Association of hypercapnia on admission with increased length of hospital stay and severity in patients admitted with community-acquired pneumonia: a prospective observational study from Pakistan

OBJECTIVE To determine whether the presence of hypercapnia on admission in adult patients admitted to a university-based hospital in Karachi, Pakistan with community-acquired pneumonia (CAP) correlates with an increased length of hospital stay and severity compared with no hypercapnia on admission. STUDY DESIGN A prospective observational study. SETTINGS Tertiary care hospital in Karachi, Pakistan. METHODS Patients who met the inclusion criteria were enrolled in the study. The severity of pneumonia was assessed by CURB-65 and PSI scores. An arterial blood gas analysis was obtained within 24 hours of admission. Based on arterial PaCO2 levels, patients were divided into three groups: hypocapnic (PaCO2 <35 mm Hg), hypercapnic (PaCO2 >45 mm Hg) and normocapnic (PaCO2 <35-45 mm Hg). OUTCOMES The primary outcome was the association of hypercapnia on admission with mean length of hospital stay. Secondary outcomes were the need for mechanical ventilation, ICU admission and in-hospital mortality. RESULTS A total of 295 patients of mean age 60.20±17.0 years (157 (53.22%) men) were enrolled over a 1-year period. Hypocapnia was found in 181 (61.35%) and hypercapnia in 57 (19.32%) patients. Hypercapnic patients had a longer hospital stay (mean 9.27±7.57 days), increased requirement for non-invasive mechanical ventilation (NIMV) on admission (n=45 (78.94%)) and longer mean time to clinical stability (4.39±2.0 days) compared with the other groups. Overall mortality was 41 (13.89%), but there was no statistically significant difference in mortality (p=0.35) and ICU admission (p=0.37) between the three groups. On multivariable analysis, increased length of hospital stay was associated with NIMV use, ICU admission, hypercapnia and normocapnia. CONCLUSION Hypercapnia on admission is associated with severity of CAP, longer time to clinical stability, increased length of hospital stay and need for NIMV. It should be considered as an important criterion to label the severity of the illness and also a determinant of patients who will require a higher level of hospital care. However, further validation is required.