Earned Outcomes Correlate with Reliability-Adjusted Surgical Mortality after Abdominal Aortic Aneurysm Repair and Predict Future Performance

OBJECTIVES

Cumulative, probability-based metrics are regularly used to measure quality in professional sports, but these methods have not been applied to health care delivery. These techniques have the potential to be particularly useful in describing surgical quality, where case volume is variable and outcomes tend to be dominated by statistical "noise". The established statistical technique used to adjust for differences in case volume is reliability-adjustment which emphasizes statistical "signal"but has several limitations. We sought to validate a novel measure of surgical quality based on earned outcomes methods (deaths above average, DAA) against reliability-adjusted mortality rates, using abdominal aortic aneurysm (AAA) repair outcomes to illustrate the measure's performance.

METHODS

Earned outcomes methods were used to calculate the outcome of interest for each patient: deaths above average (DAA). Hospital-level DAA were calculated for non-ruptured open AAA repair and EVAR in the Vascular Quality Initiative (VQI) database from 2016-2019. DAA for each center is the sum of observed - predicted risk of death for each patient; predicted risk of death was calculated using established multivariable logistic regression modeling. Correlations of DAA with reliability-adjusted mortality rates and procedure volume were determined. Because an accurate quality metric should correlate with future results, outcomes from 2016-2017 were used to categorize hospital quality based on (1) risk-adjusted mortality, (2) risk- and reliability-adjusted mortality, and (3) DAA. The best performing quality metric was determined by comparing the ability of these categories to predict 2018-2019 risk-adjusted outcomes.

RESULTS

During the study period, 3,734 patients underwent open repair (106 hospitals), and 20,680 patients underwent EVAR (183 hospitals). DAA was closely correlated with reliability-adjusted mortality rates for open repair (r=0.94, P<0.001) and EVAR (r=0.99, P<0.001). DAA also correlated with hospital case volume for open repair (r=-.54, P<0.001), but not EVAR (r=0.07, P=0.3). In 2016-2017, most hospitals had 0% mortality (55% open repair, 57% EVAR), making it impossible to evaluate these hospitals using traditional risk-adjusted mortality rates alone. Further, zero mortality hospitals in 2016-2017 did not demonstrate improved outcomes in 2018-2019 for open repair (3.8% vs 4.6%, P=0.5) or EVAR (0.8% vs 1.0%, P=0.2) compared to all other hospitals. In contrast to traditional risk-adjustment, 2016-2017 DAA evenly divided centers into quality quartiles which predicted 2018-2019 performance with increased mortality rate associated with each decrement in quality quartile (Q1 3.2%, Q2 4.0%, Q3 5.1%, Q4 6.0%). There was a significantly higher risk of mortality at worst quartile open repair hospitals compared to best quartile hospitals (OR 2.01, [95% CI 1.07-3.76], P=0.03). Using 2016-2019 DAA to define quality, highest quality quartile open repair hospitals had lower median DAA compared to lowest quality quartile hospitals (-1.18 DAA vs +1.32 DAA, P<0.001), correlating with lower median reliability-adjusted mortality rates (3.6% vs 5.1%, P<0.001).

CONCLUSIONS

Adjustment for differences in hospital volume is essential when measuring hospital-level outcomes. Earned outcomes accurately categorize hospital quality and correlate with reliability-adjustment but are easier to calculate and interpret. From 2016-2019, highest quality open AAA repair hospitals prevented >40 perioperative deaths compared to the average hospital, and >80 perioperative deaths compared to lowest quality hospitals.

Early Relative Growth Rate of Abdominal Aortic Aneurysms and Future Risk of Rupture or Repair

OBJECTIVE

This study aimed to test whether the relative growth rate of subthreshold abdominal aortic aneurysms (AAAs) in the first 24 months of surveillance predicts the risk of future rupture or repair.

METHODS

This was a single centre retrospective observational analysis of all small (< 45 mm diameter) and medium (45 - 54 mm in men, 45 - 50 mm in women) AAAs entered into ultrasound surveillance between January 2002 and December 2019, which received ≥ 24 months of surveillance. Relative growth rates were calculated from measurements taken in the first 24 months of surveillance. The Kaplan-Meier method was used to estimate intervention and rupture free proportions five years following diagnosis for AAAs growing by < 5% and by ≥ 5% in the first 24 months of surveillance. Multivariable Cox regression analysis was used to further analyse this relationship by adjusting for factors found to be significantly associated with outcome in univariable analysis.

RESULTS

A total of 556 patients with AAAs (409 men, 147 women) were followed for ≥ 24 months. This included 431 small AAAs. Of these, 109 (25.3%) grew by < 5% in the first 24 months of surveillance and had a cumulative event free proportion of 0.98 ± 0.05 at five years compared with 0.78 ± 0.05 for the ≥ 5% growth group (p < .001). Of 125 medium AAAs, 26 (20.8%) grew by < 5% in the first 24 months of surveillance and had a cumulative event free proportion of 0.73 ± 0.11 at five years compared with 0.29 ± 0.13 for the ≥ 5% growth group (p = .024). Baseline diameter and early relative growth rate were strongly and independently predictive of future intervention or rupture with hazard ratios of 9.16 (95% CI 5.98 - 14.03, p < .001) and 4.46 (95% CI 2.45 - 8.14, p < .001), respectively.

CONCLUSION

The results suggest that slow expansion of small (< 45 mm) AAAs observed over an isolated 24 month period is indicative of a very low risk of rupture or repair in the medium term. Isolated growth rates may be a useful tool with which to triage low risk AAAs and prevent unnecessary surveillance.

Comparative analysis of open abdominal aortic aneurysm repair outcomes across national registries

OBJECTIVE

In a recent analysis, we discovered lower mortality after open abdominal aortic aneurysm repair (OAAA) in the Society for Vascular Surgery Vascular Quality Initiative (VQI) database when compared with previously published reports of other national registries. Understanding differentials in these registries is essential for their utility because such datasets increasingly inform clinical guidelines and health policy.

METHODS

The VQI, American College of Surgeons National Surgical Quality Improvement Program (NSQIP), and National Inpatient Sample (NIS) databases were queried to identify patients who had undergone elective OAAA between 2013 and 2016. χ² tests were used for frequencies and analysis of variance for continuous variables.

RESULTS

In total, data from 8775 patients were analyzed. Significant differences were seen across the baseline characteristics included. Additionally, the availability of patient and procedural data varied across datasets, with VQI including a number of procedure-specific variables and NIS with the most limited clinical data. Length of stay, primary insurer, and discharge destination differed significantly. Unadjusted in-hospital mortality also varied significantly between datasets: NIS, 5.5%; NSQIP, 5.2%; and VQI, 3.3%; P < .001. Similarly, 30-day mortality was found to be 3.5% in VQI and 5.9% in NSQIP (P < .001).

CONCLUSIONS

There are fundamental important differences in patient demographic/comorbidity profiles, payer mix, and outcomes after OAAA across widely used national registries. This may represent differences in outcomes between institutions that elect to participate in the VQI and NSQIP compared with patient sampling in the NIS. In addition to avoiding direct comparison of information derived from these databases, it is critical these differences are considered when making policy decisions and guidelines based on these "real-world" data repositories.

Comparison of treatment options for aortic necks outside standard endovascular aneurysm repair instructions for use

OBJECTIVE/BACKGROUND

Endovascular aneurysm repair (EVAR) is associated with worse outcomes in patients whose anatomy does not meet the device instructions for use (IFU). However, whether open surgical repair (OSR) and commercially available fenestrated EVAR (Zenith Fenestrated [ZFEN]) represent better options for these patients is unknown.

METHODS

We identified all patients without prior aortic surgery undergoing elective repair of abdominal aortic aneurysms with neck length ≥4 mm at a single institution with EVAR, OSR, and ZFEN. We applied device-specific aneurysm neck-related IFU to EVAR patients, and a generic EVAR IFU to ZFEN and OSR patients. Long-term outcomes were studied using propensity scores with inverse probability weighting. We compared outcomes in patients undergoing EVAR by adherence to IFU and outcomes by repair types in the subset of patients not meeting IFU.

RESULTS

Of 652 patients (474 EVAR, 34 ZFEN, 143 OSR), 211 had measurements outside of standard EVAR IFU (109 EVAR [23%], 27 ZFEN [80%], and 74 OSR [52%]). Perioperative mortality was 0.5% overall. For EVAR, treatment outside the IFU was associated with significantly higher adjusted rates of long-term type IA endoleak (22% at 5 years compared to 2% within IFU, hazard ratio [HR]: 5.8 [3.1-10.9], P < .001), and lower survival (5- and 10-year survival: 56% and 34% vs 81% and 53%, HR: 2.3 [1.2-4.3], P = .01). There was no difference in reinterventions or open conversion. In patients not meeting IFU, ZFEN was associated with higher adjusted rates of reinterventions (EVAR as referent: HR: 2.6 [1.5-4.4, P < .001), whereas OSR and EVAR patients experienced similar reintervention rates (HR: 0.7 [0.4-1.1], P = .13). Patients outside the IFU experienced lower mortality with OSR compared with either EVAR (HR: 0.4 [0.2-0.9], P = .005) or ZFEN (HR: 0.3 [0.1-0.7], P = .002). When restricted to patients outside the IFU deemed fit for open repair, OSR patients remained associated with lower adjusted mortality compared with ZFEN (HR: 0.2 [0.1-0.5], P < .001), but statistical significance was lost in the comparison to EVAR (HR: 0.6 [0.3-1.1], P = .1).

CONCLUSIONS

Treatment outside device-specific IFU is associated with adverse long-term outcomes. Open surgical repair is associated with higher long-term survival in patients who fall outside of the EVAR IFU and should be favored over EVAR or ZFEN in suitable patients. A three-vessel-based fenestrated strategy may not be a durable solution for difficult aortic necks, but more data are needed to evaluate the performance of newer, four-vessel devices.

Stress testing before abdominal aortic aneurysm repair does not lead to a reduction in perioperative cardiac events

OBJECTIVE

Stress testing is often used before abdominal aortic aneurysm (AAA) repair. Whether stress testing leads to a reduction in cardiac events after AAA repair has remained unclear. Our objective was to study the national stress test usage rates and compare the perioperative outcomes between centers with high and low usage of stress testing.

METHODS

We used the Vascular Quality Initiative to study patients who had undergone elective endovascular AAA repair (EVAR) or open AAA repair (OAR). We measured the usage rates of stress testing across centers and compared the Vascular Study Group of New England cardiac risk index (VSG-CRI) among patients who had and had not undergone preoperative stress testing. We determined the rate of major adverse cardiac events (MACE), a composite of perioperative myocardial infarction, stroke, heart failure exacerbation, and death across the centers. We compared the MACE and 1-year mortality between the centers in the highest quintile of stress test usage and the lowest quintile.

RESULTS

We studied 43,396 EVAR patients and 8935 OAR patients across 324 centers. The median proportion of stress test usage across centers before EVAR was 35.9% and varied from 10.2% (5th percentile) to 73.7% (95th percentile), with similar variability for OAR (median, 57.9%; 5th percentile, 13.0%; 95th percentile, 86.0%). The mean VSG-CRI for the EVAR group with preoperative stress testing was 5.6 ± 2.1 compared with 5.4 ± 2.1 (P < .001) for the EVAR group without preoperative stress testing. The findings were similar for OAR, with a VSG-CRI of 5.1 ± 2.0 vs 4.8 ± 2.1 (P < .001) for those with and without preoperative stress testing, respectively. The rate of MACE was 1.8% after EVAR and 11.6% after OAR. The 1-year mortality was 4.6% for EVAR and 6.6% for OAR. The centers in the highest quintile of stress testing had a higher adjusted likelihood of MACE after both EVAR (odds ratio [OR], 1.78; 95% confidence interval [CI], 1.37-2.30) and OAR (OR, 1.99; 95% CI, 1.53-2.59) but similar 1-year mortality (EVAR: OR, 1.18; 95% CI, 1.02-1.37; OAR: OR, 0.87; 95% CI, 0.65-1.17) compared with the centers in the lowest quintile. The VSG-CRI was not different between the high stress test centers (EVAR, 5.5 ± 2.1; OAR: 5.0 ± 2.0), and low stress test centers (EVAR, 5.5 ± 2.1; P = .403; OAR, 4.9 ± 2.0; P = .563).

CONCLUSIONS

Stress test usage before AAA repair varied widely across Vascular Quality Initiative centers despite similar patient risk profiles. No reduction was observed in MACE or 1-year mortality among centers with high stress test usage. The value of routine stress testing before AAA repair should be reconsidered, and stress testing should be used more selectively, given these findings and the associated costs of widespread testing.

Association between surgeon case volume and years of practice experience with open abdominal aortic aneurysm repair outcomes

BACKGROUND

Widespread adoption of endovascular aneurysm repair has led to a consequential decline in the use of open aneurysm repair (OAR). This evolution has had significant ramifications on vascular surgery training paradigms and contemporary practice patterns among established surgeons. Despite being the subject of previous analyses, the surgical volume-outcome relationship has remained a focus of controversy. At present, little is known about the complex interaction of case volume and surgeon experience with patient selection, procedural characteristics, and postoperative complications of OAR. The purpose of the present analysis was to examine the association between surgeon annual case volume and years of practice experience with OAR.

METHODS

All infrarenal OARs (n = 11,900; elective, 70%; nonelective, 30%) included in the Society for Vascular Surgery Vascular Quality Initiative from 2003 to 2019 were examined. Surgeon experience was defined as years in practice after training. The experience level at repair was categorized chronologically (≤5 years, n = 1667; 6-10 years, n = 1887; 11-15 years, n = 1806; ≥16 years, n = 6540). The annual case volume was determined by the number of OARs performed by the surgeon annually (median, five cases). Logistic regression was used to perform risk adjustment of the outcomes across surgeon experience and volume (five or fewer vs more than five cases annually) strata for in-hospital major complications and 30-day and 1-year mortality.

RESULTS

Practice experience had no association with unadjusted mortality (30-day death: elective, P = .2; nonelective, P = .3; 1-year death: elective, P = .2; nonelective, P = .2). However, more experienced surgeons had fewer complications after elective OAR (25% with ≥16 years vs 29% with ≤5 years; P = .004). A significant linear correlation was identified between increasing surgeon experience and performance of a greater proportion of elective OAR (P-trend < .0001). Risk adjustment (area under the curve, 0.776) revealed that low-volume (five or fewer cases annually) surgeons had inferior outcomes compared with high-volume surgeons across the experience strata for all presentations. In addition, high-volume, early career surgeons (≤5 years' experience) had outcomes similar to those of older, low-volume surgeons (P > .1 for all pairwise comparisons). Early career surgeons (≤5 years) had operated on a greater proportion of elective patients with American Society of Anesthesiologists class ≥4 (35% vs 30% [≥16 years' experience]; P = .0003) and larger abdominal aortic aneurysm diameters (mean, 62 vs 59 mm [≥16 years' experience]; P < .0001) compared with all other experience categories. Similarly, the use of a suprarenal cross-clamp occurred more frequently (26% vs 22% [≥16 years' experience]; P = .0009) but the total procedure time, estimated blood loss, and renal and/or visceral ischemia times were all greater for less experienced surgeons (P-trend < .0001).

CONCLUSIONS

Annual case volume appeared to be more significantly associated with OAR outcomes compared with the cumulative years of practice experience. To ensure optimal OAR outcomes, mentorship strategies for "on-boarding" early career, as well as established, low-volume, aortic aneurysm repair surgeons should be considered. These findings have potential implications for widespread initiatives surrounding regulatory oversight and credentialing paradigms.

Medicare costs for endovascular abdominal aortic aneurysm treatment in the Vascular Quality Initiative

BACKGROUND

Reintervention after endovascular repair (EVR) of abdominal aortic aneurysms is common. However, the cumulative financial impact of reintervention after EVR on a national scale is poorly defined. Our objective was to describe the cost to Medicare for aneurysm treatment (EVR plus reinterventions) among a cohort of patients with known follow-up for 5 years after repair.

METHODS

We identified patients who underwent EVR within the Vascular Quality Initiative who were linked to their respective Medicare claims file (n = 13,995). We excluded patients who underwent EVR after September 30, 2010, and those who had incomplete Medicare coverage (n = 12,788). The remaining cohort (n = 1207) had complete follow-up until death or 5 years (Medicare data available through September 30, 2015). We then obtained and compiled the corresponding Medicare reimbursement data for the index EVR hospitalization and all subsequent reinterventions.

RESULTS

We studied 1207 Medicare patients who underwent EVR and had known follow-up for reinterventions for 5 years. The mean age was 76.2 years (±7.1 years), 21.6% of patients were female, and 91.1% of procedures were elective. The Kaplan-Meier reintervention rate at 5 years was 18%. Among patients who underwent reintervention, 154 (73.7%) had a single reintervention, 40 (19.1%) had two reinterventions, and 15 (7.2%) had three or more reinterventions. The median cost to Medicare for the index EVR hospitalization was $25,745 (interquartile range, $21,131-$28,774). The median cost for subsequent reinterventions was $22,165 (interquartile range, $17,152-$29,605). The cumulative cost to Medicare of aneurysm treatment (EVR plus reinterventions) increased in a stepwise fashion among patients who underwent multiple reinterventions, with each reintervention being similar in cost to the index EVR.

CONCLUSIONS

The overall cost incurred by Medicare to reimburse for each reintervention after EVR is roughly the same as for the initial procedure itself, meaning that Medicare cost projections would be greater than $100,000 for any individual who undergoes an EVR with three reinterventions. The long-term financial impact of EVR must be considered by surgeons, patients, and healthcare systems alike as these cumulative costs may hinder the fiscal viability of an EVR-first therapeutic approach and highlight the need for judicious patient selection paradigms.

Cardiorespiratory fitness fails to predict short-term postoperative mortality in patients undergoing elective open surgery for abdominal aortic aneurysm

INTRODUCTION

Preoperative cardiopulmonary exercise testing aids surgical risk stratification and is an established predictor of mid- to long-term survival in patients undergoing elective open abdominal aortic aneurysm repair. Whether cardiopulmonary exercise testing also predicts 30-day mortality in this population remains to be established.

MATERIALS AND METHODS

Data for 109 patients (mean age 72 years) who underwent cardiopulmonary exercise testing to assess risk for surgical abdominal aortic aneurysm repair was analysed. Patients were classified according to cardiopulmonary fitness as fit (peak oxygen uptake ≥ 15ml O₂.kg^-1.min^-1) or unfit (peak oxygen uptake less than 15ml O₂.kg^-1.min^-1) and further stratified according to clamp position (infrarenal or suprarenal). Between-group postoperative outcomes were compared for in-hospital 30-day mortality, postoperative morbidity scale scores (day 5) and hospital length of stay.

RESULTS

Seventy-nine patients underwent open surgery and 30 patients were treated conservatively. No deaths were recorded at 30 days post-surgery. Unfit patients with infrarenal clamping exhibited higher postoperative morbidity scale scores (64% vs 26%) and longer length of stay (four days) than fit patients (p < 0.05). Conversely, with suprarenal clamping, postoperative morbidity scale scores were similar and length of stay longer (three days) in fit compared with unfit patients (p < 0.05).

DISCUSSION AND CONCLUSION

Preoperative fitness level defined by peak oxygen uptake failed to identify patients at risk of 30-day mortality when undergoing elective abdominal aortic aneurysm repair. Postoperative morbidity and length of stay in patients with suprarenal clamping was high independent of cardiopulmonary fitness. These findings suggest that cardiopulmonary exercise testing may be a useful predictor of complications following infrarenal rather than suprarenal clamping but may not be a good predictor of 30-day mortality.

A Nationwide Study Assessing Preventable Hospitalization Rate on Mortality After Major Cardiovascular Surgery

Despite the use of various factors to measure hospital quality, most measures have not resulted in long-term improvements in patient outcomes. This study's purpose is to determine the effect of a previously unassessed measure of quality of care-a hospital's preventable hospitalization rate-on 30-day mortality at both the hospital and individual levels after three major cardiovascular surgery procedures. This is a population-based study using Taiwan's National Health Insurance database. We retrieved data from 2001 to 2014 for patients who had undergone abdominal aortic aneurysm (AAA) repair, coronary artery bypass graft, or aortic valve replacement (AVR). Preventable hospitalizations are hospitalizations for 11 chronic conditions that are considered preventable with effective primary care. The outcome was 30-day surgical mortality. Our dataset contained 65,863 patients who had undergone surgery for one of the three cardiovascular procedures. Preventable hospitalization rate was significantly associated with higher hospital mortality rates for all procedures. At the patient level, the adjusted odds of mortality after AAA repair were increased 55% (P < 0.01) for every 2% increase in the preventable hospitalization rate. For coronary artery bypass graft, preventable hospitalization was not a significant predictor of mortality, but rather patient factors and surgeon factors were significant. For AVR, the adjusted odds of mortality were increased 7% (P < 0.01) for every 1% increase in preventable hospitalization rate. High preventable hospitalization rate may serve as a hospital quality measure that could signal increased odds of mortality for selected cardiovascular procedures, especially for higher risk-lower volume procedures such as AAA repair and AVR.

Disparities in mortality after abdominal aortic aneurysm repair are linked to insurance status

OBJECTIVE

The objective of this study was to determine differences in mortality after abdominal aortic aneurysm (AAA) repair based on insurance type.

METHODS

In this retrospective cohort study, data from all-payer patients in nonpsychiatric hospitals in New York, Maryland, Florida, Kentucky, and California from January 2007 to December 2014 (excluding California, ending December 2011) were extracted from the State Inpatient Databases, Healthcare Cost and Utilization Project, Agency for Healthcare Research and Quality. There were 90,102 patients ≥18 years old with available insurance data who underwent open AAA repair or endovascular aneurysm repair (EVAR) identified using International Classification of Diseases, Ninth Revision, Clinical Modification procedure codes 3844, 3925, and 3971. EVAR patients were identified using the procedure code 3971, and the remainder of cases were categorized as open. Patients were divided into cohorts by insurance type as Medicare, Medicaid, uninsured (self-pay/no charge), other, or private insurance. Patients were further stratified for subgroup analyses by procedure type. Unadjusted rates of in-hospital mortality, the primary outcome, as well as secondary outcomes, such as surgical urgency, 30-day and 90-day readmissions, length of stay, total charges, and postoperative complications, were examined by insurance type. Adjusted odds ratios (ORs) for in-hospital mortality were calculated using multivariate logistic regression models fitted to the data. The multivariate models included patient-, surgical-, and hospital-specific factors with bivariate baseline testing suggestive of association with insurance status in addition to variables that were selected a priori.

RESULTS

Medicaid and uninsured patients had the highest rates of mortality relative to private insurance beneficiaries in all cohorts. Medicaid patients incurred a 47% increase in the odds of mortality, the highest among the insured, after all AAA repairs (OR, 1.47; 95% confidence interval [CI], 1.23-1.76), whereas uninsured patients experienced a 102% increase in the odds of mortality (OR, 2.02; 95% CI, 1.54-2.67). Subgroup analyses for open AAA repair and EVAR corroborated that Medicaid insurance (open repair OR, 1.37 [95% CI, 1.14-1.64]; EVAR OR, 2.06 [95% CI, 1.40-3.04]) and uninsured status (open repair OR, 1.85 [95% CI, 1.35-2.54]; EVAR OR, 2.96 [95% CI, 1.82-4.81]) were associated with the highest odds of mortality after both procedures separately.

CONCLUSIONS

This study demonstrates that Medicaid insurance and uninsured status are associated with higher unadjusted rates and adjusted ORs for in-hospital mortality after AAA repair relative to private insurance status. Primary payer status therefore serves as an independent predictor of the risk of death subsequent to AAA surgical interventions.

State of the art and meta-analysis of secondary open aortic procedure after abdominal endovascular aortic repair

BACKGROUND

Secondary open aortic procedures (SOAP) treat complications of endovascular aneurysm repair, when further endovascular options are exhausted. We aimed at depicting the state of the art of SOAP with high-level evidence.

METHODS

A systematic review of the SOAP literature, with a meta-analysis of its outcomes (primary outcome operative mortality; secondary outcome major morbidity) and metaregression of risk factors for mortality (PROSPERO 42017075631).

RESULTS

Twenty-eight studies (1093 patients) were elected for analysis. SOAP was performed within the same hospitalization of or 30 days from domestic endovascular aneurysm repair (early SOAP) in 0.2% of the patients (85/40,256), and in a nonelective setting in 24.3% (95% confidence interval, 21.8-26.9). Most frequent indications were endoleak (44.4%; 95% confidence interval, 41.4-47.3) and rupture (12.7%; 95% confidence interval, 10.4-15.1). The most common procedures were infrarenal aortic replacement (85.2%; 95% confidence interval, 82.6-87.7) with high use of supravisceral clamping (suprarenal, 25% [95% confidence interval, 21.9-28.1] and supraceliac, 20.7% [95% confidence interval, 17.8-23.6]), and axillobifemoral bypass with stent explant (6.9%; 95% confidence interval, 5.1-8.7). Operative mortality (in-hospital or 30-day) was 10.9% (95% confidence interval, 8.7-13.5). The most frequent morbidities were respiratory (11.4%; 95% confidence interval, 8.1-15.9) and renal (9.5%; 95% confidence interval, 8.1-15.9). Risk factors for mortality were supravisceral clamping (Z = 3.007; Q = 9.044; P = .003) and nonelective status (Z = 3.382; Q = 11.440; P = .001).

CONCLUSIONS

Endoleak is the main indication for SOAP, which mostly consists of infrarenal aortic replacement. Risk factors for operative mortality are nonelective status and supravisceral clamping.

Outcomes associated with hyperglycemia after abdominal aortic aneurysm repair

OBJECTIVE

We evaluated the association between postoperative hyperglycemia and outcomes after abdominal aortic aneurysm (AAA) repair.

METHODS

We used diagnosis and procedure codes (International Classification of Diseases, Ninth Revision, Clinical Modification) to identify patients who underwent open or endovascular repair of a nonruptured AAA from September 2008 to March 2014 from the Cerner Health Facts database (Cerner Corporation, North Kansas City, Mo). We evaluated the association between postoperative hyperglycemia (glucose concentration >180 mg/dL) and infections, in-hospital mortality, readmission, patients' characteristics, length of hospital stay, and medications. Multivariable logistic models examined the association of postoperative hyperglycemia with in-hospital infection and mortality.

RESULTS

Of 2478 patients, 2071 (83.5%) had good postoperative glucose control (80-180 mg/dL), and 407 (16.5%) had suboptimal control (hyperglycemia). Patients who had postoperative hyperglycemia experienced longer hospital stays (9.5 vs 4.7 days; P < .0001), higher infection rates (18% vs 8%; P < .0001), higher in-hospital mortality (8.4 vs 1.2%; P <.0001), and more acute complications (ie, acute renal failure, fluid and electrolyte disorders, respiratory complications). After adjusting for patients' characteristics and medications, multivariable logistic regression models demonstrated that patients receiving postoperative insulin had nearly 1.6 times the odds of having an infectious complication (odds ratio [OR], 1.6; 95% confidence interval [CI], 1.12-2.2; P = .007) than those who did not. Hyperglycemic patients had 3.5 times the odds of in-hospital mortality (OR, 3.48; 95% CI, 1.78-6.80 [P = .0003]; 2.3% vs 1.2%; P < .001). When stratified by procedure type, patients with hyperglycemia who underwent endovascular repair had nearly 2 times the odds of an infectious complication (OR, 1.85; 95% CI, 0.98-3.51; P = .05) and 7.5 times the odds of in-hospital mortality (OR, 7.54; 95% CI, 1.95-29.1; P = .003). Patients who underwent an open AAA repair and who had hyperglycemia had three times the odds of dying in the hospital (OR, 3.05; 95% CI, 1.29-7.21; P = .01).

CONCLUSIONS

Among patients undergoing elective AAA repair, approximately one in six had postoperative hyperglycemia. After AAA repair in patients with and without diabetes, postoperative hyperglycemia was associated with adverse events, including in-hospital mortality and infections. Compared with those who had open surgery, patients undergoing endovascular repair who had postoperative hyperglycemia had greater risk of infection and death. After controlling for insulin administration and postoperative hyperglycemia, a diabetes diagnosis was associated with lower odds of both infection and in-hospital mortality. Our study suggests that hyperglycemia may be used as a clinical marker as it was found to be significantly associated with inferior outcomes after elective AAA repair. This retrospective study, however, cannot imply causation; further study using prospective methods is needed to elucidate the relationship between postoperative hyperglycemia and patient outcomes.