Micronutrient and Amino Acid Losses During Renal Replacement Therapy for Acute Kidney Injury

Abstract

Introduction Malnutrition is common in patients with acute kidney injury (AKI), particularly in those requiring renal replacement therapy (RRT). Use of RRT removes metabolic waste products and toxins, but it will inevitably also remove useful molecules such as micronutrients, which might aggravate malnutrition. The RRT modalities vary in mechanism of solute removal; for example, intermittent hemodialysis (IHD) uses diffusion, continuous veno-venous hemofiltration (CVVH) uses convection, and sustained low-efficiency diafiltration (SLEDf) uses a combination of these. Methods We assessed micronutrient and amino acid losses in 3 different RRT modalities in patients with AKI (IHD, n = 27; SLEDf, n = 12; CVVH, n = 21) after correction for dialysis dose and plasma concentrations. Results Total losses were affected by modality; generally CVVH >> SLEDf > IHD (e.g., amino acid loss was 18.69 ± 3.04, 8.21 ± 4.07, and 5.13 ± 3.1 g, respectively; P < 0.001). Loss of specific trace elements (e.g., copper and zinc) during RRT was marked, with considerable heterogeneity between RRT types (e.g., +849 and +2325 μg/l lost during SLEDf vs. IHD, respectively), whereas effluent losses of copper and zinc decreased during CVVH (effect size relative to IHD, −3167 and −1442 μg/l, respectively). B vitamins were undetectable in effluent, but experimental modeling estimated 40% to 60% loss within the first 15 minutes of RRT. Conclusion Micronutrient and amino acid losses are marked during RRT in patients with AKI, with variation between RRT modalities and micronutrients.

Serum Levels and Removal by Haemodialysis and Haemodiafiltration of Tryptophan-Derived Uremic Toxins in ESKD Patients

“…In acute kidney injury, additional modalities of renal replacement therapy are used that increase amino acid loses. Thus, continuous veno-venous hemofiltration resulted in threefold higher amino acid losses that haemodialysis and sustained low-efficiency diafiltration in 50% higher losses than haemodialysis [13].…”

“…Clinical study data was acquired from four separate dialysis centres from countries with diverse life expectancy, renal replacement therapy incidence and kidney transplant rates: 1 higher amino acid losses that haemodialysis and sustained low-efficiency diafiltration in 50% higher losses than haemodialysis [13].…”

“…ESKD is usually treated with haemodialysis. However, haemodialysis does not selectively remove toxic uremic solutes, it removes also neutral and necessary solutes, including amino acids [11] such as Trp [12][13][14][15][16][17], potentially contributing to the negative impact of haemodialysis. In addition, uraemia-associated disruption of biochemical homeostasis (e.g., low concentrations of Trp due to malnutrition and removal by haemodialysis), are also suspected to negatively contribute to patient well-being [18][19][20].…”

Acute Kidney Injury Incidence in Hospitalized Patients and Implications for Nutrition Support

“…Loss of amino acids appears to be RRT‐modality dependent, with convective therapies, such as CRRT, resulting in greater amino acid loss than diffusive clearance, as used in HD. Loss of amino acids across different modalities, including CVVH, sustained low efficiency dialysis, and conventional hemodialysis, has been measured to be 18.7 g/d, 8.2 g, and 5.1 g, respectively, as measured by amino acid analyzer 97 . From our review, there has not been a comparison of amino acid losses across the different CRRT therapies.…”

“…Loss of amino acids across different modalities, including CVVH, sustained low efficiency dialysis, and conventional hemodialysis, has been measured to be 18.7 g/d, 8.2 g, and 5.1 g, respectively, as measured by amino acid analyzer. 97 From our review, there has not been a comparison of amino acid losses across the different CRRT therapies. In a study of critically ill patients with AKI, >30% of patients had tryptophan, taurine, histidine, and hydroxyproline levels below normal at 6 days post-CRRT, supporting the concept that patients with AKI have altered amino acid balance.…”