Prostaglandin and thromboxane levels during endotoxin-induced respiratory failure in pigs

Arterial plasma concentrations of thromboxane B₂ (TxB₂), prostaglandin F_2α (PGF_2α) and 6-keto-prostaglandin F_lα (PGF_1α) were measured during endotoxin-induced acute respiratory failure (ARF) in anesthetized 10–12 wk old pigs. A 4.5 hour (hr) infusion of endotoxin resulted in a biphasic pattern of ARF. Phase 1 (0–2 hr) was characterized by increased pulmonary artery pressure, pulmonary vascular resistance (PVR), and alveolar-arterial O₂ gradient (ΔA-aO₂), and decreased cardiac index (CI) and lung dynamic compliance (LDC). Following a return of PVR and CI values towards baseline, a second phase (2–4.5 hr) of deteriorating function occurred and was characterized by additional increases in PVR and ΔA-aO₂ and decreases in CI and LDC. Baseline (i.e., 0 hr) plasma TxB₂ concentrations were 241 ± 24 pg/ml; these values peaked at 0.5 hr (3228 ± 712 pg/ml) and declined to 1635 ± 453 pg/ml at 4.5 hr. Plasma concentrations of PGF_2α slowly increased from a baseline value of 154 ± 32 pg/ml to 2355 ± 738 pg/ml at 4.5 hr, while PGF_1α values increased from 54 ± 2 pg/ml at 0 hr to 503 ± 172 pg/ml at 4.5 hr. Time-matched control pigs showed no changes in pulmonary hemodynamics or in plasma TxB₂, PGF_2α or PGF_1α levels. These results indicate that cyclooxygenase products are increased during both phases of endotoxin-induced ARF in pigs.