Association between operation volume and postoperative mortality in the elective open repair of infrarenal abdominal aortic aneurysms: systematic review

Background

An inverse association between the case volume per hospital and surgeon and perioperative mortality has been shown for many surgical interventions. There are numerous studies on this issue for the open treatment of infrarenal aortic aneurysms.

Aim

To present the available data on the association between the case volume per hospital and surgeon and perioperative mortality in the elective open repair of infrarenal aortic aneurysms in a systematic review.

Materials and methods

Using the PubMed, Cochrane Library, Web of Science Core Collection, CINAHL, Current Contents Medicine (CCMed), and ClinicalTrials.gov databases, a systematic search was performed using defined keywords. From the search results, all original papers were included that compared the elective open repair of an infrarenal aortic aneurysm in a “high volume” center with a “low volume” center or by a “high volume” surgeon with a “low volume” surgeon, as defined in the respective study.

Results

After deduplication, the literature search yielded 1021 hits of which 60 publications met the inclusion criteria. Of these, 37/43 studies showed a lower mortality in “high volume” compared to “low volume” centers and 14/17 comparisons showed a lower mortality for “high volume” compared to “low volume” surgeons. The effect measures, usually odds ratios, ranged from 0.37 to 0.99 for volume per hospital and 0.31 to 0.92 for volume per surgeon. Regarding the threshold values for the definition of “high volume” and “low volume,” a clear heterogeneity was shown between the individual studies.

Discussion

The available data on the association between the case volume per hospital and surgeon and perioperative mortality in the elective open repair of infrarenal aortic aneurysms show that interventions performed in “high volume” centers or by “high volume” surgeons are associated with lower mortality. To ensure the best possible outcome in terms of low perioperative mortality in the open repair of infrarenal aortic aneurysms, the aim should be centralization with high case volume per hospital and surgeon.

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.

Endograft Infection After Endovascular Abdominal Aortic Aneurysm Repair: A Systematic Review and Meta-analysis

Purpose: To report a meta-analysis of the published evidence on the outcomes of aortic endograft infection after endovascular aneurysm repair (EVAR). Methods: A search of electronic information sources (PubMed/MEDLINE, SCOPUS, CENTRAL) and bibliographic reference lists identified 12 studies reporting on 362 patients (mean age 72 years; 279 men). The methodological quality of the selected studies was assessed using the Newcastle-Ottawa scale. Endpoints were 30-day/in-hospital mortality and follow-up mortality. Pooled estimates are reported with the 95% confidence interval (CI). The review was registered at the International Prospective Register of Systematic Reviews in Health and Social Care (CRD42016034166). Results: The incidence of graft infection after EVAR was 0.6% (95% CI 0.4% to 0.8%). The time from implantation to diagnosis ranged from 1 to 128 months (mean 25). The majority of patients (293, 81%) underwent surgical treatment (95% CI 77% to 83%); 9 (2.5%) patients (95% CI 21% to 43%) received conservative treatment. Aortic replacement with a prosthetic graft was performed in 58% (95% CI 52% to 62%), whereas cryopreserved allografts and autologous grafts were used in 31% (95% CI 28% to 33%) and 11% (95% CI% 8 to 14%), respectively. Less than half of the patients (40%) had emergency surgery. The pooled estimate of 30-day/in-hospital mortality was 26.6% (95% CI 16.9% to 39.2%). The pooled 30-day/in-hospital mortality for 9 patients treated conservatively was 63.3% (95% CI 30.7% to 87.0%). The pooled overall follow-up mortality was 45.7% (95% CI 36.4% to 55.4%) vs 58.6% (95% CI 28.8% to 83.3%) for the 9 patients receiving conservative treatment. Conclusion: Aortic endograft infection is a rare complication after EVAR. Surgical treatment with complete explantation of the infected endograft seems to be the optimal management in selected patients. Supportive medical treatment without surgical intervention has a significant associated mortality.

[Patient volume and quality in surgery for abdominal aortic aneurysm]

BACKGROUND Patient volume is assumed to affect quality, whereby complex procedures are best performed by those who perform them frequently. We have conducted a systematic review of the research on the association between patient volume and quality of vascular surgery. In this article we describe the outcomes for abdominal aortic aneurysm surgery.MATERIAL AND METHOD We undertook systematic searches in relevant databases. We searched for systematic reviews, and randomised and observational studies. The search was concluded in December 2015. We have summarised the results descriptively and assessed the overall quality of the evidence.RESULTS Forty-six observational studies fulfilled our inclusion criteria. We found a possible association for both hospital and surgeon volume. Higher patient volume may possibly be associated with lower 30-day mortality and lower hospital mortality for both open and endovascular surgery. Although the association appears to apply to both elective and acute hospitalisations, there is greater uncertainty with regard to the most ill patients. For hospital volume there may also be fewer complications for open and endovascular surgery, as well as for all surgery assessed as a whole. We considered the evidence base to be medium to very low quality.INTERPRETATION We found a possible correlation between patient volume and quality indicators such as mortality and complications. It may be advantageous to allocate planned procedures to institutions and surgeons with high volume, while this is less certain with regard to acute hospitalisations.

Does Categorization Method Matter in Exploring Volume-Outcome Relation? A Multiple Categorization Methods Comparison in Coronary Artery Bypass Graft Surgery Surgical Site Infection

BACKGROUND

Volume-infection relation studies have been published for high-risk surgical procedures, although the conclusions remain controversial. Inconsistent results may be caused by inconsistent categorization methods, the definitions of service volume, and different statistical approaches. The purpose of this study was to examine whether a relation exists between provider volume and coronary artery bypass graft (CABG) surgical site infection (SSI) using different categorization methods.

METHODS

A population-based cross-sectional multi-level study was conducted. A total of 10,405 patients who received CABG surgery between 2006 and 2008 in Taiwan were recruited. The outcome of interest was surgical site infection for CABG surgery. The associations among several patient, surgeon, and hospital characteristics was examined. The definition of surgeons' and hospitals' service volume was the cumulative CABG service volumes in the previous year for each CABG operation and categorized by three types of approaches: Continuous, quartile, and k-means clustering.

RESULTS

The results of multi-level mixed effects modeling showed that hospital volume had no association with SSI. Although the relation between surgeon volume and surgical site infection was negative, it was inconsistent among the different categorization methods.

CONCLUSIONS

Categorization of service volume is an important issue in volume-infection study. The findings of the current study suggest that different categorization methods might influence the relation between volume and SSI. The selection of an optimal cutoff point should be taken into account for future research.

Which Kind of Provider's Operation Volumes Matters? Associations between CABG Surgical Site Infection Risk and Hospital and Surgeon Operation Volumes among Medical Centers in Taiwan

BACKGROUND

Volume-infection relationships have been examined for high-risk surgical procedures, but the conclusions remain controversial. The inconsistency might be due to inaccurate identification of cases of infection and different methods of categorizing service volumes. This study takes coronary artery bypass graft (CABG) surgical site infections (SSIs) as an example to examine whether a relationship exists between operation volumes and SSIs, when different SSIs case identification, definitions and categorization methods of operation volumes were implemented.

METHODS

A population-based cross-sectional multilevel study was conducted. A total of 7,007 patients who received CABG surgery between 2006 and 2008 from 19 medical centers in Taiwan were recruited. SSIs associated with CABG surgery were identified using International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9 CM) codes and a Classification and Regression Trees (CART) model. Two definitions of surgeon and hospital operation volumes were used: (1) the cumulative CABG operation volumes within the study period; and (2) the cumulative CABG operation volumes in the previous one year before each CABG surgery. Operation volumes were further treated in three different ways: (1) a continuous variable; (2) a categorical variable based on the quartile; and (3) a data-driven categorical variable based on k-means clustering algorithm. Furthermore, subgroup analysis for comorbidities was also conducted.

RESULTS

This study showed that hospital volumes were not significantly associated with SSIs, no matter which definitions or categorization methods of operation volume, or SSIs case identification approaches were used. On the contrary, the relationships between surgeon's volumes varied. Most of the models demonstrated that the low-volume surgeons had higher risk than high-volume surgeons.

CONCLUSION

Surgeon volumes were more important than hospital volumes in exploring the relationship between CABG operation volumes and SSIs in Taiwan. However, the relationships were not robust. Definitions and categorization methods of operation volume and correct identification of SSIs are important issues for future research.

Impact of hospital-acquired infection on long-term outcomes after endovascular and open abdominal aortic aneurysm repair

BACKGROUND

We hypothesized that infectious complications after open surgery (OPEN) and endovascular repair (EVAR) of nonruptured abdominal aortic aneurysms (AAAs) negatively affected long-term outcomes.

METHODS

Elective OPEN and EVAR cases were selected from 2005-2007 Medicare databases, and rates of postoperative infection, readmission, and longitudinal mortality were compared.

RESULTS

Forty thousand eight hundred ninety-two EVARs and 16,669 OPEN AAA repairs were evaluated. Patients with OPEN developed infection during and after the index hospitalization (12.8% and 4.9%, respectively) more often than those who had undergone EVAR (3.2% and 3.9%, respectively; P < 0.0001 for both). Patients with hospital-acquired infection compared to noninfectious ones were more likely to die during the index hospitalization (odds ratio [OR]: 3.7 [95% confidence interval {CI}: 3.22-4.30]) and within 30 days after discharge (OR: 3.6 [95% CI: 2.83-4.45]). They also were more likely to be readmitted to the hospital during 30 days after index discharge (OR: 1.8 [95% CI: 1.63-1.94]). Index infections associated with the greatest readmission were urinary tract infection after OPEN and sepsis after EVAR. Hospital-acquired infection significantly increased the duration of hospital stay (14.2 ± 13.2 vs 4.0 ± 4.4 days; P < 0.0001) and total hospital charges ($133,070 ± $136,100 vs $66,359 ± $45,186; P < 0.0001). The most common infections to develop 30 days after initial discharge were surgical site infection after EVAR (1.27%) and urinary tract infection after OPEN (1.38%).

CONCLUSION

Hospital-acquired infections had a dramatic effect by increasing hospital and 30-day mortality, readmission rates, and hospital resource use after AAA repair. Programs minimizing infectious complications may decrease future readmissions and mortality after AAA repair.

Renal transplantation: relationship between hospital/surgeon volume and postoperative severe sepsis/graft-failure. a nationwide population-based study

BACKGROUND AND OBJECTS: We explored the relationship between hospital/surgeon volume and postoperative severe sepsis/graft-failure (including death).

METHODS

The Taiwan National Health Insurance Research Database claims data for all patients with end-stage renal disease patients who underwent kidney transplantation between January 1, 1999, and December 31, 2007, were reviewed. Surgeons and hospitals were categorized into two groups based on their patient volume. The two primary outcomes were severe sepsis and graft failure (including death). The logistical regressions were done to compute the Odds ratios (OR) of outcomes after adjusting for possible confounding factors. Kaplan-Meier analysis was used to calculate the cumulative survival rates of graft failure after kidney transplantation during follow-up (1999-2008).

RESULTS

The risk of developing severe sepsis in a hospital in which surgeons do little renal transplantation was significant (odds ratio [OR]; p = 0.0115): 1.65 times (95% CI: 1.12-2.42) higher than for a hospital in which surgeons do many. The same trend was true for hospitals with a low volume of renal transplantations (OR = 2.39; 95% CI: 1.62-3.52; p < 0.0001). The likelihood of a graft failure (including death) within one year for the low-volume surgeon group was 3.1 times higher than for the high-volume surgeon group (p < 0.0001); the trend was similar for hospital volume. Female patients had a lower risk than did male patients, and patients ≥ 55 years old and those with a higher Charlson comorbidity index score, had a higher risk of severe sepsis.

CONCLUSIONS

We conclude that the risk of severe sepsis and graft failure (including death) is higher for patients treated in hospitals and by surgeons with a low volume of renal transplantations. Therefore, the health authorities should consider exporting best practices through educational outreach and regulation and then providing transparent information for public best interest.