Disease Models, Animal; Hypoxia/complications; Ileum/blood supply; Ischemia/therapy; Reperfusion Injury/etiology; Reperfusion Injury/prevention & control; Reperfusion/methods; Animals; Biopsy; Blood Gas Analysis; Fluid Therapy/methods; Hypoxia/metabolism; Ileum/pathology; Inflammation; Interleukin-1/blood; Lung/pathology; Male; Mesenteric Artery, Superior; Multiple Organ Failure/etiology; Multiple Organ Failure/pathology; Multiple Organ Failure/prevention & control; Oxygen/blood; Random Allocation; Reactive Oxygen Species/metabolism; Reperfusion/adverse effects; Reperfusion Injury/pathology; Swine; Systemic Inflammatory Response Syndrome/etiology; Systemic Inflammatory Response Syndrome/prevention & control; Time Factors; Treatment Outcome