogging.

Severely malnourished patients need lower calorie levels at the start (15 to 20 kilocalories per kilogram) because of the refeeding syndrome risk.8 Careful monitoring and repletion of electrolytes, particularly potassium, magnesium, and phosphorus, and vitamin supplementation may be necessary.8 After the refeeding risk has passed, additional calories are needed for weight gain, with attention to glucose control to ensure utilization of carbohydrate.

For some patients with dysphagia, improvement in swallowing function may be possible, and EN can be weaned. A nocturnal EN cycle can be used or one half to one can of EN formula can be taken at various times during the day to supplement meals and snacks until patients are able to meet full nutritional needs orally.

Patient Education
Prior to hospital discharge, patients and caregivers need to be aware of timing medications, EN schedule, EN formula and water needs, glucose monitoring plans, and the signs and symptoms of hypoglycemia. Keeping a log of blood glucose values is important, as is knowledge of what to do in situations of elevated or low glucose readings. Patients should be taught what is actually considered high or low, as some have the misconception that glucose greater than 200 milligrams per deciliter is "normal" during the feeding. Instructions should also be given on medication adjustment in times of illness or skipped feedings.

Complications
Gastroparesis
Delayed gastric emptying is common in both type 1 and type 2 DM, although it can also occur in many other disorders.9 Management of DM gastroparesis involves oral diet modification, antiemetic and prokinetic medications, and, in some cases, surgery.10 Glucose control is important, as it may improve symptoms enough to alleviate the need for EN.10 If other therapies fail, EN becomes necessary. Some patients may need EN only to supplement an oral diet consisting of small meals low in fiber and fat. Liquids are better tolerated because of quicker gastric emptying. Other patients cannot tolerate even small amounts of food by mouth. EN products that contain 1.5 kilocalories per milliliter are useful to help limit the volume of EN to meet nutritional needs.

Signs of gastroparesis in the EN-fed patient include nausea, fullness, persistent high gastric residual volumes, reflux, and vomiting. Gastric feeding tolerance can be improved by prokinetic medications and slowing the EN infusion rate with the use of gravity feeding bags. If necessary, a feeding pump can provide more control. In severe gastroparesis, a jejunal feeding tube or G tube with a jejunal feeding extension (PEG-J or G-J) is used to allow pump-facilitated EN directly into the small bowel. The gastric port of G-J tubes can be used for venting of stomach contents to help control nausea and vomiting. Patients with gastroparesis are at a higher risk for small bowel bacterial overgrowth, in which case fiber-free formulas are generally better tolerated as fiber can aggravate symptoms of gas and bloating.10

Diarrhea
Diarrhea is a common complaint for some EN patients. Determining the cause is necessary for effective management. Possible causes include GI infection (such as Clostridium difficile), motility disorders, and malabsorption.11 Episodic diarrhea, alternating with periods of constipation, can occur because of diabetic autonomic neuropathy.1,12 Some medications, such as sorbitol-containing elixirs, potassium and magnesium replacements, and antibiotics, can cause diarrhea. One should also check for use of stool softeners and laxatives. Small bowel bacterial overgrowth can cause a malabsorptive diarrhea, or steatorrhea. Steatorrhea can also occur in pancreatic exocrine insufficiency in patients with pancreatitis, cystic fibrosis, or after partial pancreatectomy.

To treat diarrhea, offending medications can be removed, and crushed tablets can replace some sorbitol-containing elixirs. Antibiotics are used to treat intestinal infections. For pancreatic exocrine insufficiency, pancreatic enzyme replacement with standard EN formulas or elemental EN formulas can be used.13 The addition of a soluble fiber supplement or change to a fiber-containing formula may be helpful to help promote formed stools and improve colon health.14 For motility disorders, or if other methods fail, various antidiarrheal medications can be used. Evaluation for celiac disease, inflammatory bowel disease, or other GI disorders may also be necessary.11

Hypoglycemia
The treatment for hypoglycemia (glucose less than 70 milligrams per deciliter) is administration of 15 to 20 grams of glucose.15 Fruit juice or other beverages containing sugar can be used via the feeding tube. A response should be seen in 10 to 20 minutes, and further testing should be done after 15 minutes to one hour.1 Patients who are fed on a nocturnal EN cycle but have a recurrent period of hypoglycemia during the day can adjust their schedule by taking a small portion of their EN during the daytime.

Electrolyte Abnormalities
As insulin facilitates entry of glucose into cells, hypokalemia and hypophosphatemia can occur because of intercellular shift of potassium and phosphorus. Potassium and phosphorus may need to be supplemented until glucose levels are stabilized, especially during treatment of DM ketoacidosis and malnutrition.8
Hyperglycemia causes abnormalities in serum sodium because of the shift of water from intracellular to extracellular fluid. An increase of 100 milligrams per deciliter of glucose above normal decreases serum sodium level by approximately greater than 1.6 milliequivalents per liter and is termed hypertonic hyponatremia.16,17 Awareness of this condition helps to prevent inappropriate treatment, as it may be misinterpreted as a free water excess or a sodium deficit. The sodium level normalizes when glucose is normalized.17

Enteral Formulas
Generally, standard EN formulas can be used for DM patients. During the past decade, however, interest has grown and several studies have been published regarding the use and efficacy of specialized EN formulas for DM patients in both critical care and long-term settings.18 These formulas are lower in carbohydrate and higher in fat—primarily higher in monounsaturated fats—than standard formulas. Monounsaturated fats are used to promote healthier plasma lipid profiles. Fiber is included, as it is thought to improve glucose control through delay in both gastric emptying and intestinal absorption of glucose.14 Fructose is used as part of the carbohydrate content, theorized to help decrease glycemic response.19,20

A meta-analysis that involved seven studies of EN and 16 studies of oral supplements showed improved glycemic control with specialized DM compared with standard formulas.18 Some of the studies, however, were of small sample size, short duration, and/or used poorly described methods. Reduced insulin requirements with use of specialized DM formulas for EN-fed patients were reported in several studies, and others showed lower postprandial and peak glucose levels with specialized DM as compared with standard products.18,21

The routine use of specialized formulas for DM patients is controversial. First, the macronutrient content does not "match" with previous oral diet recommendations of the National Academy of Sciences for 45% to 65% of calories as carbohydrate (mostly complex) and 20% to 35% of calories as fat.22 Secondly, current available research is unclear as to the long-term effects of specialized DM as compared with standard formulas. Clinical outcomes, such as complication rates, and mortality have not been evaluated with longer term use.18 Thirdly, healthcare professionals will need proof that the clinical benefits will outweigh the higher cost of these products.

More research is needed on the use and efficacy of specialized DM formulas, as well as well-designed, long-term studies with larger sample sizes for adequate statistical power and to address possible differences for treatment of type 1 and type 2 DM and clinically relevant outcomes. The American Diabetes Association, in a recent position statement, recommends that either a standard formula that contains 50% of calories as carbohydrate or a specialized formula containing only 33% to 40% of calories from carbohydrate may be used for EN tube feedings.15

With the right knowledge and appropriate monitoring skills, RDs can optimize care and outcomes for patients with DM. There is always more to learn as the field of diabetes care is continuously advancing.

— Theresa A. Fessler, MS, RD, CNSD, is a nutrition support specialist at the University of Virginia Health System in Charlottesville and a freelance writer.

References

1. American Diabetes Association. Nutrition Recommendations and Interventions for Diabetes: A position statement of the American Diabetes Association. Diabetes Care. 2007;30 Suppl 1:S48-65.

2. Forsmark CE. "Chronic Pancreatitis." In: Feldman M, Friedman LS, Sleisenger MH (eds). Sleisenger and Fordtran's Gastrointestinal and Liver Disease: Pathophysiology/Diagnosis/Management, 7th Edition. Saunders, 2002.

3. Butler SO, Btaiche IF, Alaniz C. Relationship between hyperglycemia and infection in critically ill patients. Pharmacotherapy. 2005;25(7):963-976.

4. Van den Berghe G, Wouters P, Weekers F, et al. Intensive insulin therapy in critically ill patients. N Engl J Med. 2001;345(19):1359-1367.

5. Van den Berghe G, Wilmer A, Hermans G, et al. Intensive insulin therapy in the medical ICU. N Engl J Med. 2006;354(5):449-461.

6. Lacy CF, Armstrong LL, Goldman MP, et al. Drug Information Handbook: A Comprehensive Resource for All Clinicians and Healthcare Professionals, 15th Edition. Hudson, Ohio: Lexi-Comp, Inc., 2007.

7. Boucher JL, Swift CS, Franz MJ, et al. Inpatient management of diabetes and hyperglycemia: Implications for nutrition practice and the food and nutrition professional. J Am Diet Assoc. 2007;107(1):105-111.

8. McCray S, Walker S, Parrish CR. Much ado about refeeding. Pract Gastroenteroly. 2005;29(1):26-44.

9. Jones MP. Management of diabetic gastroparesis. Nutr Clin Pract. 2004;19(2):145-153.

10. Parrish C, Yoshida C. Nutrition Intervention for the patient with gastroparesis: An update. Pract Gastroenterol. 2005;29:29-66.

11. Malone AM, Seres DS, Lord L. "Complications of Enteral Nutrition." In: Gottschlich MM (ed). The A.S.P.E.N. Nutrition Support Core Curriculum: A Case-Based Approach — The Adult Patient. Silver Spring, Md.: American Society for Parenteral and Enteral Nutrition, 2007:246-263.

12. Kim DD, Ryan JC. "Gastrointestinal Manifestations of Systemic Diseases." In: Feldman M, Friedman LS, Sleisenger MH (eds). Sleisenger and Fordtran's Gastrointestinal and Liver Disease: Pathophysiology/Diagnosis/Management, 7th Edition. Saunders, 2002.

13. Giger U, Stanga Z, DeLegge MH. Management of chronic pancreatitis. Nutr Clin Pract. 2004;19(1):37-49.

14. Zimmaro Bliss D, Jung HJG. "Fiber." In: Gottschlich MM (ed). The A.S.P.E.N. Nutrition Support Core Curriculum: A Case-Based Approach — The Adult Patient. Silver Spring, Md.: American Society for Parenteral and Enteral Nutrition, 2007:88-103.

15. American Diabetes Association. Nutrition Recommendations and Interventions for Diabetes: A position statement of the American Diabetes Association. Diabetes Care. 2007;30 Suppl 1:S-48-65.

16. Adrogue HJ, Madias NE. Hyponatremia. N Engl J Med. 2000;342(21):1581-1589.

17. Hillier TA, Abbott RD, Barrett EJ. Hyponatremia: Evaluating the correction factor for hyperglycemia. Am J Med. 1999;106(4):399-403.

18. Elia M, Ceriello A, Laube H, et al. Enteral nutritional support and use of diabetes-specific formulas for patients with diabetes: A systematic review and meta-analysis. Diabetes Care. 2005;28(9):2267-2279.

19. Charney P, Hertzler SR. Management of blood glucose and diabetes in the critically ill patient receiving enteral feeding. Nutr Clin Pract. 2004;19(2):129-136.

20. Moore MC, Davis SN, Mann SL, et al. Acute fructose administration improves oral glucose tolerance in adults with type 2 diabetes. Diabetes Care. 2001;24(11):1882-1887.

21. Pohl M, Mayr P, Mertl-Roetzer M, et al. Glycaemic control in type II diabetic tube-fed patients with a new enteral formula low in carbohydrates and high in monounsaturated fatty acids: a randomised controlled trial. Eur J Clin Nutr. 2005;59(11):1221-1232.

22. Food and Nutrition Board. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). Washington, D.C.:National Academies Press, 2005.

23. Nestlé Nutrition. "Complete Nutrition Support with PREBIO1TM for Patients with Hyperglycemia." Available here. Accessed May 28, 2007.

24. Ross.com Product Handbook. Available here. Accessed May 1, 2007.

25. Novartis Medical Nutrition Product List. Available here. Accessed May 28, 2007

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