|
THE
BURN NUTRITION MODULE
Section
II
HOW
TO ASSESS ENERGY NEEDS (KCALS/KG/DAY)
|
Calculation
using formulas based on burn size, body weight
|
|
Actual
measurement of energy needs based on O2 consumed and CO2
produced.
-
Advantage:
patient specific
-
Disadvantage:
requires expertise to perform
|
The first
step is to assess the patients energy needs or Kilocalories required
per day. There are two approaches used. The initial approach is to
utilize a calculation of needs based on burn size, age and weight. A
variety of formulas can be utilized to arrive at a number. The
formulas are based on population studies and provide a
‘ballpark’ value.
The second
approach is the direct measurement of energy needs, using a
calorimetry method (to be described) often performed weekly as
energy needs change during the course of injury.
How
Do You Determine Energy Needs By The Use Of Standard Formulas?
|
Common
Components of Formulas
- Basal
Metabolic Rate (BMR)
- Activity
Factor (1.2 - 1.4 BMR)
- Stress
Factor (based on % TBS burn) reflects
increase in BMR caused by the burn
- Age
|
Formulas
(Estimates)
- Harris-Benedict
- any age
- Curreri
- Adult, Child
- Wilmore
- Adult
Typical Values
- Adult
: 35-40 Kcal/kg/day
- Child:
40(plus) Kcal/kg/day
|
There
are a number of formulas that can be used that produces slightly
different values but all have common components (see
definitions).
COMPONENTS
INCLUDE:
1)
Basal metabolic rate, (BMR)
2)
An activity factor as a multiplier to BMR
3)
An assessment of the percent increase in hyper metabolism caused
by the burn and age.
There
are different formulas for Adults and Children.
|
The
usual estimated Kcals/day for a severe burn is 35-40 Kcal/Kg/day
in an adult and 40(plus) Kcals/Kg/day in a child.
|
The actual
measurement of energy needs is known as indirect calorimetry. The
technique uses the measurement of oxygen consumed (and CO2 produced)
as a measure of Calories consumed (see definitions).
The patient
breathing 100% oxygen from a bag thru a mouthpiece (or via
endotracheal tube) for a set time period (20-30 minutes). The
patient exhales back into the reservoir, thus consuming O2
and replacing it with CO2. The amount of O2
consumed can be converted into energy used (Kilocalories burned). Advantages
are a specific energy measure in each individual with reassessment,
since energy use will change. Formulas are population based and do
not change.
The disadvantage
is the need for a ‘steady state’ i.e. no change in
activity, or body temperature etc during the study, as well as
expertise in performing the test and the necessary equipment.
|
