Influence of Low Admission Levels of Arterial Carbon Dioxide on Clinical Outcomes in Patients with Acute Decompensated Heart Failure

Background: Influence of admission levels of arterial carbon dioxide (CO₂) levels, which may be suggestive of severe disease state, on clinical outcomes in patients with acute decompensated heart failure (ADHF) are not well-established. We hypothesized that low admission levels of partial pressure of arterial carbon dioxide (PaCO₂) possibly due to severe pulmonary congestion is associated with worse clinical outcomes in patients with ADHF. Methods: We studied eligible ADHF patients admitted to the cardiac intensive-care unit from 2007–2011. All patients were categorized into 3 groups according to the tertiles of admission PaCO₂. Association between admission PaCO₂ and long-term mortality was assessed by multivariable Cox proportional regression. Results: Among 435 eligible patients, 26.4% died at a median follow-up of 1.8 years. In the multivariable analysis including tertiles of PaCO₂ and other baseline variables (age, sex, body mass index, ischemic etiology, atrial fibrillation, heart rate, B-type natriuretic peptide, hemoglobin, C-reactive protein, sodium and potassium levels), patients in the lowest tertile (PaCO₂ <31.7 Torr) showed a greater risk of mortality (hazard ratio (HR), 2.18; P = .025) whereas those in the highest tertile (PaCO₂ >36.8 Torr) did not (HR, 1.22; P = .587) compared with those in the middle tertile (PaCO₂ ranged from 31.7 to 36.8 Torr). Conclusion: In patients with ADHF, the lower the PaCO₂ level on admission, the greater the risk of long-term mortality.