2. Formula Osmolality
• The osmolality of an enteral formula is an
important consideration in terms of tolerance.
• Osmolality is the number of molecules and
ions per kilogram of a solution.
• It may be easier to think of osmolality as the
number of particles per kilogram of water.
3. Formula Osmolality
Osmolality of Body Fluid and
Formulas
• The osmolality of body fluid is
around 300 milliosmoles per liter.
• The osmolality of most enteral
formulas ranges from 250 to 800
milliosmoles per liter.
4. Formula Osmolality
Isotonic Formulas
• If the enteral formula has an osmolality near
that of the body fluid it is considered an
isotonic formula.
• Isotonic formulas are generally well tolerated
by patients.
5. Formula Osmolality
Hypertonic Formulas
• If the enteral formula has an
osmolality greater than that of the
body fluid it is considered a
hypertonic formula.
• Hypertonic formulas create an
osmotic gradient that attracts water
from the body into the lumen of the
GI tract.
6. Formula Osmolality
Complications of Hypertonic Formulas
Monomeric formulas tend to be the most
hypertonic. When hypertonic formulas draw
water into the lumen of the GI tract, the
following symptoms can occur:
• Cramping
• Nausea
• Vomiting
• Diarrhea
7. Formula Osmolality
Tolerance of Hypertonic Formulas
• It may take time for the body to adapt
to a hypertonic formula; therefore,
hypertonic formulas must be
introduced slowly or diluted* until
adaptation occurs. This is particularly
important if the patient has been
without feedings (NPO) for a while.
8. Formula Osmolality
Tolerance of Hypertonic Formulas
• Additionally, patients with low serum albumin
concentrations may have a lower than normal
body fluid osmolality. These patients are at
particular risk for symptoms related to hypertonic
formulas.
• For most patients, gradual administration of the
formula is sufficient - dilution of the formula is
usually not necessary and is now rarely practiced.
10. Nutritional Needs of Tube Fed Patients
Volume of Formula
• The volume of enteral formula
that a person needs varies
depending on individual
requirements. Caloric and
protein requirements of a TF
patient are calculated the
same as for any other patient.
11. Nutritional Needs of Tube Fed Patients
Kcaloric and Protein Needs of TF Patients
• There are several methods to determine kcaloric
and protein needs of tube fed patients.
• When you calculate your patient's requirements,
remember that the mathematical equations you
use give you estimates of needs.
• Individual needs vary; so you must monitor your
patient and adjust energy intake as appropriate.
12. Nutritional Needs of Tube Fed Patients
Calculation of Protein Needs
• Protein requirements vary with disease state.
Protein needs can be estimated by multiplying
kg of body weight by a factor or by a nitrogen
balance study.
• Grams protein/ kg Method
• Nitrogen Balance Method
• NPC:Ratio
13. Nutritional Needs of Tube Fed Patients
Gram/kg Method to Determine Protein Needs
• The simplest, but least precise, method to
estimate protein needs is by multiplying IBW in
kilograms by a factor appropriate for the patient's
condition.
• If this method is used, the patient must be
monitored for protein status to determine if
adjustment in the protein prescription is
necessary.
14. Nutritional Needs of Tube Fed Patients
*RequirementHealth Status
0.8 – 1.0Normal
1.0 – 2.0Moderately stressed (infection, fracture, surgery)
2.0 – 2.5Severely stressed (burns, multiple fractures)
Renal Disease
0.6 – 0.8Predialysis
1.1 – 1.4Hemodialysis
1.2 – 1.5Peritoneal dialysis
Adults
*values represent grams of protein per kilogram of IBW per day.
15. Nutritional Needs of Tube Fed Patients
StressedNormalAge (years)
2.2 – 3.02.00.0 – 0.5
1.6 – 3.01.60.5 – 1.0
1.2 – 3.01.21 – 3
1.1 – 3.01.14 – 6
1.0 – 2.51.07 – 10
1.0 – 2.51.011 – 14
1.0 – 2.50.8515 – 24
Pediatrics
*values represent grams of protein per kilogram of IBW per day.
16. Nutritional Needs of Tube Fed Patients
Example Gram/kg Calculation:
• IBW : 120 lb; 54.5 kg (120/2.2)
Moderate stress:
[factor = 1.5 (from chart)]
• 54.5 x 1.5 = 81.75 (82) grams protein/day
18. Nutritional Needs of Tube Fed Patients
Nitrogen Balance Method
• A nitrogen balance study is
the comparison of nitrogen
being consumed (orally or
via IV) compared to the
amount of nitrogen being
lost from the body.
• Most nitrogen is lost via
the urine, but some is lost
with feces, sweat &
sloughed off skin cells.
Nitrogen In
Food
TPN AA
Nitrogen Out
- Urine - Feces
- Sweat - Skin
19. Nutritional Needs of Tube Fed Patients
Three Scenarios of Nitrogen Balance
( 1 ) N-Equilibrium: Nitrogen in = Nitrogen Out
The person is in a state of maintenance where their
body is neither losing or gaining body protein.
( 3 ) Negative N-Balance( 2) Positive N-Balance
Nitrogen in < Nitrogen Out
The person is losing body
protein. Negative nitrogen
balance is an undesirable state
that occurs with weight loss,
traumatic injury and some
illnesses.
Nitrogen in > Nitrogen Out
The person is gaining body
protein. Positive Nitrogen balance
occurs during periods of growth,
including pregnancy, with protein
repletion therapy, and with weight
lifting exercise that builds muscle.
20. Nutritional Needs of Tube Fed Patients
Steps to Calculate Nitrogen Balance
1. Determine nitrogen lost in urine by a 24 hour
urinary urea nitrogen test.
2. Add 4* to the UUN to account for non-
urinary losses of nitrogen
3. Determine nitrogen intake by dividing the
daily protein intake by 6.25
4. N-bal.= value from #3 - value from #4
*a factor of 4 is used to estimate the nitrogen losses from non-urine sources (sweat,
feces, etc.)
21. Nutritional Needs of Tube Fed Patients
• If the nitrogen balance is 0, the person is
consuming the correct amount of protein for
maintenance.
• If the nitrogen balance is negative, increase
the protein intake by a factor determined by
multiplying the nitrogen balance figure by
6.25.
• If goal is repletion, increase protein intake
over what would result in nitrogen
equilibrium.
22. Nutritional Needs of Tube Fed Patients
Example N-balance Calculation
• Protein intake: 90 gm protein
• 24 hr UUN : 20 gm N
N intake = 90 / 6.25 = 14.4 gm N
20 + 4 = 24 gm N (total output)
N-balance = 14 - 24 = -10 gm N
This person is losing 10 X 6.25 = 62.5 gm
protein per day
24. Nutritional Needs of Tube Fed Patients
Calculation of Energy Needs
• ( 1 ) Basal energy expenditure x activity factor x stress factor
BEE x AF x IF Method
• ( 2 ) Kcals per kilogram body weight according to weight &
activity classification
Kcal / kg Method
25. Nutritional Needs of Tube Fed Patients
BEE x AF x IF Method
• There are two main methods to ascertain
basal energy expenditure (BEE) - - indirect
calorimetry and via a prediction equation.
• The most common of which is the Harris
Benedict Equation (HBE).
• Once BEE has been determined, that figure is
multiplied by an activity factor (AF) then an
injury factor (IF) to determine total energy
needs.
26. Nutritional Needs of Tube Fed Patients
The Harris-Benedict Equation
• Men:
BEE (kcal/d) = 66.5 + (13.8 x W) + (5.0 x H) - (6.8 x A)
• Women:
BEE (kcal/d) = 655.1 + (9.1 x W) + (1.8 x H) - (4.7 x A)
• Where: W = weight in kg H = height in cm A = age in
years
27. Nutritional Needs of Tube Fed Patients
Example Calculation of BEE:
• Male; W = 60kg; H = 150 cm; A = 30 y
BEE (kcal/d) = 66.5 + (13.8 x 60) + (5.0 x 150) -
(6.8 x 30)
66.5 + 828 + 750 - 204 = 1440 kcal/day
29. Nutritional Needs of Tube Fed Patients
Example calculation of energy needs:
Estimated energy needs (kcals) = BEE x AF X IF
• BEE = 1000; AF = 1.2; IF = 1.2
• Energy needs = 1000 x 1.2 x 1.2 = 1440
kcal/day
30. Nutritional Needs of Tube Fed Patients
Activity and Injury Factors
Activity Factor (AF)
1.2Bed rest
1.3Ambulatory
33. Nutritional Needs of Tube Fed Patients
Vitamins and Minerals in Formula
• Most enteral formulas provide 100% of the
RDA for vitamins and minerals in ml,
depending on the formula.
34. Fluid Needs of Tube Fed Patients
• Fluid needs are important to consider for TF
patients.
• Specific water needs for an individual can be
calculated as 1 ml/kcal or 35 ml/kg usual body
weight (UBW).
• Patients who have large water losses through
perspiration or oozing wounds may require
more fluids.
35. Fluid Needs of Tube Fed Patients
Sample Fluid Needs Calculation:
• 80 kg patient, intake 2500 kcal
• 80kg x 35ml/kg = 2800ml water/d
or
2500 kcal x 1ml/kcal = 2500ml water/d
37. Fluid Needs of Tube Fed Patients
Free water
• Most enteral formulas contain 80-85% free
water, and fluid needs can be met with a small
amount of additional water.
• However, calorically dense formulas contain as
little as 60% free water, so the failure to
supplement water with the denser formulas
can result in dehydration.
38. Fluid Needs of Tube Fed Patients
Example Free Water Calculation:
• Fluid requirement for patients: 2000ml
Formula intake: 2200ml
Formula: 80% free water
• 2200 ml formula x 0.80 = 1760 ml free water
• Additional water needs:
2000 ml – 1760 ml = 240 ml water
40. Fluid Needs of Tube Fed Patients
Obligatory Fluid Output
• One way to assess the appropriateness of fluid
intake is to monitor the pateint's urine output.
• Obligatory fluid output is the minimum output
of urine necessary to remove wastes and is
estimated to be 700 ml per day or 30 ml per
hour.
• For the tube fed patient, obligatory fluid
output can be determined more precisely
using the renal solute load of the formula.
41. Fluid Needs of Tube Fed Patients
Renal Solute Load
• The renal solute load (RSL) is the sum of the
materials that must be excreted via the urine,
including urea, sodium, potassium, and
chloride.
42. Fluid Needs of Tube Fed Patients
Renal Solute Load
• Each gram of protein ingested yields a RSL of
5.8 mOsm in adults and 4.0 mOsm in children.
• Protein yields a lower RSL in growing children
and those in anabolic states since more
dietary protein is being used to synthesize
body proteins.
• On the other hand, the RSL will be higher in
catabolic patients.
• Each mEq of electrolyte yields a RSL of 1
mOsm.
43. Fluid Needs of Tube Fed Patients
• The renal solute load from a tube feeding can
be calculated as follows:
Renal Solute Load = (gm prot x 5.8) + mEq(Na
+ K+Cl)
• Substitute 4.0 for 5.8 if the patient is a child.
44. Fluid Needs of Tube Fed Patients
Example RSL/Fluid Needs Calculation:
• Formula intake: 2000ml
Protein content: 50 grams/L
Sodium content: 20 mEq/L
Potassium content: 25 mEq/L
Chloride content: 50 mEq/L
• RSL = (50 gm pro x 5.8) + mEq (20 + 25 + 50)
= 290 + 20 + 25 + 50
= 385 mOsm/L X 2L = 770 mOsm
46. Fluid Needs of Tube Fed Patients
Obligatory Urine Output for Tube Feeding
• For optimum kidney
function, the total urine
output should be 1.5 - 2
times the renal solute load.
• Desired Urine Output = 1.5 x
RSL
47. Fluid Needs of Tube Fed Patients
Example Desired Urine Output Calculation:
• RSL: 385
• Desired Urine Output
• = 1.5 -2 x RSL
= 1.5 -2 x 385
= 510 - 770 ml or cc
49. Tube Feeding Administration
Methods to administer tube feedings:
( 1 ) Continuous Drip Feeding
• The continuous drip method is
most commonly used. Continuous
drip is administered via gravity or a
pump and is usually tolerated better
than bolus feeding
50. Tube Feeding Administration
( 2 ) Bolus Feedings
Bolus feedings allow for more mobility than
continuous drip feedings because there are
breaks in the feedings, allowing the patient to
be free from the TF apparatus for activities
such as physical therapy.
( 3 ) Combination
A combination of continuous drip (at night)
and bolus feedings (during the day) can be
used.
51. Tube Feeding Administration
Continuous Drip vs. Bolus Feedings
The rate of the continuous drip
administration can be controlled
with a pump, and the initial rate
should be slow to allow for adaption
to a hyperosmolar formula and to
monitor for tolerance.
Bolus feedings should consist of 250 -
300 mL given over 15 minutes,
followed by 25-60 mL water which
helps prevent dehydration and
clogging of the tube. At least 3
hours should elapse between each
bolus feeding.
52. Tube Feeding Administration
• Residual Volume
Before each bolus feeding, gastric contents
should be suctioned out and returned to the
stomach before a new feeding is administered
to ensure that minimal residue remains from
the previous feeding.
53. Tube Feeding Administration
• residual volume should be checked every 3-5
hours when feeding is by continuous drip.
Excess residual volume (>100 -150 mL) may
indicate an obstruction or some other
problem that must be corrected before
feeding can be continued.
54. Tube Feeding Administration
Patients placed on continuous
drip TF often cannot tolerate
large volumes of hypertonic
formulas with greater than 500
mOsm/L. Therefore, hypertonic
formulas may need to be
diluted at first to 1/2 to 1/3
strength*.
Administering for Maximum Tolerance
55. Tube Feeding Administration
• Formulas should be administered slowly at
first, about 50 ml per hour, then increased by
25 ml per hour every 8-12 hours as tolerated
until the required volume of formula is met. A
typical final rate is 100-125 ml /hr.
56. Tube Feeding Administration
• Determination of Final Rate
• To determine the desired final rate of formula
delivery, divide the required volume of formula
by 24 hours. If the formula is diluted, strength can
be increased slowly after the final rate has been
achieved.
• Remember, however, that recent literature
suggests that most patients can tolerate full
strength formulas from the start.
57. Tube Feeding Administration
• Example Final Rate Calculation:
• Required volume is 2800 ml
• 2,800 ml / 24 hr = 117 mL /hr
(which is close to 120 mL/hr)
58. Tube Feeding Administration
• Hypoalbuminemia is commonly implicated in
the development of diarrhea among TF
patients. If the albumin value is less than
3.5g/dl it is best to dilute the formula. If the
albumin value is less than 2.5g/dl enteral
feeding may not be tolorated at all.
59. Tube Feeding Administration
• If the patient is not tolerating
the formula, the rate should be
slowed and/or concentration
should be diluted until
tolerance is achieved.
• Signs of intolerance include
diarrhea, nausea, vomiting,
dehydration and cramping.
Another factor
which often
causes diarrhea in
the TF patient is
antibiotic
therapy.
60. Tube Feeding Administration
• Careful administration of TF helps
prevent bacterial contamination.
Blenderized formulas should be
prepared under sanitary
conditions and should be used
within 24 hours to reduce the risk
of bacterial infection.
Prevention of Bacterial Contamination
61. Tube Feeding Administration
• Unopened cans of formula can be stored at
room temperature, but must be refrigerated
once opened and used within 24 hours.
• Fresh formula should never be added to
formula remaining in the feeding bag. The
feeding bag and tubing (except tubing
connected to the patient) should be changed
every 12 -24 hours.
62. Tube Feeding Administration
• Body Positioning The pateint's
body position is also important
when administering a TF for both
continuous drip and bolus
feedings. The patient's head should
be elevated at least 30 degrees
during and after the feeding to
prevent regurgitation.
• If the patient is receiving a tube
feeding into the intestine,
positioning is not critical.
63. Administration of Medicine
• Medications are often administered via the
feeding tube, but this should be avoided if
possible because: pills can be crushed and
mixed with water before being added to the
feeding tube, but particles may clog the tube.
• Some pills cannot be crushed because they
have time released coatings.
64. Administration of Medicine
• The feeding tube should be flushed
with 30 ml of water or saline
before and after administration of a
drug. Liquid forms of medication
should be used if possible.
• Some medications can be added to
the TF formula, but drug-nutrient
interaction may occur. Some drugs
can cause the formula to clump and
clog the feeding tube.
Flush the tube
with water or
saline after
administration
of a medication.
65. Administration of Medicine
• Placement of the feeding tube can affect drug
action. Some drugs require the acidic
environment of the stomach to be dissolved,
and therefore may not be well absorbed if the
feeding tube is placed in the intestine.
66. Monitoring Tolerance
The TF patient must be carefully monitored for
tolerance of formula, hydration status, and
adequacy of nutrition support. Tolerance of
formula has been discussed previously.
Symptoms to look for include: diarrhea
• nausea
• cramping
• constipation
• aspiration
67. Monitoring Tolerance
• Hydration status can be monitored via daily
weights, hematocrit, blood urea nitrogen
(BUN), and electrolytes. High values for the
above parameters indicate dehydration. A
weight change of 2.2 pounds represents 1 L of
fluid if the weight change is due to fluid.
• Nutritional assessment indicators of protein
status can be used to determine adequacy of
protein intake, and weight can be used to
determine adequacy of kcalories, unless the
patient is retaining fluid.
