Relation between hospital volume and outcome of elective surgery for abdominal aortic aneurysm: a systematic review.

OBJECTIVES: Our aim was to analyse the relation between hospital volume and peri-operative mortality in abdominal aortic aneurysm surgery. DESIGN: Systematic review. METHOD: The Medline, Embase and Cochrane databases were searched to identify all population based studies reporting on the volume outcome relationship published between 1966 and 2006. Two independent observers performed methodological quality assessment and data extraction. Outcome was 30-day or in-hospital mortality in relation to hospital volume. RESULTS: Twenty-four articles were included. Overall peri-operative mortality ranged from 2.3 to 9.9%. The cut-off values for a high- or low-volume hospital appeared to range from 8 to 50 operations annually. The peri-operative mortality in low volume hospitals (LVH) ranged from 3.0 to 13.8% (median 6.2%) and from 1.8 to 7.4% in high volume hospitals (HVH) (median 4.3%). In 14 studies a significantly lower mortality was found in HVH as opposed to LVH; in 10 articles no such difference between HVH and LVH could be proved. CONCLUSION: We found some evidence for a relation between the volume of AAA surgery and peri-operative mortality. There seems to be a nonsignificant trend in favour of high volume hospitals. However we could not derive an unequivocal volume threshold for safely performing AAA surgery.     

Meta-analysis and systematic review of the relationship between surgeon annual caseload and mortality for elective open abdominal aortic aneurysm repairs

OBJECTIVE: To assess the relationship between the annual caseload of elective open abdominal aortic aneurysm (AAA) repairs performed by individual surgeons and mortality. METHODS: PubMed, EMBASE, and the Cochrane library were searched for articles on the volume-outcome relationship in AAA surgery. The review conformed to the QUOROM statement. The data were meta-analyzed to compare the mortality rates of higher- and lower-volume surgeons. A critical volume threshold was calculated for better practice. RESULTS: Fourteen relevant articles were retrieved from the searches. A systematic review was performed, and six were meta-analyzed. A total of 115,273 elective open AAA repairs were considered, with a mean mortality rate of 5.56%. Significant relationships between higher surgeon caseload and lower mortality were demonstrated in 12 of 14 studies. From the meta-analysis, the pooled effect estimate was an odds ratio of 0.56 (95% confidence interval, 0.54-0.57) in favor of higher-volume surgeons. A critical volume threshold was identified as 13 cases per annum for individual surgeons. CONCLUSIONS: As surgeons performed higher annual volumes of elective open AAA repairs, significantly lower mortality rates were demonstrated. Surgeons wishing to perform elective AAA repairs should achieve a minimum case volume of 13 repairs per annum.     

Epidemiological study of the relationship between volume and outcome after abdominal aortic aneurysm surgery in the UK from 2000 to 2005

BACKGROUND: The aim was to assess the relationship between hospital volume and outcome after abdominal aortic aneurysm (AAA) surgery in the UK. METHODS: Hospital Episode Statistics (2000-2005) were classified as elective, urgent or ruptured AAA repair. Analysis was by modelling of mortality rate, complication rate and length of hospital stay with regard to the annual operative volume, after risk adjustment. RESULTS: There were 112,545 diagnoses, or repairs, of AAAs, of which 26,822 were infrarenal aneurysms. The mean mortality rate was 7.4, 23.6 and 41.8 per cent for elective, urgent and ruptured AAA repair respectively. Elective AAA repair undertaken at high-volume hospitals showed volume-related improvements in mortality (P < 0.001). Patients were discharged from hospital earlier (P < 0.001). The critical volume threshold was 32 elective AAA repairs per year. For urgent repair, patients at high-volume hospitals had a reduced mortality rate (P = 0.017) with an increased length of stay (P = 0.041). There was no relationship between volume and outcome for ruptured AAA repairs. CONCLUSION: Increased annual volumes were associated with significant reductions in mortality for elective and urgent AAA repair, but not for repair of ruptured AAAs.     

Meta-analysis and systematic review of the relationship between hospital volume and outcome following carotid endarterectomy.

OBJECTIVES: This study investigated the relationship between annual hospital volume and the outcomes in carotid endarterectomy and quantified critical volume threshold for this procedure. DATA SOURCES: PubMed, EMBASE and the Cochrane library were searched for all articles on the volume-outcome relationship in CEA. REVIEW METHODS: Articles were included if they presented data on post-operative mortality and/or stroke rates and annual hospital volume of CEA. The review conformed to the QUOROM statement. The data were meta-analysed and a pooled effect estimate of volume on the stroke and/or mortality rates from CEA quantified, along with the critical volume threshold. RESULTS: Twenty-five articles, encompassing 936 436 CEA, were analysed. Significant relationships between mortality rate and stroke rate and annual volume were seen. Overall, the pooled effect estimate was odds ratio 0.78 [95% confidence interval 0.64-0.92], in favour of surgery at higher volume units, with a critical volume threshold of 79 CEA per annum. CONCLUSIONS: Significantly lower mortality and stroke rates were achieved at hospitals providing a higher annual hospital volume of CEA. Hospitals wishing to provide CEA should adhere to minimum volume criteria.     

腹主动脉瘤与CD40的关系

目的 探讨腹主动脉瘤(AAA)发病与患者血清CD40及其配体(CD40L)浓度的相关性.方法 对30例诊断明确的腹主动脉瘤患者(病例组)与26例健康人群(正常组)进行对照研究,酶联免疫吸附试验(ELISA)双抗体夹心法测定标本中CD40和CD40L水平,应用统计学独立样本t检验分析CD40/CD40L与腹主动脉瘤的关系.结果 病例组血清CD40浓度为(96.20±26.26) ng/L,高于正常组的(76.22±6.39) ng/L,两者差异有统计学意义(P＜0.05).病例组血清CD40L浓度为(746.20±215.46) ng/L,明显高于正常组的(503.07±75.32) ng/L,两者差异有统计学意义(P＜0.05).结论 AAA患者血清CD40和CD40L浓度明显高于健康人群,提示CD40/CD40L可能参与了AAA的发病.     

A systematic review of simulation in open abdominal aortic aneurysm repair

ObjectiveConcerns about the long-term durability of endovascular aortic aneurysm repair and the requirement for explantation of stents in the case of infection demonstrate the continued need for open abdominal aortic aneurysm (AAA) repair. However, with the increased complexity and decreasing volume of open cases performed, maintenance of skills and training of younger surgeons are challenging. The aim of this review was to identify and to examine studies pertaining to open AAA simulation, with focus on methods and outcomes.MethodsWe performed a systematic review of the literature to identify primary research pertaining to open AAA repair through the use of simulators. The primary outcome was to identify predominant modes of simulator design and validated assessment tools that could demonstrate improvement in trainee skills. Secondary outcomes included identifying participant numbers needed to power studies and whether tools not validated externally contributed to the studies.ResultsThere were 309 unique papers identified, from which five papers met the inclusion criteria. The selected papers used a combination of synthetic (commercial and homemade) and cadaveric simulators. A variety of validated and nonvalidated assessment metrics were used, including Objective Structured Assessment of Technical Skills, global rating scales, and realism surveys. Three of the five papers used blinding as part of their assessments. Mean participant numbers were 30.8 ± 25.7 and with the exception of one paper consisted entirely of surgical trainees in dedicated general or vascular surgery training programs.ConclusionsSeveral options are currently available for open AAA simulation, all of which demonstrate improved scoring metrics after simulator use. Validated scoring systems, the Objective Structured Assessment of Technical Skills in particular, were most frequently used to deliver objective results. Whereas junior trainees derive the most benefit, senior trainees also showed significant improvements, demonstrating that simulation benefits all levels of surgical trainees. Low numbers of participants were sufficient to achieve statistical benefit within individual studies.     

The strange relationship between diabetes and abdominal aortic aneurysm

In a 1997 report of a large abdominal aortic aneurysm (AAA) screening study, we observed a negative association between diabetes and AAA. Although this was not previously described and negative associations between diseases are rare, the credibility of the finding was supported by consistent results in several previous studies and by the absence of an obvious artifactual explanation. Since that time, a variety of studies of AAA diagnosis, both by screening and prospective clinical follow-up, have confirmed the finding. Other studies have reported slower aneurysm enlargement and fewer repairs for rupture in diabetics. The seeming protective effect of diabetes for AAA contrasts with its causal role in occlusive vascular disease and so provides a strong challenge to the traditional view of AAA as a manifestation of atherosclerosis. Research focused on a protective effect of diabetes has already increased our understanding of the etiology of AAA, and might eventually pave the way for new therapies to slow AAA progression.     

Impact of smoking on endovascular abdominal aortic aneurysm surgery outcome.

OBJECTIVE: Smoking plays a major role in deficiencies of the vascular system, and seems to have consequences for the treatment of cardiovascular diseases. We hypothesized that smokers have a higher mortality and more complications after endovascular abdominal aortic aneurysm surgery than non-smokers. METHODS: We assessed mortality and complications of 3270 patients who underwent endovascular abdominal aortic aneurysm surgery in Europe between January 1994 and July 2001. Survival and (post) operative complications were assessed by smoking status. RESULTS: Mortality did not significantly differ between smokers and non-smokers. Smokers had a higher number of intra-operative additional procedures, but a lower number of late endoleaks in comparison to non-smokers. In addition, smokers had a reduced risk of late type II endoleaks in comparison with non-smokers. CONCLUSION: There seems to be no significant difference in endovascular abdominal aortic aneurysm surgery outcome between smokers and non-smokers, although there were significant differences in intra-operative additional procedures and late endoleaks.     

The relationship between aortic wall distensibility and rupture of infrarenal abdominal aortic aneurysm

OBJECTIVE: A more accurate means of prediction of abdominal aortic aneurysm (AAA) rupture would improve the clinical and cost effectiveness of prophylactic repair. The purpose of this study was to determine whether AAA wall distensibility can be used to predict time to rupture independently of other recognized risk factors. METHODS: A prospective, six-center study of 210 patients with AAA in whom blood pressure (BP), maximum AAA diameter (Dmax), and AAA distensibility (pressure strain elastic modulus [Ep] and stiffness [beta]) were measured at 6 months with an ultrasound scan-based echo-tracking technique. A stepwise, time-dependent, Cox proportional hazards model was used to determine the effect on time to rupture of age, gender, BP, Dmax, BP, Ep, beta, and change in Dmax, Ep, and beta adjusted for time between follow-up visits. RESULTS: Median (interquartile range) AAA diameter was 48 mm (41 to 54 mm), median age was 72 years (68 to 77 years), and median follow-up period was 19 months (9 to 30 months). In the Cox model, female gender (hazards ratio [HR], 2.78; 95% CI, 1.23 to 6.28; P =.014), larger Dmax (HR, 1.36 for 10% increase in Dmax; 95% CI, 1.12 to 1.66; P =.002), higher diastolic BP (HR, 1.13 for 10% increase in BP; 95% CI, 1.13 to 1.92; P =.004), and a decrease in Ep (increase in distensibility) over time (HR, 1.38 for 10% decrease in Ep over 6 months; 95% CI, 1.08 to 1.78; P =.010) significantly reduced the time to rupture (had a shorter time to rupture). CONCLUSION: Women have a shorter time to AAA rupture. The measurement of AAA distensibility, diastolic BP, and diameter may provide a more accurate assessment of rupture risk than diameter alone.     

Comparison of perioperative factors of elective abdominal aortic aneurysm surgery and those of ruptured abdominal aortic aneurysm surgery

BACKGROUND: Currently the mortality rate of elective abdominal aortic aneurysm (eAAA) surgery has improved. However the mortality rate of ruptured abdominal aortic aneurysm (rAAA) surgery remains high. We compared perioperative variables of eAAA surgery and those of rAAA surgery. METHODS: From 1997 to 2002, 98 consecutive patients who had undergone graft replacement of infrarenal AAA (56 eAAA and 42 rAAA) were evaluated retrospectively. RESULTS: Significant differences existed between eAAA and rAAAs in following perioperative variables: agg (eAAA: 74.2 +/- 6.8 years, rAAA: 74.2 +/- 8.6 years), duration from the admission to the time of starting operation (eAAA: 62 +/- 11 min, rAAA: 28 +/- 17 min), duration from the time of starting operation to the aortic cross clamping (eAAA: 87 +/- 29 min, rAAA: 29 +/- 32 min), duration of the aortic cross clamping (eAAA:59 +/- 19 min, rAAA: 71 +/- 29 min), blood loss (eAAA: 1297 +/- 1046 ml, rAAA: 4619 +/- 4960 ml), total amount of blood products required (eAAA: 1058 +/- 953 ml, rAAA: 5619 +/- 4945 ml), intensive and/or high care unit stay (eAAA: 1.8 +/- 1.2 days, rAAA: 6.4 +/- 8.1 days), the postoperative mortality rate (eAAA: 0%, rAAA: 19%), and postoperative complications (eAAA: 14%, rAAA: 48%), CONCLUSIONS: Patients who had undergone rAAA surgery had higher mortality and more postoperative complications than those after eAAA surgery. Elective rapair before AAA ruptures is recommended.     

腹主动脉瘤的可视化仿真手术

目的研究可视化仿真手术在腹主动脉瘤(AAA)手术中的应用价值。方法 1例AAA患者64排螺旋CT动脉期、静脉期DICOM数据,用MxLite View DICOM Viewer、DICOM查看器及ACDSeePhoto Manager等软件进行图像重建前处理,然后导入自主开发的医学图像处理系统(MIPS)对CTA图像中的腹部实质脏器及血管进行分割及三维重建,将重建后的各脏器及血管模型导入到FreeForm Model-ing System进行修饰和平滑,使用该系统的力反馈设备PHANToM进行AAA修复术的仿真手术。结果重建的各个腹腔脏器及血管模型形态逼真,立体感强,相互关系明晰;在FreeForm Modeling System仿真环境中,仿真手术符合临床手术过程。结论可视化仿真手术演练可熟悉手术过程,缩短手术时间。