The Acute Physiology and Chronic Health Evaluation II classification system is a valid marker for physiologic stress in the critically ill patient.

OBJECTIVE: To compare the Acute Physiology and Chronic Health Evaluation (APACHE II) score with resting energy expenditure obtained from indirect calorimetry to determine whether the APACHE II scoring system is an accurate, objective measure of the degree of critical illness and physiologic stress between groups of patients. DESIGN: Prospective study. SETTING: University hospital, tertiary referral center. PATIENTS: Seventy critically ill patients, consecutively sampled from burn, surgical, and medical intensive care units. INTERVENTIONS: Indirect calorimetric studies were performed on each patient using a metabolic cart. The acute physiologic score component of the APACHE II scoring system was determined at the time of metabolic testing, a mean of 15.9 days after hospital admission. MEASUREMENTS AND MAIN RESULTS: True resting energy expenditure was calculated by adjusting the measured energy expenditure for diet-induced thermogenesis and fever. A predicted resting energy expenditure was calculated for each patient using the Harris-Benedict equation alone, and by using the Harris-Benedict value corrected for previously published metabolic activity factors. To eliminate differences in body composition and size, true resting energy expenditure was divided by weight, body surface area, and Harris-Benedict resting energy expenditure. Results showed no significant correlation between APACHE II scores and either the Harris-Benedict resting energy expenditure or the Harris-Benedict value corrected by metabolic activity factors. However, there was a significant (p < or = .001; r2 = .18 to .20) relationship between increasing APACHE II scores and both increasing measured and true resting energy expenditure. The true resting energy expenditure divided by body surface area, kilogram body weight, and Harris-Benedict predicted value, were all shown to be significantly (p < .01) related to APACHE II score, but showed no better degree of correlation (r2 = .12 to .23) than comparison of APACHE II score with measured or true resting energy expenditure. CONCLUSIONS: The APACHE II classification may be a valid marker of physiologic stress as demonstrated by its statistically significant (although weak) relationship with indirect calorimetric measures of energy expenditure associated with varying degrees of critical illness.

Clinical application of the metabolic cart to the delivery of total parenteral nutrition.

In critically ill patients, the inaccuracy of predictive formulas for nutritional assessment often leads to inappropriate and potentially detrimental feeding regimens. This study evaluates the clinical utility of the metabolic cart in an urban university hospital setting. Twenty-six studies were performed on each of 26 patients (18 surgical, 8 medical) using an MMC Horizon metabolic cart. Although 58% of patients were overweight, 42% were still shown to have a kwashiorkorlike pattern of malnutrition. Three patients demonstrated a marasmic-like pattern. Fifteen percent of studies showed patients to be hypometabolic and 62% hypermetabolic. Harris-Benedict resting energy expenditure, based on actual or ideal body weight, underestimated needs; however, addition of a metabolic activity factor overestimated needs. Only 32% of patients were fed appropriately; 41% were underfed, and 27% were overfed. Urine area nitrogen correlated poorly with energy expenditure. Measured RQ appropriately reflected substrate utilization in 77% of studies; multiple factors may have caused differences between measured and predicted RQ in 23%. Use of the metabolic cart determines precisely the metabolic state, identifies problems with substrate utilization, and enables the physician to design the most efficacious nutritional regimen.

Total parenteral nutrition. Conquering the complexities.

Delivery of total parenteral nutrition (TPN) is a complex procedure requiring a basic knowledge of nutritional physiology and an understanding of the impact of various disease states on utilization of nutrient substrates. The goals of TPN are to reverse catabolism, promote anabolism, and build structural protein. It is important to infuse an adequate amount of calories and protein but to avoid the stress of overfeeding. Various laboratory values may be monitored to ensure that each of the nutrients administered is being adequately tolerated by the patient. Keeping these principles in mind, primary care physicians can deliver a TPN regimen specifically suited for individual patients and can anticipate and prevent any potential complications.