A modified Gamblegram for the visual representation of acid-base disorders according to the Stewart-Figge approach

The Gamblegram consists of two bars, each of which represents the sum of the charges of individual positively and negatively charged ions and is commonly used for visualizing changes in acid-base and electrolyte charges. However, according to the Stewart-Figge theory, the metabolic independent acid-base variables include the strong ion difference ([SID]) and the total concentrations of weak acids (albumin and inorganic phosphate), which are not shown in the conventional Gamblegram. Thus, the Gamblegram in its current form is unsuitable for visualizing acid-base perturbations using the Stewart-Figge approach. To overcome this problem the following modifications are proposed: 1) The positive bar is represented exclusively by strong ion difference ([SID]) 2) The negative bar is comprised of [HCO₃̄], unmeasured ion charge ([X]) and albumin and inorganic phosphate charges which are considered proportional to their total concentrations assuming a standard pH of 7.4 (0.28⋅[Albumin] (g/l) and 1.8⋅[Phosphate] (mmol/l), respectively). The proposed method treats [HCO₃̄] as a global index of the metabolic acid-base status, whose concentration is expressed as a function of the Stewart-Figge independent acid-base variables ([SID], [Albumin], [Phosphate] and [X]).