The purpose of our study was to examine in patients hospitalized with community-acquired pneumonia (CAP) the association between abnormal Paco2 and ICU admission and 30-day mortality.
A retrospective cohort study was conducted at two tertiary teaching hospitals. Eligible subjects were admitted with a diagnosis of CAP. Arterial blood gas analyses were obtained with measurement of Paco2 on admission. Multivariate analyses were performed using 30-day mortality and ICU admission as the dependent measures.
Data were abstracted on 453 subjects with a documented arterial blood gas analysis. One hundred eighty-nine patients (41%) had normal Paco2 (35-45 mm Hg), 194 patients (42%) had a Paco2 < 35 mm Hg (hypocapnic), and 70 patients (15%) had a Paco2 > 45 mm Hg (hypercapnic). In the multivariate analysis, after adjusting for severity of illness, hypocapnic patients had greater 30-day mortality (OR = 2.84; 95% CI, 1.28-6.30) and a higher need for ICU admission (OR = 2.88; 95% CI, 1.68-4.95) compared with patients with normal Paco2. In addition, hypercapnic patients had a greater 30-day mortality (OR = 3.38; 95% CI, 1.38-8.30) and a higher need for ICU admission (OR = 5.35; 95% CI, 2.80-10.23). When patients with COPD were excluded from the analysis, the differences persisted between groups.
In hospitalized patients with CAP, both hypocapnia and hypercapnia were associated with an increased need for ICU admission and higher 30-day mortality. These findings persisted after excluding patients with CAP and with COPD. Therefore, Paco2 should be considered for inclusion in future severity stratification criteria to appropriate identified patients who will require a higher level of care and are at risk for increased mortality.