Fluid and Electrolyte Disturbances Associated with …

1 Chapter 12 Fluid and Electrolyte Disturbances Associated with Tube FeedingsClinicians generally agree with the philosophy that Whenthe gut works, use it. That is, if gastrointestinal function ispresent, enteral feedings should be favored over parenteralnutrition. Aside from being less expensive, enteral feedingsare Associated with better preservation of both immunefunction and intestinal function. Nevertheless, tube feed-ings are not without problems. Primarily, these problemsarise because many tube-fed patients have preexisting fluidand Electrolyte imbalances Associated with their underlyingillnesses. A multitude of enteral products are available;some are disease specific and others are standard (suit-able for most patients). It is important to review some ofthe characteristics of enteral formulas to understand theirpotential impact on Fluid and Electrolyte OSMOLALITYO smolality is an important characteristic of an enteral for-mula; it is primarily a function of the number and size ofmolecular and ionic particles in a given volume.

2 Table 12-1shows the wide variance in osmolalities of some com-mercially available tube feeding formulas. Whereas someformulas approximate the osmolality of plasma (300mOsm/kg) and, therefore, are deemed isotonic, othershave considerably higher osmolalities and are referred to as hypertonic. Isotonic formulas are generally well toler-ated; in contrast, hypertonic formulas can slow gastric em-ptying and cause nausea, vomiting, and distention. Whenhypertonic formulas are administered in the small bowel,179 Table 12-1 Characteristics of Selected Enteral FormulasContent (mg) per 8 Ounces of FormulaFormulaCal/mLOsmolalityNaKCaPMgGl ucerna 35522037017017067 Glucerna : All of the formulas are made by Abbott Laboratories, Abbott Park, Illinois. Formulations may have changed since this table was prepared; refer to themanufacturer s 9/14/10 11:42 AM Page 179 Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning.

3 LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION they create an osmotic gradient that pulls water into theintestine. If the Fluid is not adequately absorbed, crampingand diarrhea may result. For this reason, hypertonic for-mulas are introduced slowly until the body has time toadapt to formula s osmolality affects the renal solute load andthus the water requirements. Renal solute load can bedefined as the sum of substances that must be excreted bythe kidneys (such as urea, potassium, sodium, and chlo-ride). A high renal solute load (created by nutrient use)requires a large water volume for excretion. If enough wateris not provided, the patient will become dehydrated. There-fore, the renal solute load imposed by a formula should beconsidered in patients with impaired renal function and inthose with increased losses of body fluids (such as fromfever or diarrhea).

4 A number of liquid medications administered via feedingtubes are hyperosmolar and can cause osmotic diarrhea ifgiven undiluted, especially into the small intestine. Amongthese products are acetaminophen, potassium chloride, andphosphosoda. For example, the osmolality of an acetamino-phen solution can range between 3000 and 6000 delivery of hyperosmolar preparations should be lim-ited to the stomach; even then, the medications should bediluted before administration and water flushes giventhrough the tube before and after delivery. This action notonly dilutes the medication, but also enhances its absorp-tion. Of course, it is important to keep any Fluid restrictionsin mind. At times, the parenteral route may be necessary forelectrolyte supplements when they are not tolerated by theGI OF FORMULASC ommercial sources supply standardized as well as special-ized products targeted to patients with specific problems,such as renal, hepatic, and respiratory failure.

5 Becausenumerous enteral formula products are available, it isimportant to read the literature supplied by formulas are classified as standard, elemental, or spe-cialized, with multiple formulas available in each FormulasA standard formula contains intact protein and is similar toan average diet for healthy individuals; it can be adminis-tered to patients with normal digestion. These formulas areavailable with and without added fiber. Unless there is evi-dence to the contrary, a standard formula is the product ofchoice for the majority of tube-fed FormulasA calorie-dense formula usually contains kilocaloriesper milliliter of Fluid and is used in patients who requirefluid restriction for example, patients with congestiveheart failure, syndrome of inappropriate antidiuretic hor-mone (SIADH), or renal failure. For instance, for a patientrequiring 1800 kcal/day, the amount of water delivered inthe formula could be reduced by 900 mL merely by convert-ing from a calorie per milliliter formula to a caloriesper milliliter FormulasFiber-containing formulas may be helpful in patients withdiarrhea or constipation.

6 The fiber added to the formulaincreases stool bulk and helps to regulate bowel that the colon is the final site of water and elec-trolyte absorption and ultimately determines fecal composi-tion. In patients who can tolerate high-residue formulas,use of a high-fiber formula is thought to increase thesodium and water absorptive ability of the colon, therebyminimizing fecal Fluid loss. For example, in a study of agroup of 20 critically ill patients randomized to either a sol-uble fiber formula or a fiber-free formula, the number ofliquid stools was significantly lower in the fiber been recommended that this type of formula be consid-ered in patients for whom tube feedings will be the solesource of nutrition for a long period of time, especially ifintestinal disease is FormulasAn elemental formula contains hydrolyzed protein and sim-ple sugars; further, it has a low fat type of for-mula is administered to patients with severe malabsorption,such as may be seen with intestinal atrophy or loss of absorp-tive surface Associated with profound malnutrition, criticalillness, and acquired immune deficiency syndrome (AIDS).

7 Research reports focusing on the efficacy of elementaldiets provide mixed findings. For example, several studieshave indicated that peptide-based formulas are helpful inavoiding diarrhea in hypoalbuminemic, critically ,9In contrast, a larger prospective study did notdemonstrate any advantage in a peptide-based formula overa standard, polymeric , a meta-analysis of10 trials involving a total of 334 patients found no significant180 CHAPTER12 Fluid ANDELECTROLYTEDISTURBANCESASSOCIATED 9/14/10 11:42 AM Page 180 Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning.

8 LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION difference in the efficacy of elemental versus One group of investigators recommended thatthe use of elemental formulas be limited to specific condi-tions in which absorption has been definitely shown to Another group of investigators indicated thatenteral feeding with elemental diets can lessen diarrhea inpatients infected with human immunodeficiency virus(HIV).13 Elemental formulas are more expensive than stan-dard formulas and have an unpleasant taste and FormulasFormulas for Renal DiseaseCompared to standard enteral formulas, formulas designedspecifically for renal patients are calorically dense, are lowerin protein, and have lower concentrations of potassium,magnesium, and phosphorus. Such a formulation is usedbecause patients with renal failure have difficulty excretingurea (the end product of protein metabolism), electrolytes(especially potassium, phosphorus, and magnesium), andfluid.

9 Thus an enteral formula for a renal failure patient notreceiving dialysis should be calorically dense and restrictedin protein and minerals. The renal enteral formula containsa high percentage of essential amino acids (allowing for pro-tein synthesis with minimal production of urea). Patientswith renal failure who are being tube fed require frequentmonitoring of Electrolyte values and Fluid status. Standardenteral formulas are usually acceptable for patients withmild renal impairment or those who are on for Chronic Obstructive PulmonaryDiseaseCompared to standard formulas, enteral formulas for pa-tients with chronic obstructive pulmonary disease (COPD)are lower in carbohydrate and higher in fat a formulationintended to lower carbon dioxide production and, there-fore, improve pulmonary status. Recall that metabolism ofcarbohydrate yields more carbon dioxide than does metab-olism of fat. Lessening the formation of carbon dioxidereduces the workload on the lungs, which are responsiblefor eliminating carbon has been pointed out that the amount of carbon dioxidegenerated is more a function of the number of calories deliv-ered than of the formula s fat-to-carbohydrate reason, it is important to not overfeed pulmonarypatients.

10 Moreover, it is more difficult to wean a patient froma mechanical ventilator when excessive calories are for Hepatic DiseaseFor patients with hepatic insufficiency who cannot toleratethe protein contained in standard enteral formulas, special-ized products are available that are calorically dense and lowin protein (to minimize ammonia production). Hepaticformulas contain increased amounts of branched chainamino acids and reduced amounts of aromatic , hepatic enteral formulas shouldreduce the neurological symptoms that occur with products are expensive, however,and their use is generally limited to patients with hepaticfailure Associated with for DiabetesThe carbohydrate content in standard enteral formulas maynot be tolerated by patients with diabetes or stress-inducedglucose intolerance. Thus use of a formula with complexcarbohydrates (such as fructose) and fiber improves bloodsugar control by delaying gastric emptying and reducingintestinal transit toward better glycemic con-trol with the use of specialized diabetic formulas have beenreported in several small 21 However, it is unclearif the difference in glycemic control between specializeddiabetic formulas and standard formulas is clinically signifi-cant.