@article {Gu{\'e}rin1453, author = {Claude Gu{\'e}rin and Pascale Nesme and V{\'e}ronique Leray and Florent Wallet and Gael Bourdin and Fr{\'e}d{\'e}rique Bayle and Mich{\`e}le Germain and Jean-Christophe Richard}, title = {Quantitative Analysis of Acid-Base Disorders in Patients With Chronic Respiratory Failure in Stable or Unstable Respiratory Condition}, volume = {55}, number = {11}, pages = {1453--1463}, year = {2010}, publisher = {Respiratory Care}, abstract = {BACKGROUND: The Stewart approach theorizes that plasma pH depends on PaCO2, the strong ion difference, and the plasma total concentration of non-volatile weak acids (Atot). The conventional approach measures standardized base excess, bicarbonate (HCO3{\textendash}), and the anion gap. OBJECTIVE: To describe acid-base disorders with the Stewart approach and the conventional approach in patients with chronic respiratory failure. METHODS: This was an observational prospective study in a medical intensive care unit and a pneumology ward of a university hospital. There were 128 patients included in the study, of which 14 had more than one admission, resulting in 145 admissions. These were allocated to 4 groups: stable respiratory condition and elevated HCO3{\textendash} (Group 1, n = 23), stable respiratory condition and non-elevated HCO3{\textendash} (Group 2, n = 41), unstable respiratory condition and elevated HCO3{\textendash} (Group 3, n = 44), and unstable respiratory condition and non-elevated HCO3{\textendash} (Group 4, n = 37). Elevated HCO3{\textendash} was defined as >= 3 standard deviations higher than the mean value we found in 8 healthy volunteers. Measurements were taken on admission. RESULTS: In groups 1, 2, 3, and 4, the respective mean {\textpm} SD values were: HCO3{\textendash} 33 {\textpm} 3 mM, 26 {\textpm} 3 mM, 37 {\textpm} 4 mM, and 27 {\textpm} 3 mM (P \< .001); strong ion difference 45 {\textpm} 3 mM, 38 {\textpm} 4 mM, 46 {\textpm} 4 mM, and 36 {\textpm} 4 mM (P \< .001); and Atot 12 {\textpm} 1 mM, 12 {\textpm} 1 mM, 10 {\textpm} 1 mM, 10 {\textpm} 2 mM (P \< .001). Non-respiratory disorders related to high strong ion difference were observed in 12\% of patients with elevated HCO3{\textendash}, and in none of those with non-elevated HCO3{\textendash} (P = .003). Non-respiratory disorders related to low strong ion difference were observed in 9\% of patients with non-elevated HCO3{\textendash}, and in none of those with elevated HCO3{\textendash} (P = .02). Hypoalbuminemia was common, especially in unstable patients (group 3, 66\%; group 4, 65\%). Normal standardized base excess (16\%), HCO3{\textendash} (28\%), and anion gap (30\%) values were common. The Stewart approach detected high effective strong ion difference in 13\% of normal standardized base excess, and in 20\% of normal anion gap corrected for albuminemia, and low effective strong ion difference in 22\% of non-elevated HCO3{\textendash}. CONCLUSIONS: In patients with chronic respiratory failure the acid-base pattern is complex, metabolic alkalosis is present in some patients with elevated HCO3{\textendash}, and metabolic acidosis is present in some with non-elevated HCO3{\textendash}. The diagnostic performance of the Stewart approach was better than that of the conventional approach, even when corrected anion gap was taken into account.}, issn = {0020-1324}, URL = {https://rc.rcjournal.com/content/55/11/1453}, eprint = {https://rc.rcjournal.com/content/55/11/1453.full.pdf}, journal = {Respiratory Care} }