INDIRECT CALORIMETRY IN CRITICALLY ILL PATIENTS - CLINICAL-APPLICATIONS AND PRACTICAL ADVICE

Indirect calorimetry is the method by which metabolic rate and substra te utilization are estimated in human beings starting from respiratory gas exchange measurements and urinary nitrogen excretion. This method is based on some models and assumptions that must be known and taker, into consideration to correctly interpret the results obtained. Recen t advances in technology and the availability of precise and portable metabolic carts have made this technique practical at the bedside even in critically ill patients. It must be considered that, particularly in the ICU, there may be several sources of error and many technical d ifficulties in applying this methodology. Taking into account the rele vant clinical studies related to the outcomes of critically ill patien t, this article defines when the assessment of energy expenditure by i ndirect calorimetry may provide useful and valid information. Review o f the literature suggests that the clinical application of indirect ca lorimetry in critically ill patients, although promising, requires fur ther evaluation. Currently, the potential useful clinical applications of indirect calorimetry in this category of patients can be summarize d as follows: (1) assessment of energy expenditure in patients who fai l to adequately respond to the estimated nutritional needs; (2) assess ment of energy expenditure in patients with single- or multiple-organ dysfunction who need prolonged ICU care and artificial nutritional sup port; (3) assessment of the effects induced by artificial nutrition on the cardiocirculatory and respiratory systems in mechanically ventila ted patients with acute respiratory failure; and (4) monitoring of VO2 during weaning from mechanical ventilation. (C)Elsevier Science Inc. 1997.