Prolonged recirculation is required to detect secondary metabolic and hemodynamic deterioration after superior mesenteric artery occlusion.

We evaluated late (4 hrs) effects of reperfusion on hemodynamics after 30 or 60 min occlusion of the superior mesenteric artery (SMA) in a rat model. Spontaneously breathing animals (n=30) underwent occlusion of the SMA for 0 (sham), 30 (SMAO_30) or 60 min (SMAO_60) followed by reperfusion with normal saline. Abdominal blood flow (ABF), SMA blood flow (SBF), arterial blood pressure and heart rate were recorded continuously. Systemic vascular resistance (SVR) and SMA vascular resistance (MVR) were calculated at baseline and after 240 min reperfusion (240R). All animals survived in SMAO_30 and sham, two died in SMAO_60 after 120R. ABF remained constant in all groups. SVR increased in SMAO_30 and sham and decreased in SMAO_60 at 240R. SBF was significantly lower after reperfusion in ischemia groups as compared to sham. After 120R, SBF had increased significantly in SMAO_60 versus SMAO_30. MVR increased significantly in SMAO_30 but not in SMAO_60 and sham at 240R. 60 minutes SMA occlusion revealed early hemodynamic changes of septic circulation with increased blood flow in the SMA, decreased SVR, and pseudo-normalization of MVR. Prolonged observation periods are required to detect these significant changes which are overlooked when only studying 120 minutes of reperfusion as usually done.