This computational study was the first to assess blood flow characteristics at the site of infrarenal AAA rupture in realistic aortic geometries. In contradiction to our initial hypothesis, rupture occurred not at sites of high pressure and WSS but rather at regions of predicted flow recirculation, where low WSS and thrombus deposition predominated. These findings raise the possibility that this flow pattern may lead to thrombus deposition, which may elaborate adventitial degeneration and eventual AAA rupture.

Objectives: This study evaluated the safety and hospital impact of transition from a routine to a selective policy of postoperative transfer to the intensive care unit (ICU) for elective open abdominal aortic aneurysm (AAA) repair.Methods: This retrospective study included all open elective AAA repairs from August 8 2010, to December 1, 2014, performed in our center. The study was approved by the Institutional Review Board, and informed consent was waived. Patients were identified through our prospective database, and electronic records were reviewed to extract patient characteristics, operative details, and postoperative complications. Patients operated on before March 13, 2012, were routinely sent to the ICU after operation (group A). Patients treated after this date were sent directly to an intermediate care unit with a ratio of one nurse for three patients (group B), unless otherwise determined preoperatively by the surgeon or after intraoperative complications. We evaluated the safety of our change in practice, looking at complications and mortality rate, length of stay, and transfer from an intermediate care unit to the ICU.Results: The study included 310 patients (266 men, 44 women), with a mean age 70 of years, and a mean AAA diameter 65 mm. Group A and B included 118 and 192 patients, respectively. The postoperative mortality rate was similar in each group (1%). ICU admission in group B was spared in 78% (149 of 192) of patients. Only two patients (1%) from the intermediate care unit were subsequently admitted to the ICU. There was no increase in mortality in group B (0.5%) compared with group A (0.8%) during hospital stay. Hospital lengths of stay were similar between groups group A (8.6 days) and group B (8.0 days; P ¼ NS).Conclusions: Our results confirm the safety of a selective ICU pathway after open elective AAA repair, with most patients sent directly to an intermediate care unit.

IntroductionGoal-directed therapy (GDT) has been shown in numerous studies to decrease perioperative morbidity and mortality. The mechanism of benefit of GDT, however, has not been clearly elucidated. Targeted resuscitation of the vascular endothelium with GDT might alter the postoperative inflammatory response and be responsible for the decreased complications with this therapy.MethodsThis trial was registered at ClinicalTrials.gov as NCT01681251. Forty patients undergoing elective open repair of their abdominal aortic aneurysm, 18 years of age and older, were randomized to an interventional arm with GDT targeting stroke volume variation with an arterial pulse contour cardiac output monitor, or control, where fluid therapy was administered at the discretion of the attending anesthesiologist. We measured levels of several inflammatory cytokines (C-reactive protein, Pentraxin 3, suppressor of tumorgenicity--2, interleukin-1 receptor antagonist, and tumor necrosis factor receptor-III) preoperatively and at several postoperative time points to determine if there was a difference in inflammatory response. We also assessed each group for a composite of postoperative complications.ResultsTwenty patients were randomized to GDT and twenty were randomized to control. Length of stay was not different between groups. Intervention patients received less crystalloid and more colloid. At the end of the study, intervention patients had a higher cardiac index (3.4 ± 0.5 vs. 2.5 ± 0.7 l/minute per m2, p < 0.01) and stroke volume index (50.1 ± 7.4 vs. 38.1 ± 9.8 ml/m2, p < 0.01) than controls. There were significantly fewer complications in the intervention than control group (28 vs. 12, p = 0.02). The length of hospital and ICU stay did not differ between groups. There was no difference in the levels of inflammatory cytokines between groups.ConclusionsDespite being associated with fewer complications and improved hemodynamics, there was no difference in the inflammatory response of patients treated with GDT. This suggests that the clinical benefit of GDT occurs in spite of a similar inflammatory burden. Further work needs to be performed to delineate the mechanism of benefit of GDT.Trial registrationClinicalTrials.gov Identifier: NCT01681251. Registered 18 May 2011.

The role of CD18 antibody (anti-CD18) in remote and local injury in a model of ruptured abdominal aortic aneurysm repair was investigated. Rats were divided into sham, shock, clamp, and shock + clamp groups. Shock + clamp animals received anti-CD18 or a control monoclonal antibody. One hour of hemorrhagic shock was followed by 45 min of supramesenteric aortic clamping. Intestinal and pulmonary permeability to125I-labeled albumin was determined. Myeloperoxidase (MPO) activity, F2-isoprostane levels, and transaminases were also measured. Only shock + clamp resulted in statistically significant increases in pulmonary and intestinal permeability, which were associated with significant increases in MPO activity and F2-isoprostane levels. Treatment with anti-CD18 significantly decreased intestinal and pulmonary permeability in shock + clamp animals. These reductions were associated with significantly reduced intestinal and hepatic MPO activity and pulmonary F2-isoprostane levels and reduced alanine and aspartate aminotransferase levels; however, anti-CD18 had no effect on intestinal or hepatic F2-isoprostane levels or on pulmonary MPO activity. These results suggest CD18-dependent and -independent mechanisms of local and remote organ injury in this model of ruptured abdominal aortic aneurysm.