parenteral nutrition and enteral nutrition

Enteral and
Parenteral Nutrition
Practical
Dr. Behnaz Shahrokhisahneh

● May be used for:
◦ Total nutrition,
◦ Supplemental nutrition,
◦ Transitional phase for patients coming off parenteral nutrition.
● Tube feedings may be:
◦ Intermittent,
◦ Continuous.
● Takes into account:
◦ Patient’s caloric requirements,
◦ Patient’s need for protein, carbohydrate and fat, vitamins
and minerals, dietary fiber, electrolytes, and fluids.

● Commercial formulas for enteral feeding are multiple and
varied:
1. Some are designed specifically for pediatric or adult patients.
2. Some provide a balanced or general requirement;
3. Others are high in calories, protein, amino acids, fat, and/or fiber;
4. Others are low in carbohydrate, sodium, or cholesterol.
● Some commercial formulas are designed to meet the
disease-specific requirements of certain patients:
◦ Renal or hepatic disease,
◦ Diabetics, lactose intolerant, or allergic to specific foods.
● As required, additions may be made to commercial
formulas to meet the needs of a specific patient.

● The osmolality of an enteral formula is an important
consideration.
● Some patients exhibit intolerance to a hyperosmolar
formula, resulting in:
1. Vomiting,
2. Osmotic diarrhea,
3. Abdominal distention,
4. Other symptoms…
● Osmolalities of Enteral Nutrition Formulas:
◦ Most infant formulas: 150-380 mOsmol/kg,
◦ Most adult formulas: 270-700 mOsmol/kg.
Osmolality of extracellular fluid:
◦ 285-295 mOsmol/kg.

● When necessary, medications can be administered
through the enteral feeding tubes, preferably with liquid
dosage forms.
● Liquid medications with high osmolalities (some
>1000 mOsmol/kg) can be diluted with 10-30 mL of sterile
water prior to administration.
● Medications generally are administered separately from
the nutrient formulas:
◦ to avoid drug incompatibilities with nutritional components,
◦ to consider a medication’s possible gastrointestinal effects
(e.g. diarrhea or constipation),
◦ to make certain that no residual medication remains in the
feeding tubes after medication delivery.

● Parenteral nutrition (PN) = intravenous
hyperalimentation (IVH or HAL):
◦ Partial parenteral nutrition (PPN): is nutritional support
that supplements oral intake and provides only part of
daily nutritional requirements.
◦ Total parenteral nutrition (TPN): provides all the
patient’s daily nutritional requirements.

parenteral nutrition and enteral nutrition

● Note that the prescribing physician may select the standard
formulas or modifications for central or peripheral
administration.
● Typically, parenteral nutrition formulas contain:
◦ Macronutrients:
❑ Carbohydrate (e.g. dextrose)
❑ Protein (e.g. amino acids)
❑ Fat (e.g. lipid emulsions)
Micronutrients:
❑ Electrolytes
❑ Vitamins
❑ Trace elementsSterile water for injection

● Parenteral nutrition formulas:
◦ can be obtained commercially,
◦ can be prepared in the pharmacy “automated mixing devices”.
● Nutritional requirements and formulations differ based on:
◦ Age groups (e.g., neonates, general pediatrics, adults).
◦ Patient-specific diseases (e.g., renal, liver, pulmonary).
● In preparing formulas for parenteral nutrition, pharmacists would use:
◦ Small-volume parenterals (ampuls and vials): as the source of
electrolytes, vitamins, and minerals,
◦ Large-volume parenterals (LVPs): as the source of amino acids, dextrose,
and sterile water for injection.

● Typically, infusion rates:
◦ Begin at about 25-50 mL / hour;
◦ Adjust every 8-12 hours as dictated by the patient’s condition and fluid and
nutritional status.
● TPN solutions may be administered:
◦ Continuously, over a 24-hour period,
◦ Cyclically, depending on a patient’s requirements.
● Infusions may be administered by:
◦ Gravity flow,
◦ Automated pumping devices.
● In many instances, parenteral nutrition begun in an institutional
setting is continued on an outpatient basis at home.

● Nutritional requirements:
◦ The quantities of macronutrients and micronutrients needed for
a patient to obtain or maintain the desired nutritional status.
● The quantitative amounts of fluid and specific
nutrients required vary with an individual’s:
◦ Age,
◦ Gender,
◦ Physical parameters,
◦ Disease state,
◦ Current nutritional status.
● The purpose is to provide only general considerations.

● A factor of:
◦ 30 mL/kg of body weight,
◦ 1500 mL/BSA “m2
”,
◦ “BSA=Body Surface Area”
◦ or 1 mL/kcal of nutrition required
● On a case-by-case basis, these values may be:
◦ Increased (e.g., for patients who are dehydrated),
◦ Decreased (e.g., for patients with renal failure or
congestive heart failure).
● A daily requirement of between 2 and 3 liters per day is
usual for adults.
Daily

● For neonates, infants, children, and adolescents without
abnormal water losses, the approximate daily water requirement
may be calculated by:

● Kilocalorie (kcal):
◦ The amount of heat required to raise the temperature of
1 kg of water 1Cº.
● The caloric requirements for patients vary.
● The Harris-Benedict equations are commonly used to
estimate the Basal Energy Expenditure (BEE)
requirements for non-protein calories.
◦ Basal Energy Expenditure (BEE) = Resting Metabolic
Energy (RME) = Resting Energy Expenditure (REE).

● An alternative to the use of the Harris-Benedict equations,
BEE for adults:
25 kcal/kg/day for mildly stressed hospitalized patients,
up to 35 kcal/kg/day for moderately stressed patients,
up to 45 kcal/kg/day for postoperative patients,
up to 60 kcal/kg/day for hypercatabolic patients.
● Energy requirements for infants, children, and teenagers are different than those for adults and
vary according to:
◦ age, growth rate, and clinical/metabolic status.
◦ The caloric requirements are:
◦ 100 kcal/kg/day for infants,
◦ 80 to 100 kcal/kg/day for children,
◦ 35 to 60 kcal/kg/day for teenagers.

● Carbohydrates are the primary source of cellular energy.
● Minimal daily required quantity is around 130g/day.
● Maximum daily required quantity is around
5mg/kg/min.
❑ For parenteral nutrition, Dextrose provides 3.4 kcal/gram;
e.g. each 100 mL of a 25% dextrose injection provides 85 kcal of
energy. HOW?
❑ For enteral nutrition, the factor used is 4 kcal/g.
WHY?

● In TPN, protein is provided as either:
◦ Protein hydrolysate,
🞄A sterile solution of amino acids and peptides prepared from
protein by acid or enzymatic hydrolysis and used
intravenously for patients unable to take ordinary food proteins.
◦ Amino acids.
● The purpose of the protein support:
◦ not to produce energy “although energy is produced by proteins
by a factor of 4 kcal/g”,
◦ but rather to build tissues and body strength.
● A patient’s caloric needs should be provided by non- protein
calories.

● The daily quantity of protein required in adults:
◦ 0.8 g/kg/day in an unstressed patient;
◦ 0.8 to 1 g/kg for a mildly stressed patient;
◦ 1.2 g/kg for a renal dialysis patient;
◦ 1.1 to 1.5 g/kg for a moderately stressed patient;
◦ 1.5 to 2 g/kg for a severely stressed patient and those
with a critical illness or trauma;
◦ 3 g/kg for a severely burned patient.
● For non-adult population:
◦ Infants may require 2 to 3 g/kg/day,
◦ Children 1.5 to 2 g/kg/day,
◦ Teenagers 1 to 1.5 g/kg/ day of protein.

● Lipids may be used to provide energy when the body cannot obtain all the
necessary energy requirement from carbohydrates.
● The proportion of calories provided by lipids is usually restricted to 30% to
40% of the total daily calories.
● Average daily required quantity is around 1.5g/kg/day or less.
● Dietary lipids provide 9 kcal/gram.
● Lipids are generally administered in the form of an emulsion containing
carbohydrate-based emulsifying agents, which also contribute to the caloric
content.
● It has been determined that:
◦ 10% lipid emulsion provides 11 kcal/g of total energy,
◦ 20% to 30% lipid emulsion provides 10 kcal/g of total energy.

● Dietary guidelines generally recommend a daily
intake of 14 g of fiber for each 1000 calories
consumed.
● This translates to approximately:
◦ 21 to 25 grams of daily fiber for women,
◦ 30 to 38 g for men.
● Insoluble fiber reaches the large intestine after
ingestion and is associated with good bowel function.
● Soluble fiber partially dissolves in the upper
gastrointestinal tract and is associated with reduced
absorption of dietary fat and cholesterol.

● The standard quantities of electrolytes may be used as
parenteral nutrition or modified as required.

● Be careful about units conversion:
◦ 1 foot = 30.48 cm
◦ 1 inch = 2.54 cm
◦ 1 kg ~= 2.2 lb.
◦ 1 quart ~= 946 ml

● (a) How many milliliters of ENSURE should this
patient receive daily to meet his caloric
requirements?

● (b) How many grams each of protein,
carbohydrates, and lipids would this volume
provide?

● (c) If the product contains 85% free water,
does it meet the patient’s daily water
requirement?

● (d) If the formula is to be delivered
continuously over a 24-hour period, what
would be the flow rate in mL/hr?

● (e) If the patient is to continue receiving
this formula at home by intermittent
feedings over 40 minutes every 4 hours,
what volume would be administered with
each feeding, and what would be the flow
rate in mL/hr?

● Notes:
◦ In some clinical practices; a patient’s actual body weight, the ideal
body weight, or some middle ground may be used in the calculations,
◦ The energy provided by the protein, in addition to that from lipids, may
or may not be taken into account.
◦ Formulas of BMI & BSA might be useful.
● In addition to the former steps, TPN calculations also can
include:
◦ Determination of the quantities of the pharmaceutical sources of the
macronutrients and micronutrients to use to obtain the required
components,
◦ Determination of the total TPN volume,
◦ The number of TPN bags to be prepared,
◦ The rate of flow.

● Calculate the parenteral nutrition and fluid
requirements for a 58-year-old woman who is 5 ft.
3 in. tall and weighs 140 lb., assuming that she has
no disease states that would alter her nutritional
requirements.
◦ Note: Lipid used is the 10% emulsion.

● Using the Harris-Benedict equation, calculate the
caloric requirement for a mildly stressed 56-year
old hospitalized female patient weighing 121 lb.
and measuring 5 ft 3 in. in height.
◦ Supposing an average factor of 1.3 for mild stress.

● Calculate the daily quantity of protein required for
that 55-kg-patient based on 0.8 g/kg and the caloric
value based on 4 kcal/g for proteins.

● From the previous two example
problems, calculate the number of
milliliters of 50% dextrose solution (170
kcal/dL) that may be used to provide the
additional kilocalories required.

parenteral nutrition and enteral nutrition

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