Acute mesenteric ischemia (AMI) is a severe condition that might occur after cardiovascular surgery. Several risk factors for AMI, such as multimorbidity, the use of vasopressors, and an increase in inflammatory markers have been identified in the past. However, these risk factors also seem to influence the blood and urine levels of I-FABP. This prospective pilot study intends to evaluate the value of perioperatively assessed I-FABP levels and to correlate these values with clinical or angiographic findings in mesenteric ischemia to improve a standardised diagnosis.

Extracorporeal circulation (ECC) in the form of cardiopulmonary bypass (CPB) counts among the contemporary strategies for organ protection during major cardiovascular surgery. Despite protecting the organs from severe ischemia-reperfusion injury, it generates a significant inflammatory response that may produce organ dysfunction. An aortic cross-clamp is a key step in open cardiovascular surgery to interrupt the blood flow across the aorta for operation. After aortic cross-clamp release, peripheral vascular resistance decreases by 70 to 80%, causing hypotension in the lower half of the body. During the ischemia-reperfusion period Oxygen-free radicals and inflammatory cytokines produced, which may contribute to inflammation-induced tissue injury. As an inflammatory reaction after the cardiac surgery involving CPB, capillary leak syndrome is associated with increased morbidity and mortality. Microcirculatory alterations in the mesenteric artery during or after CPB contribute to the intestinal hypoperfusion. A suboptimal microperfusion and ischemia-reperfusion of the intestinal tissue during ECC are the trigger of altered gut permeability and a systemic inflammatory response syndrome in turn. The main mechanism of intestinal ischemia after Cardiovascular surgery is a non-occult mesenteric ischemia (NOMI). Contrarily to occlusive mesenteric ischemia by emboli or thrombosis, NOMI is related to a reduction in the splanchnic blood flow. NOMI is considered to be a rare (incidence around 1%) but severe and very often fatal complication after a cardiac surgery with a mortality rate up to 90%, in which the perfusion of the intestine is limited. In the diagnosis of a NOMI, an invasive angiography with a digital subtraction angiography (DSA) is considered to be the gold standard. And a common therapy for it is to correct the underlying vascular pathology and diffuse vasospasm with application of vasodilators. That is performed through an angiographically and precisely placed catheter in the superior mesenteric artery. clinical appearance of NOMI presents a myriad of symptoms and can be confusing, or might even be completely masked. In addition, there is still a lack of highly sensitive and specific biomarkers to predict the NOMI.

Furthermore, patients with postoperative NOMI had significantly high coincidence for acute kidney injury (AKI). NOMI has also been shown to correlate with renal insufficiency. Metzger et al. hypothesised that similar Pathophysiological mechanisms may trigger AKI in association with NOMI.

The aim of the study is to prospectively evaluate the level of perioperatively assessed I-FABP tests for NOMI and to correlate those with clinical or angiographic findings.

Inclusion Criteria:

• All consecutive patients undergoing cardiac or vascular surgery with extracorporeal circulation

Exclusion Criteria:

• endocarditis or bacterial sepsis,
• hepatitis or HIV on the patient's medical history,
• cases in which informed consent to participate in the study could not be obtained

All consecutive patients undergoing cardiac or vascular surgery with extracorporeal circulation in University Hospital Giessen