NDT Advance Access originally published online on November 26, 2007
Nephrology Dialysis Transplantation 2008 23(4):1456-1457; doi:10.1093/ndt/gfm686
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Risk factors of the progression of abdominal aortic calcification in patients on chronic haemodialysis
Sir,
We read with great interest the article by Yamada et al. [1], pointing out for the first time that the perdialytic increase of serum calcium (SCa) was related to the progression of aortic calcification over 3 years, despite the use of a dialysate calcium concentration of 1.50 mmol/l. This concentration is equivalent to the mean of diffusible calcium when albuminemia, pH and total calcium (2.50 mmol/l) are normal, since only 40% of this total calcium is then fixed on albumin. Theoretically, use of such a dialysate calcium concentration should maintain a neutral calcium balance during dialysis. However, this is not the case when mean predialysis total SCa is only 2.25 mmol/l as in Yamada's patients, and therefore diffusible calcium 1.35 mmol/ml, the resulting concentration gradient promoting calcium diffusion from the dialysate to the patient.
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Whereas we readily understand that lower pre-haemodialysis SCa concentration and greater ultrafiltration magnify perdialytic SCa increase, we have greater difficulty in understanding how vitamin D analogues blunt this increase, other than by increasing pre-haemodialysis SCa concentration. Therefore, we would be interested to know whether this preventing effect of vitamin D analogues on perdialytic serum Ca increase is actually independent of predialysis SCa, and what was the precise nature of these vitamin D analogues, as well as the vitamin D status of the patients, in terms of serum 25 OH vitamin D levels.
Indeed the nature of the vitamin D treatment in uraemic patients may play a critical role in their risk of cardiovascular calcifications. This was suggested by the comparison of two German cohorts of young adults with childhood onset of ESRD [2], since the prevalence of coronary and valvular calcification was 92% and 30% in that of Heidelberg, in which the vitamin D treatment was based mainly on activated vitamin D derivatives, and 10% and zero in that of East Berlin, in which this treatment was mainly based on high daily dose of cholecalciferol (5750 IU). Although not measured in East Berlin, the 25 OH vitamin D levels induced by such a dose of cholecalciferol in teenagers on haemodialysis are, according to Michel Garabedian of Necker Hospital, about 63±33 ng/ml (see PS), i.e. 2 folds the lower limit of 25 OH vitamin D serum levels recommended in the 2003 KDOQI [3].
In relation to this observation, it should be recalled that the effect of 25 OH vitamin D on osteoid calcification has been shown to be much greater than that of alfacalcidol, for the same increase of SCa and phosphate concentration and the same suppression of parathyroid hormone and osteoclastic surfaces [4].
In contrast to the vascular calcifying effect of non-hypercalcaemic dose of calcitriol in uraemic rats resulting in shorter survival [5], a high calcium diet has been shown to increase survival of uraemic rats while decreasing proteinuria, hypertension and vascular calcifications [6].
Therefore, we suggest using higher doses of CaCO3 (given with the meals as phosphate binder) than those used by Yamada et al., in association with native or 25 OH vitamin D3 analogue, in order to increase predialysis SCa concentrations up to 2.37 mmol/l (which is the upper limit of the optimal SCa concentration range recommended by the KDOQI [3]), while using a dialysate calcium concentration equal to 60% of this concentration (i.e. 1.42 mmol/l) in order to blunt the calcium concentration gradient between the dialysate and the patient diffusible calcium.
Conflict of interest statement. None declared.
1 Nephrology department, Amiens CHU, France 2 INSERM, ERI-12, Amiens France and UPJV, Amiens, France 3 CNRS, St-Vincent de Paul, Paris CHU, France
References
- Yamada K, Fujimoto S, Nishiura R, et al. Risk factors of the progression of abdominal aortic calcification in patients on chronic haemodialysis. Nephrol Dial Transplant (2007) 22:2032–2037.
[Abstract/Free Full Text] - Fournier A, Harbouche L, Mansour J, et al. Impact of calcium and vitamin D therapy on arterial and cardiac disease in young adults with childhood-onset end stage renal disease. Nephrol Dial Transplant (2007) 22:956–957.
[Free Full Text] - Monge M, Shahapuni I, Oprisiu R, et al. Reappraisal of 2003 NKF-K/DOQI guidelines for management of hyperparathyroidism in chronic kidney disease patients. Nat Clin Pract Nephrol (2006) 2:326–336.[CrossRef][Web of Science][Medline]
- Fournier A, Bordier P, Gueris J, et al. Comparison of 1 alpha-hydroxycholecalciferol and 25-hydroxycholecalciferol in the treatment of renal osteodystrophy: greater effect of 25-hydroxycholecalciferol on bone mineralization. Kidney Int (1979) 15:196–204.[Web of Science][Medline]
- Haffner D, Hocher B, Muller D, et al. Systemic cardiovascular disease in uremic rats induced by 1,25(OH)2D3. J Hypertens (2005) 23:1067–1075.[Web of Science][Medline]
- Porsti I, Fan M, Koobi P, et al. High calcium diet down-regulates kidney angiotensin-converting enzyme in experimental renal failure. Kidney Int (2004) 66:2155–2166.[CrossRef][Web of Science][Medline]
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