Short bowel syndrome (SBS) Flashcards
1
Q
SBS is a malabsorptive syndrome resulting from extensive intestinal resection. These pts frequently experience chronic diarrhea, dehydration and macro/micro deficiencies, and often require EN or PN support.
- SBS generally becomes clinically apparent when about 3/4 of the small bowel has been removed.
A
- The most common causes of SBS are multiple resections for Crohn’s disease, massive resections d/t catastrophic mesenteric vascular events, radiation enteritis, adhesive obstruction and trauma.
2
Q
Anatomic and Physio Considerations pg 512
- The proximal 200cm of the jejunum is the primary site of CHO, PRO, and water soluble Vit absorption.
- Fat absorption occurs over a larger length of the small bowel, a length that increases as the amt of fat ingested increases.
- Na absorption in the jejunum can only occur against a concentration gradient, and is dependent upon H20 fluxes, and is coupled to the absorption of Glu.
A
- In contrast to the jejunum, the ileum has tighter intercellular junction - hence less movement of H20 and Na.
- The ileum is the major site of carrier mediated bile salts and B12 absorption, and site for production of many GI hormones such as glucagon like peptide 1 & 2, and YY (imp for control of bowel motility and intestinal epithelial growth.
- > 100cm of resected ileum, bile salt pool cld be depleted leading to impaired micelle formation and ↓ed solubility of fat - resulting in malabsorption of fat.
3
Q
Anatomic & Physio Considerations pg 512
- The colon plays a pivotal role in the reabsorption of fluids and electrolytes. A complete loss of the colon often leads to dehydration and electrolytes abnormalities for SBS pts.
- Enteroglucagon, neurotensin, and peptide YY are produced in the proximal colon (and ileum) and are responsible for the jejunal, ileal, and colonic brake phenomena that slows small intestines transit in response to fat intake.
A
- In addition to the resorptive capabilities of the colon, bacterial fermentation of malabsorbed CHO to SCFA w/ subsequent absorption in the colon provides an additional energy source up to 1000kcal.
4
Q
Nutritional Assessment. pg 513
- Monitor fluid intake and output (urine & stool output)
- BUN/creatinine ratio may provide a measure of hydration status (>20:1 may indicated decreased bld volume to kidneys e.g. dehydration or CHF)
A
Oral diet and SBS. pg 514
- Most stable adult SBS pts absorb only abt 1/2 to 2/3 as much energy as normal; thus dietary intake must be ↑ed by at least 50% from their estimated needs (hyperphagic diet). It is best tolerated throughout the day in 5 - 6 meals.
- SBS pt respond differently to dietary manipulation depending on the presence or absence of a colon. If colon is present, a high complex carb (50-60%), low fat (20-30%) diet has been shown to ↓ed fecal calorie loss, steatorrhea, mg and Ca loss, and oxalate absorption.
5
Q
Oral diet and SBS cont’d
- High Ca food intake or Ca supplementation along w/ a oxalate restricted diet is important in SBS pts w/ a colon in decreasing oxalate nephropathy.
- High carb/low fat diet has not shown benefits in increasing absorption in SBS patients w/out a colon.
- Regardless of bowel anatomy, the provision of complex macronutrients in the diets of SBS is preferred. They (including starch) reduces the osmotic load and may exert a + effect on the adaptation process.
A
- Concentrated sugars, fruit juices in particular, shld be avoided bcuz they generate a high osmotic load and potentiate stool output.
- Nitrogen absorption is least affected by the decreased absorptive surfaces in SBS pt, so no change in dietary PRO is necessary especially the use of peptide based diets.
- MCTs are absorbed by both the small and large bowels, don’t require digestion by the pancreatic enzymes for their absoprtion, and may be a useful alternate fuel in the presence of bile or pancreatic insufficiency.
6
Q
Oral diet and SBS cont’d
- Negatives abt MCT:
1. They are not well tolerated in the long term.
2. They have slightly lower caloric density vs LCT (8.3 vs 9kcal/g).
3. Do not contain EFA
4. They exert a greater osmotic load in the bowel.
A
Oral diet and SBS cont’d
- Provision of EFA [linoleic acid(an omega-6 FA) and linolenic acid (omega-3 FA)] {found in safflower and soybean oil} is imp in the setting of low fat diets and fat malabsorption. Polyunsaturated (PUFA) is a good source of EFA.
- Soluble fiber is useful because of its potential effect on enhancing adaptation, slowing gastric emptying, and providing an additional energy source from the bacterial fermentation of SCFA. However, it may cause ↑ed gas and bloating and ↑ stool output for pt
7
Q
Oral fluids and SBS Pg 515
- Osmolality refers to the conc of particles, molecules, and ions in the fluid. If fluid is iso-osmolar(isotonic), it will be same as bld and extrcellular fluid (~300mOsm/ml). Hyperosmolar fluids are concentrated and pull fluids from enterocytes in an attempt to dilute the concentration of the luminal contents. In contrast, hypo-osmolar fluids don’t contain Na or Glu necessary to optimally facilitate absorption in an end-jejunostomy pt and may lead to dehydration if consumed in large amts.
A
- Note: Intestinal luminal Na and Glu play important roles in promoting fluid absorption.
- SBS pts w/out a colon generally require the use of a glu-electrolyte Oral rehydration system (ORS) to enhance absorption and reduce secretion, whereas most pts w/ a colon can maintain adequate hydration w/out excessive fluid loss w/ hypotonic fluids. An ORS will promote fluid absorption and help reduce diarrhea and optimize hydration status.
- The optimal Na conc of ORS to promote jejunal absorption is 90 to 120mEq Na+/L.
- Regardless of bowel anatomy, hyperosmolar fluids such as soda and fruit juices shld be avoided bcuz they will aggravate stool losses.
8
Q
Enteral feeding and SBS
- Slow continuous infusion is recommended. This type of infusion into the stomach instead of bolus or infusion directly into the small bowel is advised in order to maximize intestinal transit time, improve nutrient contact and absorption, reduce diarrhea.
- Polymeric or semi-elemental formulas are acceptable but elemental formulas shld be avoided because of their hypertonicity, expense, and lack of evidence supporting any benefits over the standard formulas.
A
Parenteral fluids (IVs) - IVs are usually needed in these pts when stool output consistently exceeds fluid intake.
9
Q
Parenteral Nutrition and SBS
- Medicare criteria requirement for PN coverage for SBS is resection performed w/in 3 mths of start of Home PN and that residual small intestine
A
- 2 criteria can be used to demonstrate malabsorption. 1) a fecal fat level of at least 50% of an intake of not
10
Q
Clinical factors predictive of successful weaning from PN.
- Length of remaining bowel
- Presence of colon
- Presence of an ileum/ileocecal value
- Absence of residual mucosal disease in the owel
- Degree to which intestinal adaptation has occur
A
- Patient Age
- Duration of time on PN
- Nutritional status prior to attempted weaning PN
- Fasting plasma citrulline level (an a.a produced in the intestine and in the liver but only the intestines contribute significantly to the bld) - may a marker for small bowel absorptive integrity and an appropriate surrogate for functional length of the small intestine.
11
Q
Criteria to Consider Before Weaning PN
- Hydration: PN reductions shld be considered only when the daily fluid intake goal is consistently achieved, urine output exceeds 1L/day, and is at least .5ml/kg/hr on nights w/out PN. If urine cannot be easily measured, serum creat, BUN, urine NA, and osmolarity can be used as surrogate measures of hydration.
- Caloric goal: At least 80% of the caloric goal shld be met in the absence of symptoms limiting oral intake.
A
- Body wt: Patients shld be able to maintain a stable body wt (ie, no >1.5kg loss between PN reductions).
- Labs: Stable serum electrolytes w/ or w/out supplementation.
- Enteral balance (oral fluid intake - stool output): should be positive (at least 500ml/day).
