Critically ill patient on renal replacement therapy: Nutritional support by enteral and parenteral routes

Acute kidney injury (AKI) in critically ill patients often occurs as a component of themultiple organ failure syndrome, in the course of the severe and prolonged catabolic phases of critical illness, and is intensified by the specific metabolic derangements associated with the acute loss of kidney function. Patients with AKI often develop protein-energy wasting (PEW), which by itself represents a major negative prognostic factor. Nutritional support is frequently required in this clinical setting, in the form of parenteral and/or enteral nutrition, even though there is no evidence from randomized controlled studies concerning its favorable effect on major outcomes. Patients with AKI on renal replacement therapy (RRT) should receive at least 1.5 g/kg/day of proteins and nomore than 25 nonprotein calories or 1.3 BEE (basal energy expenditure) calculated by the Harris–Benedict equation, with lipid supply representing about 30–35 % of energy intake. To compensate for protein and amino acid losses during renal replacement therapy, protein supply should be increased by 0.2 g/kg/day. Even in patients with AKI, the enteral route represents the preferred method of nutrient delivery; however, parenteral nutrition is often required to meet nutritional requirements. Since AKI comprises a highly heterogeneous group of patients, with nutrient needs which vary widely even during the clinical course in the same patient, nutritional requirements should be frequently reassessed, individualized, and carefully integrated with renal replacement therapy. Nutrient needs in patients with AKI can be difficult to estimate and should be directly measured, especially in the intensive care unit setting.