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Archived Comments for: Renal replacement therapy in acute kidney injury: controversy and consensus

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  1. Carbon dioxide overload: the neglected caveat of renal replacement therapy.

    Marco Marano, Maria Rosaria Clinc

    3 June 2015

    If  renal replacement therapy are offered as support to AKI as well as to multiple organ failure, I am quite surprised to find no notice of dialysis bath, because it could be a source of  carbon dioxide (CO2), not a negligible issue [1].  

    In such fluid a buffer has the obvious role to support metabolic derangement, but  an acid inevitably exists - and this is not so intuitive - to avoid  salts precipitation. The chemical reaction between the acid and the buffer generates CO2 which  ultimately acidifies dialysis fluid and keeps salts in their soluble form.   As largely  expected by  physical properties,  CO2 easy crosses the filtering membrane and flows in patient’s bloodstream [2,3,4].

    Severely ill patients and those with cardio-pulmonary marginal status should   withstand the CO2 overload from dialysate. This  is not an academic  caveat because  extracorporeal CO2 removal can be offered in series with RRT, as underlined  by  the authors. Also, and above all,  acetate-free biofiltration   - a buffer-free technique with sodium bicarbonate reinfusion - does not return to the  patient unphysiological amount of carbon dioxide as other dialysis techniques possibly do [4]. Evidences to support this technique as treatment of choice to prevent  CO2 overload in critically ill patients are lacking,  and in my opinion  this conjecture deserves further researches, however this neglected and unwanted  effect must kept in mind in the choice of kind and dose of RRT.


    1. Golper TA, Fissel R, Fissel WH, Hartle M, Sanders ML, Schulman G: Hemodialysis: core curriculum 2014. Am J Kidney Dis 2014;63(1):153-163
    2. Sombolos KI, Bamichas GI, Christidou FN Gionanlis LD, Karagianni AC, Anagnostopoulos TC, Natse TA: pO2 and pCO2 increment in post-dialyzer blood: the role of dialysate. Artif Organs 2005;29:892-8
    3. Symreng T, Flanigan MJ, Lim VS: Ventilatory and metabolic changes during high efficiency hemodialysis. Kidney Int 1992;41:1064-9
    4. Marano M, D'Amato A, Patriarca A, Di Nuzzi LM, Giordano G, Iulianiello G. Carbon Dioxide and Acetate-Free Biofiltration: A Relationship to be Investigated. Artif Organs. 2015 May 1. doi: 10.1111/aor.12477

    Competing interests

    The Author declares no conflict of interest