Prostaglandin mediation of hemodynamic responses to pulmonary microembolism in rabbits: effects of ibuprofen and meclofenamate.

The effect of the cyclooxygenase inhibitors ibuprofen and meclofenamate were studied to assess the role of prostaglandin release in mediating the hemodynamic response to acute pulmonary microembolism in awake rabbits. In Group I (n = 10), a control group receiving only saline infusion, there was no change in pulmonary artery pressure, thermodilution cardiac output, or pulmonary vascular resistance. Group II (n = 12) received sequential intravenous doses of polyacrylamide microspheres averaging 34 mu in diameter, and demonstrated a progressive decrease in cardiac output and stroke volume and increases in pulmonary artery pressure and pulmonary vascular resistance. Pretreatment with either ibuprofen (Group III; n = 10) or meclofenamate (Group IV; n = 9) resulted in no change in resting hemodynamics and only minimally altered the effect of microembolism on pulmonary artery pressure. However, both ibuprofen and meclofenamate abolished the microembolism-induced decrease in cardiac output and stroke volume and blunted the increases in pulmonary artery pressure and pulmonary vascular resistance. The hemodynamic consequences of pulmonary microembolism in awake rabbits, particularly the decrease in cardiac output, are partly mediated by prostaglandin release, which alters pulmonary vascular tone and/or myocardial function.