In some patients, however, elevation of these values persisted, probably due to irreversible lung damage. Zaman and White have also found lower mean serum LDH levels in survivors than nonsurvivors (340 IU vs 441 IU, compared with the present study in which serum LDH values were 394 IU vs 719 IU, respectively).
Elevation of serum LDH levels has been reported in diseases that cause alveolar damage such as alveolar proteinosis. An increased LDH level has occasionally been reported in pneumococcal as well as Legionella pneumonia. Hemolysis may be responsible in the former, while liver dysfunction may contribute to its elevation in the latter. When normal pulmonary tissue is homogenized and assayed for LDH, the isoenzyme pattern found is characteristically isoenzymes 3, 4, and 5. buy ventolin inhaler
This specific “pulmonary” isoenzyme pattern is found in the serum of patients with pulmonary infarction. Increased LDH-3 and LDH-4 (which predominate in lung tissue) found in some AIDS patients with P carinii pneumonia may reflect alveolar damage. However, this pattern was only seen in one third of the patients in the present series and infrequently in the series of Silverman and Rubinstein. Recently, Smith et al explained this discrepancy between serum and lavage LDH isoenzymes in AIDS patients with Pneumocystis.
An elevated serum LDH level may be due to a backflow of BAL-LDH through a more permeable alveolar-capillary. Cationic isoenzymes LDH 3, 4, and 5 are preferentially retained in the air spaces. In particular, selective backflow of BAL-LDH isoenzyme 2 may be responsible for the isomorphic pattern seen in the serum of patients with PCP.
Elevations of P(A-a)02 gradient and serum LDH have diagnostic and prognostic value in AIDS patients with P carinii pneumonia. Serum LDH is elevated in most AIDS patients with Pneumocystis in contrast to other pulmonary processes in AIDS patients. Serum LDH and P(A-a)02 gradients return to the normal range with therapy.