Nutrient intake in critically ill patients: too many or too few calories?

We studied the relationship of caloric needs and total caloric intake in a series of 61 critically ill patients in an intensive care unit. All patients were receiving only central parenteral nutrition. On the basis of the ratio of total caloric intake to resting energy expenditure (REE), the nonprotein respiratory quotient (npRQ), and, when appropriate, Lusk's table for analysis of the oxidation of mixtures of carbohydrate and fat, the patients could be categorized into three groups. The group with inadequate caloric intake had a ratio of total calories to REE of less than 1.0. The group with net lipolysis had a ratio of caloric intake to REE of 1.0 or more and npRQ values of less than 1.0. The group with net lipogenesis had a ratio of caloric intake to REE of 1.0 or more and either npRQ values or equivalent npRQ values of 1.0 or more. Equivalent npRQ values in patients who were receiving amino acids, dextrose, and lipids were determined by using Lusk's table and the percentage of total caloric intake as fat.