Pulmonary hemodynamic responses during superior mesenteric artery occlusion.
We investigated the possibility that the reestablishment of blood flow to the intestine after a 2-h occlusion of the superior mesenteric artery (SMA) may liberate vasoactive substances in quantities sufficient to cause pulmonary vasoconstriction. Experiments were conducted in dogs in which we compared the hemodynamic responses of the animal's left lower lung lobe (LLL), which was perfused at constant flow with blood pumped from the animal's pulmonary artery, with those of its intact right lung. Changes in systemic hemodynamics were similar to those reported by others for this stress. By 1 h after the release of the occlusion, cardiac output and stroke volume had fallen by 41.1 and 50.0%, respectively. Comparable changes were not observed in sham-operated control animals. Following the release of the occlusion, we observed an average 0.9 torr (P less than 0.10) increase in LLL arterial pressure, no significant changes in left atrial pressure, and a 11.9% increase (P less than 0.025) in LLL vascular resistance. In the intact right lung, no significant changes in pulmonary arterial pressure were observed at this time. Although the responses of the LLL suggested that some very small increase in vasomotor tone may have occurred, the small magnitude of the response indicated that the lung vasculature is only minimally affected during the early phases of this stress.
D000818:Animals; D004285:Dogs; D006439:Hemodynamics; D007422:Intestines / Q000098:blood supply; D007511:Ischemia / Q000503:physiopathology; D008638:Mesenteric Arteries / Q000503:physiopathology; D008641:Mesenteric Vascular Occlusion / Q000503:physiopathology*; D011652:Pulmonary Circulation; D014661:Vasoconstriction