Management of ruptured abdominal aortic aneurysm in the endovascular era

Article Outline

• Abstract
• Methods
• Statistical methods
• Results
  • Study population characteristics
  • Thirty-day mortality
  • In-hospital mortality
  • Factors related to mortality for EVAR and open repair
    • Age
    • Gender
    • Systolic blood pressure
    • Serum HCT and creatinine
    • Comorbidities
    • Transfusion requirement
    • Rupture and transport time
    • Operative time
    • Cardiopulmonary resuscitation
    • Aortic occlusion balloon
    • Abdominal compartment syndrome
• Discussion
• Conclusions
• Author contributions
• References
• Copyright

Objectives

Our institution treats about 30 patients per year with ruptured abdominal aortic aneurysms (rAAA). Between 2002 and 2007, our 30-day mortality averaged 58%. In July 2007, we implemented an algorithm to promote endovascular aneurysm repair (EVAR) when feasible. This report describes the outcome with this approach.

Methods

Data on patients presenting with rAAA between July 1, 2002, and June 30, 2007, were reviewed and used for comparison to prospectively collected data. Data on patients presenting between July 1, 2007, and April 30, 2009, were collected on all patients after implementation of a structured protocol. The primary outcome measure was 30-day mortality. Data were analyzed using logistic regression. Kaplan-Meier survival curves and a log-rank test were performed to compare survival times for three groups (pre-protocol, post-protocol with open surgery, and post-protocol with EVAR).

Results

During the study period, 187 patients with rAAA presented to our institution. Before implementation of the algorithm, 131 patients with rAAA presented and 128 were treated. The 30-day mortality rate was 57.8%. After implementation of the protocol, 56 patients with rAAA were managed. Twenty-seven patients (48%) underwent successful EVAR, and 24 patients (43%) underwent open repair. Five patients (9%) underwent comfort care only. In the post-protocol period, 5 patients in the EVAR group (18.5%) and 13 patients in the open group (54.2%) died during the follow-up period for an overall 30-day mortality rate of 35.3% (P = .008 vs 57.8% pre-protocol). After implementation of a structured protocol for managing rAAA, there was a relative risk reduction in 30-day mortality of 35% compared to the time before implementation of the protocol (95% confidence interval [CI], 14%-51%) corresponding to an absolute risk reduction of 22.5% (95% CI, 6.8%-38.2%) and an odds ratio of 0.40 (95% CI, 0.20-0.78; P = .007). After adjusting for key factors predicting mortality, the odds ratio is 0.25 (95% CI, 0.10-0.57; P = .001).

Conclusion

Use of an algorithm favoring endovascular repair resulted in a highly significant reduction in rAAA mortality in our urban hospital. Thirty-day mortality for open repair was no different between pre- and post-protocol eras. With modern techniques of resuscitation and surgical management, a majority of patients presenting with rAAA can survive.

Harborview Medical Center is a level 1 trauma center serving five states with a geographic area 27% of the land mass of the United States. Just over 10 million people are served, representing 3.4% of the U.S. population in 2007.¹ Because of this unique setting, our institution treats a wide range of aortic pathology, including between 30 and 50 patients per year with ruptured abdominal aortic aneurysm (rAAA). In 1991, Johansen et al² published a 10-year experience of 186 patients with rAAA treated at Harborview Medical Center.² The overall 30-day mortality was a somber 70%.

With the advent of elective endovascular aortic aneurysm repair (EVAR), randomized controlled trials and population-based studies have shown a marked reduction in 30-day mortality when compared with standard open repair.³, ⁴, ⁵ Since the first successful endovascular repair of an rAAA by Marin and Veith et al⁶ in 1994, few institutions have adopted this approach in a structured fashion for the management of this devastating disease. The use of EVAR for rAAA has not been associated with improved outcomes in most series, although some have suggested that a structured approach may have this result.⁷, ⁸

A recent internal review of our own experience revealed a modest but significant decrease in overall 30-day mortality over the 27-year interval comparing the period between 2002 and 2007 (59%; n = 131) with the period between 1980 and 1989 (70%; n = 186) P = .04. In July 2007, we implemented an algorithm to manage these patients with a preference for endovascular repair when feasible. The objective of the current study is to evaluate the effect of this algorithm on mortality.

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Methods 

In July of 2007, we implemented an Institutional Review Board-approved protocol for managing patients with rAAA. This was a prospective nonrandomized intent-to-treat study with comparison to historic controls. All patients presenting with a diagnosis of rAAA were included in the analysis, and data were collected prospectively. Our algorithm for managing these patients was adapted from Mehta et al⁸ and is depicted in Fig 1. Briefly, patients presenting with an rAAA are divided into one of two groups, those who are hemodynamically stable (systolic blood pressure [SBP] >80 mm Hg) or unstable (SBP <80 mm Hg or with lack of neurocognitive ability). Stable patients who arrived without having a computed tomographic angiogram (CTA) rapidly received one. Stable patients were then transferred urgently to the operating room when the CTA was available. Unstable patients were immediately transferred to the operating room without a CTA. Once in the operating room, the patients were initially managed awake with a preference for local or no anesthesia and percutaneous transfemoral placement of a prophylactic aortic occlusion balloon (CODA balloon, COOK-Medical, Bloomington, Ind) with sheath support as described by Malina et al.⁹ The balloon was briefly inflated to profile to determine the amount of dilute contrast required for blind inflation and aortic occlusion if needed. Patients presenting in hemorrhagic shock often require no anesthesia for percutaneous placement of a sheath in the femoral artery. The added time required to inject local anesthesia in these unstable patients was deemed excessive. Balloons were only placed in those patients thought to be unstable and in patients undergoing open repair by a surgeon familiar with endovascular techniques. Once an assessment was made of the anatomic suitability for EVAR, the patient was either electively intubated for open repair under general anesthesia with the use of a protective aortic occlusion balloon as needed or underwent rapid EVAR with a preference for local or no anesthesia. Heparin was used selectively. Dilute heparinized saline solution was used to flush sheaths in patients receiving no systemic heparin. The majority of patients underwent EVAR with a COOK Zenith modular bifurcated endoprosthesis (COOK-Medical). Type 1 endoleaks were managed in the operating room. If a type 2 endoleak was identified on completion imaging, no intervention was performed at that time.

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• Fig 1. 

  Structured algorithm for managing patients with ruptured abdominal aortic aneurysms (rAAA). SBP, Systolic blood pressure; CTA, computed tomographic angiogram; Fr, French size; AOB, aortic occlusion balloon; IVUS, intravascular ultrasound; GETA, general endotracheal anesthesia; EVAR, endovascular aneurysm repair.

A strong emphasis was made to only place bifurcated grafts to mimic native anatomy. Unibody systems were used only when coexistent unilateral iliac occlusion was present or if prolonged attempts at gate cannulation were futile. Traditional crossover femoral-femoral bypass was conducted at the completion of any unibody construct.

An rAAA was defined by evidence of blood outside of the aorta at any time during evaluation. Conventional exclusion criteria for EVAR were utilized and included: (1) aortic neck diameter of no greater than 32 mm, neck length shorter than 15 mm, significant calcification (circumferential), thrombus (>40%) or greater than 60 degrees of aortic neck angulation; and (2) iliac vessels less than 6.5 mm in diameter for delivery of the main body graft or with significant tortuosity. Over the study period, as our experience increased, these selection criteria became less stringent. Included in this study were patients with juxta- and pararenal ruptured aneurysms as well; the majority underwent open repair.

An estimate was made based on patient presentation, discussion with family members, and chart documentation as to the estimated time of rupture. “Rupture time” was defined as the time between estimated time of rupture and arrival in the Harborview Emergency Department (ED). Transport time was calculated as the duration between time of arrival in the ED and time of arrival in the operating theater.

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Statistical methods 

The primary outcome measure was 30-day mortality rate. We also examined in-hospital mortality rate. We calculated and compared the proportion of subjects who died before 30 days for the pre-protocol era (July 1, 2002 to June 30, 2007) and the post-protocol era (July 1, 2007 to April 30, 2009). Within the post-protocol era, we compared subjects undergoing open surgery to those undergoing EVAR. Proportions were compared using a χ² test. In situations where the expected cell sizes were less than five, we used Fisher's exact test. In addition to examining the 30-day mortality rate, we also constructed Kaplan-Meier survival curves and performed a log-rank test comparing survival times for the three groups (pre-protocol, post-protocol with open surgery, and post-protocol with EVAR). We used logistic regression to test for a difference in 30-day mortality in the pre- and post-protocol era, using the pre-protocol era as the reference. We also used logistic regression to test for univariate associations between 30-day mortality and substrata of demographic, pre-hospital, and presenting characteristics. We constructed a multivariate logistic model to examine differences in 30-day mortality in the pre- and post-protocol eras adjusting for key factors that were significantly associated with mortality in the univariate analysis. We present odds ratios (ORs) and 95% confidence intervals (CIs). Note, the OR should not be interpreted as an approximation of the relative risk because our outcome is not rare. We were able to calculate rupture and transport times for 147 of 179 subjects. Rupture time was calculated as the duration between the estimated time of rupture and arrival at the Harborview ED. Transport time was calculated as the duration between time of arrival at the ED and time of arrival to the operating room. We used a t test to compare transfusion requirements, rupture times, and transport times. Because this analysis was exploratory, we did not adjust for multiple comparisons. All analysis was performed using SPSS (SPSS Inc, Chicago, Ill) and STATA (StataCorp, College Station, Tex).

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Results 

Study population characteristics 

During the study period, 187 patients with rAAA presented to our institution. Demographics for the entire study population are divided into pre- and post-protocol groups and are listed in Table I. Before implementation of the algorithm, 131 patients with rAAA presented to our hospital, and 128 were treated. A single patient during this time period was treated with EVAR and survived. Sixty-five percent of these patients were hypotensive (SBP <80 mm Hg) on presentation. After implementation of the protocol, 56 patients with rAAA were managed. Twenty-seven patients (48%) underwent EVAR, and 24 patients (43%) underwent open repair. Five patients (9%) underwent comfort care only. In the post-protocol group, 37/51 (72.6%) presented with hypotension. There was no significant difference in the incidence of hypotension between pre- and post-protocol groups or between post-protocol EVAR and open groups. CT scans were more common in later years, as was the incidence of patients presenting with renal insufficiency. The mean follow-up period was 164 days (range, 0-365 days). For patients who did not die in the first 30 days, the mean follow-up period was 332 days (range, 68-365 days).

Table I. Basic demographics and pre-hospital characteristics^a

Characteristic		Post-protocol
	Pre-protocol	Total	Open	EVAR
N	128	51	24	27
Male	100(78.2%)	40(78.4%)	17(70.8%)	23(85.2%)
Age
<60	7(5.5%)	0	0	0
60-69	35(27.6%)	10(19.6%)	4(16.7%)	6(22.2%)
70-79	41(32.3%)	19(37.3%)	7(29.2%)	12(44.4%)
80-89	42(33.1%)	20(39.2%)	12(50.0%)	8(29.6%)
90+	2(1.2%)	2(4.0%)	1(4.2%)	1(3.7%)
SBP <80	83(64.9%)	37(72.6%)	19(79.2%)	18(66.7%)
CPR	4(3.2%)	5(9.8%)	3(12.5%)	2(7.4%)
CT scanb	76(65.5%)	42(93.3%)	16(88.9%)	26(96.3%)
Hematocrit ≤25	28(21.9%)	12(23.5%)	4(16.7%)	8(29.6%)
Creatinine >2	47(36.7%)	27(52.9%)	15(62.5%)	12(44.4%)
Rupture time >10 hours	28(23.3%)	8(19.5%)	2(10.0%)	6(28.6%)
CAD	66(56.9%)	23(51.1%)	10(47.6%)	13(54.2%)
HTN	73(62.9%)	34(75.6%)	18(85.7%)	16(66.7%)
COPD	33(28.4%)	15(33.3%)	8(38.1%)	7(29.2%)
Renal insufficiencyb	7(6.03%)	11(24.4%)	3(14.3%)	8(33.3%)
Diabetes	14(12.2%)	5(11.1%)	2(9.5%)	3(12.5%)

SBP, Systolic blood pressure.

Thirty-day mortality 

The 30-day mortality rate for the pre-protocol group was 57.8% (Table II). During the post-protocol era, 5 patients in the EVAR group (18.5%) and 14 patients in the open group (54.2%) died for an overall 30-day mortality rate of 35.3%. The absolute risk difference was 22.5% (95% CI, 6.8%-38.2%). The OR comparing the post-protocol group to the pre-protocol group was 0.40 (95% CI, 0.20-0.78; P = .007; Table III). After adjustment for age, pre-hospital systolic blood pressure, hematocrit (HCT), and the number of transfused units, the OR was even lower (OR = 0.25; 95% CI, 0.10-0.57; P = .001; Table IV).

Table II. Thirty-day survival

EVAR, Endovascular aneurysm repair; N, number.

Relative risk: 35% reduction (95% CI, 14%-51%).

Absolute risk difference: 22.5% (95% CI, 6.8%-38.2%).

Table III. Univariate odds ratios of 30-day mortality for different patient characteristics

Characteristic	Odds ratio	95% CI	P value
Time period
Pre-protocol	Reference
Post-protocol	0.40	0.20-0.78	.007
Gender
Male	Reference
Female	1.14	0.56-2.33	.71
Age group
<70 years	Reference
70-79 years	1.77	0.82-3.79	.14
80+ years	3.78	1.75-8.13	.001
Pre-hospital systolic blood pressure <80
No	Reference
Yes	4.64	2.34-9.19	<.001
HCT ≤25
No	Reference
Yes	0.23	0.10-0.51	<.001
Serum creatinine >1.5
No	Reference
Yes	1.09	0.60-1.98	.77
Transfusion units >10
No	Reference
Yes	2.31	1.21-4.39	.010

CI, Confidence interval; HCT, hematocrit.

Table IV. Odds ratios of 30-day mortality from a multivariate model

Characteristic	Odds ratio	95% CI	P value
Time period
Pre-protocol	Reference
Post-protocol	0.25	0.10-0.57	.001
Age group
<70 years	Reference
70-79 years	3.01	1.19-7.62	.020
80+ years	6.53	2.50-17.01	<.001
Pre-hospital systolic blood pressure <80
No	Reference
Yes	5.01	2.23-11.2	<.001
HCT ≤25
No	Reference
Yes	0.28	0.11-0.72	.008
Transfusion units >10
No	Reference
Yes	2.41	1.10-5.30	.028

CI, Confidence interval; HCT, hematocrit.

Kaplan-Meier survival curves of patients undergoing EVAR or open repair in the pre- and post-protocol era are shown in Fig 2. There was a significant difference in survival between pre- and post-protocol groups that favored the structured algorithm (P = .005). There was also a significant difference between EVAR and open groups in the post-protocol era favoring EVAR (P = .006).

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• Fig 2. 

  Kaplan-Meier survival curve up to 30 days for all three groups; pre-protocol open (green), post-protocol open (red), and post-protocol EVAR, Endovascular aneurysm repair (blue).

We evaluated the percentage of patients treated with EVAR and the resultant 30-day mortality by time periods. We furthermore evaluated the percentage of patients treated with EVAR by year and the 30-day mortality rate for both open surgery and EVAR by year. There is an overall trend for a higher percentage of patients treated with EVAR in the second year of the study (63.2% in year 2 vs 46.3% in year 1; P = .20). Similarly, there is a trend for improved survival of EVAR patients over time. The 30-day survival for EVAR patients in year 2 of the study is 91.7% (P= .14 comparing year 1 and year 2 in the EVAR group; Fig 3).

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• Fig 3. 

  The 30-day mortality for both open surgery and endovascular aneurysm repair (EVAR) by year in the post-protocol period. There is a trend for improved survival of EVAR patients over time (P = .14 comparing year 1 and 2 in the EVAR group).

In-hospital mortality 

Two patients surviving >30 days experienced in-hospital mortality. One patient in the pre-protocol group and 1 patient in the post-protocol EVAR group died in the hospital after 30 days. In-hospital mortality was 58.6% for pre-protocol, 54.2% for post-protocol open surgery, and 22.2% for post-protocol EVAR. For patients who did not die in the first 30 days, the mean hospital stay in the pre-protocol era was 31.3 days (range, 3-232), and the mean hospital stay in the post-protocol era was 18.63 days (range, 1-67). Although the time is shorter for the post-protocol group, this was not a statistically significant difference (P =.10). Within the post-protocol era, the mean hospital stay for patients with open surgery who did not die in the first 30 days was 27.4 days (range, 6-67) and 14.2 days (range, 1-57) for patients with EVAR. The difference between the two groups was statistically significant (P = .037).

Factors related to mortality for EVAR and open repair 

Patients undergoing EVAR tend to be younger than those who undergo open surgery (Table I - basic demographics), although this is not statistically significant. In both the pre- and post-protocol periods, mortality increases with increasing age and is statistically different (P = .008 in the pre-protocol era and P = .016 in the post-protocol era). In the post-protocol era, mortality is 0% for people under 70 in both the EVAR and open groups (Fig 4). In the post-protocol era, mortality is lower with EVAR than open repair for all ages.

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• Fig 4. 

  The 30-day mortality by age group. Mortality increases with increasing age (P = .008 in the pre-protocol era and P = .016 in the post-protocol era).

A higher proportion of patients undergoing EVAR are male (85.2%), compared to patients undergoing open surgery (70.8%); although this is not significantly different (P = .31). The small number of women undergoing EVAR (4 patients total) do not have the same reduction in mortality as their male counterparts. The women undergoing EVAR are all older, but this does not explain the disparity in mortality when one evaluates the overall relationship between age and mortality for the EVAR group above.

For patients presenting with SBP <80 mm Hg at any time before definitive intervention, there is a significant mortality risk for both pre- and post-protocol groups (Table III, Table IV). For patients having SBP greater than 80 mm Hg in the post-protocol era, survival is 100%. In the pre-protocol era, 65.4% of patients had a pre-hospital SBP <80 mm Hg and in post-protocol open-treated patients, it was 79.2% (P = .24).

Overall, serum HCT of ≤25% on presentation was associated with lower 30-day survival compared to HCT >25% (P < .001; Table III, Table IV). A similar trend was observed in the pre- and post-protocol era and in both the open surgery and EVAR arms, but this difference was not statistically significant. In the pre-protocol era, 21.9% of patients had an HCT <25%, and in post-protocol open-treated patients, it was 16.7% (P = .39). Within the post-protocol group, 30-day mortality for the 4 patients with HCT ≤25% treated with open repair was 100%, compared to only 37.5% for the 8 patients with HCT ≤25% in the EVAR group. In contrast, there was no significant association between serum creatinine and survival for either a cutpoint of 1.5 or 2.0 mg/dL (data not shown).

None of the comorbidities (coronary artery disease, hypertension, chronic obstructive pulmonary disease, renal insufficiency, and diabetes mellitus) were associated with mortality in any time period or group (data not shown).

The transfusion requirement in the pre-protocol era (mean = 10.6; range, 0-37) was significantly higher than in the post-protocol era (mean = 5.4; range, 0-19); P < .001. In the post-protocol era, the EVAR group had a mean transfusion requirement of 2.11 units (range, 0-13), and the open group had a mean requirement of 12.5 units (range, 2-19); P < .001.

Overall blood transfusion requirement was a significant predictor of mortality. Overall, there was no association with a cutoff of two units (OR = 1.26; 95% CI, 0.69-2.32; P = .45). There was an association with a cutoff of five units (OR = 1.92; 95% CI, 1.06-3.47; P = .032) and with a cutoff of 10 units (OR = 2.31; 95% CI, 1.21-4.39; P = .01). However, it is worth noting that within categories (ie, within pre-protocol, post-protocol open, and EVAR) there was no statistical difference in the number of transfused units between those who survived and those who died (all P > .4).

There was a trend for both rupture and transport times to be longer for patients who died within 30 days, although there was only a statistically significant association with mortality for transport time and not rupture time in patients with open surgery. In the pre-protocol era, the mean rupture time was 6 hours 55 minutes (range, 32 minutes-24 hours 0 minutes) for patients who survived to 30 days, and 6 hours 13 minutes (range, 5 minutes-23 hours 50 minutes) for patients who died within 30 days (P value comparing the two groups = .56). In the post-protocol era for patients undergoing open surgery, the average rupture time was 5 hours 35 minutes (range, 2 hours 40 minutes-12 hours 0 minutes) for patients who survived to 30 days, and 3 hours 54 minutes (range, 24 minutes-10 hours 27 minutes) for those who died (P = .28). For patients undergoing EVAR, the average rupture time was 8 hours 33 minutes (range, 45 minutes-23 hours 30 minutes) for patients who survived to 30 days, and 6 hours 37 minutes (range, 3 hours 7 minutes-8 hours 45 minutes) for those who died (P= .64).

In the pre-protocol era, the mean transport time was 1 hour to 23 minutes (range, 5 minutes-11 hours 32 minutes) for patients who survived to 30 days, and 52 minutes (range, 0 minutes-4 hours 24 minutes) for patients who died within 30 days (P value comparing the two groups = .059). In the post-protocol era for patients undergoing open surgery, the average transport time was 1 hour 56 minutes (range, 26 minutes-4 hours 50 minutes) for patients who survived to 30 days and 42 minutes (range, 8 minutes-3 hours 0 minutes) for those who died (P = .025). For patients undergoing EVAR, the average transport time was 1 hour 49 minutes (range, 13 minutes-10 hours 45 minutes) for patients who survived to 30 days and 1 hour 31 minutes (range, 43 minutes-4 hours 11 minutes) for those who died (P = .83).

The mean operative times for EVAR cases was 2 hours and 47 minutes (range, 1 hour 16 minutes-7 hours flat). It is important to note that operative time was calculated from the patient's arrival to the operating room until the patient exited from the operating room. There was no improvement in operative times for EVAR over the study period (2 hours, 15 minutes in year 1, 3 hours and 23 minutes in year 2). There was also no association between operative time and mortality for EVAR patients. The mean time was 2 hours and 48 minutes for those who survived 30 days and 2 hours, 40 minutes for those who died within 30 days (P = .86). Prolonged operative times for EVAR did not translate into an increase in mortality risk.

There are 9 patients listed as having cardiopulmonary resuscitation (CPR) in the pre-hospital time period, 4 in the pre-protocol group, 3 in the post-protocol open, and 2 in the post-protocol EVAR groups. None of the patients in the pre-protocol group survived, 1 of 3 in the post-protocol open group, and 2 of 2 in the post-protocol EVAR group survived. These numbers are too small to do any meaningful statistics, but there were indeed survivors among patients who had CPR before going to the operating room.

Transfemoral aortic occlusion balloons were placed in 21 patients over the entire study period. In the pre-protocol group, 4 patients had balloons placed. Two of these balloons were used for aortic occlusion and both patients died. Two were never inflated and 1 patient survived. In the post-protocol period, 17 patients had balloons placed. Nine were actually used to occlude the aorta; four in patients having open repair all of whom died (100%) and five in patients undergoing EVAR where only 1 patient died (20%). Eight balloons were placed and not used; three in patients having open repair where 1 patient died (33%) and five in patients undergoing EVAR where only 1 patient died (20%). Use of balloons in the open repair cohort was associated with a 71% mortality rate, whereas use in the EVAR cohort was associated with a 20% mortality rate (P = .03). There were no noted complications related to balloon occlusion.

Abdominal compartment syndrome (ACS) was documented in 32 patients over the study period. In the pre-protocol period, 24 patients had ACS (all open repairs) and 9 survived (62.5% mortality rate). In the post-protocol period, 8 patients had ACS; six open repairs with one survivor (83% mortality) and two EVARs with one survivor (50% mortality). One early endoleak (type 1) was initially undetected on completion imaging, and this patient died. This endoleak was identified on reoperation and conversion to open repair.

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Discussion 

Over 100 years ago, William Osler stated, “There is no disease more conducive to clinical humility than aneurysm of the aorta.” This statement has resonance for those practitioners involved in the current management of patients presenting with a diagnosis of rAAA. Recent large population-based studies have shown a significant benefit of endovascular repair over open repair for the elective management of patients presenting with aneurysmal disease.³ In an analysis of over 60,000 patients in the Medicare database between 2001 and 2004, endovascular repair was associated with significantly lower adverse perioperative outcomes to include death, medical, and surgical complications compared to open repair. In fact, a patient presenting with an aortic aneurysm was four times as likely to die, seven times as likely to undergo a tracheostomy, and 12 times as likely to undergo lysis of adhesions due to bowel obstruction with an open repair as compared to EVAR.³

Aortic aneurysms are repaired to prevent death due to rupture. The overall mortality of rAAAs is 85% (95% CI, 80%-91%) with nearly two-thirds of patients dying before reaching a hospital.¹⁰ For those patients surviving to undergo operation, the perioperative mortality rate is 41% to 48%.¹¹, ¹² This mortality rate for open repair of rAAAs has not changed significantly in over 2 decades.

EVAR for the repair of ruptured aneurysms (REVAR) has recently been increasingly utilized and published mortality rates with this approach vary between 24% and 46%.¹³, ¹⁴, ¹⁵ In a recent systematic review and meta-analysis, Mastracci et al¹⁶ identified the pooled mortality after REVAR to be 21% (95% CI, 13%-29%), but it was unclear whether this was due to publication bias or benefit of the technique. A significant finding in this review was that algorithms or structured protocols served as surrogates for an organized approach and could be an overall marker for good quality care. In studies that utilized a structured protocol, the mortality rate after REVAR was 18% (95% CI, 10%-26%), whereas in those studies without such protocols, the mortality rate was 32% (95% CI, 20-44). The current study strongly supports these findings. The implementation of a standardized protocol for the efficient evaluation and treatment of rAAAs is arguably at least as important as the introduction of REVAR for improvement in survival rates. Preparation is the hallmark of success to any emergency protocol.

In a large American population-based study analyzing 28,123 admissions for rAAA between 2001 and 2004, the utilization of REVAR increased from 6% to 11% with an associated decline in mortality from 43% to 29% over the same interval.¹⁷ Not surprisingly, the mortality rate from open repair did not change, 40% to 43%. Patients undergoing REVAR had lower mortality, shorter hospital stays, and were more likely to be discharged to home. Another interesting finding in this study was that mortality for REVAR was significantly lower in teaching hospitals (21%) vs nonteaching or community-based hospitals (55%).

There have been questions in the recent literature as to the true value of REVAR, and it has been cited as a “strategy in need of definitive evidence”.⁷ Hinchliffe et al⁷ reviewed 26 studies of REVAR vs open repair of rAAA between 1994 and 2009. Of all of these studies reviewed, not a single study demonstrated a significant difference in 30-day mortality between REVAR and open repair. The largest study reviewed, however, encompassed 56 patients, and the mortality varied across all studies between 0% and 53% for REVAR. The same review analyzed results from several large population-based studies, which did in fact demonstrate a significant benefit of REVAR over open repair in all studies.¹⁷, ¹⁸, ¹⁹, ²⁰, ²¹

A large review of our own experience with open repair of rAAA published by Johansen et al² in 1991, demonstrated a mortality rate that exceeded that of the national standard over the same time frame. Over a 10-year period ending in 1989, 186 patients with rAAA were managed at Harborview Medical Center. Ninety percent of patients had a pre-hospital SBP of <90 mm Hg on presentation. Factors associated with a >90% likelihood of death were age >80, female gender, hematocrit <25%, or transfusion requirement >15 units. No patient undergoing CPR survived >24 hours. The high mortality rate was attributed to the unique pre-hospital system in Seattle that brings patients to care faster than in other large urban centers, where similar patients would not survive longer transport times.

The results of our study are quite compelling in support of the use of structured algorithms for the management of patients presenting with rAAA. When comparing our own single-institution experience in the contemporary era, we reduced overall mortality from 57.8% to 35.3%. Unlike other studies, hypotension or hemodynamic instability on presentation was not used as a discriminator for candidacy for REVAR or open repair. Much like contemporary large population-based studies, our mortality from open repair did not change significantly between the two time periods (57.8%-54.2%). However, mortality associated with REVAR was an impressive 18.5%. We demonstrated an absolute risk reduction of 22.5% (95% CI, 6.8%-38.2%) with a relative risk reduction of 35% (95% CI, 14%-51%) and an OR of 0.40 (95% CI, 0.20-0.78). The association was still highly significant and clinically important after adjustment for key factors predicting mortality (adjusted OR = 0.25; 95% CI, 0.10-0.57). The Kaplan-Meier analysis for late survival is meaningful only in that there was no convergence of the survival curves in EVAR and open-treated patients. Therefore, once patient's survived the perioperative period, they behaved similarly, regardless of treatment. In the post-protocol period, as our experience increased, there was a trend for increased utilization of EVAR to treat rAAA from 46.3% of patients in year 1 to 63.2% in year 2 (P = .20). One might expect the mortality rate for open repair to actually rise in this setting due to the increased complexity of repairing ruptured para- and juxtarenal aneurysms or those with significant iliac calcification who were not candidates for EVAR. Our mortality rate for open repair did not change in the post-protocol period suggesting a positive effect of a structured algorithm on the open management of rAAAs.

In both the pre- and post-protocol periods of this study, mortality increased with increasing age. When we separated morality by EVAR vs open in the post-protocol era, we found that mortality was lower with EVAR for all age groups. A lower percentage of women underwent EVAR in this study, and those that did tended to have higher mortality rates, although the numbers were too small to rule out this being due to chance.

Never having SBP <80 mm Hg in the pre-hospital period was associated with 100% survival rate in the modern post-protocol era. This was true for both open treatment and EVAR groups. It seems intuitive that a more hemodynamically stable patient with a ruptured aneurysm would have a better overall outcome, and our results support this, although the 100% survival rate is based on only 19 patients. Overall, transfusion requirement was associated with survival rate; however, within each time period, there is no correlation between transfusion requirement and mortality. Part of what is at play is that the transfusion is lower in the post-protocol than in the pre-protocol, and in the post-protocol group, it is lower for EVAR than for open repair. When we looked at rupture times, there was evidence that longer rupture times were associated with better survival. This may be because those patients who are able to survive long rupture and transport times are inherently more stable than those who die en route. This statement, of course, is purely speculative.

Important specific considerations for implementing a structured algorithm for managing patients with rAAA can be divided into those involving the pre-hospital system and the index hospital admission. Pre-hospital considerations involve effective communication between pre-hospital personnel and the institution. Early notification is clearly paramount. Furthermore, education of pre-hospital personnel on the use of permissive hypotension, warming, and avoidance of intubation to avoid exacerbation of hemodynamic instability have become routine in our management of these patients.

Hospital considerations involve efficiency with the performance of REVAR. Those performing the procedure should be highly experienced and capable of performing EVAR in an expedient fashion in an area with equipment and personnel who can rapidly convert to an open repair if needed. At Harborview Medical Center, we are privileged to have a “rupture room” that is prepared and maintained after normal business hours and on weekends specifically for the endovascular management of ruptured aneurysms. Robust inventory is yet another hospital-specific consideration for implementing a REVAR program. The ability to place the appropriately sized components in any patient represents efficient use of resources and is best overall for the patient.

Changing routines and cultures within hospitals can be challenging. Required is a physician champion who is passionate about the disease process and willing to train other providers and staff to handle these emergencies. We have convinced our anesthesiologists to keep patients awake through the early phases of this process and believe that this has significantly affected mortality. The best overall anesthetic management strategy has yet to be elucidated but represents an area for future research. Also critically important are the circulating and scrub nurses. Streamlining instrument sets and simplifying processes help facilitate rapid and seamless care.

Limitations of this study include the relative small size of patients in the post-protocol period and the retrospective nature of the data collection on the historic control group. In addition, at the beginning of this study, a majority of vascular surgeons in our practice did not possess the endovascular skills required to independently perform EVAR. This led to a bias for open repair in a small number of patients early in the series. We anticipate that our mortality rates for both REVAR and open repair will actually decline even further as time goes on.

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Conclusions 

Endovascular repair of rAAAs saves lives. Implementation of a treatment algorithm with a preference for endovascular repair of rAAAs is associated with a highly significant reduction in 30-day mortality. Successful implementation of a structured protocol relies on a dedicated experienced team of physicians, nurses, and support staff, coordination of pre-hospital/preoperative care, ready availability of equipment for either open or endovascular repair, and robust in-house stent graft inventory. Hospitals caring for patients with rAAAs should have structured protocols in place and offer endovascular repair. In a single urban hospital utilizing modern techniques of resuscitation and surgical management, a majority of patients presenting with an rAAA can survive.

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Author contributions 

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References 

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