Diets and Specific Nutrient Requirements

All diets should be lactose-free, because the intestine will have lost a significant portion of its surface area and, therefore, its disaccharidase synthetic capacity following a massive resection. In addition, patients should avoid consumption of caffeine-containing products and osmotically active medications or sweeteners (sorbitol for example) that stimulate motility and lead to a further decrease in intestinal transit.

Oral Rehydration Solutions water should be avoided because additional fluid and electrolyte losses may result. Isotonic fluids such as oral rehydration solutions (ORS) should be used instead. ORSs are useful for the maintenance of normal hydrational status in short bowel syndrome as well as in acute diarrhea. Such solutions are based on the mechanism of the sodium-glucose cotransporter, whereby both solutes are actively absorbed together by the enterocyte. Water is pulled in with both sodium and glucose (solvent drag). There are several different commercially available preparations, but most importantly, for adults, these solutions should contain 90 to 120 meq/L of sodium for optimal effectiveness. ORSs may be made up at home by dissolving sodium chloride/table salt (2.5 g), potassium chloride (1.5 g), Na2CO2 (2.5 g), and glucose/table sugar (20 g) in 1 L of water. Patients should drink ORSs whenever they are thirsty because thirst is a good sign of dehydration. ORSs will not decrease fluid losses, but will enhance fluid absorption. Because ileal water absorption is unaffected by glucose, the presence of glucose in oRSs in patients without residual jejunum is not relevant. Recent data actually suggests that hypotonic ORSs (but not water) may be preferential because of the ability of these solutions to enhance intestinal water absorption (without sodium absorption). Sodas and juices are quite hypertonic and should be avoided. An attempt should be made to have the patient consume dry solids first, followed by isotonic liquids 1 hour later. However, this may be quite difficult in practice.

Diets

Human studies have shown no benefit from high fat or high carbohydrate (in the absence of a colon) diets, or so-called "elemental" (small peptide or free amino acid-based enteral formulas), on stool weight, or energy, nitrogen, electrolyte, or mineral absorption. Dietary fat restriction will decrease steatorrhea, but will not increase fat absorption. Medium-chain triacylglycerols (MCT) are absorbed independently of bile salts and may provide a useful energy loss in patients with significant steatorrhea. There is also some colonic absorption. However, they are expensive, often unpalatable (despite modern recipes), cannot be used with cooking oil because of a low smoke temperature, may worsen diarrhea in excessive doses (> 40 g daily), and may have an adverse effect on intestinal adaptation. There have been a few case reports that suggest replacement of bile salts with ox bile may lead to improve in long chain triglyceride absorption (Hofmann, 2000).

Fats

Residual colon becomes an important instrument for nutrient digestion and absorption. Therefore, dietary recommendations may vary depending on whether colon is present. Unlike in the patient with a jejunostomy, dietary fat intake should be restricted in the patient with remaining colon, although not to the extent as to render the diet unpalatable. Patients should also be provided with a diet low in oxalate content.*

OXYLATES

Normally, dietary oxalate (and bile acids) is bound to calcium in the intestinal tract. This renders oxalate unavailable for absorption. However, when significant steatorrhea is present, unabsorbed fatty acids preferentially bind to calcium, the free oxalate enters the colon and is absorbed. The absorbed oxalate is then filtered by the kidneys where it becomes free to bind calcium with the potential for kidney stone formation. Foods such as chocolate, tea, cola, spinach, celery, and carrots should be avoided, as should dehydration. Although some of the vitamin C in the TPN solutions may be converted to oxalate with a resultant hyperoxaluria, patients without a colon do not appear at increased risk for oxalate nephrolithiasis.

^Editor's Note: Dietary fat should not be replaced with MCT because essential fat (linoleic acid) is not supplied. In order to prevent essential fatty acid deficiency, linoleic acid must constitute at least 2 to 4% of the total absorbed calories. It is presently unclear whether linolenic fatty acid is essential as well.

In the normal individual, aside from fluid and limited calcium absorption, the colon has little importance nutritionally. However, in short bowel syndrome with significant carbohydrate malabsorption, the colon plays a much greater role nutritionally. Soluble fibers (eg, pectin, but less so soy, oats, or wheat bran, but not lignin) and starch are metabolized by normal colonic flora to the short chain fatty acids (SCFAs) acetate, butyrate, and propionate. These SCFAs (most notably butyrate) are the preferred fuel for the colonocyte, stimulate sodium and water absorption (although bicarbonate secretion may increase), and may account for upwards of 1,000 kcal daily in energy absorption! Therefore, the residual colon and a diet containing, substantial amounts of soluble fiber, complex carbohydrate, and some insoluble nonstarch polysaccharides provides an opportunity for colonic energy salvage. Patients with a colonic mucus fistula should be re-anastomosed as soon as possible.

Fat-Soluble Vitamins

For the patient who can be maintained without PN, regardless of the presence or absence of a colon, various vitamin and mineral supplements are often necessary (Table 64-1). Fat-soluble vitamins (A, D, E, and K) should be routinely monitored in non-TPN dependent patients, or in those who are only partially TPN-dependent. Vitamin A (10,000 to 50,000 U/d), vitamin D (1,600 U DHT/d or 50,000 U of parent vitamin D) and/or vitamin E (30 U/d) supplements may be necessary. In the presence of significant steatorrhea, the water-soluble forms of vitamin A and E, as well as the 25-OH2D3 form maybe preferable. Patients with significant renal insufficiency may require supplementation with 1,25-OH2D3 (1,25-dihydroxyvitamin D3). Since vitamin D enhances intestinal calcium absorption, simultaneous calcium supplementation should also be provided. Adequate

TABLE 64-1. Vitamin and Mineral Supplements for Patients with Short Bowel Syndrome

Vitamin A

10,000 to 50,000 units daily

Vitamin B12

300 |jg subcutaneously monthly for

those with terminal ileal

resections or disease

Vitamin C

200 to 500 mg

Vitamin D

1600 units DHT daily; may require

25-OH or 1,25 (OH2)-D3

Vitamin E

30 IU daily

Vitamin K

10 mg weekly

Calcium

See text

Magnesium

See text

Iron

As needed

Selenium

60 to 100 g daily

Zinc

220 to 440 mg daily (sulfate form)

Bicarbonate

As needed

The table lists rough guidelines only. Vitamin and mineral supplementation must be routinely monitored and tailored to the individual patient because relative absorption and requirements may vary.

The table lists rough guidelines only. Vitamin and mineral supplementation must be routinely monitored and tailored to the individual patient because relative absorption and requirements may vary.

sun exposure may also be an inexpensive alternative to vitamin D supplementation. The serum calcium should be monitored, as well as vitamin A and D concentrations because toxicity can result from excessive intake of any of these. Vitamin E is thought to be essentially nontoxic, although the clotting activity may be further suppressed in patients taking warfarin simultaneously. Adequacy of supplementation should also be routinely monitored by measurement of serum vitamin A, vitamin D (25-OH), and vitamin E concentrations. Vitamin E concentration may vary in relation to the serum total lipid concentration. Therefore, total serum lipids should be measured simultaneously and the ratio of vitamin E to total serum lipids should actually be used as the index of vitamin E status. Because enteric bacteria synthesize much of the daily vitamin K requirement (approximately 1 mg/d), in addition to that contained in the diet, supplementation is not usually necessary, although the prothrombin time should be monitored.

Water-Soluble Vitamins

Deficiencies of water-soluble vitamins are relatively rare in short bowel patients. However, they may occur and it is therefore important that patients ingest 1 or 2 B-complex vitamin supplements and 200 to 500 mg of vitamin C daily. Vitamin B12 should be administered at a dose of 1,000 |g intramuscularly every 3 months in patients who have had significant gastric or ileal resections, or in those who have active Crohn's disease in their remaining terminal ileum. The adequacy of vitamin B12 supplementation is best measured by following the serum methylmalonic acid (MMA) concentration. In the absence of sufficient B12, the MMA concentration will remain elevated because it will not be metabolized to succinyl coenzyme A. Similarly, folate is required for the metabolism of homocysteine to methionine. The Schillings test is not a test to determine vitamin B12 status, but to determine why a particular patient is vitamin B12 deficient. Once neuropathy (B12) or megaloblastic anemia (either) are present, deficiency has probably been present for some period of time. Although the B vitamins are essentially nontoxic, excessive vitamin C ingestion has been associated with calcium oxalate nephrolithiasis, which the patients may already have a predisposition to.

Zinc

Zinc supplements (see Table 64-1) are routinely necessary because of the significant fecal losses (17 mg/L). To put these losses in perspective, standard TPN solutions typically contain 2 mg of zinc daily. Usually one or two 220 mg zinc sulfate tablets will be sufficient. Although there is considerable debate on the appropriate test for measurement of zinc status, the serum concentration should be followed. Zinc is bound to albumin. Therefore, the serum zinc concentration maybe depressed in the presence of a low serum albumin, although physiologic zinc status may be normal. Unfortunately, no conversion factor is available. Zinc deficiency has also been associated with increased diarrhea, which may be ameliorated with zinc supplementation.

Electrolytes and Minerals

Patients with excessive fecal volume losses are also losing significant amounts of bicarbonate, magnesium, and selenium. Replacement of bicarbonate can be accomplished with sodium bicarbonate tablets. This may be necessary to maintain normal acid-base status, and help prevent development of osteoporosis. Magnesium replacement may be difficult because of the cathartic effect of all currently available oral supplements and the poor bioavailability of the enteric-coated tablets. Replacement via injection is painful. Therefore, periodic IV replacement may be required. Because the vast majority of magnesium is found intra-cellularly, measurement of serum concentration may not accurately reflect magnesium status. Therefore, 24-hour urine magnesium should be routinely followed. Values above 70 mg daily suggest adequate magnesium stores.

Selenium status can be followed by measurement of the plasma selenium concentration by a laboratory experienced in the measurement of this trace metal. It can be supplemented (60 to 120 |ig/d) if necessary. Deficiency has been associated with cardiomyopathy, macrocytosis, myositis, and pseudoalbinism. Copper deficiency is very rare, as most excretion is biliary in origin. Deficiency has been associated with anemia, cardiomyopathy, neutropenia, neuropathy, osteoporosis, retinal degeneration, and testicular atrophy.

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Constipation Prescription

Constipation Prescription

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