NDT Advance Access originally published online on November 19, 2007
Nephrology Dialysis Transplantation 2008 23(4):1462-1463; doi:10.1093/ndt/gfm822
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Reply
hndt512{at}bellsouth.netSir,
We thank Dr. Diskin for his kind remarks and are in agreement with his comments regarding our paper on trace element removal during continuous haemodialysis [1]. Reduction in plasma selenium concentrations due to tissue selenium redistribution may occur in critically ill patients, probably as a result of the systemic inflammatory response syndrome (SIRS) [2,3]. Furthermore, exposure of a renal failure patient's blood to the dialysis membrane is another source of oxidative stress, potentially resulting in low serum selenium concentrations and reduced glutathione peroxidase activity [4].
As pointed out by Dr. Diskin, selenium concentrations in blood, plasma and serum are different, notwithstanding a typographical error on page 2975 of our paper, in the second paragraph of the Discussion section. The statement ‘Plasma serum concentrations of trace elements’ should read ‘Plasma concentrations of trace elements’. We measured plasma selenium concentrations in our study because these concentrations correlate with short-term selenium status better than whole blood, and better reflect the actual selenium status of our critically ill patients treated with continuous haemodialysis [5].
Selenium is highly bound to plasma proteins, which prevents significant dialytic clearance. Our critically ill study patients (sepsis, organ failure) with (mean ± SD) serum albumin concentration (2.1 ± 0.72 g/dL) are illustrative of patients commonly seen in our intensive care units. The mean albumin concentration of these study patients suggests that there may have been reduced binding sites for selenium, and consequently, more unbound selenium would be available for dialytic clearance. However, during acute inflammation, plasma alpha-2 globulin concentrations are often increased as part of the acute phase response, which as Dr. Diskin points out, may also serve as a binding site for selenium. In our study, all but one patient received trace element supplementation that included selenium, either in parenteral or enteral nutrition. Consequently, an increase in free selenium or the portion cleared by continuous haemodialysis might be higher than that in patients who are not supplemented with selenium. The effects of these and other changes on selenium binding to circulating plasma proteins depend on many factors and are difficult to predict.
Despite the complexities involved in trace element binding and extracorporeal removal, we reported a very low clearance rate for selenium and other trace elements during continuous haemodialysis. Although almost all of our subjects were receiving some concurrent trace element supplementation, the observed trace element clearance was considerably less than that usually administered in a typical daily trace element supplementation regimen. Our published trace element extraction coefficients and continuous dialysis clearance rates should be interpreted as what would be observed in critically ill patients receiving nutrition and continuous haemodialysis.
Conflict of interest statement. None declared.
1 Department of Pharmacy Practice, College of Pharmacy, University of Toledo, Toledo, OH, USA 2 Renal Replacement Therapy Kinetic Study Group, USA 3 Department of Clinical, Social, and Administrative Sciences, College of Pharmacy, University of Michigan, Ann Arbor, MI, USA
References
- Churchwell MD, Pasko DA, Btaiche IF, et al. Trace element removal during in vitro and in vivo continuous haemodialysis. Nephrol Dial Transplant (2007) 22:2970–2977.
[Abstract/Free Full Text] - Berger MM, Chiolero RL. Antioxidant supplementation in sepsis and systemic inflammatory response syndrome. Crit Care Med (2007) 35(9 Suppl):S584–S590.[CrossRef][Medline]
- Forceville X, Vitoux D, Gauzit R, et al. Selenium, systemic immune response syndrome, sepsis, and outcome in critically ill patients. Crit Care Med (1998) 26:1536–1544.[CrossRef][Web of Science][Medline]
- Yavuz O, Bicik Z, Cinar Y, et al. The effect of different dialysis membranes on oxidative stress and selenium status. Clin Chim Acta (2004) 346:153–160.[CrossRef][Web of Science][Medline]
- Nichoalds GE. Selenium. In: The Clinical Guide to Parenteral Micronutrition—Baumgartner TG, ed. (1997) Fujisawa USA, Inc. 387–400.
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