Appendix F
Energy Requirements

A. Calculated Energy Estimate Based on Body Size and Metabolic Stress

1. Calculate Basal Energy Expenditure (BEE).
   BEE refers to the metabolic activity necessary to sustain life (i.e., respiration, pulse, body temperature) and can be estimated using the following equation:

   Harris-Benedict equation:
   

   BEE(kcal/day):Males = 66.5 + (13.7 X W) + (5.0 X H) - (6.8 X A)

   Females = 655 + (9.6 X W ) + (1.7 X H) - (4.7 X A)

   where:

   W = usual or adjusted weight in kilograms

   H = height in centimeters

   A = age in years

2. Calculate Total Energy Expenditure (TEE)

BEE Correction Factors for Physical Activity and Clinical Status*

Physical Activity	Factor	Clinical Status	Factor
strict bedrest	1.2	fever	1.0 + 0.13/°C
out of bed	1.3	elective surgery	1.0-1.1
shivering/thrashing	1.3	peritonitis	1.2-1.5
quadriparesis	0.8	soft tissue trauma	1.1-1.4
paralysis	0.9	multiple fractures	1.2-1.4
hemiparesis	1.2-1.3	closed head injury	1.5-1.8
		severe infection/sepsis	1.4-1.8
		cancer	1.1-1.3
		COPD	1.2-1.3
		major burns	1.5-2.0
		AIDS	1.5-1.8

* The factors listed apply to both adult men and women.

B. Indirect Calorimetry by use of the Metabolic Cart ** Available at HMC only

Indirect calorimetry is the most accurate method for determining resting energy expenditure (REE) for hospitalized individuals. REE is slightly higher than BEE, accounting for the energy expended by the body at rest while awake. REE is calculated indi rectly using measurements of oxygen consumption and CO₂ production according to the following formula:

REE (kcal/day) = [3.9(VO₂) + 1.1 (VCO₂)] x 1.44

where:

VO₂ = oxygen consumption (mL/min.)

VCO₂ = carbon dioxide production (mL/min.)

Indirect calorimetry should be reserved for the following patients:

• hypermetabolic patients (burns, trauma, sepsis, head injury)
• starvation-adapted or malnourished patients
• extremely obese patients (>=200% of ideal body weight)
• patients with non-healing wounds
• patients with abnormal body composition (multiple sclerosis, cerebral palsy, cystic fibrosis, spinal cord injury, amputations)
• patients who can benefit from education about appropriate calorie intake.
• research study patients for whom indirect calorimetry is included in the protocol
• patients with increased minute ventilation for whom determinations of dead space (V_D/V_T) and CO₂ production are informative for ventilation decisions.

The following considerations will help avoid errors and enhance the reliability of metabolic cart testing:

• Metabolic testing becomes less accurate as FiO₂ increases and results are not clinically useful if FiO₂ >=0.60.
• Metabolic testing is inaccurate in patients with known system leaks (chest tube, tracheostomy cuff, endotracheal tube leaks).
• Metabolic tests do not represent steady states until >=4 hours after hemodialysis or anesthesia.
• Non-intubated patients on supplemental O₂ can be tested using an external blender. These patients must have an FiO₂ >=0.60 and must be able to tolerate a tight fitting face mask or canopy hood. Accurate tests cannot be obtaine d in patients with uncuffed tracheostomy tubes an supplemental O₂.
• The patient should not be moving. The exception may be the patient who postures or seizes continuously throughout the day, such that movement is more his usual state than non movement.

Specific recommendations for metabolic cart studies:

• The patient should be NPO or receiving PN or continuous tube feeding for at least 12 hours before testing to assure a stable baseline. For patients who are eating or receiving bolus tube feeds, tests should not be done until 2 hours after the meal /bolus.
• Patients who are agitated or experiencing pain should be given sedatives/analgesics an hour or more before testing.
• The environment should be quiet, controlled and at normal room temperature. The patient should not be shivering.
• Any ventilator alterations should be made 30 minutes or more before metabolic testing.
• Nursing care, physical and occupational therapies should be completed at least 1 hour before testing.
• Patients under the canopy hood should not speak during testing because this falsely elevates CO₂ production and precludes equilibrium.
• Desiccant cartridges of the metabolic cart need to be changed when the color begins to turn pink.

C. Fick Equation

The Fick equation can be used to calculate energy expenditure in ICU patients who have a pulmonary artery/Swan catheter. Twenty four hour energy expenditure is approximately seven times the VO₂in mL/min. VO₂is calculated from cardiac output (CO) in L/min, content of venous O₂ (CvO₂) in mL/dL, and content of arterial O₂ (CaO₂) in mL/dL according to the following formula:

Where:
CaO₂ - CvO₂ = 1.39 X Hb(g/dL) X (SaO₂ - SvO₂)

SaO₂ and SvO₂ are respectively arterial and mixed venous oxygen saturation as a fraction

VO₂ = [(CaO₂ - CvO₂)] x 10 x CO

VO₂ (in mL/min) x 7 = 24 hour energy expenditure in kcal/day units

Venous blood gases must be determined at approximately the same time as cardiac output. Repeated measurements performed over several days are helpful in increasing the accuracy of the estimate and in determining trends in energy expenditure.