Appropriate nutritional support improves the care of the critically ill patient by improving wound healing, and by reducing inflammation, infections, and the rate of complications. In addition, it has been shown to reduce overall ventilator days and intensive care unit (ICU) length of stay. Traditional approaches to the assessment of nutrition in the ICU have included a number of metabolic formulas. The most well known of these is the Harris-Benedict equation, which measures the resting energy expenditure (REE) and then “adjusts” that value based upon the overall stressors of the patient. The Harris-Benedict equation is represented by the following formulas:

REE (men) = 66 + (13.7 × weight in kilos) + (5 × height in centimeters) – (6.8 × age)

REE (women) = 655 + (9.6 × weight in kilos) + (1.8 × height in centimeters) – (4.7 × age)

In the presence of invasive monitoring such as the pulmonary artery catheter, where accurate values for oxygen consumption are available, the Weir equation may allow a better approximation of energy expenditure.