Intraluminal oxygen mitigates acute mesenteric ischaemia: a systematic review of methods and outcomes in animal studies.

BACKGROUND: Acute Mesenteric Ischaemic (AMI) is a rare condition with significant morbidity and mortality. Many causes of AMI exist, which usually begin with mucosal injury. Onset is insiduous and there is frequent diagnostic delay. Current treatments can only control established injury and prevent propagation, hence new interventions are needed. The prevention and treatment of AMI by intraluminal delivery of oxygen has yet to be investigated in the clinical setting. This article aims to systemically review experimental studies investigating this novel therapy. METHODS: Following the PRISMA guidelines, searches of PubMed and Ovid MEDLINE databases were performed up to June 2022. Two independent investigators extracted the data. RESULTS: There were 20 experimental studies, 16 of which used an occlusive ischaemia reperfusion model. Six different formulations were used to deliver intraluminal oxygen, with perflurocarbon being the most common. Studies consistently showed local and systemic benefits. Intraluminal oxygen therapy improved histological severity of mucosal injury in all studies when oxygen was delivered during the ischaemia phase, but could cause harm if given during the reperfusion phase. Improvement was also demonstrated in endpoints assessing intestinal function, biomarkers of intestinal damage, measures of systemic physiological derangement and mortality. CONCLUSION: Intraluminal oxygenation appears to be an effective treatment for AMI. There remain significant questions regarding optimal timing and delivery formulation before clinical translation of this treatment strategy.

Meta-Analysis of the Composition of Human Intestinal Gases.

BACKGROUND: Understanding intestinal gases volume and composition may contribute to diagnosing digestive diseases and the microbiome's status. This meta-analysis aimed to define the composition of human intestinal gases and changes associated with diet. METHODS: Studies were identified by systematic research of the MEDLINE(Ovid), Scopus, and Cochrane databases. Studies that measured the concentration of intestinal gases in healthy adult humans were retrieved. The JBI critical appraisal tool was used to evaluate the risk of bias. The primary outcomes analysed were the concentration of the most prevalent colonic gases. Participants were divided into groups according to dietary fibre content. RESULTS: Eleven studies were included. The following gases were identified in similar concentrations across all studies (mean ± standard deviation): nitrogen (65.1 ± 20.89%), oxygen (2.3 ± 0.98%), carbon dioxide (9.9 ± 1.6%), hydrogen (2.9 ± 0.7%), and methane (14.4 ± 3.7%). Differences according to the dietary fibre were observed, with a positive correlation between fibre and volume of gas produced, particularly in fermented gases (carbon dioxide, hydrogen, and methane). DISCUSSION: The meta-analysis has found defined concentrations of the five most common gases present in human colonic gas. Limitations included heterogenic methodologies, a low number of participants, and few recent studies. These findings may be helpful in diagnostic applications where colonic gas volume and composition are crucial factors, including functional disorders, microbiome analyses, and bowel perforation diagnostics.