Patients who develop acute kidney injury (AKI) often have pre-existing or hospital acquired protein-energy malnutrition, which is a major negative prognostic factor in this clinical condition. Despite the lack of evidence, the enteral or parenteral route appears clinically indicated in most cases of ICU-acquired AKI to prevent deterioration in nutritional state and complications. Extrapolating from data in other conditions, it seems intrinsically unlikely that starvation of a catabolic patient is more beneficial than appropriate nutritional support by an expert team with the skills to avoid the potential complications of EN and PN.
The primary goals of nutritional support in AKI are the same as those for critically ill patients with normal renal function, i.e., to ensure the delivery of adequate nutrition, to prevent protein-energy wasting with its attendant metabolic complications, to promote wound healing and tissue repair, to support immune system function, to accelerate recovery, and to reduce mortality.
Chronic kidney disease (CKD) patients are sensitive to protein-energy wasting (PEW), and adequate nutritional therapy can yield remarkable improvements in the symptoms of the disease, quality of life, morbidity, mortality and the progression of renal failure. Evaluation of nutritional state in CKD and assessment of dietary intake, including supplements and compliance are steps of crucial importance. The principal causes involve poor dietary intake, abnormal metabolism of amino acids, proteins, lipids and carbohydrates, and metabolic acidosis promoting catabolism. In many complicated CKD patients, the main reason for PEW is chronic inflammation.
Insufficient nutritional care and metabolic disturbances mainly due to metabolic acidosis, hormonal disturbances, chronic inflammation and partially from loss of nutrients in heavy proteinuria, are considered as main causes of PEW;
Protein-energy wasting is found in approximately 25% of End-stage Renal Disease Patients on Haemodialysis (ESRD-HD) patients and has a major impact on survival.
Present data show that: 1) nutritional support, preferably in the form of ONS, is able to improve nutritional status; 2) morbidity and mortality can be reduced when improvement of nutritional status, as assessed by a transthyretin increase of 30 mg/l, is obtained during nutritional support. Early administration of nutritional support and rational timing of ONS consumption may improve the efficacy of nutritional support.
All peritoneal dialysis (PD) patients should be regularly monitored in order to detect early signs of PEW. In some groups of PD patients at higher risk of PEW, i.e. anuric PD patients, those with cardiac congestion, inflammation and low nutritional intakes, intensified nutrition counselling and nutritional support, preferably in the form of ONS, may help to cover nutritional requirements. Once PEW is established, ONS or AA-IPPN may improve nutritional status. Whether morbidity and mortality can be reduced by nutritional support in these patients is unknown, although it is likely that it will, considering the positive data obtained in HD patients. The reduction in glucose load obtained by using glucose-sparing solutions improves the metabolic profile of PD patients, although the impact of these solutions on body composition and patient outcomes still needs to be addressed.