Risk factors and associated outcomes of postoperative delirium after open abdominal aortic aneurysm repair.

OBJECTIVE: Open abdominal aortic aneurysm repair (OAR) is a major vascular procedure that incurs a large physiologic demand, increasing the risk for complications such as postoperative delirium (POD). We sought to characterize POD incidence, identify delirium risk factors, and evaluate the effect of delirium on postoperative outcomes. We hypothesized that POD following OAR would be associated with increased postoperative complications and resource utilization. METHODS: This was a retrospective study of all OAR cases from 2012 to 2020 at a single tertiary care center. POD was identified via a validated chart review method based on key words and Confusion Assessment Method assessments. The primary outcome was POD, and secondary outcomes included length of stay, non-home discharge, 90-day mortality, and 1-year survival. Bivariate analysis as appropriate to the data was used to assess the association of delirium with postoperative outcomes. Multivariable binary logistic regression was used to identify risk factors for POD and Cox regression for variables associated with worse 1-year survival. RESULTS: Overall, 198 OAR cases were included, and POD developed in 34% (n = 67). Factors associated with POD included older age (74 vs 69 years; P < .01), frailty (50% vs 28%; P < .01), preoperative dementia (100% vs 32%; P < .01), symptomatic presentation (47% vs 27%; P < .01), preoperative coronary artery disease (44% vs 28%; P = .02), end-stage renal disease (89% vs 32%; P < .01) and Charlson Comorbidity Index score >4 (42% vs 26%; P = .01). POD was associated with 90-day mortality (19% vs 5%; P < .01), non-home discharge (61% vs 30%; P < .01), longer median hospital length of stay (14 vs 8 days; P < .01), longer median intensive care unit length of stay (6 vs 3 days; P < .01), postoperative myocardial infarction (7% vs 2%; P = .045), and postoperative pneumonia (19% vs 8%; P = .01). On multivariable analysis, risk factors for POD included older age, history of end-stage renal disease, lack of epidural, frailty, and symptomatic presentation. A Cox proportional hazards model revealed that POD was associated with worse survival at 1 year (hazard ratio, 3.8; 95% confidence interval, 1.6-9.0; P = .003). CONCLUSIONS: POD is associated with worse postoperative outcomes and increased resource utilization. Future studies should examine the role of improved screening, implementation of delirium prevention bundles, and multidisciplinary care for the most vulnerable patients undergoing OAR.

Outcomes of endovascular abdominal aortic aneurysm repair conversion in octogenarians treated at a high-volume aorta center.

BACKGROUND: Endovascular abdominal aortic aneurysm repair (EVAR) has become the dominant treatment strategy for infrarenal abdominal aortic aneurysms but has been especially preferred for octogenarian (age ≥80 years) patients because of concerns surrounding comorbidity severity and physiologic frailty. However, EVAR failure resulting in subsequent open conversion (EVAR-c) has been increasingly reported in older patients, although a paucity of literature focusing on the outcomes in this subgroup is available. The purpose of the present analysis was to evaluate our experience with EVAR-c for octogenarians (age ≥80 years) compared with that for younger patients (age <80 years). METHODS: A retrospective review of all nonmycotic EVAR-c procedures (2002-2020) at a single high-volume academic hospital with a dedicated aorta center (available at: https://www.uf-health-aortic-disease-center) was performed. A total of 162 patients were categorized into octogenarian (age ≥80 years; n = 43) and nonoctogenarian (age <80 years; n = 119) cohorts and compared. The primary end point was 30-day mortality. The secondary end points included complications, 90-day mortality, and overall survival. Cox regression was used to determine the effects of selected covariates on mortality risk. The Kaplan-Meier method was used to estimate survival. RESULTS: No differences in the preadmission EVAR reintervention rates were present (octogenarians, 42%; nonoctogenarians, 43%; P = 1.00) although the interval to the first reintervention was longer for the octogenarians (41 months) than for the nonoctogenarians (15 months; P = .01). In addition, the time to EVAR-c was significantly longer for the octogenarian patients (61 months) than for the nonoctogenarian patients (39 months; P < .01). No difference in rupture presentation was evident (14% vs 10%; P = .6). However, elective EVAR-c occurred less frequently for octogenarians (42%) than for nonoctogenarians (59%; P = .07). The abdominal aortic aneurysm diameter was significantly larger for elective octogenarian EVAR-c (7.8 ± 1.9 cm) than for nonoctogenarian EVAR-c (7.0 ± 1.5 cm; P = .02), and the presence of a type Ia endoleak was the most common indication overall (58%; n = 91). A trend toward greater 30-day mortality was evident for octogenarian patients (16%) compared with nonoctogenarian patients (7%; P = .06). Similarly, the 90-day mortality was greater for the octogenarian patients (26%) than for the nonoctogenarian patients (10%; P = .02). However, the incidence of any complication (56% vs 49%; P = .5), readmission rate (12% vs 6%; P = .3), unplanned reoperation rate (10% vs 5%; P = .5), and length of stay (11 days vs 9 days; P = .3) were not significantly different between the two groups. Age ≥80 years was predictive of short-term mortality after nonelective but not after elective surgery. However, increasing comorbidities, nonelective admission, and renal or mesenteric revascularization showed the strongest association with mortality risk. Survival at 1 and 3 years was not different between the two groups when comparing all patients after the first 90 days postoperatively. CONCLUSIONS: Although the unadjusted perioperative mortality was greater for octogenarian patients, the risk-adjusted elective outcomes were comparable to those for younger EVAR-c patients when treated at a high-volume aortic surgery center. This finding underscores the importance of appropriate patient selection and modulation of operative complexity when feasible to achieve optimal results. Providers caring for octogenarian patients with EVAR failure should consider timely elective referral to high-volume aorta centers to reduce resource usage and the frequency of nonelective presentations.

Editor's Choice - Optimal Threshold for the Volume-Outcome Relationship After Open AAA Repair in the Endovascular Era: Analysis of the International Consortium of Vascular Registries.

OBJECTIVE: As open abdominal aortic aneurysm (AAA) repair (OAR) rates decline in the endovascular era, the endorsement of minimum volume thresholds for OAR is increasingly controversial, as this may affect credentialing and training. The purpose of this analysis was to identify an optimal centre volume threshold that is associated with the most significant mortality reduction after OAR, and to determine how this reflects contemporary practice. METHODS: This was an observational study of OARs performed in 11 countries (2010 - 2016) within the International Consortium of Vascular Registry database (n = 178 302). The primary endpoint was post-operative in hospital mortality. Two different methodologies (area under the receiving operating curve optimisation and Markov chain Monte Carlo procedure) were used to determine the optimal centre volume threshold associated with the most significant mortality improvement. RESULTS: In total, 154 912 (86.9%) intact and 23 390 (13.1%) ruptured AAAs were analysed. The majority (63.1%; n = 112 557) underwent endovascular repair (EVAR) (OAR 36.9%; n = 65 745). A significant inverse relationship between increasing centre volume and lower peri-operative mortality after intact and ruptured OAR was evident (p < .001) but not with EVAR. An annual centre volume of between 13 and 16 procedures per year was associated with the most significant mortality reduction after intact OAR (adjusted predicted mortality < 13 procedures/year 4.6% [95% confidence interval 4.0% - 5.2%] vs. ≥ 13 procedures/year 3.1% [95% CI 2.8% - 3.5%]). With the increasing adoption of EVAR, the mean number of OARs per centre (intact + ruptured) decreased significantly (2010 - 2013 = 35.7; 2014 - 2016 = 29.8; p < .001). Only 23% of centres (n = 240/1 065) met the ≥ 13 procedures/year volume threshold, with significant variation between nations (Germany 11%; Denmark 100%). CONCLUSION: An annual centre volume of 13 - 16 OARs per year is the optimal threshold associated with the greatest mortality risk reduction after treatment of intact AAA. However, in the current endovascular era, achieving this threshold requires significant re-organisation of OAR practice delivery in many countries, and would affect provision of non-elective aortic services. Low volume centres continuing to offer OAR should aim to achieve mortality results equivalent to the high volume institution benchmark, using validated data from quality registries to track outcomes.

Impact of hospital volume on patient safety indicators and failure to rescue following open aortic aneurysm repair.

OBJECTIVE: Failure to rescue (FTR), a patient safety indicator (PSI) defined, codified, and adjudicated by the Agency for Healthcare Research and Quality, is classified as a preventable inpatient death following major complications. FTR has been reported to be a significant driver of postoperative mortality after open abdominal aortic aneurysm (OAAA) repair. The association between hospital volume (HV) and mortality is well known; however, the mechanisms responsible for these improved outcomes and relative contribution to observed interhospital variation is poorly understood. Similarly, HV influence on specific complications predictive of FTR is unknown; therefore, we sought to determine how HV influences risk and contributes to interhospital variation in PSI events leading to FTR and/or in-hospital mortality after OAAA repair. METHODS: The Vizient database (174 academic/nonacademic hospitals) was queried for all OAAA repairs (elective, n = 2827; nonelective, n = 1622) completed from 2012 to 2014. The primary endpoint was combined FTR and/or in-hospital 30-day mortality. Risk-adjusted rates of complications, Agency for Healthcare Research and Quality-designated PSIs, and FTR were determined. Additional modeling identified PSIs associated with FTR, whereas HV effects on PSIs and FTR were evaluated using mixed-effect models accounting for interhospital variation. Proportion of variation attributable to HV was estimated by contrasting hospital random effect variances in the presence/absence of volume effects. RESULTS: The combined overall FTR/in-hospital 30-day mortality rate was 9.3% (n = 414). For elective and nonelective cases, the overall FTR and 30-day mortality rates were: FTR, 1.6%, 4.9%; and 30-day in-hospital mortality, 3.4%, 17.5%, respectively. HV significantly influenced FTR/30-day in-hospital mortality (P < .0001). FTR/30-day mortality odds for hospitals with 3-year volumes of 50, 100, 150, and 200 cases were 1.4, 2.0, 2.7, and 3.0 times lower, respectively, than hospitals performing ≤25 cases/3 years. The proportion of interhospital variation attributed to HV was greatest for FTR/30-day mortality (62%). Procedural volume accounted for 41% and 38% of interhospital variation in postoperative bleeding and myocardial infarction, respectively. Preoperative predictors of FTR included coagulopathy, arrhythmia (nonelective cases); congestive heart failure, obesity (elective cases); and age, neurological disease, hypertension, and valvular disease (all cases). CONCLUSIONS: OAAA FTR/30-day in-hospital mortality strongly correlated with annual case volume with higher volume centers having the lowest risk. Notably, HV accounted for a significant proportion of the observed variation in FTR and specific complications providing direct evidence for how the volume-outcome relationship may influence perioperative mortality. These findings can inform stakeholders to strategically enable them to implement processes of care directed at the most vulnerable patients that are designed to reduce the likelihood of preventable adverse events and death after OAAA repair. Furthermore, these results underscore the need to regionalize OAAA repair and potentially other complex operations, to HV centers because of their improved ability to rescue patients experiencing complications associated with postoperative mortality.

Association of hospital volume with patient selection, risk of complications, and mortality from failure to rescue after open abdominal aortic aneurysm repair.

OBJECTIVE: The association of higher hospital volume with lower mortality after open abdominal aortic aneurysm (OAAA) repair is well known; however, the underlying mechanism for improved outcomes is poorly understood. Better patient selection, lower risk of complications, and improved ability to rescue patients after adverse events are assumed mechanisms, but few data exist to validate this hypothesis. The purpose of this analysis was to determine the association of hospital volume with patient selection, incidence of complications, and failure to rescue (FTR) after adverse events resulting from OAAA repair. METHODS: The Vizient (Irving, Tex) database (>95% of all academic hospitals) was reviewed for OAAA repairs (elective, n = 2827; nonelective, n = 1622) performed from 2012 to 2014. Presentation type (elective vs nonelective) was considered in all analyses. Elixhauser comorbidity index and van Walraven weighted scores were assigned to patients and volume-outcome relationships explored. By use of logistic regression, risk-adjusted complications (including preventable complications; Agency for Healthcare Research and Quality patient safety indicators [PSIs]) and FTR rates were determined. Predicted risk scores were assigned to delineate hospital volume association with these outcomes. RESULTS: Overall, no relationship between hospital volume and composite patient comorbidity severity score was identified (Elixhauser comorbidity index and van Walraven weighted scores: Pearson [ρ, 0.02], P = .2; [ρ, -0.01], P = .4; Spearman correlation coefficient [ρ, 0.02], P = .4; [ρ, -0.02], P = .2). The lack of correlation persisted in considering elective vs nonelective status. However, for elective cases, differences in specific comorbidities were noted because high-volume hospitals were more likely to repair patients with a history of peripheral vascular disease (P = .01), diabetes (P = .07), obesity (P = .004), and alcohol abuse (P = .05). Lower volume hospitals more frequently repaired patients with hypothyroidism (P = .05), fluid and electrolyte disorders (P = .007), and chronic blood loss anemia (P = .05). No specific individual comorbidity differences were detected for nonelective cases. In examining hospital volume effects on the likelihood for development of any complication (45%), PSIs (12%), and FTR (9%), a significant risk reduction was noted in high-volume institutions. Specifically, a nonlinear relationship between hospital volume and risk of any complication (P = .0004), PSI (P = .0004), and FTR (P =. 0003) was present. In exploring the risk of specific complications or PSI events, greater hospital volume was strongly correlated to a lower likelihood of multiple adverse outcomes. CONCLUSIONS: Although high-volume institutions performing OAAA repair do not necessarily operate on patients with more comorbidities, there are important differences in the patients selected compared with lower volume hospitals. The risk for development of multiple specific postoperative complications as well as for preventable adverse events preceding FTR is significantly lower in high-volume centers. These findings provide benchmarks for multiple selected quality indicators and further support national initiatives to incentivize regionalization of OAAA care.

The evolution of open abdominal aortic aneurysm repair at a tertiary care center.

BACKGROUND: The characteristics of and indications for open abdominal aortic aneurysm (AAA) repair have evolved over time. We evaluated these trends through the experience at a tertiary care academic center. METHODS: A retrospective review was conducted for patients undergoing open AAA repair (inclusive of type IV thoracoabdominal aortic aneurysms) from 2005 to 2018 at an academic institution. Trends over time were evaluated using the Spearman test; Cox regression was used to determine predictors of mortality and to generate adjusted survival curves. RESULTS: There were 628 patients (71.5% male; 88.2% white) with a mean age of 70.5 ± 9.4 years who underwent open AAA repair with a mean aneurysm diameter of 6.2 ± 1.5 cm. The median length of stay was 10 days, and the median intensive care unit length of stay was 3 days. Urgent repair was undertaken in 21.1%; 22.3% were type IV thoracoabdominal aortic aneurysm repairs, and 9.9% were performed for explantation. Our series favored a retroperitoneal approach in the majority of cases (82.5%). The proximal clamp sites were supraceliac (46.1%), suprarenal (29.1%), and infrarenal (24.8%), with approximately a third requiring renal artery reimplantation. The average cross-clamp time was 25.5 ± 14.9 minutes; the mean renal ischemia time for supraceliac and suprarenal clamp sites was 28.4 ± 12.3 minutes and 23.5 ± 12.7 minutes, respectively. Postoperative renal dysfunction occurred in 19.6% of the overall cohort, with 6.2% requiring hemodialysis. Of those requiring postoperative hemodialysis, the majority (75%) received an urgent repair. The in-hospital mortality was 2.3% for elective cases vs 20.9% for urgent repair, and 29.8% of patients were discharged to rehabilitation, with an overall 30-day readmission rate of 7.9%. Over time, there were trends of increased aneurysm repair complexity, with decreasing infrarenal clamp sites, increasing supraceliac clamp sites, increasing proportion of explantations, and increasing need for bifurcated grafts. The acuity of aneurysm repair likewise changed, with the proportion of urgent repairs increasing over time, largely attributable to the rise in explantations. Clamp site influenced the frequency of perioperative complications. Urgent repairs and age at operation were associated with mortality, whereas mortality was not associated with need for explantation and clamp location. CONCLUSIONS: Aneurysm repair reflected increasing complexity over time, with the need for explantation among urgent repairs significantly on the rise. Urgency and clamp location independently predicted long-term mortality, even after adjustment for age. These findings underscore the changing landscape of open AAA repair in the current era.

Ensuring Competency in Open Aortic Aneurysm Repair - Development and Validation of a New Assessment Tool.

OBJECTIVE: The aims of this study were to develop a procedure specific assessment tool for open abdominal aortic aneurysm (AAA) repair, gather validity evidence for the tool and establish a pass/fail standard. METHODS: Validity was studied based on the contemporary framework by Messick. Three vascular surgeons experienced in open AAA repair and an expert in assessment and validation within medical education developed the OPEn aortic aneurysm Repair Assessment of Technical Expertise (OPERATE) tool. Vascular surgeons with varying experiences performed open AAA repair in a standardised simulation based setting. All procedures were video recorded with the faces anonymised and scored independently by three experts in a mutual blinded setup. The Angoff standard setting method was used to establish a credible pass/fail score. RESULTS: Sixteen novices and nine experienced open vascular surgeons were enrolled. The OPERATE tool achieved high internal consistency (Cronbach's alpha .92) and inter-rater reliability (Cronbach's alpha .95) and was able to differentiate novices and experienced surgeons with mean scores (higher score is better) of 13.4 ± 12 and 25.6 ± 6, respectively (p = .01). The pass/fail score was set high (27.7). One novice passed the test while six experienced surgeons failed. CONCLUSION: Validity evidence was established for the newly developed OPERATE tool and was able to differentiate between novices and experienced surgeons providing a good argument that this tool can be used for both formative and summative assessment in a simulation based environment. The high pass/fail score emphasises the need for novices to train in a simulation based environment up to a certain level of competency before apprenticeship training in the clinical environment under the tutelage of a supervisor. Familiarisation with the simulation equipment must be ensured before performance is assessed as reflected by the low scores in the experienced group's first attempt.

Effects of Ischemic Preconditioning on Abdominal Aortic Aneurysm Repair: A Systematic Review and Meta-analysis.

BACKGROUND: Ischemic preconditioning is an innate mechanism of cytoprotection against ischemia, with potential for end-organ protection. The primary goal of this study was to systematically review the literature to determine the effect of ischemic preconditioning on outcomes after open and endovascular abdominal aortic aneurysm (AAA) repair. METHODS: The methodology followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. We included randomized clinical trials that evaluated the effect of remote ischemic preconditioning (RIPC) in reducing morbidity and mortality in patients undergoing open or endovascular AAA repair surgery. The primary outcomes were death, myocardial infarction, and renal impairment. Outcomes were addressed separately for open AAA repair and endovascular AAA repair (EVAR). Data were collected on patient characteristics, methodology, and preconditioning protocol for each trial. RESULTS: Nine trials of ischemic preconditioning in aortic aneurysm surgery were included with a total of 599 patients; 336 patients were included in the open AAA repair meta-analysis, and 263 patients were included in the EVAR meta-analysis. For both open and endovascular repairs, ischemic preconditioning did not have a significant effect on death, myocardial infarction, or renal impairment requiring dialysis. CONCLUSIONS: The randomized clinical trials investigating the effect of ischemic preconditioning on outcomes after open and endovascular AAA repair that have been completed to date have not been adequately powered to evaluate improvements in patient-important outcomes. The evidence is insufficient to support the use of ischemic preconditioning for AAA repair in clinical practice. The variability in treatment effect across studies may be explained by clinical and methodological heterogeneity.

Risk Factors for Incisional Hernia After Open Abdominal Aortic Aneurysm Repair.

BACKGROUND/AIM: Incisional hernia is among the most prevalent complications associated with open abdominal aortic aneurysm repair. However, risk factors for incisional hernias in patients with abdominal aortic aneurysm are multifactorial. Therefore, this study evaluated the risk factors of incisional hernia after open abdominal aortic aneurysm repair, including surgical factors. PATIENTS AND METHODS: We retrospectively extracted data from patients with incisional hernias after abdominal aortic aneurysm repair between 2012 and 2019 and investigated their perioperative characteristics and wound closure techniques. RESULTS: The mean follow-up periods were 41.5±30.3 months, and 30 of 131 (22.9%) patients suffered an incisional hernia. Regarding the underlying disease, only diabetes mellitus was significantly more common in the incisional hernia group (11 of 30 patients, 36.6%), and no significant differences were found in the patients' perioperative data. Interrupted sutures were used in all 30 patients in the hernia group. Moreover, in 8 of the 101 remaining cases, barbed sutures were used, and no incisional hernia occurred in any of these cases. CONCLUSION: In addition to diabetes mellitus, abdominal aortic aneurysm is a significant risk factor for incisional hernia after abdominal aortic aneurysm repair. Therefore, employing the barbed suture technique may effectively prevent incisional hernias after abdominal aortic aneurysm repair.

Open Surgery for Abdominal Aortic Aneurysm: 980 Consecutive Patient Outcomes from a High-Volume Centre in the United Kingdom.

BACKGROUND: Controversy persists regarding the optimal treatment for large abdominal aortic aneurysm (AAA), highlighted by the publication of the National Institute for Health and Care Excellence (NICE) guideline (NG156) on March 2020. The pendulum of opinion swings once more from endovascular to open surgical treatment. We report our experience over the last 15 years in treating consecutive AAA by open surgery. METHODS: A retrospective review of a prospectively collected vascular database of all patients undergoing infra-renal open abdominal aortic aneurysm repair (OR) repair from 2004 to 2019 at the largest aneurysm centre in the United Kingdom. OR for elective and emergency (ruptured and symptomatic) outcomes included early morbidity and 30-day mortality, and long-term survival. RESULTS: 1017 patients underwent OR between 2004-2019, on application of our inclusion-criteria 994 patients formed our cohort for analysis (81.2% male) with a mean age 73.6 ± 7.8 years treated by OR for AAA. In that group 672 were elective and 308 were emergency (for ruptured or symptomatic). Overall 30 day mortality was 11.3%, elective 30 day mortality was 2.5%, and emergency 30 day mortality was 29.9%. 30 day re-intervention rate was 9.5%, (elective 7.0%, emergency 15.9%). Survival at 1000 days for elective repair was 72 v 46.7% for emergency and at 2000 days was 43.4% for elective v 25% for emergency. CONCLUSION: Our data confirm that open surgery for AAA can be performed in large volume centres quite safely. Elective and Emergency surgery does affect early 30 day mortality but does not influence long-term outcome.

Has EVAR changed the outcomes of ruptured abdominal aortic aneurysms? A decades worth of experience in an Australian Teaching Hospital.

BACKGROUND: Ruptured abdominal aortic aneurysms (rAAA) are associated with significant mortality, and equipoise remains as to whether patients managed with endovascular stent grafts (rEVAR) demonstrate better outcomes when compared to traditional open repair (OR). This study sought to examine the outcomes of patients presenting with rAAA to our institution and assess the perioperative outcomes and outpatient mortality of patients over the past decade. METHODS: A retrospective analysis was conducted. Patients treated for rAAA between 2010 and 2019 were identified from a search of the hospital database for ACHI and ICD-10 codes for repair of AAA. Demographic, operative and post-operative variables were collected from electronic medical records of identified patients. RESULTS: Eighty patients were identified, 51 of whom presented with a rAAA. The majority of repairs were rEVARs (59%). Median age was 76 years. Median length of admission to ICU was 3 days, and median length of hospital admission was 10 days. Overall in-patient mortality was 26%, with rates of 39% at 3 years and 47% at 5 years. No significant difference in outpatient mortality was found in patients undergoing rEVAR compared to OR, with rates of 61% at 5 years compared to 65% at 5 years, respectively (p = 0.8). CONCLUSION: Perioperative outcomes of our cohort of patients undergoing endovascular repair compared to open repair for ruptured and symptomatic AAAs are comparable over the past decade. Given equipoise remains between repair methods, further observational studies are required to quantify benefits of OR and endovascular repairs for ruptured and symptomatic AAAs.

Lower Extremity Microembolism in Open vs. Endovascular Abdominal Aortic Aneurysm Repair.

Although previous studies have documented the occurrence of microembolization during abdominal aortic aneurysm (AAA) repair by both open and endovascular approaches, no study has compared the downstream effects of these two repair techniques on lower extremity hemodynamics. In this prospective cohort study, 20 patients were treated with endovascular aneurysm repair (EVAR) (11 Zenith, 8 Excluder, and 1 Medtronic) and 18 patients with open repair (OR) (16 bifurcated grafts, 2 tube grafts). Pre- and postoperative ankle-brachial indices (ABIs) and toe-brachial indices (TBIs) were measured preoperatively and on postoperative day (POD) 1 and 5. Demographics and preoperative ABIs/TBIs were identical in EVAR (0.97/0.63) and OR (0.96/0.63) patients (p = 0.21). There was a significant decrease in ABIs/TBIs following both EVAR (0.83/0.52, p = 0.01) and OR (0.73/0.39, p = 0.003) on POD #1, although this decrease was greater following OR than EVAR (p = 0.002). This difference largely resolved by POD #5 (p = 0.41). In the OR group, TBIs in the limb in which flow was restored first was significantly reduced compared to the contralateral limb (0.50 vs. 0.61, p = 0.03). In the EVAR group, there was also a difference in TBIs between the main body insertion side and the contralateral side (0.50 vs. 0.59, p = 0.02). Deterioration of lower extremity perfusion pressures occurs commonly after AAA repair regardless of repair technique. Toe perfusion is worse in the limb opened first during OR and on the main body insertion side following EVAR, suggesting that microembolization plays a major role in this deterioration. The derangement following OR is more profound than after EVAR on POD #1, but recovers rapidly. This finding suggests that microembolizarion may be worse with OR or alternatively that other factors associated with OR (e.g., the hemodynamic response to surgery with redistribution of flow to vital organs peri-operatively) may play a role.