Rhiannon Champagne

Background: Acute mesenteric ischemia (AMI) is a vascular emergency commonly characterized by decreased blood supply from the superior mesenteric artery to the bowel, leading to irreversible transmural intestinal necrosis (ITIN). Although AMI constitutes 1-2% of acute abdomen cases, it is represented in nearly 10% of emergent abdomen cases within elderly populations, and mortality can reach up to 100% after ITIN onset.^{1,2,3,4,5,6,7} AMI is difficult to diagnose due to non-specific symptoms, and with no reliable biomarkers available, contrast CT angiography is considered the gold standard. Even so, the results of the imaging do not always yield abnormal results.^1,2,3,4,5,7 Recent studies suggested that short-term reduction in microbiome with oral antibiotics could prevent ITIN.^6,8,9 Because reperfusion treatment or surgical resection after ITIN can be ineffective, prophylactic treatments, such as oral antibiotics, for ITIN should be explored.^1,2,3,4,5

Objective: Herein, we explored mechanisms of ITIN, evaluated current antibiotic approaches to treating AMI, and discussed clinical studies conducted to reduce the morbidity and mortality of AMI.

Search Methods: A PubMed database search was conducted from 2018-2024 using the following keywords: “acute mesenteric ischemia,” “treatments”, and “oral antibiotics.”

Results: During ITIN, translocation of gut bacteria through the damaged epithelial barrier is thought to be responsible for recruitment of polymorphonuclear cells (PMNs) to the intestinal wall, which causes further infarction of bowel tissue.^8,9 It was shown that gut flora has an impact on the extent of damage incurred. A mesenteric ischemia-reperfusion injury model of germ-free (GF) mice and conventionally raised (CONV-R) mice with normal gut colonization were used to determine the extent of PMN adherence.⁹ Findings indicated that GF mice experienced markedly decreased PMN adherence, which was reversed with colonization of GF (CONV-D) mice over 14 days.⁹ Additionally, GF mice experienced an increased formation of neutrophil extracellular traps (NETs), which paradoxically lead to NET-associated injury.⁹ This NET formation was reduced in CONV-D mice over 14 days.⁹ Therefore, short-term depletion of gut flora can be effective in alleviating ITIN. Furthermore, a prospective cohort study of 67 AMI patients were provided with a care management regimen, such as fasting, proton pump inhibitors, anticoagulants, antiplatelets, arterial revascularization, blood products, as well as oral and/or IV antibiotics.⁸ It was shown that oral antibiotics (gentamicin 80 mg/day + metronidazole 1.5g/day) protected against ITIN in 37 patients after adjusting the hazard ratio (95% CI 0.03-0.62; p = 0.01).⁸ The mortality rate of those experiencing ITIN was 35% versus 2% in patients without ITIN after taking the oral antibiotic regimen.⁸ This study demonstrates that in addition to established regimens, oral antibiotics are potentially effective at preventing ITIN.

Conclusions: ITIN is associated with PMN adherence to the damaged intestinal wall.⁹ Depletion of gut flora reduces adherence dynamically, therefore short-term reduction in microbiome can be effective in preventing ITIN. However, prolonged depletion of gut flora can contribute to NET formation-associated injury.⁹ A clinical study demonstrated that oral antibiotics, in addition to established treatments for AMI, are a promising prophylactic that could be implemented in a clinical setting.⁸

 Works Cited:

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