Prognostic implications of arterial blood gases in acute decompensated heart failure.

BACKGROUND The prognostic value of arterial blood gases (ABG) in patients with acute decompensated heart failure (ADHF) is not well-established. We therefore conducted the present study to determine the relationship between ABG on admission and long-term mortality in patients with ADHF. METHODS We studied 588 patients consecutively admitted to our department with ADHF. ABG and classical prognostic variables were determined at patients' arrival to the emergency department. The independent association among the main variables of ABG (pO2, pCO2 and pH) and mortality was assessed with Cox regression analysis. RESULTS At a median follow-up of 23months, 221 deaths (37.6%) were registered. 308 (52.4%), 54 (9.2%) and 50 (8.5%) patients showed hypoxemia (pO2<60mmHg), hypercapnia (pCO2>50mmHg) and acidosis (pH<7.35), respectively. Patients with hypoxemia, hypercapnia and acidosis did not show higher mortality rates (38% vs. 37.1%, 42.6% vs. 37.1%, and 48% vs. 36.6%, respectively; p-value=ns for all comparisons). In multivariate analysis, after adjusting for well-known prognostic covariates, pO2, pCO2 and pH did not show a significant association with mortality. Hazard ratios (HR) for these variables were: pO2, per increase in 10mmHg: 0.99 (95% CI: 0.90-1.09), p=0.861; pCO2, per increase in 10mmHg: 1.12 (95% CI: 0.91-1.39), p=0.262; pH per increase in 0.1: 1.01 (95% CI: 0.99-1.04), p=0.309. When dichotomizing these variables according to established cut-points, the HR were: hypoxemia (pO2<60mmHg):1.07 (95% CI: 0.81-1.40), p=0.637; hypercapnia (pCO2>50mmHg): 0.98 (95% CI: 0.62-1.57), p=0.952; acidosis (pH<7.35): 1.38 (95% CI: 0.87-2.19), p=0.173. CONCLUSION In patients admitted with ADHF, admission arterial pO2, pCO2 and pH were not associated with all-cause long-term mortality.