Community-acquired pneumonia: evidence of functional inactivation of alpha 1 proteinase inhibitor

Quantitative and qualitative elastase inhibitory capacity (EIC) alpha 1 proteinase inhibitor (alpha 1 PI) was measured in pulmonary arterial and systemic arterial blood of patients with community-acquired pneumonia (CAP). Eleven patients with uncomplicated CAP were compared with 16 patients with fulminating pneumonia requiring intensive care management. An appropriate increase in quantitative alpha 1 PI was demonstrated in all patients. A significant functional inactivation of alpha 1 PI was demonstrated in the ICU-treated patients that was not apparent in the uncomplicated CAP patients (p less than .01). This low EIC returned to normal 4 wk after hospital discharge in all survivors. A significant (p less than .02) difference in EIC between the pulmonary arterial and systemic arterial blood was found in the nonsurvivors on admission, which suggests that alpha 1 PI is inactivated in the lungs of patients with fulminating CAP. The present data demonstrate that alpha 1 PI is functionally inactivated in patients with fulminating CAP. This low serum functional alpha 1 PI may result in proteolytic lung damage and an unfavorable outcome.