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A. Definitions and Administrationnavigator

  1. Parenteral Nutrition: provision of nutrients via a non-gastrointestinal (GI) route
  2. Total Parenteral Nutrition (TPN): nutritionally complete diet via a parenteral route
  3. Routes of Administration: Peripheral and Central
  4. Peripheral Vein
    1. Prolonged infusion of hyperosmolar solutions leading to thrombophlebitis
    2. Adult limit is 650 mOsm/L
    3. Unless a fairly large (such as "midline") vein is canulated, restricted to 5% glucose
  5. Central Venous Line
    1. High flow dilutes hyperosmolar solution (superior vena cava dilution ~ 1:1000)
    2. Percutaneous cannulation of subclavian vein usually preferred by patient
  6. Enteral nutrition should be used rather than TPN in inpatients with functional GI tracts [2]

B. Proteinnavigator

  1. Critical Role of Proteins in Severely Ill Patients
    1. Stress associated with increased protein turnover (catabolism)
    2. Also associated with negative nitrogen balance
    3. Skeletal muscle function comprised by protein breakdown
    4. Respiratory muscle weakness leads to increased problems and complications
    5. High levels of APR especially TNFa are likely etiologies
    6. Treatment of critically ill adults with recombinant human growth hormone to reverse these catablic effects has lead to 1.9-2.4 fold increased mortality [5]
  2. Enteral: intestinal hydrolysis to free amino acids, liver uptake. Adults: 0.43g/kg/day
  3. Parenteral: crystalline L-amino acids into systemic circulation. Adults: <0.8g/kg/day
  4. Essential Amino Acids: Lys, Trp, Phe, Met, Thr, Leu, Ile, Val
  5. Nonessential: Ala, Arg, Asp, Cys, Glu, Gly, His, Pro, Ser, Tyr
  6. Nitrogen Balance
    1. Dietary protein degraded to amino acids, deaminated, producing amines, ammonia, urea
    2. Carboxylic acid byproducts used in energy metabolism
    3. Nitrogen balance depends on nitrogen intake and energy intake.
    4. If energy requirements are met, use amino acids only for nitrogen requirements
  7. Additional glutamine may provide some benefits including more rapid recoveries

C. Energy Sourcesnavigator

  1. Sources of Energy: Summary
    1. Glucose (carbohydrate)
    2. Fat
    3. Protein
  2. Glucose (Dextrose)
    1. High biologic utility
    2. Inexpensive
    3. Caution with glucose intolerance, hyperosmolar states
    4. Will increase acid production with increased CO2 load
    5. Control of glucose levels associated with improved outcomes in intensive care unit (ICU) [9]
  3. Fat
    1. Isotonic, low CO2 load, high caloric density
    2. Expensive
    3. Platelet adhesion decreased
    4. Pulmonary vascular resistance increased
    5. Increased risk of intrahepatic cholestasis (may be progressive) [7]
    6. Hypertriglyceridemia can precipitate pancreatitis
    7. 10% and 20% fat emulsions (1.1 and 2.0 kcal/mL)
    8. 1.2% egg phospholipids and 2.5% glycerin in water
  4. Glucose infusions increase insulin and thereby suppresses lipolysis
    1. Therefore, if giving large quantities of dextrose, need to supplement lipids
    2. Otherwise, insulin will decrease lipolysis and lower secretion of fats leading to fatty acid deficiency
    3. Increased exogenous insulin administration is associated with increased death in ICU patients [9]
    4. However, good glucose control is associated with reduced death in ICU [9]
  5. Protein
    1. Essential
    2. Poor hepatic tolerance, increase NH4 leading to encephalopathy
    3. Renal intolerance with increasing BUN

D. Adult Energy and Cofactor Requirementsnavigator

  1. Basal Energy Expenditure (BEE) in KCals/day
    1. Male BEE = 66.5 + 13.8x(Ideal Kg wt) + (cm height) - 6.8x(age in years)
    2. Female BEE = 655.1 + 9.6x(Ideal Kg wt) + 1.8x(cm height) - 4.7x(age in years)
    3. Total energy requirement depends on BEE and Metabolic Activity Factor (MAF)
    4. MAF varies from 1.0 (normal) to 1.6 for elective surgery to 2.7 with 70% burns
  2. Electrolytes
    1. NaCl or NaOAc 60-120mEq
    2. KCl or KOAc or KPi 75-150 mEq
    3. Chloride as KCl or NaCl 80-120 mEq
    4. Mg, Ca also
    5. Acetate (Na or K): bicarbonate precursor, more stable in TPN; prevents acidosis
    6. Phosphate (Na or K): required for normal anabolism, along with K and Mg
  3. Vitamins
    1. Fat soluble: A, D, and E
    2. Vitamin C (Ascorbic Acid)
    3. Folacin
    4. B complex: Thiamin, Riboflavin, Niacin, Pyridoxine (B6), Cyanocobalamin (B12)
    5. Pantothenic Acid and Biotin
  4. Trace Elements
    1. Zinc and Copper
    2. Chromium and Manganese
    3. Selenium
  5. Glutamine enriched solutions are being evaluated

COMPLICATIONS OF PARENTERAL NUTRIATION

A. Catheter Relatednavigator
  1. Overall rate is ~10%; major problems ~2%
  2. Any anatomic structure between ears and diaphragm may be injured by central line

B. Metabolic navigator

  1. These are usually iatrogenic
  2. Minimize by careful monitoring
  3. Deficiencies, usually of intracellular ions K+, Mg2+, phosphate and essential fatty acids
  4. Excesses of fluids, major extracellular ions (Na, Cl), glucose and ammonia
  5. Others: acid/base disturbances, liver enzyme elevations, other deficiencies
  6. Cholestasis [7]
    1. Cholestatic liver disease occurs in 15-85% of patients on prolonged TPN
    2. Longer duration of therapy is major risk factor
    3. Cholestasis may progress to fibrosis and cirrhosis
    4. May contribute to ~20% of deaths in patients on long term TPN
    5. Parenteral intake of omega-6 rich long-chain triglycerides lipid emulsion may reduce risk
    6. Metronidazole may improve TPN-induced cholestasis, especially in Crohn's Disease patients

C. Infections navigator

  1. Catheter sepsis: Staphylococcus aureas and epidermidis, Candida ssp, G negative bacteria
  2. Contamination of solutions: especially Tinea versicolor (fungus)
  3. Increased risk of C. difficile diarrhea with enteral feedings, particularly post-pyloric [4]

INDICATIONS FOR PARENTERAL NUTRITION

A. Requirements for Normal Enteric Alimentationnavigator
  1. Access:
    1. Oral
    2. Nasogastric
    3. Naso-duodenal
    4. Feeding Gastrostomy / Jejunostomy
  2. Peristalsis
    1. Gastric Emptying
    2. Intestinal Motility
  3. Digestion
    1. Pancreatic Enzymes
    2. Mucosal Enzymes (Disaccharidases, Enterokinase)
  4. Absorption
    1. Micelle formation
    2. Jejunal Surface area
    3. Portal Vein (nutrients) and Lymphatics (Fats)
  5. In patients with functional GI tracts, enteral nutrition is prefered over TPN [2]

B. Patient Selectionnavigator

  1. Do not use parenteral nutrition when the gut is functioning
  2. Use only if nutritional needs not met by external route
  3. Established (proven) benefit
    1. Patients unable to eat or absorb nutrients for extended period
    2. neurological deficits
      1. short bowel syndrome
      2. premature infants
      3. oropharyngeal dysfunction
    3. Normal patients who cannot eat for more than 10-14 days
    4. Severely malnourished patients undergoing major elective surgery
    5. Patients with major trauma, head trauma, burns
    6. Bone marrow transplant recipients undergoing intensive chemotherapy
    7. No clear improvement in mortality overall with use of TPN [3]
    8. Clearly improves morbidity in malnourished patients [3]
    9. Enteral (tube feeding) nutrition is not beneficial in patients with dementia [6]
  4. Benefits of Parenteral Nutrition Unproven
    1. GI fistulas and other GI dysfunction (pancreatitis)
    2. May induce remission in Crohn Disease
    3. Acute renal failure, hepatic failure
    4. AIDS - particularly wasting syndrome
    5. Cancer patients with neoplasm associated wasting
    6. Critically ill patients - medical intensive care unit (non-trauma)
  5. Patients with high chronic levels of stress response proteins may not benefit
  6. In patients with gastrointestinal cancer post-surgery, early enteral nutrition reduces post-operative stay and complication rate, compared with parenteral nutrition [8]

C. Definition of Starvationnavigator

  1. >10% weight loss in 6 months
  2. Albumin < 3.5 g/dL
  3. Total lymphocyte count <1500.

D. Weaning off of TPNnavigator

  1. TPN is temporary support measure with nearly all cases will be weaned off
  2. Reduce TPN to 50% of calculated needs when patient resumes eating
  3. Continue decreasing (weaning) as patient's oral/enteral intake increased
  4. This helps to "re-train" the GI tract

References navigator

  1. Souba WW. 1997. NEJM. 336(1):41
  2. Zaloga GP. 2006. Lancet. 367(9516):1101 abstract
  3. Heyland DK, MacDOnald S, Keefe L, Drover JW. 1998. JAMA. 280(23):2013 abstract
  4. Bliss DZ, Johnson S, Savik K, et al. 1998. Ann Intern Med. 129(12):1012 abstract
  5. Takala J, Ruokonen E, Webster NR, et al. 1999. NEJM. 341(11):785 abstract
  6. Finucane TE, Christmas C, Travis K. 1999. NEJM. 282(14):1365 abstract
  7. Cavicchi M, Beau P, Crenn P, et al. 2000. Ann Intern Med. 132(7):525 abstract
  8. Bozzetti F, Braga M, Gianotti L, et al. 2001. Lancet. 358(9292):1487 abstract
  9. Finney SJ, Zekveld C, Elia A, Evans TW. 2003. JAMA. 290(15):2041 abstract