Contemporary Mortality Following Emergent Open Repair of Complex Abdominal Aortic Aneurysms

Abstract

Objective

Mortality following open repair for emergent complex abdominal aortic aneurysm (cAAA) is poorly defined. This study evaluates the 30-day mortality of open cAAA repair performed for rupture or other emergent indication, using a national surgical registry. We subsequently identified factors associated with mortality.

Methods

The Targeted Vascular Module from the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) was queried to identify patients undergoing open repair for juxtarenal and suprarenal abdominal aortic aneurysm (AAA), or type IV thoracoabdominal aneurysms (TAAA) for rupture or other emergent indication from 2011–2017. Univariate analyses were performed using the Fisher’s Exact test for categorical variables and the Wilcoxen rank-sum test for continuous variables. Multivariable logistic regression was performed to identify factors independently associated with mortality.

Results

We included 374 patients who underwent an emergent complex open AAA repair over the study period. One hundred and forty-two (38%) cases were performed for rupture with hypotension, 141 (38%) were performed for rupture without hypotension, 40 (11%) were for symptomatic AAA, and 51 (14%) were performed for another indication. The distribution by aneurysm type was 224 juxtarenal AAA, 122 suprarenal AAA, and 28 type IV TAAA. Overall, there was a 30-day mortality of 32% (118 deaths). For those with juxtarenal AAA repair, 67 (30%) patients died within 30-days; there were 38 (31%) deaths within 30-days in those with suprarenal AAA, and 13 (46%) deaths within 30-days in those with type IV TAAA. On univariate analysis, pre-operative variables associated with death were increasing age, use of a trans-peritoneal surgical approach, lower pre-operative estimated glomerular filtration rate (eGFR), low baseline albumin (<3.5 g/dL), need for preoperative transfusion, low BMI (<18.5), and hypotension at presentation. Intraoperative variables associated with mortality were supraceliac clamp location and concurrent renal revascularization. On multivariable analysis, factors independently associated with death included rupture with associated hypotension (ref: other emergent indication) [AOR 3.28, CI:1.75–5.41, p<0.001], age >60 years (ref <60 years) [AOR 1.59, CI: 1.18–2.13, p=0.002], longitudinal laparotomy incision (ref: retroperitoneal) [AOR 3.28, CI: 1.756.16, p<0.001] and supraceliac cross-clamp (ref: clamp above one renal artery) [AOR: 2.14, CI: 1.31–3.50, p=0.003].

Conclusion

Nearly one-third of patients die within 30 days of emergent open complex AAA repair. Mortality is particularly high for patients with type IV TAAAs, with mortality approaching 50%. Predictors of 30-day mortality include rupture with associated hypotension, increasing age, supra-celiac clamp location, and longitudinal transperitoneal repair approach. These results will help inform surgical decisions pre-and intraoperatively.

TABLE OF CONTENT SUMMARY

In this NSQIP study the 30-day mortality for emergent open complex abdominal aortic aneurysm (AAA) repair was 31.6%. Predictors of mortality included rupture with associated hypotension, older age, transperitoneal approach and supraceliac cross-clamping. These data may serve as benchmarks for complex endovascular procedures under emergent conditions.

Introduction

While literature evaluating outcomes of emergent open repair infrarenal abdominal aortic aneurysm (AAA) is plentiful, there is a paucity of data regarding outcomes on open repair of complex abdominal aortic aneurysms (cAAA) under emergency conditions. Series of open repair of all ruptured AAAs has demonstrated a perioperative mortality of 25% to 53%^1–5. However, these studies had different entry criteria with regard to patient hemodynamic status and methodology, which is partly why there is a such a large discrepancy in outcomes. Pecoraro et al. looked at all emergent open AAA repairs and found the mortality rate to be 30% at 30 days⁶. While there have been subsets of patients with cAAA in many of these studies, there have been no studies specifically evaluating outcomes of emergent cAAA repairs. Additionally, as suitable anatomy for endovascular repair is rapidly increasing, it is important to thoroughly define real-world mortality rates regarding open repair of emergency complex abdominal aortic aneurysm (cAAA) for accurate comparison of outcomes^7–9.

Previously, the Vascular Study Group of New England (VSGNE) score identified the following independent predictors of death in ruptured abdominal aortic aneurysms: age greater than 76, preoperative cardiac arrest, loss of consciousness, and suprarenal clamp location¹⁰. This cohort largely included infrarenal aneurysms, as 59% of patients received an infrarenal aortic cross-clamp. Another recent study identified lower systolic blood pressure and low hemoglobin level at presentation as the independent predictors¹¹. This study only had 57 patients and did not focus on complex AAAs. Therefore, the goal of this study was to identify pre- and intraoperative factors associated with emergent complex AAA 30-day mortality, and to define the mortality rates in a national surgical registry.

Methods

Data Source

Data was derived from the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) Targeted Vascular Module. This module has been available since 2011, and the years 2011 to 2017 were utilized for data collection. The NSQIP is a nationwide registry that draws from a collection of surgical operations performed at over 700 participating centers, mainly located in North America. Data collection is performed by data abstractors and trained clinical research nurses and data are collected for over 270 variables, which includes patient demographics, comorbid conditions, procedural information, and pre-defined outcome variables up to 30 days out from the index procedure. Since 2011, additional procedure-specific data is available in procedure-specific targeted modules, such as the one utilized in this study. This module has the advantage of providing additional anatomical and surgical characteristics of open AAA repair that are not collected in the traditional NSQIP. The vascular-targeted module drew from 95 total hospitals. The NSQIP registry has been validated previously^12,13. The Institutional Review Board of the Massachusetts General Hospital and Beth Israel Deaconess Medical Center approved this study without requiring informed consent, due to the deidentification of subjects within the registry.

Patient Cohort

All patients who underwent an open emergent repair for a juxtarenal, pararenal, suprarenal and type IV thoracoabdominal aneurysms between 2011–2017 were identified. Emergency case is defined by the NSQIP as a case performed within a short interval of time between diagnosis in which patient’s well-being or outcome is threatened by a delay in surgery. The case must be designated by emergent by either the surgeon and/or anesthesiologist. While data abstractors are given guidance regarding the anatomic distinction between the NSQIP’s definition of pararenal and suprarenal AAA extents, the final distinction is still up to some interpretation by the surgeon and/or the data abstractors, and there may be disagreement between the definition of certain aneurysms. Given that both extents are treated similarly clinically, we combined those extents into one category and referred to them as suprarenal. Those with a listed infrarenal clamp location were eliminated. Additionally, all patients who did not have an “emergent procedure”, defined by NSQIP as a case qualified as emergent by the attending surgeon and/or anesthesiologist, or the indication for procedure listed as “rupture with associated hypotension or use of pressors” or “rupture without hypotension or the use of pressors” were eliminated from the analysis.

Clinical and Outcome Variables

Baseline characteristics, including patient demographics and comorbid conditions, as well as procedural and anatomical characteristics were compared between study groups. Estimated glomerular filtration rate (eGFR; mL/min/1.72m²) was calculated according to the Chronic Kidney Disease (CKD) Epidemiology Collaboration equation¹⁴ We categorized preoperative renal function into eGFR>60, eGFR 30–60, eGFR ≤30 or on dialysis. Mortality was defined as patient death within 30-days from the index surgery.

Pulmonary adverse events were defined as any patient with a 30-day reintubation, failure to wean from ventilation or pneumonia. Cardiac complications were defined as post-operative myocardial infarction or cardiac arrest. Major Adverse event (MAE) was created as a composite outcome consisting of death, pulmonary complications, cardiac complications, renal failure requiring dialysis, ischemic colitis,, lower extremity ischemia requiring revascularization, septic shock, stroke, DVT/PE (deep venous thrombosis/pulmonary embolism) and unplanned reoperation. Non-arterial repair refers to mention in the operative report of a secondary non-vascular procedures (i.e. small bowel resection, splenectomy etc.).

Statistical Analysis

Categorical and dichotomous variables are presented as counts and percentages. Differences in baseline, procedural, and outcome variables were univariately tested for significance using the Fisher’s exact test for categorical and dichotomous variables.

A separate category for missing data to preserve power during multivariable analysis. Significant missing data was present in the BMI category (23.5%), pre-operative CKD stage (6.4%) and distal aneurysmal extent (11.2%). Otherwise, incomplete data was <5% for all other variables considered for multivariable analysis.

Multivariable logistic regression models were constructed to identify independent pre-operative predictors associated with mortality. Covariables for these models were selected via a reverse stepwise method starting with entry criteria of p<0.3 on univariate analysis and exit level of p>0.05 on multivariable analysis. Age was evaluated as an ordinal variable.

Two multivariable analyses were performed, one with all emergent cases, and another with only ruptured cAAA. A sensitivity analysis was performed with proximal aneurysm extent forced into the model as a categorical variable to confirm our initial findings, and a post-hoc sensitivity analysis was performed to evaluate retroperitoneal versus midline incision mortality with hemodynamically unstable patients excluded To address concerns regarding group heterogeneity, a supplementary table was included stratifying all complications by indication. Analyses were performed using Stata 15.1 (StataCorp, College station, Texas, USA), an alpha level of 0.05 was utilized as the cutoff for statistical significance, and all tests were two-sided.

Results

There were 374 patients who underwent an emergent open complex AAA repair. Of these, 224 (59.9%) were juxtarenal, 122 (32.6%) were suprarenal, and 28 (7.5%) were type IV thoracoabdominal aneurysms (TAAA).. Most patients were male (70.6%) and median age was 73 (IQR 66, 79) years. 11% of the emergent repairs were qualified as non-ruptured symptomatic. Mortality by indication and extent are found in figure 1. The full indications for surgery are listed in table I.

Figure 1:

30-day mortality rates by surgical indication and by proximal extent

Table I:

Deaths by surgical indication, p<0.001

Indication	N (%)	Death (%)
Other emergent indication	51 (13.6)	14 (27.5)
Non-ruptured Symptomatic	40 (10.7)	3 (7.5)
Rupture without hypotension	141 (37.7)	33 (23.4)
Rupture with hypotension	142 (38.0)	68 (47.9)
Any indication	374 (100)	118 (31.6)

The overall 30-day mortality rate for the entire cohort was 32%. Including all emergent cases, pre-operative univariate associations with death were increasing age (p=0.02), midline laparotomy surgical approach (p=0.001), worse preoperative eGFR (p=0.001), albumin <3.5 g/dL (p=0.045), preoperative transfusion (p-0.01),BMI <18.5 (p=0.02) and ruptured with hypotension or pressor requirement (p<0.001). Intraoperative associations including concurrent renal revascularization, which was protective (p=0.02), and supraceliac clamp location (p=0.005). The median ICU LOS (length of stay) was 4 [IQR: 2, 9] and the median total LOS was 9.5 [IQR: 5, 17], table II.

Table II:

Demographics and Univariate analysis for death at 30 days.

Variable	Total cohort Median [IQR] or N (% of total)	Death Median [IQR] or N (% dead)	P-value
Total cohort	374	118 (31.6)
Age group (years):
<60	19 (5.1)	4 (21.1)
60–70	125 (33.4)	28 (23.7)	0.02
70–80	145 (38.8)	47 (32.4)
>80	85 (22.7)	39 (45.9)
Diameter (cm)	8 [6.5, 9]	8 [6.6, 9]	0.42
Proximal aneurysmal extent:
Juxtarenal	224 (59.9)	67 (29.9)
Suprarenal	122 (32.6)	38 (31.2)
Type IV TAAA	28 (7.5)	13 (46.4)	0.08
Surgical approach:
Retroperitoneal	91 (25.0)	16 (17.6)
Trans-peritoneal (Midline)	263 (72.3)	96 (36.5)	0.001
Trans-peritoneal (Transverse)	10 (2.8)	1 (10.0)
Prior Open Abdominal Surgery:	94 (29.3)	32 (34.0)	0.43
History of severe COPD	76 (20.3)	24 (31.6)	1.0
Transferred prior to repair	260 (69.5)	79 (30.4)	0.47
Pre-operative functional status:
Independent	355 (95.7)	113 (31.8)
Partially dependent	11 (3.5)	2 (18.2)	0.51
Completely dependent	3 (0.9)	1 (33.3)
ASA category:
1 or 2	8 (2.1)	4 (50.0)
3	32 (8.6)	6 (18.8)	0.16
4 or 5	334 (89.3)	108 (32.3)
Female	110 (29.4)	36 (32.7)	0.81
Diabetes:	34 (9.1)	10 (29.4)	0.86
CHF	9 (2.4)	2 (22.2)	0.73
Bleeding disorder:	48 (12.8)	17 (35.4)	0.62
Pre-operative eGFR:
>60	187 (53.4)	42 (22.5)
30–60	120 (34.3)	47 (39.2)	0.001
<30	43 (12.3)	20 (46.5)
Current Smoker:	188 (50.3)	54 (28.7)	0.27
Hypertension	255 (68.2)	86 (33.7)	0.19
Low Albumin (<3.5 g/dL)	192 (51.3)	70 (36.5)	0.045
Distal extent:
Aorta	181 (54.5)	54 (29.8)	0.28
Iliac	151 (45.5)	54 (35.8)
BMI:
18.5–25	108 (37.8)	31 (28.7)
<18.5	9 (3.1)	4 (44.4)
25–30	100 (35.0)	23 (23.0)	0.02
30–39.9	66 (23.1)	19 (28.8)
>40	3 (1.0)	1 (33.3)
Hematocrit < 21	6 (1.7)	2 (33.0)	1.0
Preoperative transfusion	80 (21.4)	35 (43.7)	0.01
Rupture with hypotension	142 (37.9)	68 (47.9)	<0.001
Intraoperative variables:
Renal revascularization:	53 (14.2)	9 (17.0)	0.02
Visceral revascularization:	18 (4.8)	5 (27.8)	0.8
Abdominal non-arterial repair or excision:	24 (6.4)	10 (41.7)	0.27
Management of IMA:
Chronically occluded	37 (23.1)	10 (27.0)
Implanted	14 (8.8)	3 (21.4)	0.41
Ligated	106 (68.0)	29 (27.4)
Clamp location:
Above one renal	94 (27.2)	20 (21.3)
Suprarenal	99 (28.6)	25 (25.3)	0.005
Supraceliac	153 (45.6)	62 (40.5)
Post-operative variables:
ICU LOS	4 [2, 9]	2 [1, 7]	<0.001
Survivors only	4 [2, 8]
Total LOS	9.5 [5, 17]	2 [1, 7]	<0.001
Survivors only	10 [7, 17]

IMA=Inferior Mesenteric Artery. LOS=length of stay

For all emergent cases, pre-operative factors independently associated with death included rupture with associated hypotension (ref: other emergent indication) [AOR 3.28, CI:1.75–5.41, p<0.001], age >60 [AOR 1.59 for each decade after 60, CI: 1.18–2.13, p=0.002], longitudinal laparotomy incision (ref: retroperitoneal) [AOR 3.28, CI: 1.75–6.16, p<0.001] and supraceliac cross-clamp (ref: clamp above one renal artery) [AOR: 2.14, CI: 1.31–3.50, p=0.003], table III.

Table III:

Independent associations with 30-day mortality for all emergent indications.

Independent Associations	AOR [95% CI]	P value
Rupture with associated hypotension (ref: all other emergent indications)	3.28 [1.75–6.16]	<0.001
Advancing Age Group (ref <60)	1.59* [1.18–2.13]	0.002
Longitudinal laparotomy incision (ref: retroperitoneal approach)	3.28 [1.75–6.16]	<0.001
Supraceliac cross-clamp (ref: clamp above one renal artery)	2.14 [1.31–3.50]	0.003

^*Represents AOR for each decade after age 60 until 90, then >90 years.

Overall, 61% of patients experienced a major adverse event. The most common overall complication was requirement of a post-operative transfusion, with 90% of the cohort receiving a transfusion post-operatively. The next most common complications were pulmonary (39%), cardiac (20%), unplanned reoperation (18%) and post-operative dialysis (18%). Both cardiac complications and renal failure requiring dialysis post-operatively were associated with increased mortality with 43% of those who suffered a cardiac event dying (p<0.001) and 56% of those suffering from renal failure requiring dialysis dying (p<0.001). Other complications associated with mortality were lower extremity ischemia requiring revascularization (5.1% of cohort, p<0.001), and post-operative septic shock (11.0% of cohort, p=0.002). Rate of ischemic colitis was 9.6% and was not significantly associated with 30-day mortality. However, when stratified according to ischemic colitis requiring surgical therapy (n=20, 55% mortality), this was associated with 30-day mortality (p=0.001).pulmonary complications were not associated with mortality nor were unplanned reoperation, wound dehiscence, nor post-operative blood transfusion requirement. Readmission rate was 5.9%, table IV. Outcomes are further stratified by indication in supplementary table 1.

Table IV:

Complications and association with 30-day mortality.

Complication	N (%)	Death (%)	P-value
Pulmonary	144 (38.5)	47 (32.6)	0.73
Cardiac	76 (20.3)	51 (43.2)	<0.001
Renal failure requiring dialysis	66 (17.7)	37 (56.1)	<0.001
Ischemic colitis	36 (9.6)	16 (44.4)	0.09
Required Surgical therapy	20 (5.4)	12 (60.0)	0.01
Lower extremity ischemia requiring revascularization	19 (5.1)	14 (73.7)	<0.001
Septic shock	41 (11.0)	22 (53.7)	0.002
Bleeding requiring transfusion	335 (89.6)	106 (31.6)	1.0
Wound dehiscence	4 (1.1)	0 (0.0)	0.31
Stroke	8 (3.1)	0 (0.0)	0.06
DVT/PE	19 (5.1)	4 (21.1)	0.45
Unplanned Reoperation	64 (18.2)	27 (42.2)	0.06
Readmission	14 (5.9)	0 (0.0)	0.006
MAE	229 (61.2)

DVT/PE=deep venous thrombosis/pulmonary embolism. MAE=Major adverse event

When only ruptures were considered, there were 283 total patients. One hundred and one (36%) of this cohort died. One hundred forty-two (50%) presented with hemodynamic instability (hypotension or a pressor requirement). Thirty-three (23%) of the hemodynamically stable group died and sixty-eight (48%) of the hemodynamically unstable group died (p<0.001), table V. Independent associations with death in the rupture-only cohort were the same four identified in the entire emergency cohort and are identified in table VI.

Table V:

Deaths by surgical indication (only ruptures considered), p<0.001

Indication	N (%)	Death (%)
Rupture without hypotension	141 (49.8)	33 (23.4)
Rupture with hypotension	142 (50.2)	68 (47.9)
All Ruptures	283 (100)	101 (35.7)

Table VI:

Independent associations with 30-day mortality for ruptured aneurysms.

Independent Associations	OR [95% CI]	P value
Rupture with associated hypotension (ref: all other emergent indications)	2.94 [1.69–5.11]	<0.001
Longitudinal laparotomy incision (ref: retroperitoneal approach)	4.10 [1.98–8.52]	<0.001
Advancing Age group (ref: <60 years)	1.93* [1.38–2.71]	<0.001
Supraceliac cross-clamp (ref: clamp above one renal artery)	1.95 [1.12–3.40]	0.018

^*Represents AOR for each decade after age 60 until 90, then >90 years.

On sensitivity analysis, with adjustment of the primary model for aneurysm extent as an ordinal variable, all four predictors remained predictive, with the adjusted OR for supraceliac clamp remaining similar [AOR 1.96, CI: 1.18–3.25, p-0.009]. Proximal extent was not predictive in this model (p=0.11), and the standard error for supraceliac clamp location decreased from 0.54 to 0.51.

If hemodynamically unstable patients are excluded from the analysis, 159 patients receive a midline traditional laparotomy, 52 receive a retroperitoneal incision and 6 receive a transverse midline. Seven (11.3%) died with an RP incision, 40 (25.2%) died with a traditional midline laparotomy incision and 1 (16.7%) died with a midline transverse incision (p=0.06).

Discussion

Utilizing a national registry, we demonstrated that the 30-day mortality rate of open complex AAA repair under emergency conditions was 32%. The rate was higher at nearly 50% for type IV TAAA, which is not surprising given the larger extent of the aneurysm and the increased complexity involved with repair. We believe these data represent a more accurate level of mortality and complication rates in nationwide practice compared to single-center or regional studies.

There was a subset of patients that met the emergency case criteria but were symptomatic cAAAs as opposed to ruptured cAAAs. While still necessitating repair with decreased time for physiological optimization and operative planning, urgent repairs tend to fair far better than their rupture counterparts with perioperative mortality near eight percent^15–17. Indeed, in our series, our symptomatic cohort had a mortality rate of 7.5%, slightly lower than previous estimates even though all repairs were for cAAA16. When only ruptures were considered, our mortality moved to 35.7%, with hemodynamically unstable patients with rupture dying at a rate of 47.9%. Overall, the mortality rates were similar to series with largely infrarenal AAA ruptures, indicating that the additional anatomic complexity plays less of a role in the mortality outcomes of these patients when all cAAA are considered¹⁸. However, this is likely driven by the large percentage of juxtarenal and suprarenal cAAA in this study, as nearly 50% of the type IV TAAA cohort died in the study. This was the most complex lesion included in the study and requires a supraceliac clamp and visceral reconstruction.

The pulmonary, cardiac, and renal complication rates were similar to previous estimates in the rupture literature¹⁸. Cardiac complications (MI/cardiac arrest), renal failure requiring dialysis, post-operative rupture, lower extremity ischemia requiring intervention and septic shock were the complications most strongly associated with mortality. Notably, 74% of the cohort who suffered from lower extremity ischemia post-operatively died. It has been shown in the literature previously that post-operative lower extremity ischemia is a grave complication, greatly increasing the mortality risk after AAA repair¹⁹. Furthermore, it has also been suggested that early vascular reconstruction in cases involving critical limb ischemia following rupture AAA improves outcomes²⁰. Therefore, surgeons should carefully note and follow a patient’s post-operative lower extremity examinations for signs of critical ischemia, and have an aggressive posture toward revascularization, when indicated.

Independent associations with mortality defined in our study included hemodynamic instability, represented by hypotension or the need for vasopressors prior to the operating room, supraceliac clamp location, increasing age, and a midline vertical laparotomy incision. This held true for all emergency operations, and when only ruptures were considered. Transperitoneal approach, older age, hypotension at presentation and increased age have previously been identified as predictive of mortality in the literature in a series which was largely composed of infrarenal AAA ruptures¹⁸. Indeed, Siracuse et al. recommended a retroperitoneal approach whenever possible based on their findings, and our findings would support this claim. Compared to a transperitoneal approach under elective conditions, a retroperitoneal technique is associated with decreased ventilatory support, a lower incidence of renal and cardiac complications, a shorter length of stay, higher rates of late complications and readmissions^21–23; under emergent conditions it is associated with reduced ventilatory support, shorter length of stay and improved mortality²⁴. It seems likely that those who receive a retroperitoneal incision may be more stable than those who receive a transperitoneal incision, but hemodynamic status was adjusted for in the analysis. This also may be a marker for a more experienced surgeon, as many central aortic surgeons exclusively utilize a retroperitoneal approach due to the ease with which the proximal aorta can be accessed, ability to utilize extracorporeal circulation techniques and the variety of visceral reconstruction options afforded by the ability to completely control all visceral vessels.

Supraceliac cross-clamp was associated with increased mortality, which is not surprising given the complete visceral ischemia inflicted by this clamp location. It may be argued that the proximal extent of the aneurysm was the main driver of this phenomenon, but the sensitivity analysis would suggest otherwise. Even when adjusting for aneurysm extent in our model, proximal clamp location was predictive and proximal aneurysm extent was not. This is particularly salient in the juxtarenal and suprarenal cohort, as these are the patients in which there may be a decision on clamp position, as all type IV repairs should require a supraceliac clamp, by definition. The implications for practice are that surgeons should strive to avoid a supraceliac cross-clamp in ruptured juxta and suprarenal AAAs whenever possible as supraceliac clamp location is an independent driver of mortality in these patients.

Hemodynamic instability is known to be predictive of mortality, regardless of interventional approach, and is intuitive as these patients are more likely to represent a free rupture with ongoing bleeding²⁵.

It should be noted that this analysis utilized the NSQIP targeted vascular module and the targeted database contains many high-volume referral centers. Therefore, the generalizability may be somewhat in question. However, Soden et al. demonstrated previously that there was no demonstrable difference between having an operation for a rupture AAA at a standard NSQIP hospital and the targeted hospitals, and this held true for complex open repairs²⁶. Therefore, these results are likely fairly generalizable to the real-world experience.

The value of these data is severalfold. First, surgeons with enough technical expertise using a retroperitoneal approach, should use this as their preferred approach to cAAAs unless hemodynamic circumstances absolutely preclude this. Additionally, when possible, surgeons should try to avoid a supraceliac clamp unless the extent of the lesion absolutely demands a supraceliac clamp or the patient is so unstable that a supraceliac clamp location is all that can be obtained in an appropriately expeditious manner. Other independent associations, such as age group and rupture with hypotension on presentation can be used to anticipate higher mortality rates in patients who are older and more unstable.

Another point of discussion is the inclusion of type IV TAAAs. Though this subgroup was small relative to the Juxtarenal and Suprarenal cohort, their mortality was higher. The authors decided to include these lesions in the analysis as these are fully abdominal lesions that are usually repaired with a clamp-and-sew technique unlike other TAAAs with a thoracic component and gives us a subgroup that requires supraceliac clamping for comparison. Regarding the retroperitoneal versus laparotomy incision outcomes, the numbers are greatly reduced during this sensitivity analysis, limiting our ability to perform an adequate statistical analysis in this cohort. However, the trend would suggest that retroperitoneal incision performs better in the cohort of hemodynamically stable patients.

One final concern which warrants discussion is the inclusion of all emergent indications for aneurysm repair. This analysis was intended to include any cAAA that was repaired under emergent fashion and this method was selected a priori. The majority of the repairs were for ruptures and symptomatic aneurysms, as expected. The “other category” included aneurysms that were designated by indication as “Diameter”, “Dissection”, “Other indication for surgery”, “Prior endovascular intervention with unsatisfactory result”, and “Prior open intervention with unsatisfactory result”. While we not privy to the granular detail required to discern why these other aneurysms required emergent repair, it is telling that the mortality rate was quite high in this aggregate group (27.5%), and thus the group believed it appropriate to include these patients in the analysis.

According to the most recent SVS guidelines on ruptured AAA management, when it is anatomically feasible, EVAR is recommended over open repair for ruptured AAA.²⁷ As anatomic criteria is rapidly expanding, and more vascular surgeons are becoming facile with complex endovascular techniques, it is likely that endovascular therapy will play a larger role in the treatment of these complex lesions under emergent conditions. The mortality and complication rates identified in this study can be used as a benchmark for complex endovascular interventions performed under emergent conditions.

Strengths and limitations

A major strength of this study was the high number of patients and events, affording us power to detect several independent associations with mortality. Additionally, the data set allows us to study multi-center data and identify outcomes that are representative of national outcomes, as opposed to just single-center or regional outcomes. Additionally, the NSQIP allows for study of 30-day outcomes, allowing us to discern outcomes after hospital discharge.

Limitations of our study include poor recording of pre-operative coronary artery disease (CAD) comorbid data, which limits our ability to identify CAD as a potential association with poor outcomes in our study. Additionally, we are unable to discern hospitals by size, geography, and volume of complex aortic procedures performed, transport distance for transported patients, nor are we able to discern any information on which institutions have established rupture or other emergent aortic emergency protocols. Also, certain operative details, such as individual surgeon who performed the case, appropriate adjustment for teaching versus non-teaching hospitals, volume of intraoperative blood transfusion, visceral ischemia and total cross-clamp times which are missing from these data which prevents us from evaluating these as potential intraoperative covariates that may be associated with worse outcomes. A final limitation is the small number of patients given the 95 participating institutions, meaning that certain institutions may be contributing few or no patients to the study and the volume may not be distributed evenly. It is also possible that there may be underrepresentation secondary to misclassification of certain aneurysm types.

Conclusion

Nearly one-third of patients die within 30 days of emergent open complex AAA repairs. Mortality is particularly high for patients with type IV TAAAs, with mortality approaching 50%. Independent associations with death include rupture with associated hypotension, advanced age, longitudinal laparotomy approach, and supraceliac clamp location. These data may serve as a mortality and complication benchmark for complex endovascular procedures performed under emergent conditions.

ARTICLE HIGHLIGHTS.

Type of research: Retrospective review of prospectively collected data from the National Surgical Quality Improvement Program (NSQIP).

Key Finding: Thirty-day mortality for emergent open complex AAA repair was 31.6%. Predictors of mortality included rupture with associated hypotension, older age, transperitoneal approach and supraceliac cross-clamp.

Take Home Message: These data serve as benchmarks for complex emergent endovascular procedures.