Role of prostacyclin and thromboxane in the circulatory changes of acute bacteremic Pseudomonas pneumonia in dogs.

We investigated the role of prostacyclin (PGI2) and thromboxane A2 (TxA2), as evidenced by changes in their stable metabolites, 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TxB2), in the pathophysiology of acute bacteremic gram-negative pneumonia. Three groups of dogs were inoculated endotracheally: Group I (n = 5) with sterile broth, and Groups II (n = 5) and III (n = 10) with Pseudomonas aeruginosa. Gas exchange, hemodynamics, and plasma prostaglandins were measured before inoculation and hourly thereafter for 5 h in Groups I and II but only once in Group III, 5 h after inoculation. All animals were then killed, and the extent of pneumonia was assessed by lung wet weight and measurement of the percentage of cardiac output (CO) perfusing pneumonic lung using radionuclide-labeled microspheres. None of these measurements changed significantly in Group I, but all dogs in Groups II and III developed severe pneumonia. In Group II, mean arterial oxygen tension fell from 575 +/- 17 to 237 +/- 59 mm Hg (FIO2 = 1.0), with an increase in pulmonary shunt from 6 +/- 2% to 24 +/- 6%. Although TxB2 levels did not change, plasma 6-keto-PGF1 alpha rose progressively as pneumonia developed from baseline levels (less than 100 pg/ml) to a peak level of 890 +/- 114 pg/ml 5 h after inoculation.(ABSTRACT TRUNCATED AT 250 WORDS)