KDIGO Clinical Practice Guideline for Acute Kidney Injury
Protein Intake: Recommendations and Rationale

• 3.3.3: We suggest to avoid restriction of protein intake with the aim of preventing or delaying initiation of RRT. (2D)
• 3.3.4: We suggest administering 0.8–1.0 g/kg/d of protein in noncatabolic AKI patients without need for dialysis (2D), 1.0–1.5 g/kg/d in patients with AKI on RRT (2D), and up to a maximum of 1.7 g/kg/d in patients on continuous renal replacement therapy (CRRT) and in hypercatabolic patients. (2D)

Rationale

Protein hypercatabolism driven by inflammation, stress, and acidosis is a common finding in critically ill patients.^157,165,166 The optimal amount of protein supplementation in AKI patients is unknown. Patients with AKI are at high risk of malnutrition. Since malnutrition is associated with increased mortality in critically ill patients, nutritional management should aim at supplying sufficient protein to maintain metabolic balance. Hence, nutritional protein administration should not be restricted as a means to attenuate the rise in BUN associated with declining GFR. On the other hand, there is little evidence that hypercatabolism can be overcome simply by increasing protein intake to supraphysiologic levels. While, in a crossover study of AKI patients, nitrogen balance was related to protein intake and was more likely to be positive with intakes larger than 2 g/kg/d,¹⁶⁷ only 35% of patients achieved a positive nitrogen balance in a study applying a nutrient intake as high as 2.5 g/kg/d protein.¹⁶⁸ No outcome data are currently available concerning the clinical efficacy and the safety of such high protein intakes, which may contribute to acidosis and azotemia, and increase dialysis dose requirements.

Due to their continuous nature and the high filtration rates, CRRT techniques can better control azotemia and fluid overload associated with nutritional support but may also result in additional losses of water-soluble, low-molecularweight substances, including nutrients.¹⁶⁹ Normalized protein catabolic rates of 1.4 to 1.8 g/kg/d have been reported in patients with AKI receiving CRRT.^170-172 In a recent study in critically ill cancer patients with AKI and treated with sustained low-efficiency dialysis (SLED), those with higher BUN and serum albumin levels, which were associated with infusion of higher amount of total parenteral nutrition, had a lower mortality risk.¹⁷³

In CRRT, about 0.2 g amino acids are lost per liter of filtrate, amounting to a total daily loss of 10–15 g amino acids. In addition, 5–10 g of protein are lost per day, depending on the type of therapy and dialyzer membrane. Similar amounts of protein and amino acids are typically lost by peritoneal dialysis (PD). Nutritional support should account for the losses related to CRRT, including PD, by providing a maximum of 1.7 g amino acids/kg/d.