Patient classification: substrate requirements. Ideally, a nutritional program should be designed for each individual acute renal failure (ARF) patient. In clinical practice, it has proved useful to distinguish three groups of patients based on the extent of protein catabo-lism associated with the underlying disease and resulting levels of dietary requirements.
Group I includes patients without excess catabolism and a UNA of less than 6 g of nitrogen above nitrogen intake per day. ARF is usually caused by nephrotoxins (aminogly-cosides, contrast media, mismatched blood transfusion). In most cases, these patients are fed orally and the prognosis for recovery of renal function and survival is excellent.
Group II consists of patients with moderate hypercatabolism and a UNA exceeding nitrogen intake 6 to 12 g of nitrogen per day. Affected patients frequently suffer from complicating infections, peritonitis, or moderate injury in association with ARF. Tube feeding or intravenous nutritional support is generally required, and dialysis or hemofiltration often becomes necessary to limit waste product accumulation.
Group III are patients who develop ARF in association with severe trauma, burns, or overwhelming infection. UNA is markedly elevated (more than 12 g of nitrogen above nitrogen intake). Treatment strategies are usually complex and include parenteral nutrition, hemodialysis or continuous hemofiltration plus blood pressure and ventilatory support. To reduce catabolism and avoid protein depletion nutrient requirements are high and dialysis is used to maintain fluid balance and blood urea nitrogen below 100 mg/dL. Mortality in this group of patients exceeds 60% to 80%, but it is not the loss of renal function that accounts for the poor prognosis. It is superimposed hypercatabolism and the severity of the underlying illness. (Adapted from Druml ; with permission.)
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