Michalis Agrafiotis1, Dimitrios Mpliamplias2, Maria Papathanassiou3, Fotini Ampatzidou4, Georgios Drossos4. 1. Department of Pulmonary Medicine, "Georgios Papanikolaou" General Hospital of Thessaloniki, G. Papanikolaou Ave, 57010, Exohi, Greece. m.agrafiotis@gmail.com. 2. Department of Anesthesiology, "Papageorgiou" General Hospital of Thessaloniki, Nea Efkarpia, Greece. 3. Department of Pulmonary Medicine, "Georgios Papanikolaou" General Hospital of Thessaloniki, G. Papanikolaou Ave, 57010, Exohi, Greece. 4. Department of Cardiothoracic Surgery, "Georgios Papanikolaou" General Hospital of Thessaloniki, Exohi, Greece.
Abstract
PURPOSE: To suggest a simplified method for strong ion gap ([SIG]) calculation. PATIENTS AND METHODS: To simplify [SIG] calculation, we used the following assumptions: (1) the major determinants of apparent strong ion difference ([SIDa]) are [Na+], [K+] and [Cl-] (2) [Ca2+] and [Mg2+] do not contribute significantly to [SIDa] variation and can be replaced by their reference concentrations (3) physiologically relevant pH variation is at the order of 10-2 and therefore we can assume a standard value of 7.4. In the new model, [SIDa] is replaced by its adjusted form, i.e. [SIDa,adj] = [Na+] + [K+] - [Cl-] + 6.5 and [SIG] is replaced by "bicarbonate gap", i.e. [BICgap] = [SIDa,adj] - (0.25·[Albumin]) - (2·[Phosphate]) - [HCO3-]. The model was tested in 224 postoperative cardiac surgical patients. RESULTS: Strong correlations were observed between [SIDa,adj] and [SIDa] (r = 0.93, p < 0.0001) and between [BICgap] and [SIG] (r = 0.95, p < 0.0001). The mean bias (limits of agreement) of [SIDa,adj] - [SIDa] and of [BICgap]-[SIG] was - 0.6 meq/l (- 2.7 to 1.5) and 0.2 meq/l (- 2 to 2.4), respectively. The intraclass correlation coefficients between [SIDa,adj] and [SIDa] and between [BICgap] and [SIG] were 0.90 and 0.95, respectively. The sensitivities and specificities for the prediction of a [lactate-] > 4 meq/l were 73.4 and 82.3% for a [BICgap] > 12.2 meq/l and 74.5 and 83.1% for a [SIG] > 12 meq/l, respectively. CONCLUSIONS: The [BICgap] model bears a very good agreement with the [SIG] model while being simpler and easier to apply at the bedside. [BICgap] could be used as an alternative tool for the diagnosis of unmeasured ion acidosis.
PURPOSE: To suggest a simplified method for strong ion gap ([SIG]) calculation. PATIENTS AND METHODS: To simplify [SIG] calculation, we used the following assumptions: (1) the major determinants of apparent strong ion difference ([SIDa]) are [Na+], [K+] and [Cl-] (2) [Ca2+] and [Mg2+] do not contribute significantly to [SIDa] variation and can be replaced by their reference concentrations (3) physiologically relevant pH variation is at the order of 10-2 and therefore we can assume a standard value of 7.4. In the new model, [SIDa] is replaced by its adjusted form, i.e. [SIDa,adj] = [Na+] + [K+] - [Cl-] + 6.5 and [SIG] is replaced by "bicarbonate gap", i.e. [BICgap] = [SIDa,adj] - (0.25·[Albumin]) - (2·[Phosphate]) - [HCO3-]. The model was tested in 224 postoperative cardiac surgical patients. RESULTS: Strong correlations were observed between [SIDa,adj] and [SIDa] (r = 0.93, p < 0.0001) and between [BICgap] and [SIG] (r = 0.95, p < 0.0001). The mean bias (limits of agreement) of [SIDa,adj] - [SIDa] and of [BICgap]-[SIG] was - 0.6 meq/l (- 2.7 to 1.5) and 0.2 meq/l (- 2 to 2.4), respectively. The intraclass correlation coefficients between [SIDa,adj] and [SIDa] and between [BICgap] and [SIG] were 0.90 and 0.95, respectively. The sensitivities and specificities for the prediction of a [lactate-] > 4 meq/l were 73.4 and 82.3% for a [BICgap] > 12.2 meq/l and 74.5 and 83.1% for a [SIG] > 12 meq/l, respectively. CONCLUSIONS: The [BICgap] model bears a very good agreement with the [SIG] model while being simpler and easier to apply at the bedside. [BICgap] could be used as an alternative tool for the diagnosis of unmeasured ion acidosis.
Entities:
Keywords:
Anion gap; Base excess; Metabolic acidosis; Stewart–Figge acid–base model
Authors: Arnaldo Dubin; María M Menises; Fabio D Masevicius; Miriam C Moseinco; Daniela Olmos Kutscherauer; Elizabeth Ventrice; Enrique Laffaire; Elisa Estenssoro Journal: Crit Care Med Date: 2007-05 Impact factor: 7.598