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Nutrition. . . and the surgical patient Carli Schwartz, RD,LDN * * * * * * Complications of Enteral Nutrition Support Issues with access, administration, GI ... – PowerPoint PPT presentation

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Title: Nutrition

  • . . . and the surgical patient
  • Carli Schwartz, RD,LDN

Nutrition and Surgery
  • Malnutrition may compound the severity of
    complications related to a surgical procedure
  • A well-nourished patient usually tolerates major
    surgery better than a severely malnourished
  • Malnutrition is associated with a high incidence
    of operative complications and death.

Normal Nutrition (
The Newest Food Guide Pyramid
  • Balancing Calories   ? Enjoy your food, but eat
    less.   ? Avoid oversized portions.    
  • Foods to Increase   ? Make half your plate fruits
    and vegetables.   ? Make at least half your
    grains whole grains.   ? Switch to fat-free or
    low-fat (1) milk.    
  • Foods to Reduce   ? Compare sodium in foods like
    soup, bread, and frozen meals ? and choose the
    foods with lower numbers.   ? Drink water instead
    of sugary drinks.   
  • Website http//
  • Includes interactive tools including a
    personalized daily food plan and food tracker

  • Carbohydrates
  • Main sources include grains, fruits and beans
  • Limited storage capacity, needed for CNS
    (glucose) function
  • Yields 3.4 kcal/gm
  • Recommended 45-65 total daily calories.
  • Fats
  • Main sources include oil, nuts, butter, milk and
  • Major endogenous fuel source in healthy adults
  • Yields 9 kcal/gm
  • Too little can lead to essential fatty acid
    (linoleic acid) deficiency and increased risk of
  • Recommended 20-30 of total caloric intake
  • Protein
  • Main sources include fish, beef, poultry and
    dairy products
  • Needed to maintain anabolic state (match
  • Yields 4 kcal/gm
  • Must adjust in patients with renal and hepatic
  • Recommended 10-35 of total caloric intake.

Normal Nutrition
  • Requirements
  • HEALTHLY male/female
  • (weight maintenance)
  • Caloric intake25-30 kcal/kg/day
  • Protein intake0.8-1gm/kg/day (max150gm/day)
  • Fluid intake 30 ml/kg/day

Nutritional Needs for the Surgery Patient
Comparison of Protein/Energy Demands
HEALTHLY 70 kg MALE Caloric intake 25-30
kcal/kg/day Protein intake 0.8-1gm/kg/day
(max150gm/day) Fluid intake 30 ml/kg/day
SURGERY PATIENT Caloric intake Mild stress,
inpatient 25-30 kcal/kg/day Moderate stress,
ICU patient 30-35 kcal/kg/day Severe stress,
burn patient 30-40 kcal/kg/day Protein
intake 1-2 gm/kg/day Fluid intake INDIVIDUALIZED
  • The surgical patient . . . .
  • Nutrient depletion occurs in the surgical patient
    due to decreased intake, increased metabolic
    expenditure and altered nutrient use.
  • Increased risk of malnutrition due to
  • Inadequate nutritional intake
  • Metabolic response (hypermetabolism from long
    term inflammation or infectious conditions)
  • Nutrient losses without proper replenishment
  • Protein /energy store depletion
  • Diminished nutrient intake (pre/post operative)
  • Prevalence of GI obstruction, anorexia,
  • Extraordinary stressors (surgical stress,
    hypovolemia, sepsis, bacteremia, medications)
  • Wound healing
  • Anabolic state, higher demand for nutrients
    (amino acids, zinc, vitamin A C, arginine)

Perioperative Nutritional Assessment
  • Individuals are generally classified as well
    nourished or mildly, moderately, or severely
  • 1 well nourished no significant weight change
    preoperative serum albumin gt 3.5 g/dL
  • 2. Mildly malnourished lt10 wt loss
    preoperative serum albumin 3.2-3.5 g/dL
  • 3. Moderately malnourished 10-20 wt loss
    preoperative serum albumin 2.5-32 g/dL
  • 4. Severely malnourished gt20 wt loss
    preoperative serum albumin lt 2.5 g/dL
  • Nutritional assessment parameters also include a
    complete medical history, surgical history,
    social history, diet history, physical exam,
    anthropometric and laboratory evaluations.

Visceral Proteins
  • Albumin
  • Normal range 3.5-5 g/dL.
  • Synthesized in and catabolized by the liver
  • Pro often ranked as the strongest predictor of
    surgical outcomes- inverse relationship between
    postoperative morbidity and mortality compared
    with preoperative serum albumin levels
  • Con lack of specificity due to long half-life
    (approximately 20 days). Not accurate in pts
    with liver disease or during inflammatory

Visceral proteins
  • Prealbumin (transthyretin) - transport protein
    for thyroid hormone, synthesized by the liver and
    partly catabolized by the kidneys.
  • Normal range16 to 40 mg/dL values of lt16 mg/dL
    are associated with malnutrition.
  • Pro Shorter half life (two to three days) making
    it a more favorable marker of acute change in
    nutritional status. A baseline prealbumin is
    useful as part of the initial nutritional
    assessment if routine monitoring is planned.
  • Cons More expensive than albumin. Levels may be
    increased in the setting of renal dysfunction,
    corticosteroid therapy, or dehydration, whereas
    physiological stress, infection, liver
    dysfunction, and over-hydration can decrease
    prealbumin levels.

Visceral proteins
  • Transferrin acute-phase reactant and a transport
    protein for iron
  • normal range 200 to 360 mg/dL.
  • Medium half-life (8-10 days)
  • Smaller body pool than albumin, reflects more
    acute changes.
  • influenced by several factors, including liver
    disease, fluid status, inflammation, iron status
    and illness.
  • Cons not studied extensively as albumin and
    pre-albumin in relation to nutritional status,
    may indicator more about iron metabolism
  • Levels decrease in the setting of severe
    malnutrition, however unreliable in the
    assessment of mild malnutrition

Other measures of nutrition status
  • Nitrogen balance the relationship between the
    amount of nitrogen taken into the body, usually
    as food, and that excreted from the body in urine
    and feces. Most of the body's nitrogen is
    incorporated into protein.
  • Protein 16 nitrogen
  • Protein intake (gm)/6.25 - (UUN 4) balance in
  • Positive value found during periods of growth,
    tissue repair or pregnancy. This means that the
    intake of nitrogen into the body is greater than
    the loss of nitrogen from the body, so there is
    an increase in the total body pool of protein.
  • Negative value can be associated with burns,
    fevers, wasting diseases and other serious
    injuries and during periods of fasting. This
    means that the amount of nitrogen excreted from
    the body is greater than the amount of nitrogen
  • Healthy Humans Nitrogen Equilibrium
  • Cons Complex determination of balance, measures
    of losses difficult and limited utility in
    clinical setting

Feeding the patient Post-operative Nutrient
Traditional Method Diet advancement
  • Introduction of solid food depends on the
    condition of the GI tract.
  • Oral feeding delayed for 24-48 hours after
  • Wait for return of bowel sounds or passage of
  • Start clear liquids when signs of bowel function
  • Rationale
  • Clear liquid diets supply fluid and electrolytes
    that require minimal digestion and little
    stimulation of the GI tract
  • Clear liquids are intended for short-term use due
    to inadequacy

Things to Consider
  • For liquid diets, patients must have adequate
    swallowing functions
  • Even patients with mild dysphagia often require
    thickened liquids.
  • Must be specific in writing liquid diet orders
    for patients with dysphagia
  • There is no physiological reason for solid foods
    not to be introduced as soon as the GI tract is
    functioning and a few liquids are being
    tolerated. Multiple studies show patients can be
    fed a regular solid-food diet after surgery
    without initiation of liquid diets.

Diet Advancement
  • Advance diet to full liquids followed by solid
    foods, depending on patients tolerance.
  • Consider the patients disease state and any
    complications that may have come about since
  • Ex steroid-induced diabetes in a post-kidney
    transplant patient.

Patients who cannot eat . . . ?
Consider Nutrition Support!
Perioperative Nutritional Support
  • Length of time a patient can remain NPO after
    surgery without complications is unknown, however
    depends on
  • Severity of operative stress
  • Patients preexisting nutritional status
  • Nature and severity of illness
  • In uncomplicated cases, well nourished patients
    tolerate up to 10 days of starvation with no
    medical complications. Moderately or severely
    malnourished patients usually require nutritional
    support earlier. (A.S.P.E.N Nutrition Support
    Practice Manual 2nd Ed)

Goals of perioperative Nutrition Support
  • Decrease surgical mortality
  • Decrease surgical complications and infection
  • Reduce the catabolic state and restore anabolism
  • Support the depleted patient throughout the
    catabolic phase of recovery
  • Decrease hospital LOS
  • Speed the healing/recovery process
  • Ensure the prompt return of GI function to resume
    standard oral intake as soon as possible

Perioperative Nutrition Support Guidelines
  • The American Society for Parenteral and Enteral
    Nutrition evidence-based practice guidelines
  • 1. preoperative specialized nutrition support
    should be administered for 7-14 days to
    moderately or severely malnourished pts
    undergoing major surgery
  • 2. PN should not be routinely given in the
    immediate post-op period to pts undergoing major
    GI procedures
  • 3. Postoperative nutrition support should be
    administered to patients who are expected to be
    unable to meet their nutrient needs orally for
    7-10 days

Nutrition support Clinical Decision Algorithm
Nutrition Support
  • Enteral Nutrition Support
  • Parenteral Nutrition support

What is enteral nutrition?
  • Enteral Nutrition
  • Also called "tube feeding," enteral nutrition is
    a liquid mixture of all the needed nutrients.
  • Consistency is sometimes similar to a milkshake.
  • It is given through a tube in the stomach or
    small intestine.
  • If oral feeding is not possible, or an extended
    NPO period is anticipated, an access devise for
    enteral feeding should be inserted at the time of
  • Feeds can meet 100 of patients needs or can be
    used to supplement poor po intake.

Indications for Enteral Nutrition
  • When the GI tract is functional or partially
    functional and..
  • Patient has inability to consume or absorb
    adequate nutrients.
  • Patient is not meeting gt 75 of needs with po
  • Malnourished patient expected to be unable to eat
    adequately for gt 5-7 days
  • Adequately nourished patient expected to be
    unable to eat gt 10 days

Contraindications to Enteral Nutrition Support
  • Expected need less than 5-7 days if malnourished
    or 7-9 days if normally nourished
  • Severe acute pancreatitis
  • Small bowel obstruction, ileus or high output
    enteric fistula distal to feeding tube
  • Inability to gain access
  • Hemodynamic instability
  • Need for high dose pressors/vasoactives
  • MAP consistently lt 60 mmHg
  • Intractable vomiting or diarrhea
  • Those requiring massive fluid resuscitation

Enteral Access Devices
  • Nasogastric
  • Nasoenteric
  • Gastrostomy
  • PEG (percutaneous endoscopic gastrostomy)
  • Surgical or open gastrostomy
  • Jejunostomy
  • PEJ (percutaneous endoscopic jejunostomy)
  • Surgical or open jejunostomy
  • Transgastric Jejunostomy
  • PEG-J (percutaneous endoscopic gastro-jejunostomy)
  • Surgical or open gastro-jejunostomy

Feeding Tube Selection
  • Can the patient be fed into the stomach, or is
    small bowel access required?
  • 2) How long will the patient need tube feedings?

Gastric vs. Small Bowel Access
  • Gastric access If the stomach empties, use it.
  • Indications to consider small bowel access
  • Gastroparesis / gastric ileus
  • Recent abdominal surgery
  • Sepsis
  • Significant gastroesophageal reflux
  • Pancreatitis
  • Aspiration
  • Ileus
  • Proximal enteric fistula or obstruction

Short-Term vs. Long-Term Tube Feeding Access
  • No standard of care for cut-off time between
    short-term and long-term access
  • However, if patient is expected to require
    nutrition support longer than 6-8 weeks,
    long-term access should be considered

Choosing Appropriate Formulas
  • Categories of enteral formulas
  • Polymeric
  • Whole protein nitrogen source, for use in
    patients with normal or near normal GI function.
    Examples include Ensure and Jevity.
  • Monomeric or elemental
  • Predigested nutrients most have a low fat
    content or high of MCT for use in patients
    with severely impaired GI function. Examples
    include Peptamen and Optimental
  • Disease specific
  • Formulas designed for feeding patients with
    specific disease states
  • Formulas are available for respiratory disease,
    diabetes, renal failure, hepatic failure, and
    immune compromise. Examples include Glucerna and
  • well-designed clinical trials may or may
    not be available

Tulane Enteral Nutrition Product Formulary
Complications of Enteral Nutrition Support
  • Issues with access, administration, GI
    complications, metabolic complications. These
  • Nausea, vomitting, diarrhea, constipation,
    delayed gastric emptying, malabsorption,
    refeeding syndrome, hyponatremia, microbial
    contamination, tube obstruction, leakage from
    ostomy/stoma site, micronutrient deficiencies.

Implementation of Enteral Nutrition
  • Gastric feeding
  • Pump assisted Continuous feeding and cyclic
  • Allows for max nutrient absoroption and improved
  • best in sicker/hospitalized patients
  • Start at rate 30 mL/hour and advance in
    increments of 20 mL q 8 hours to goal. Check
    gastric residuals q 4 hours for tolerance
  • Gravity Controlled Bolus feeding
  • Infusion of a predetermined volume of formula at
    specified intervals. Example 1 can Glucerna (240
    ml) via PEG tube q 4 hours.
  • Easiest, least expensive, more physiologic (mimic
    normal eating pattern)
  • Small bowel feeding
  • Continuous feeding only do not bolus due to risk
    of dumping syndrome
  • Start at low volume to assess tolerance (20
  • Advance in increments of 20 mL q 8 hours to goal
  • Do not check gastric residuals

Determining Your Enteral Nutrition Prescription
  • Estimate energy, protein, and fluid needs
  • Select most appropriate enteral formula
  • Determine continuous vs. bolus feeding
  • Determine goal rate to meet estimated needs
  • Write/recommend the enteral nutrition prescription

Enteral Nutrition Case Study
  • 78-year-old woman admitted with new CVA
  • Significant aspiration detected on bedside
    swallow evaluation and confirmed with modified
    barium swallow study speech language pathologist
    recommended strict NPO with alternate means of
  • PEG placed for long-term feeding access
  • Plan of care is to stabilize the patient and
    transfer her to a long-term care facility for

Enteral Nutrition Case Study (continued)
  • Height 54 IBW 120 /- 10
  • Weight 130 / 59kg 100 IBW
  • BMI 22
  • Usual weight 130 no weight change
  • Estimated needs
  • 1475-1770 kcal (25-30 kcal/kg)
  • 59-71g protein (1-1.2 g/kg)
  • 1770 mL fluid (30 mL/kg)

Enteral Nutrition Prescription
  • Tube feeding via PEG with full strength
  • Jevity 1.2
  • Initiate at 30 mL/hour, advance by 20 mL q 8
    hours to goal
  • Goal rate 55 mL/hour continuous infusion
  • Above goal will provide 1584 kcal, 73g protein,
    1069 mL free H2O
  • Give additional free H2O 175 mL QID to meet
    hydration needs and keep tube patent
  • Check gastric residuals q 4 hours hold feeds for
    residual gt 200 mL
  • Keep HOB gt 30 at all times

What is parenteral nutrition?
  • Parenteral Nutrition
  • also called "total parenteral nutrition," "TPN,"
    or "hyperalimentation."
  • Defined as nutrients provided intravenously.
  • Components of a PN mixture include
  • Protein (Amino Acids) , carboydrates (dextrose) ,
    Fats (Long-chain fatty acids), sterile water,
    electrolytes, vitamins and trace minerals
  • For use in nutritionally compromised patients
    when enteral nutrition is contra-indicated.

Indications for Parenteral Nutrition Support
  • Malnourished patient expected to be unable to eat
    gt 5-7 days AND enteral nutrition is
  • Patient failed enteral nutrition trial with
    appropriate tube placement (post-pyloric)
  • Enteral nutrition is contraindicated or severe GI
    dysfunction is present
  • Paralytic ileus, mesenteric ischemia, small bowel
    obstruction, enteric fistula distal to enteral
    access sites

  • TPN (total parenteral nutrition)
  • High glucose concentration (15-25 final
    dextrose concentration)
  • Provides a hyperosmolar formulation (1300-1800
  • Must be delivered into a large-diameter vein
  • PPN (peripheral parenteral nutrition)
  • Similar nutrient components as TPN, but lower
    glucose concentration (5-10 final dextrose
  • Osmolarity lt 900 mOsm/L (maximum tolerated by a
    peripheral vein)
  • May be delivered into a peripheral vein
  • Because of lower concentration, large fluid
    volumes are needed to provide a comparable
    calorie and protein dose as TPN

Parenteral Access Devices
  • Peripheral venous access
  • Catheter placed percutaneously into a peripheral
  • Central venous access (catheter tip in SVC)
  • Percutaneous jugular, femoral, or subclavian
  • Implanted ports (surgically placed)
  • PICC (peripherally inserted central catheter)

Writing TPN prescriptions
  • Determine total volume of formulation based on
    individual patient fluid needs
  • Determine amino acid (protein) content
  • Adequate to meet patients estimated needs
  • Determine dextrose (carbohydrate) content
  • 70-80 of non-protein calories or 50 calorie
  • Determine lipid (fat) content
  • 20-30 non-protein calories
  • Determine electrolyte needs
  • Determine acid/base status based on chloride and
    co2 levels
  • Check to make sure desired formulation will fit
    in the total volume indicated

Parenteral Nutrition Prescription
  • Important items to consider
  • Glucose infusion rate should be lt 5 mg/kg/minute
    (maximum tolerated by the liver) to prevent
    hepatic steatosis
  • Lipid infusion should be lt 0.1 g/kg/hour
    (ideally lt 0.4 g/kg/day to minimize/prevent
    TPN-induced liver dysfunction)
  • Initiate TPN at ½ of goal rate/concentration and
    gradually increase to goal over 2-3 days to
    optimize serum glucose control

Tulane Daily Parenteral Nutrition Order Form
Parenteral Nutrition Monitoring
  • Electrolytes -adjust TPN/PPN electrolyte
    additives daily according to labs
  • Check accu-check glucose q 6 hours
  • Regular insulin may be added to TPN/PPN bag for
    glucose control as needed
  • Check triglyceride level within 24 hours of
    starting TPN/PPN
  • If TG gt250-400 mg/dL, lipid infusion should be
    significantly reduced or discontinued
  • Daily addition of Carnitine to TPN/PPN may
    improve lipid metabolism
  • 100 grams fat per week is needed to prevent
    essential fatty acid deficiency
  • Check LFTs weekly
  • If LFTs significantly elevated as a result of
    TPN, then minimize lipids to lt 1 g/kd/day and
    cycle TPN/PPN over 12 hours to rest the liver
  • If Bilirubin gt 5-10 mg/dL due to hepatic
    dysfunction, then discontinue trace elements due
    to potential for toxicity of manganese and copper
  • Check pre-albumin weekly
  • Adjust amino acid content of TPN/PPN to reach
    normal pre-albumin 18-35 mg/dL
  • Adequate amino acids provided when there is an
    increase in pre-albumin of 1 mg/dL per day
  • Acid/base balance
  • Adjust TPN/PPN anion concentration to maintain
    proper acid/base balance
  • Increase/decrease chloride content as needed
  • Since bicarbonate is unstable in TPN/PPN
    preparations, the precursoracetateis used
    adjust acetate content as needed

Complications of Parenteral Nutrition
  • Hepatic steatosis
  • May occur within 1-2 weeks after starting PN
  • May be associated with fatty liver infiltration
  • Usually is benign, transient, and reversible in
    patients on short-term PN and typically resolves
    in 10-15 days
  • Limiting fat content of PN and cycling PN over 12
    hours is needed to control steatosis in long-term
    PN patients
  • Cholestasis
  • Occurs because there are no intestinal nutrients
    to stimulate hepatic bile flow
  • May occur 2-6 weeks after starting PN
  • Indicated by progressive increase in TBili and an
    elevated serum alkaline phosphatase
  • Trophic enteral feeding to stimulate the
    gallbladder can be helpful in reducing/preventing
  • Gastrointestinal atrophy
  • Lack of enteral stimulation is associated with
    villus hypoplasia, colonic mucosal atrophy,
    decreased gastric function, impaired GI immunity,
    bacterial overgrowth, and bacterial translocation
  • Trophic enteral feeding to minimize/prevent GI

Parenteral Nutrition Case Study
  • 55-year-old male admitted with small bowel
  • History of complicated cholecystecomy 1 month
    ago. Since then patient has had poor appetite
    and 20-pound weight loss
  • Patient has been NPO for 3 days since admit
  • Right subclavian central line was placed and plan
    noted to start TPN since patient is expected to
    be NPO for at least 1-2 weeks

Parenteral Nutrition Case Study(continued)
  • Height 60 IBW 178 /- 10
  • Weight 155 / 70kg 87 IBW
  • BMI 21
  • Usual wt 175 11 wt loss x 1 mo.
  • Estimated needs
  • 2100-2450 kcal (30-35 kcal/kg)
  • 84-98g protein (1.2-1.4 g/kg)
  • 2100-2450 mL fluid (30-35 mL/kg)

Parenteral Nutrition Prescription
  • TPN via right-SC line
  • 2 L total volume x 24 hours
  • Amino acid 4.5 (or 45 g/liter)
  • Dextrose 17.5 (or 175 g/liter)
  • Lipid 20 285 mL over 24 hours
  • Above will provide 2120 kcal, 90g protein,
    glucose infusion rate 3.5 mg/kg/minute, lipid 0.9

Benefits of Enteral Nutritionover parenteral
  • Cost
  • Tube feeding cost 10-20 per day
  • TPN cost 100 or more per day!
  • Maintains integrity of the gut
  • Tube feeding preserves intestinal function it is
    more physiologic
  • TPN may be associated with gut atrophy
  • Less infection
  • Tube feedingvery small risk of infection and may
    prevent bacterial translocation across the gut
  • TPNhigh risk/incidence of infection and sepsis

Transitional Feedings
  • Parenteral to enteral feedings
  • Introduce a minimal amount of enteral feeding at
    a low rate (30-40 ml/hr) to establish tolerance.
  • Decrease PN level slowly to keep nutrient levels
    at same prescribed amount
  • As enteral rate is increased by 25-30 ml/hr
    increments every 8-24 hrs, parenteral can be
  • Discontinue PN solution if 75 of nutrient needs
    met by enteral route.
  • Parenteral/Enteral to oral feedings
  • Ideally accomplished by monitoring oral intake
    and concomitantly decreasing rate of nutrition
    support until 75 of needs are met.
  • Oral supplements are useful if needs not met 100
    by diet. Ex (Nepro, Glucerna, Boost, Ensure).

Dangers of Over and Under Feeding
  • Risks associated with over-feeding
  • Hyperglycemia
  • Hepatic dysfunction from fatty infiltration
  • Respiratory acidosis from increased CO2
  • Difficulty weaning from the ventilator
  • Refeeding syndrome
  • Risks associated with under-feeding
  • Depressed ventilatory drive
  • Decreased respiratory muscle function
  • Impaired immune function
  • Increased infection
  • Weight loss and malnutrition

Refeeding Syndrome
  • the metabolic and physiologic consequences of
    depletion, repletion, compartmental shifts, and
    interrelationships of phosphorus, potassium, and
  • Severe drop in serum electrolyte levels resulting
    from intracellular electrolyte movement when
    energy is provided after a period of starvation
    (usually gt 7-10 days)
  • Physiologic and metabolic sequelae may include
  • EKG changes, hypotension, arrhythmia, cardiac
  • Weakness, paralysis
  • Respiratory depression
  • Ketoacidosis / metabolic acidosis

Refeeding Syndrome(continued)
  • Prevention and Therapy
  • Correct electrolyte abnormalities before starting
    nutrition support
  • Continue to monitor serum electrolytes after
    nutrition support begins and replete aggressively
  • Initiate nutrition support at low
    rate/concentration ( 50 of estimated needs) and
    advance to goal slowly in patients who are at
    high risk

  • Contact Information
  • Carli Schwartz, RD,LDN
  • Clinical Dietitian, Tulane Abdominal Transplant
  • (504) 988-1176

  • References
  • American Society for Parenteral and Enteral
    Nutrition. The Science and Practice of Nutrition
    Support. 2001.
  • Han-Geurts, I.J, Jeekel,J.,Tilanus H.W,
    Brouwer,K.J., Randomized clinical trial of
    patient-controlled versus fixed regimen feeding
    after elective abdominal surgery. British Journal
    of Surgery. 2001, Dec88(12)1578-82
  • Jeffery K.M., Harkins B., Cresci, G.A.,
    Marindale, R.G., The clear liquid diet is no
    longer a necessity in the routine postoperative
    management of surgical patients. American Journal
    of Surgery.1996 Mar 62(3)167-70
  • Reissman.P., Teoh, T.A., Cohen S.M., Weiss, E.G.,
    Nogueras, J.J., Wexner, S.D. Is early oral
    feeding safe after elective colorectal surgery? A
    prospective randomized trial. Annals of Surgery.
    1995 July222(1)73-7.
  • Ross, R. Micronutrient recommendations for wound
    healing. Support Line. 2004(4) 4.
  • Krauses Food, Nutrition Diet Therapy, 11th Ed.
    Mahan, K., Stump, S. Saunders, 2004.
  • American Society for Parenteral and Enteral
    Nutrition. The Science and Practice of Nutrition
    Support. 2001.