The peri-operative morbidity and mortality of open

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1 Ann Vasc Dis Vol.4,.4; 2011; pp Annals of Vascular Diseases doi: /avd.oa Original Article Open Repair of Infra Renal Abdominal Aortic Aneurysms: A Single Center Experience from the Developing World Nalaka Gunawansa, MBBS, MD, Thushan Goonerathne, Rezni Cassim, and Mandika Wijeyaratne Introduction: In the absence of endovascular aneurysm repair due to financial constraints, Abdominal Aortic Aneurysm (AAA) in Sri Lanka is managed exclusively by open surgery. We report our experience with open AAA repair with emphasis on peri-operative morbidity and mortality. Methods: Seventy nine consecutive open AAA repairs were carried out between April 2004 and March A multiple regression model was used to identify predictors of significant peri-operative morbidity and mortality. Results: Mean age of the study cohort was 68 years. There were 63 (80%) males and 16 (20%) females. Mean aneurysm diameter was 6.4 ( ) cm. Twenty seven (34%) underwent emergency surgical repair (group-1) while 52 (66%) had elective repair (group-2). The peri-operative mortality was 10/27 (37%) in group-1, 4/52 (7.6%) in group-2, (p = ). Significant post-operative morbidity was seen in 5/17 (29%) in group-1 and 7/48 (15%) in group-2, (p = 0.27). Aneurysm diameter >7 cm (p = 0.001), emergency repair (p = 0.004), history of smoking (p = 0.002), aortic cross-clamp time >60 minutes (p = 0.044), and need for post-operative ventilwation >24 hours (p = 0.024) were found to be independent predictors of peri-operative mortality or significant morbidity. Conclusion: Open aneurysm repair still has a strong place especially in the limited resource setting, with acceptable outcomes. Keywords: open aortic aneurysm repair, peri-operative morbidity and mortality, limited resource setting Introduction Department of Vascular Surgery and Organ Transplantation, National Hospital of Sri Lanka, Colombo, Sri Lanka Received: July 12, 2011; Accepted: September 12, 2011 Corresponding author: Nalaka Gunawansa, MBBS, MD. Department of Vascular Surgery and Organ Transplantation, National Hospital of Sri Lanka, Kynsey road, Colombo 8, Colombo, Sri Lanka Tel: , Fax: nalakagunawansa@yahoo.co.uk The peri-operative morbidity and mortality of open Abdominal Aortic Aneurysm (AAA) repair varies widely among different centers, depending on case volume and surgical expertise. Most high volume centers report an operative mortality rate of less than 5% for elective repair and 30% 50% for emergency repair. 1 3) There is also a severe dearth of published data on the operative outcomes of AAA in the developing world with limited resources. We, in the University Surgical Unit at the National Hospital of Sri Lanka (NHSL), are one of just three specialized vascular units in the country serving a population of 20 million. All three units function at the NHSL, which is the largest tertiary care hospital in the country situated in the capital Colombo, with a bed-strength of over There is approximately equal distribution of cases among the units with an annual case volume of each. This is a government sponsored national health care system with free health care for all. Even for the limited number of patients seeking private health care, costs of endovascular stenting are prohibitive. Hence, the management of AAAs in Sri Lanka is exclusively by open repair. We report our experience with open AAA repair in the era of endovascular stenting, with emphasis on peri-operative morbidity and mortality. Method We performed a retrospective analysis of prospectively collected data on all AAA referred to our unit between April 2004 and March The primary prospective database was supplemented by information retrieved from individual case notes and clinic records. An AAA Annals of Vascular Diseases Vol. 4,. 4 (2011) 313

2 Gunawansa N, et al. was defined as a focal dilatation of the infra-diaphragmatic aorta with a maximal diameter of over 3 cm on cross sectional imaging with Computerized Tomography (CT) scan. All thoraco-abdominal, supra-renal and isolated iliac aneurysms were excluded from the study. All patients with clinically apparent or suspected aneurysm rupture were offered surgical repair on an emergency basis. Among those who had no evidence of rupture, all symptomatic AAAs, mycotic aneurysms and asymptomatic aneurysms with a maximal diameter of over 5.5 cm on CT were offered elective surgical repair. Those who declined surgery, or were found to be poor surgical candidates with an unacceptable mortality risk due to overwhelming comorbidities (American Society of Anesthesiologists physical status classification; ASA P4 or worse) were managed conservatively. Those who had asymptomatic AAA with a maximum diameter of <5.5 cm were entered in to a conservative management program with risk factor modifications. This latter group was followed up at six monthly intervals with abdominal ultrasonography to monitor aneurysm expansion. Those who developed new symptoms, attributable to the aneurysm or had an aneurysm expansion rate of >0.5 cm per six months, were offered elective surgical repair. All open AAA repairs were preferentially carried out via a midline trans-peritoneal approach. Polyester (Dacron) grafts were used in 14 mm and 16 mm sizes depending on the healthy native aortic diameter. The graft morphology (tube versus bifurcated) was dependent on the extent of the aneurysm. Accordingly, simple aortic end to end repair was carried out in aneurysms confined to the aorta with a favorable common ostium at the iliac bifurcation while aorto-iliac or aorto-femoral end to side repairs were carried out for aneurysms extending in to the iliac arteries. The immediate post-operative care was in the surgical Intensive Care Unit (ICU) with selective ventilation. Subsequent care was in the general surgical ward. Following discharge, all patients were followed up as outpatients at approximately 2 4 week intervals for the first 3 months. The long-term follow up was either at the NHSL or the regional hospital of the patient s choice. All patients who underwent open aneurysm repair were studied further to identify possible markers of peri-operative morbidity and mortality. The variables studied were gender (male, female), age (<70, 70), history of smoking (yes, no), diabetes (yes, no), history of coronary artery disease; CAD (yes, no), preoperative renal impairment (Serum creatinine <120 µmol/l, 120 µmol/l), maximum aneurysm diameter on CT (<7 cm, 7 cm), nature of the surgery (elective, emergency), aortic cross-clamp time (<60 mins, 60 mins), operative blood loss (<1 L, 1L), and need for post-operative ventilation (<24 hours, 24 hours). In-hospital mortality and post-operative morbidity (day 0 30) was assessed using the Clavien-Dindo (CD) classification system for surgical complications. 4) Accordingly, In-hospital mortality (CD grade V) was taken as the primary end point while significant post-operative morbidity requiring surgical, radiological or endoscopic intervention (CD grade III) or life threatening organ dysfunction (CD grade IV) were taken as secondary end points. Categorical variables were summarized with frequencies and percentages. Continuous variables were summarized with the mean ± standard deviation. Univariate analysis was performed using Spearman s rank correlation in the case of continuous variables and Wilcoxon rank-sum tests in the case of binary variables. Multiple logistic regression analysis was used to identify risk factors for significant post-operative morbidity and perioperative mortality. Statistical analysis was performed using SPSS (version 15.1) software. Results A total of 141 successive patients with infra-renal AAA were managed in our unit during the study period. The demographic and baseline characteristics of the patient population are shown in Table 1. Among them, 33 (23%) had clinical evidence of aneurysm rupture on the first assessment. Six of these patients who were in profound shock succumbed prior to reaching the operating room while the remaining 27 (Group 1) underwent emergency surgical repair. One hundred and eight patients (77%) had no clinical evidence of aneurysm rupture and were managed electively. Among them, 32 (23%) were found to have asymptomatic AAA with a maximum diameter of <5.5 cm on CT scan. These patients were managed with risk factor modifications and ultra sound surveillance at six monthly intervals. Seventeen (12%) such patients have subsequently been lost to follow up while 7 developed new symptoms or were found to have significant aneurysm expansion and were operated on an elective basis. Of the remaining 8 patients, 4 have died due to unrelated causes while the other 4 continue to be on the surveillance program. Seventy six (54%) of the patients managed electively were either symptomatic or had a maximal aneurysm diameter of >5.5 cm and were considered for elective surgical repair. Twelve such patients declined surgical intervention while 19 were found to have unacceptable peri-operative mortality risk (vide infra) and were managed conservatively. 314 Annals of Vascular Diseases Vol. 4,. 4 (2011)

3 Open Repair of Abdominal Aortic Aneurysms Table 1 Baseline characteristics of the patient population (n = 141) Variable n % Age 70 years <70 years Gender Male Female Presentation Elective Emergency Co-existing conditions Coronary artery disease Diabetes mellitus Chronic obstructive pulmonary disease Impaired renal function History of smoking Hypertension The remaining 45 patients underwent elective AAA repair. Along with the 7 patients who were operated while on surveillance, the total number of elective surgical repairs was 52 (Group 2). Figure 1 summarizes the management of all AAA referred to our unit in the period studied. Demographic and baseline characteristics of the surgically repaired AAA (Group 1 & 2) are shown in Table 2. The primary reasons for patients being considered as having unacceptable peri-operative mortality risk for elective aneurysm repair were significant cardiac disease (congestive cardiac failure, unstable angina, recent myocardial infarction within 3 months or poor cardiac functional status), 15; severe Chronic Obstructive Pulmonary Disease (COPD) with poor lung function tests, 6; and chronic kidney disease stage IV or V with serum creatinine of >200 µmol/l, 7. Nine patients had more than one of the above risk factors. The mean age of those who underwent surgical repair was 68 years (range 35 86). Sixty three (80%) were male while the remaining 16 (20%) were female. The maximal aneurysm diameter among this group ranged from cm with a mean of 6.4 cm. There were three aneurysms operated with a maximal diameter of less than 5.5 (3.5, 4.1 and 4.2) cm due to clinical and radiological evidence of infection. All three presented with a history of fever, leukocytosis, elevated inflammatory markers and a saccular aneurysm on imaging. Infection in the aneurysm wall was proven by microbiological cultures from intra-operative samples taken in two of these aneurysms (Klebsiella species and mycobacterium tuberculosis), while the third failed to show any significant microbial growth in culture despite strong clinical suspicion. The clinical presentation at the time of being considered for surgical repair is summarized in Table 3. The mean operative time in group 1 was 4.7 hours Fig. 1 The breakdown of 141 patients with infra-renal AAA managed by our unit from April 2004 March Table 2 Baseline characteristics of patients who underwent open surgical repair (n = 79) Variable n % Age 68.3 ± years <70 years Gender Male Female Presentation Elective Emergency Co-existing conditions Coronary artery disease Diabetes mellitus 9 11 Chronic obstructive pulmonary disease Impaired renal function History of smoking Hypertension Aneurysm diameter <5.5 cm 6.4 ± cm 7 cm (range 3 6 hours) compared to 4.3 hours (range 3 7 hours) in group 2 (p >0.05). The operative time was calculated as total in room time spent in the operating theatre. The duration of post-operative ventilation was significantly different between the two groups, with 22/27 (80%) of group 1 being ventilated for more than 24 hours compared to 28/52 (54%) of group 2 (p <0.01). The mean duration of ICU stay was 4 (range 1 8) days and 2 days (range 1 5) for groups 1 and 2 respectively, (p <0.01). Annals of Vascular Diseases Vol. 4,. 4 (2011) 315

4 Gunawansa N, et al. Table 3 Clinical presentation of the repaired AAA n = 79 Presentation n % Asymptomatic; diameter > Diameter 5.5 cm Asymptomatic; with Expansion >0.5 cm/6months 1 1 Abdominal pain +/ back pain Symptomatic Back pain alone Claudication / distal gangrene 3 4 Abdominal pain/ back pain Rupture/ Leaking n = 27 collapse Primary aorto-intestinal fistula 1 1 Table 4 Basic comparison of ruptured AAA repaired on an emergency basis (Group 1) and nonruptured AAA repaired electively (Group 2) Variable Group 1 (n = 27) Group 2 (n = 52) p value Operative time 3.7 hrs (2 6) 3.5 hrs (2 7) p >0.05 Post-op ventilation beyond 24 hrs 22/27 (80%) 28/52 (54%) p <0.01 Post-op ICU stay 4d (1 8) 2d (1 5) p <0.01 In-hospital mortality Post-operative morbidity 10/27 (37%) 5/17 (29%) 4/52 (7.6%) 7/48 (15%) p <0.05 p >0.05 Table 4 summarizes the findings in groups 1 and 2. The in-hospital mortality was 10/27 (37%) in group 1 and 4/52 (7.6%) in group 2, (p = ). Among the 10 deaths in group 1, 6 died per-operatively due to massive hemodynamic disturbances and blood loss. The remaining 4 died while in the ICU due to myocardial ischaemia (2) and multi organ dysfunction (2). The causes of death in group 2 were myocardial ischaemia (2), acute bilateral subdural hemorrhage (1) and multi organ dysfunction (1). Significant post-operative morbidity was seen in 5/17 (29%) of group 1 and 7/48 (15%) of Group 2, (p = 0.27). The significant morbidities included myocardial ischaemia (5), pneumonia (5), acute kidney injury (3), acute lower limb ischaemia (3), colonic ischaemia (2) and burst abdomen (1). All three patients with acute kidney injury required temporary dialysis and recovered completely between days. Two patients with acute limb ischaemia were successfully treated by embolectomy and fasciotomy respectively while the third patient required a below knee amputation. One patient with colonic ischaemia required laparotomy and colonic resection while the other who had mild ischaemic colitis responded to conservative management. Multivariate analysis of risk factors (Table 5) showed an aneurysm diameter 7 cm (p = 0.005), emergency surgical repair (p = 0.011), aortic cross-clamp time 60 minutes (p = 0.034), and the need for post-operative ventilation 24 hours (p = 0.021), as independent predictors of in-hospital mortality and significant post-operative morbidity. Other variables studied including age, gender, history of smoking, diabetes, hypertension, renal insufficiency and operative blood loss did not show statistical significance. Discussion This is an audit of 141 consecutive AAA managed in our unit during a period of 6 years. Our indications for surgical intervention were in accordance with internationally accepted protocols and recommendations. 5 8) Approximately one quarter of the AAA referred during the study period had clinical or radiological evidence of aneurysm rupture at first presentation. The in-hospital mortality for emergency repair of ruptured AAA was 37%. In addition, non-fatal significant post-operative morbidities were encountered in 29%. Among those who underwent elective surgical repair, the in-hospital mortality and significant post-operative morbidity rates were 7.6% and 15% respectively. The reported incidence of peri-operative adverse events in open AAA repair varies widely in the literature. A metaanalysis of the reported literature showed a 30-day operative mortality rate for elective infra-renal AAA repair ranging between 1.4% and 6.5%. 9) For ruptured AAA, the reported mortality rate ranges between 23% and 69%. 2, 9, 10) While certain high-volume centers of excellence report very low mortality rates (from 0% to 1.2%), 3, 11, 12) multi-institutional nationwide data continue to show significantly higher incidence of mortality ranging between 4.2% and 8.4%. 11, 12) This discrepancy has been seen as a result of the case volume related difference in outcome. Many reports have identified a strong relationship between the operative outcome and case volume of the individual surgeon or the institution. Birkmeyer and colleagues 13, 14) reported elective AAA repair mortality rate of 7.8% for low volume centers (<17/year), as opposed to 4.9% in high volume (>79/year) centers. Our own elective aneurysm repair mortality rate 316 Annals of Vascular Diseases Vol. 4,. 4 (2011)

5 Open Repair of Abdominal Aortic Aneurysms Table 5 Multivariate analysis of risk factors for peri-operative adverse events Variables Total AAA Operative mortality and repairs (N) morbidity n (%) Gender; Male (29) Female 16 8 (50) Age; 70y (34) <70y (31) History of smoking ; (43) (19) Diabetes; (44) (31) CAD; (33) (33) COPD; 29 9 (31) (34) Renal insuff.; (38) (32) AAA diameter ; 7 cm (59) <7 cm (13) Surgery; Emergency (67) Elective (15) Aortic cross clamp; 60 mins (58) <60 mins (12) Operative blood loss; 1 L (30) <1 L (34) Perop. blood transfusion; (28) (50) Periop. Myocardial isch.; 9 9 (100) (24) Postop ventil.; 24 hrs (61) <24 hrs (15) CAD: coronary artery disease; COPD: chronic obstructive airway disease Univariate analysis Multivariate analysis p OR (95% CI) p of 7.6% with a case volume of per year compares favorably with these findings. Despite many recent advances in surgical and anesthetic peri-operative management, the operative mortality after open repair of ruptured AAA has remained fairly constant. A meta-analysis by Hoornweg and colleagues 15) in 2008 which included over 100 studies and approximately patients with ruptured aneurysms showed an overall mortality rate of 48.5% for open repair. This high mortality rate is probably related to factors such as delay in recognition and intervention, extreme hemodynamic instability, profound blood loss and suboptimal peri-operative care in the emergency setting. 16, 17) The situation is no different in Sri Lanka where all suspected ruptured AAAs are referred and transferred to the NHSL for definitive care. The average travel time for transfers is around 6 hours with distances that may exceed 250 km. Further, there is very limited critical care support during transfer with only basic support available in the ambulance systems. In addition, many such patients initially present to and are investigated in nonspecialized units prior to vascular surgical referral causing considerable delay in definitive intervention. Furthermore, the logistical difficulty in obtaining emergency access to the operating theatre confounds the problem. Despite being the largest tertiary hospital in the country, there is no dedicated operating facility for vascular surgical emergencies. A single casualty operating room is shared among all general surgical emergencies including vascular emergencies. There is limited intensive care back up with only 8 ventilator beds available for elective and emergency surgical admissions. Despite a falsely reassuring 37% mortality for operated ruptured AAA compared to the international figures, the overall mortality for all ruptured aneurysms referred to our unit during this period is 48.5% (16/33). Various factors have been reported as predictive factors for peri-operative adverse events after elective open AAA repair. These include advanced age, large aneurysm diameter, pre-operative renal dysfunction, history of smoking, COPD, CAD, prolonged aortic cross-clamp time, greater operative blood loss and intra-operative myocardial ischaemia. 6, 18 21) While COPD and intraoperative myocardial ischaemia were not studied separately, we did not find gender, age, pre-operative renal dysfunction, diabetes and CAD to be independently predictive of peri-operative adverse events in our study population. History of smoking and greater operative blood loss showed a positive association with morbidity and mortality, albeit not statistically significant. However, Annals of Vascular Diseases Vol. 4,. 4 (2011) 317

6 Gunawansa N, et al. aneurysm diameter 7 cm, emergency surgical repair, aortic cross-clamp time 60 minutes and the need for post-operative ventilation 24 hours were found to be independent predictors of in-hospital mortality and significant post-operative morbidity. One limitation in the present study is its retrospective nature. However, with a comprehensive prospective data base maintained since 2002, supplemented by retrieved individual case records, we believe that the data included in the study was complete and representative with minimal bias. Another possible limitation is that we have not considered aneurysm morphology (saccular or fusiform), possible infective or inflammatory aetiology, COPD and intra-operative myocardial ischaemia as separate variables in our analysis. Aggressive investigation of all patients with cardiac enzyme assays was also not carried out in the absence of clinical justification. In addition, even though operative blood loss was considered in the analysis, we have not considered the transfusion needs or its effects. In conclusion, the management of AAA in Sri Lanka at present is almost exclusively by open surgical repair. Ours unit is one of only three specialized units in the country managing AAA with approximately equal distribution of cases numbering per year. A collective nationwide audit has not been possible as there were no published records from the other centers up to the time of writing. Our observed operative mortality and morbidity rates for open repair of infra-renal AAA compare favorably with the reported figures in the literature for both ruptured as well as non-ruptured aneurysms. References 1) Heller JA, Weinberg A, Arons R, et al. Two decades of abdominal aortic aneurysm repair: have we made any progress? J Vasc Surg 2000; 32: ) Verhoeven EL, Kapma MR, Groen H, et al. Mortality of ruptured abdominal aortic aneurysm treated with open or endovascular repair. J Vasc Surg 2008; 48: Epub 2008 Oct 1. 3) Hertzer NR, Mascha EJ, Karafa MT, et al. Open infrarenal abdominal aortic aneurysm repair: the Cleveland Clinic experience from 1989 to J Vasc Surg 2002; 35: ) Clavien PA, Barkun J, de Oliveira ML, et al. The Clavien-Dindo classification of surgical complications: five-year experience. Ann Surg 2009; 250: ) Katz DA, Littenberg B, Cronenwett JL. Management of small abdominal aortic aneurysms. Early surgery vs watchful waiting. JAMA 1992; 268: ) Brewster DC, Cronenwett JL, Hallett JW Jr, et al. Guidelines for the treatment of abdominal aortic aneurysms. Report of a subcommittee of the Joint Council of the American Association for Vascular Surgery and Society for Vascular Surgery. J Vasc Surg 2003; 37: ) Eliason JL, Clouse WD. Current management of infrarenal abdominal aortic aneurysms. 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Age versus comorbidities as risk factors for complications after elective abdominal aortic reconstructive surgery. J Vasc Surg 2001; 33: ) Roger VL, Ballard DJ, Hallett JW Jr, et al. Influence of coronary artery disease on morbidity and mortality after abdominal aortic aneurysmectomy: a populationbased study, J Am Coll Cardiol 1989; 14: Annals of Vascular Diseases Vol. 4,. 4 (2011)