Estimation of Energy Expenditure for Adult Patients

Discussion:

Estimating energy expenditure and determining the appropriate number of calories to feed hospitalized adult patients is challenging.  If available, indirect calorimetry can be used to measure an individual patient’s energy expenditure using gas exchange.  However, this technology is not available in most hospitals and when available, may not be feasible for many patients.  Furthermore, frequent measurements are required to appropriately identify a patient’s energy expenditure (1).  When indirect calorimetry is not possible, there are many predictive equations the clinician can choose to use.   Most of these predictive equations are based on a single indirect calorimetry study per patient.  The high degree of variability of an acutely ill patient’s energy needs from day to day limits the ability to make strong conclusions regarding the superiority of any prediction equation over another.

More importantly, whichever method (indirect calorimetry or predictive equation) is used, the optimal energy provision for hospitalized patients has not been determined (1). We do know that significantly underfeeding or overfeeding is harmful (2, 3). However, we have no evidence that feeding a patient the calories they are burning based on indirect calorimetry or based on any predictive equation will improve their outcome.  Acutely ill patients remain catabolic despite meeting or exceeding full calorie expenditure (4, 5).  In fact, there is evidence that feeding critically ill patients 100% of their predicted energy needs may be harmful (6).
In a recent study that compared predictive equations to continuous indirect calorimetry, the principal investigator writes, “The aim of nutrition at this time should be to provide sufficient calories and nutrients to attenuate muscle wasting and prevent deficiencies but without exacerbating metabolic derangements.  It may be that estimates derived from predictive equations are sufficiently accurate to achieve this aim but until we know the optimum energy intakes required during critical illness we will be unable to evaluate them appropriately” (1).

Without outcome data, the strength of recommendations to use one predictive equation over another is weak at best.  Nevertheless, for consistency of practice within an institution and for teaching purposes, many institutions and professional organizations (American Dietetic Association, Morrison’s, ASPEN) have identified specific predictive equations as their standard methods to calculate caloric provision.  However, there is no patient outcome data to support improved clinical outcomes from the use of any particular method of measuring or estimating calorie expenditure. 

The University of Virginia Health System dietitians use approximately 25 calories per kilogram euvolemic weight, for the non-obese patient.  This method is recommended by the American College of Chest Physicians (7).

For patients who are at risk for refeeding syndrome, the initial goal is 15-20 calories per kilogram or actual or adjusted body weight (see below).

Estimating Energy Expenditure for the Obese Population

For patients who are >130% of their ideal body weight (IBW) based on the Hamwi equation (assuming the excess weight is not lean body tissue), an adjusted body weight is used.  The adjusted body weight = {(patient’s actual euvolemic weight - ideal body weight) x 0.25 – 0.5} + IBW.   These patients are usually fed initially approximately 15 calories/kg of adjusted body weight (8).

Estimating Energy Expenditure for the Underweight Population

Underweight patients (< 90% IBW) expend closer to 35 calories per kilogram and may need more than this (after addressing refeeding issues) to improve nutrition status (9).

Estimating Energy Expenditure for Spinal Cord Injury (SCI)

Calorie needs for the patient with SCI will vary based on individual activity level and functional mass.  In general, SCI leads to reduced calorie expenditure due to denervated muscle.  Often, the metabolic needs will correlate with the level of trauma—i.e. the higher the lesion, the lower the metabolic needs.  If indirect calorimetry is not available, use of predictive equations is recommended.  See the table below for estimating calorie needs in this population (10-13).

 

  • Harris Benedict equation
  • BEE x 1.0 – 1.2
  • 20 – 25 kcals / kg for 1st month post injury
  • 22.7 kcals / kg for quadraplegic patients
  • 27.9 kcals / kg for paraplegic patients
  • Chronic SCI patients generally need 500 kcals / day less than controls (11)

 

Estimating Energy Expenditure of Burn Patients

There are >30 predictive equations for estimating energy needs of burn patients.  At UVA we use 30-35 calories per kilogram.

References:

1.  Reid CL.  Poor agreement between continuous measurements.  The use of energy expenditure and routinely used prediction equations in intensive care unit patients.  Clin Nutr. 2007;26(5):649-57.

2. Talpers SS, Romberger DJ, Bunce SB and Pingleton SK. Nutritionally associated increased carbon dioxide production. Excess total calories vs high proportion of carbohydrate calories. Chest 1992;102(2):551-5.

3. Casper K, Matthews DE and Heymsfield SB. Overfeeding: cardiovascular and metabolic response during continuous formula infusion in adult humans. Am J Clin Nutr 1990;52(4):602-9

4. Frankenfield DC, Smith JS and Cooney RN. Accelerated nitrogen loss after traumatic injury is not attenuated by achievement of energy balance. JPEN J Parenter Enteral Nutr 1997;21(6):324-9.

5. Streat SJ, Beddoe AH and Hill GL. Aggressive nutritional support does not prevent protein loss despite fat gain in septic intensive care patients. J Trauma 1987;27(3):262-6.

6. Krishnan JA, Parce PB, Martinez A, Diette GB, and Brower RG.Caloric intake in medical ICU patients: consistency of care with guidelines and relationship to clinical outcomes. Chest. 2003;124: 297–305.

7. Applied Nutrition in ICU Patients*  A Consensus Statement of the American College of Chest Physicians  Frank B. Cerra, MD, FCCP; Marta Rios Benitez, MD;
    George L. Blackburn, MD, PhD; Richard S. Irwin, MD, FCCP;  Khursheed Jeejeebhoy, MD; David P. Katz, PhD;  Susan K. Pingleton, MD, FCCP;
    James Pomposelli, MD, PhD;  John L. Rombeau, MD; Eva Shronts, MMSc, RD, CNSD; Robert R. Wolfe, PhD; and Gary Paul Zaloga, MD, FCCP  Chest 1997;
    111:769-78.

8. Krenitsky, J. Adjusted body weight, pro: evidence to support the use of adjusted body weight in calculating calorie requirements.  Nutr Clin Pract 2005;20:468-473.

9. Campbell, CG, Zander E, and Thorland W. Predicted vs measured energy expenditure in critically ill, underweight patients. Nutr Clin Pract 2005;20:276-280.

10. Mollinger LA, Spurr GB, el Ghatit AZ, et al: Daily energy expenditure and basal metabolic rates of patients with spinal cord injury. Arch Phys Med Rehabil 1985;66:420-426

11. Monroe MB, Tataranni PA, Pratley R, et al: Lower daily energy expenditure as measured by a respiratory chamber in subjects with spinal cord injury compared with control subjects. Am J Clin Nutr 1998;68:1223-1227

12. Rodriguez DJ, Benzel EC, Clevenger FW: The metabolic response to spinal cord injury. Spinal Cord 1997;35:599-604.

13. Spinal Cord Injury Evidence Analysis Project. American Dietetic Association Evidence Analysis Library. American Dietetic Association; 2007. Available at: http://www.adaevidencelibrary.com.  Accessed July 15, 2008.

 

Manual of Clinical Nutrition Management
Customized for UVA Health Sciences 2008