Nutritional assessment and delivery in renal replacement therapy patients.

The present review is aimed at illustrating and discussing literature data and recent guidelines concerning artificial nutrition in patients with acute kidney injury (AKI) on renal replacement therapy (RRT). Protein-energy wasting often complicates the clinical course of AKI in critically ill patients, increasing their morbidity and mortality risk. The most severe forms of the syndrome - those observed in ICU patients - are characterized by hypercatabolism with relevant lean body mass loss. In this clinical condition, artificial nutrition (enteral and/or parenteral nutrition) is considered an integral part of the complex therapeutic approach. Even though many issues concerning nutrition in AKI are common to other critically ill patients, the presence of AKI with the ensuing impairment of the kidney homeostatic function introduces specific problems and can make more difficult to give the patient an adequate nutrient provision. Thus, peculiarities of the syndrome - and of RRT itself - must be taken into account in nutritional planning for these patients. Recent guidelines have suggested that the enteral route should be the preferred one, even though parenteral nutrition is often required to target nutritional needs (25-30 kcal/kg body weight/day, and 1.5 + 0.2 g/kg/day to compensate for amino acid losses during RRT). Special attention should be paid to the impact of different forms of RRT on the possible loss of both macro- and micronutrients and vitamins, as well as to the risk of metabolic complications. Finally, close integration between nutritional support and RRT is required, aiming at carefully tailoring both therapies on patient's changing needs.