Angiotensin-converting enzyme in human adult respiratory distress syndrome.

Angiotensin-converting enzyme (ACE) levels, complement activation, and intravascular coagulation were studied in 36 patients with adult respiratory distress syndrome (ARDS) (17 aseptic, 19 septic), in order to investigate the possible interrelations among ACE, immunologic data, and hematologic findings. The severity of respiratory impairment was assessed with measurements of mechanical and gas exchange functional qualities of the lung. Serial measurements of ACE could be done in 14 patients during an eight-day period. During the first 24 hours, ACE levels were always normal (38 percent) or decreased (62 percent). No difference could be found between patients with septic and aseptic ARDS. Complement activation occurred in 78 percent (28/36) and used, in most cases, the classic pathway with presence of circulating immune complexes. Criteria for intravascular coagulation were present in 58 percent (21/36). No relation between coagulation, complement, and ACE could be found except for the patients with a greater respiratory impairment, who had complement activation, intravascular coagulation, and significantly lower ACE levels. In all patients together, ACE levels had no diagnostic value for aseptic cause of ARDS and a poor prognostic value. Only intravascular coagulation was linked with a higher significant mortality and a greater functional impairment. Serial measurements showed a diphasic evolution of ACE levels, with a maximum decrease between the 72nd and 96th hours and a further normalization (seventh day). The persistence of low levels seemed to be associated with evolutive sepsis or secondary aggravation and fibrosis.