Thromboxane and prostacyclin in clinical acute respiratory failure

Abstract

Plasma levels of thromboxane A 2 and prostacyclin have been elevated during experimental acute respiratory failure (ARDS). The present study evaluates the relationship of plasma levels of thromboxane A 2 and prostacyclin, measured by radioimmunoassay as the stable metabolites thromboxane B 2 (TxB) and prostaglandin 6-K-F 1α (PGI) to the incidence of clinical ARDS. Sixty-seven consecutive patients at risk for ARDS were studied prospectively. TxB, PGI, platelet, and leukocyte counts were measured daily for up to 5 days. Of 55 patients without cerebral injury, 25 (45%) developed ARDS, and 30 did not. Of 12 patients with cerebral injury, none developed ARDS. This difference was highly significant ( P < 0.01). TxB was increased and age lower with head injury ( P < 0.05). PGI was significantly lower in ARDS (110 ± 32 vs 227 ± 211 pg/ml, P < 0.05), and mean TxB was unchanged. TxB was increased in age >60 and decreased with prostaglandin inhibitors. ARDS was significantly associated with TxB >70 pg/ml, PGI below the detectable level of 103 pg/ml, TxB PGI ratio >0.7, and age >60 years. Peak TxB occurred before or simultaneously with onset of ARDS in 68%. Leukocytes were decreased in ARDS (8.6 ± 4 vs 11.1 ± 4.4 × 10 3/mm 3) and platelets were unchanged. ARDS was decreased with steroid therapy. Elevated TxB is related to a high incidence of ARDS. Elevated PGI may protect against ARDS. Cerebral injury patients in this study were resistant to ARDS in spite of increased TxB.