RT Journal Article
SR Electronic
T1 Quantitative Analysis of Acid-Base Disorders in Patients With Chronic Respiratory Failure in Stable or Unstable Respiratory Condition
JF Respiratory Care
FD American Association for Respiratory Care
SP 1453
OP 1463
VO 55
IS 11
A1 Guérin, Claude
A1 Nesme, Pascale
A1 Leray, Véronique
A1 Wallet, Florent
A1 Bourdin, Gael
A1 Bayle, Frédérique
A1 Germain, Michèle
A1 Richard, Jean-Christophe
YR 2010
UL http://rc.rcjournal.com/content/55/11/1453.abstract
AB 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–), 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– (Group 1, n = 23), stable respiratory condition and non-elevated HCO3– (Group 2, n = 41), unstable respiratory condition and elevated HCO3– (Group 3, n = 44), and unstable respiratory condition and non-elevated HCO3– (Group 4, n = 37). Elevated HCO3– 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 ± SD values were: HCO3– 33 ± 3 mM, 26 ± 3 mM, 37 ± 4 mM, and 27 ± 3 mM (P < .001); strong ion difference 45 ± 3 mM, 38 ± 4 mM, 46 ± 4 mM, and 36 ± 4 mM (P < .001); and Atot 12 ± 1 mM, 12 ± 1 mM, 10 ± 1 mM, 10 ± 2 mM (P < .001). Non-respiratory disorders related to high strong ion difference were observed in 12% of patients with elevated HCO3–, and in none of those with non-elevated HCO3– (P = .003). Non-respiratory disorders related to low strong ion difference were observed in 9% of patients with non-elevated HCO3–, and in none of those with elevated HCO3– (P = .02). Hypoalbuminemia was common, especially in unstable patients (group 3, 66%; group 4, 65%). Normal standardized base excess (16%), HCO3– (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–. CONCLUSIONS: In patients with chronic respiratory failure the acid-base pattern is complex, metabolic alkalosis is present in some patients with elevated HCO3–, and metabolic acidosis is present in some with non-elevated HCO3–. The diagnostic performance of the Stewart approach was better than that of the conventional approach, even when corrected anion gap was taken into account.