P44
MICRONUTRIENT LOSS IN RENAL REPLACEMENT THERAPY FOR ACUTE
KIDNEY INJURY
Weng C Oh 1,4, Mark Rigby 1, Bruno Mafrici 1, Andrew Sharman 4, Daniel Harvey 4, Simon
Welham3, Ravi Mahajan 4, David Gardner 2, Mark A J Devonald 1Renal and Transplant Unit,
Nottingham University Hospitals NHS Trust1, School of Veterinary Medicine and Science2 and
School of Biosciences3, Academic Anaesthesia, School of Medicine, University of Nottingham 4
INTRODUCTION: The prevalence of malnutrition in acute kidney injury (AKI) is high.
Patients with AKI may require renal replacement therapy (RRT), which could result in loss of
water-soluble micronutrients. Little is known about micronutrient losses in RRT and whether
they differ between types of RRT. The aim of this study is to quantify losses of micronutrients
(trace elements and amino acids) during RRT in patients with AKI and to compare losses in
three different RRT modalities: continuous veno-venous haemofiltration (CVVH), intermittent
haemodialysis (IHD) and sustained low-efficiency diafiltration (SLED-f).
METHODS: A prospective observational study is being conducted at NUH. All adult patients
with AKI requiring RRT are eligible to participate. A clinical assessment of the patient’s
nutritional status is undertaken. Samples of blood and RRT effluent (dialysate or filtrate) were
obtained at baseline and subsequently at mid and end-session from each participant during their
first RRT treatment. Samples were processed and stored at -80°C for subsequent analysis of
amino acids by high performance liquid chromatography (Biochrom 20) and trace elements by
inductively coupled mass spectrometry after derivatization from physiological fluids. Total
plasma concentrations of amino acids were corrected for dialysis dose using the urea reduction
ratio (for IHD & SLED-f, but not CVVH). Total losses of micronutrients during RRT were
calculated by multiplying mass-corrected concentrations by total volume of RRT effluent,
adjusted for baseline plasma concentrations and RRT dose (determined by the solute removal
index). Data were analysed by restricted maximum likelihood estimating equations (Genstat
v16, VSNi Ltd, UK). Full data were available for n=13 IHD, n=10 SLED-f and n=10 CVVH
patients.
RESULTS: 73.5% of patients were malnourished using the Subjective Global Assessment tool
(3-point scale). The prevalence of malnutrition is similar between patients receiving SLEDfvs.
IHD (70% vs. 69.2%) but was highest in patients receiving CVVH (82%). The total plasma
concentration of all standard amino acids (n=20) at baseline was similar between patients
receiving IHD vs. SLED-f (1812 ± 517 vs. 2675 ± 527 µmol/L, respectively) but was
considerably higher in patients receiving CVVH (3194 ± 564 µmol/L). RRT reduced the plasma
concentration of amino acids in patients receiving SLED-f (to 1732 ± 529 µmol/L; P=0.02), but
had no effect in those receiving IHD or CVVH (IHD; 1853 ± 523, CVVH; 2845 ± 512 µmol/L).
The average, unadjusted loss of amino acids was significantly influenced by mode of RRT
(IHD, 5.13 ± 3.1 vs. SLED-F, 8.21 ± 4.07 vs. CVVH, 18.69 ± 3.04 gms; P<0.01). 23 trace
elements were present at detectable concentrations in plasma. The total baseline plasma
concentration of trace elements was similar between patients receiving IHD, SLED-f and
CVVH (3797 ± 827, 3667 ± 791, 3642 ± 481 µg/L, respectively). By the end of each session of
RRT, the plasma concentration of trace elements in patients had reduced (IHD, to 3103 ± 827;
SLED-f, to 2805 ± 797; CVVH, to 3433 ± 481 µg/L; P=0.01). By the end of each session of
RRT total losses of trace elements were estimated at IHD, 5051 ± 2312; SLED-f, 8751 ± 2421;
CVVH, 11,258 ±2547 ug/L; P=0.02 for treatment.
CONCLUSION: Micronutrients are lost during RRT in AKI. The amount lost is influenced by
the type of RRT modality used. Micronutrient lossesarehighest in patients receiving CVVH.
The prevalence of malnutrition is high in patients in AKI stage 3.