Intensive Care Medicine

, Volume 36, Issue 9, pp 1626–1627 | Cite as

The many faces of “evidence” for dependent and independent variables in the ‘Stewart approach’: reply to Lang

  • Daniel DobererEmail author
  • Thomas Loerting
  • Karl Kirchner
  • Georg-Christian Funk

Dear Editor,

Based on our article [1], Dr. Lang presents in his letter [2] a detailed re-evaluation of the mechanism of dilutional acidosis. His recalculation of our simulations reproduces the same quantitative results, whereas the suggested chemical mechanisms differ. Furthermore, he calculates the Gibbs energy to determine the spontaneous chemical reactions and uses the phase rule as a new justification for the separation into dependent and independent variables. However, for the most part we disagree with the interpretations and conclusions involved in his analysis. In particular, the application of the phase rule is flawed. Due to the limited space we only summarize the conclusions of our reply in the following; further details can be requested from the authors.

The phase rule and the independent variables

The way Dr. Lang applies the phase rule to his example is inappropriate for several reasons: (1) The phase rule is only of interest in a system where changes of state occur and,...


Gibbs Energy HCO3 CO32 Master Equation Chemical Substance 
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  1. 1.
    Doberer D, Funk GC, Kirchner K, Schneeweiss B (2009) A critique of Stewart’s approach: the chemical mechanism of dilutional acidosis. Intensive Care Med 35:2173–2180. doi: 10.1007/s00134-009-1528-y CrossRefPubMedGoogle Scholar
  2. 2.
    Lang W (2010) Comment on: “A critique of Stewart’s approach: the chemical mechanism of dilutional acidosis”. Intensive Care Med. doi: 10.1007/s00134-010-1897-2

Copyright information

© Copyright jointly held by Springer and ESICM 2010

Authors and Affiliations

  • Daniel Doberer
    • 1
    Email author
  • Thomas Loerting
    • 2
  • Karl Kirchner
    • 3
  • Georg-Christian Funk
    • 4
  1. 1.Department of Clinical PharmacologyMedical University of ViennaViennaAustria
  2. 2.Institute of Physical ChemistryUniversity of InnsbruckInnsbruckAustria
  3. 3.Institute of Applied Synthetic ChemistryVienna University of TechnologyViennaAustria
  4. 4.Department of Respiratory and Critical Care MedicineOtto Wagner SpitalViennaAustria

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