[How to assess and monitor postoperative artificial nutrition?]

Quantitative and qualitative nutritional requirements depend on the level of energetic expenses. Various formulas, especially the tables by Harris and Benedict allow the estimation of the level of energetic expenses with an approximation of 14%. Corrective factors permit an adjustment of the figures, according to the level of body aggression. In complex cases, indirect calorimetry allows a more accurate appraisal of energetic expenses. This technique provides also indications on the utilisation of each substrate and allows therefore to determine the optimal carbohydrate-lipid ratio for each patient. The assessment of the direct benefit of artificial nutritional support relies on anthropometric techniques and at present on body composition appraisal by determination of its impedance. The changes in muscular strength are difficult to assess. Moreover the time course of body weight is not specific for nutritional status. Therefore other biological indicators such as the nitrogen balance, the concentration of plasma proteins and albumin are more often assessed; proteins with a short half-life depend on the body aggression level. The potassium balance, which is easy to obtain in clinical practice, is a relevant indicator for nitrogen balance and protein synthesis. Clinical monitoring includes the checking of hydratation and its impact on the circulatory, respiratory and renal functions. The tolerance of enteral nutrition is appraised by the quality of gastrointestinal function. Biological monitoring includes the electrolyte balance and various variables of carbohydrate, lipidic and proteic metabolisms. It allows to check the absence of hyperglycaemia, hyperlipidaemia and cholestasis. The daily checking of catheters is part of the monitoring of nutritional support.(ABSTRACT TRUNCATED AT 250 WORDS)