Fluid–structure computational analysis to investigate the link between early atherogenic events and the hemodynamic environment in an experimental model of intimal thickening

The main hemodynamic forces acting on the vessel wall are the wall shear stress (WSS), caused by the friction of the flowing blood on the endothelial surface, and the circumferential stress caused by blood pressure, acting on endothelial cells and on smooth muscle cells. Experimental studies on the effects of disturbed flow contribute to our understanding of the pathophysiological mechanisms of vascular diseases, helping in ameliorating therapeutic interventions. The perivascular placement of a silastic collar around the carotid artery represents an established model of intimal thickening in rabbits and mice for testing mechanistic hypothesis on the pathogenesis of atherosclerosis and for assessment of anti-atherosclerotic interventions. In this work we adopted a one-way coupled, fluid-structure interaction approach to investigate the immediate fluid-dynamic alterations induced by perivascular collar placement on rabbit common carotid artery and establish a correlation between the early atherogenic events and the modifications of the hemodynamic environment. The results from this computational study help quantify the role of the local fluid-dynamics among the possible factors promoting the atherogenic processes in this experimental model. In particular, values of WSS and circumferential stress lower than in the physiological situation were found in the arterial region between the two collar-vessel contact points

Body mass index and complications following major gastrointestinal surgery: A prospective, international cohort study and meta-analysis

Aim Previous studies reported conflicting evidence on the effects of obesity on outcomes after gastrointestinal surgery. The aims of this study were to explore the relationship of obesity with major postoperative complications in an international cohort and to present a metaanalysis of all available prospective data. Methods This prospective, multicentre study included adults undergoing both elective and emergency gastrointestinal resection, reversal of stoma or formation of stoma. The primary end-point was 30-day major complications (Clavien\u2013Dindo Grades III\u2013V). A systematic search was undertaken for studies assessing the relationship between obesity and major complications after gastrointestinal surgery. Individual patient meta-analysis was used to analyse pooled results. Results This study included 2519 patients across 127 centres, of whom 560 (22.2%) were obese. Unadjusted major complication rates were lower in obese vs normal weight patients (13.0% vs 16.2%, respectively), but this did not reach statistical significance (P = 0.863) on multivariate analysis for patients having surgery for either malignant or benign conditions. Individual patient meta-analysis demonstrated that obese patients undergoing surgery formalignancy were at increased risk of major complications (OR 2.10, 95% CI 1.49\u20132.96, P < 0.001), whereas obese patients undergoing surgery for benign indications were at decreased risk (OR 0.59, 95% CI 0.46\u20130.75, P < 0.001) compared to normal weight patients. Conclusions In our international data, obesity was not found to be associated with major complications following gastrointestinal surgery. Meta-analysis of available prospective data made a novel finding of obesity being associated with different outcomes depending on whether patients were undergoing surgery for benign or malignant disease