Evaluation and treatment of ruptured abdominal aortic aneurysm

Ruptured abdominal aortic aneurysm (rAAA) should be considered in all patients over 50 and those with a known AAA presenting with abdominal or back pain and hypotension Standardized protocols, clear communication, and interdisciplinary training are essential to optimize outcomes Permissive hypotension with restrictive intravenous fluid administration is recommended pre- and perioperatively Endovascular aneurysm repair is the preferred treatment option for anatomically suitable patients with rAAA. However, anatomical limitations necessitate careful case selection. Post repair patients should be monitored in the intensive care unit, with vigilance for the development of intestinal ischaemia Abdominal aortic aneurysm (AAA) can have potentially life-threatening complications. Although the prevalence and incidence of AAA vary regionally and nationally, in most high-income countries incidence has peaked and then declined over the last two decades1. This development is thought to be largely due to advances in pharmacological cardiovascular risk optimization and a reduction in the co-prevalence of modifiable risk factors such as smoking and hypertension2,3. Contemporary screening studies report a prevalence of AAA among men aged >65 years ranging from 1.2% in the UK to 1.7% in Sweden and 2.8% in the USA4–6. Corresponding with declining trends in AAA incidence, changes in cardiovascular risk patterns, and the increasing adoption of preventive elective repair through screening programmes, has resulted in a decrease in the incidence and mortality from ruptured AAA (rAAA). The widespread introduction and adoption of endovascular aneurysm repair (EVAR) has been a critical factor in reducing rAAA-related mortality rates7. Although randomized trials failed to demonstrate a significant survival benefit for EVAR in rAAAs, cumulative evidence suggests improved outcomes compared to open surgical repair, particularly in older populations8–12. Despite these encouraging trends, rAAAs remain associated with substantial mortality, with 30–50% of patients dying within 30 days. Women, excluded from AAA screening programmes, and current smokers are disproportionately affected13–15. Furthermore, the decline in rAAA cases has resulted in fewer opportunities for multidisciplinary teams to maintain expertise in the management of acute aortic cases. Therefore, standardized approaches with streamlined protocols for the initial treatment and management of rAAA are essential to improve outcomes. Patients with rAAA can present with a wide range of symptoms, including acute abdominal or back pain, pain radiating to the scrotum, circulatory instability, and haemodynamic shock. However, due to the non-specific nature of these symptoms, misdiagnosis may occur in one-third of cases, as only 25–50% of patients present with the classical triad of acute abdominal pain, a pulsatile abdominal mass, and hypotension16–18. The lower prevalence of rAAA compared to more common differential diagnoses, such as myocardial infarction, complicates its identification. The Royal College of Emergency Medicine (RCEM) recommends considering rAAA in patients over 50 years old presenting with abdominal or back pain and hypotension, as well as in patients with a known AAA who present with abdominal or back pain, hypotension, or collapse. In patients in whom an alternative diagnosis is considered more likely on the basis of clinical symptoms, rAAA must still be excluded radiologically19. Ultrasound has become a standard AAA screening modality. However, it is of limited value in the emergency assessment of patients with a suspected rAAA, as it has a low sensitivity to identify retroperitoneal haemorrhage and does not provide anatomical information to guide treatment selection. Therefore, the standard diagnostic modality in stable patients with rAAA is contrast-enhanced CT (Figure 1). This diagnostic evaluation will not cause significant delay to treatment20,21. Not only does CT identify intraperitoneal or retroperitoneal haemorrhage, it can also define the aortic morphology and other related vessels. Important anatomical considerations that can be seen on the CT scan include: the size of the aortic neck diameter, angulation, iliac vessel size and condition (for example iliac occlusion or aneurysm), and other important anatomical morphologies (for example retroaortic left renal vein). These are crucial for evaluating anatomic suitability for endovascular repair for rAAA (rEVAR) or open surgical repair (OSR)20. If the patient is haemodynamically unstable, direct transport to the operating theatre for emergency OSR or intraoperative angiography with subsequent assessment of suitability for EVAR may be performed. CT scan of an 81-year-old patient with a ruptured abdominal aortic aneurysm The Society of Vascular Surgery’s proposed management algorithm for patients with suspected or confirmed rAAA is shown in Fig. 220. Permissive hypotension with restrictive intravenous fluid administration has gained attention in clinical practice. An alert patient with a systolic pressure between 70 and 90 mmHg should be maintained. Administering large volumes of intravenous fluids in response to initial hypotension can be harmful. Rapid infusion and a sudden rise in systolic pressure may disrupt clots, dilute clotting factors, platelets, and fibrinogen, as well as lower body temperature, which can significantly impair enzyme activity critical for haemostasis22. However, blood products consisting of plasma, platelets, and red blood cells in 1 : 1 : 1 composition should be prepared immediately20. Proposed algorithm for managing patients with ruptured abdominal aortic aneurysms, adapted from Fig. 5 of the Society for Vascular Surgery practice guidelines: ‘Algorithm for management of the patient with a suspected or confirmed ruptured abdominal aortic aneurysm’ published in Journal of Vascular Surgery, January 2018, Volume 67, Issue 1, pages 2–77 Although the diagnostic work-up should not delay the transfer and treatment of the patient, an ECG and laboratory investigations (complete blood count, serum electrolytes, creatinine, troponin, blood gas) should be considered. Centralization of vascular services often mean that patients have to be transferred from smaller district hospitals to larger vascular centres. In such cases, a well-coordinated interhospital transfer to high-volume centres or teaching hospitals plays a crucial role in successful management21,23. Wherever possible, decisions about treatment and transfer should be made in close consultation with the patient and their family. Consultant-to-consultant referral is preferred, with the most senior doctor available managing the patient’s care. Paramedic crews are encouraged, but not required, for transfer. Prior to the transfer, a critical assessment of the suitability of the patient for transfer must be performed. The RCEM recommends that patients ≤85 years of age, alert or with fluctuating consciousness, with no to moderate systemic disease should be referred without delay to the receiving hospital’s on-call vascular service19,24,25. However, not all patients should be referred for transfer, particularly those unlikely to survive the transport process, such as individuals in cardiac arrest, those requiring intubation or vasoactive medications, or patients institutionalized due to severe physical infirmity. Additionally, patients who have opted for palliative care should not be referred. Given the complexity of assessing suitability for transfer, it is important to note that level of consciousness, blood pressure, and premorbid condition are more relevant than age alone in assessing suitability for transfer25. The mortality rate before reaching the hospital can reach two-thirds of cases, and the remaining 20% may deteriorate before operative treatment. Even with surgery, the mortality rate is still considered high for some patient subgroups26. Palliative treatment for those groups of patients is acceptable. Early patient risk assessment should be done to help the patient choose either to proceed with surgical repair or receive palliative treatment. There are several prognostic scoring systems to predict postoperative outcomes in rAAA (Table 1). Different prognostic scoring systems to predict mortality in patients with rAAA Age >76 years Haemoglobin level < 9 g/dl Serum creatinine concentration >190 mmol/L Ischaemic changes on an electrocardiogram History of loss of consciousness Glasgow Coma Scale score <15 Systolic blood pressure <90 mmHg Preoperative haemoglobin <9 g/dl Age >76 years Systolic blood pressure <70 mm Hg pH < 7.2 Creatinine >2.0 mg/dl Age >76 years Haemoglobin level < 9 g/dl Serum creatinine concentration >190 mmol/L Ischaemic changes on an electrocardiogram History of loss of consciousness Glasgow Coma Scale score <15 Systolic blood pressure <90 mmHg Preoperative haemoglobin <9 g/dl Age >76 years Systolic blood pressure <70 mm Hg pH < 7.2 Creatinine >2.0 mg/dl Different prognostic scoring systems to predict mortality in patients with rAAA Age >76 years Haemoglobin level < 9 g/dl Serum creatinine concentration >190 mmol/L Ischaemic changes on an electrocardiogram History of loss of consciousness Glasgow Coma Scale score <15 Systolic blood pressure <90 mmHg Preoperative haemoglobin <9 g/dl Age >76 years Systolic blood pressure <70 mm Hg pH < 7.2 Creatinine >2.0 mg/dl Age >76 years Haemoglobin level < 9 g/dl Serum creatinine concentration >190 mmol/L Ischaemic changes on an electrocardiogram History of loss of consciousness Glasgow Coma Scale score <15 Systolic blood pressure <90 mmHg Preoperative haemoglobin <9 g/dl Age >76 years Systolic blood pressure <70 mm Hg pH < 7.2 Creatinine >2.0 mg/dl Some scores rely on preoperative parameters whereas others include intraoperative conditions. One of the most widely used is the Hardman index. Additionally, more recent scores such as the Harborview Medical Center Score or the Dutch Aneurysm Score have shown satisfactory performance in predicting postoperative survival in real-world situations32–34. The Harborview Medical Center Score only includes preoperative measurements and therefore may be helpful to guide treatment and transfer decisions. However, as none of the scoring systems is sufficiently accurate to deny repair, they should not be the sole factor in decision-making7. There are currently no specific guideline available for the palliative treatment of rAAA. The evidence and recommendations in palliative care for rAAA patient also remain scarce35. However, patients who decide to choose palliative treatment should be given pharmacological symptomatic relief and an end-of-life care36. If possible, the patient might also be discharged home with anticipatory symptomatic medications (for example paracetamol, midazolam) as well as community palliative care follow-up37. For those who are proceeding to intervention, endovascular repair has become the treatment of choice for AAA management. A haemodynamically unstable patient should be transferred directly to the c-arm-equipped operating room/hybrid theatre for haemorrhage control. rEVAR is considered a minimally invasive treatment and can be performed fully using local anaesthesia (LA) alone, which in turn reduces the possible side effects of general anaesthesia (GA) agents leading to faster recovery after the operation. GA can cause relaxation of tissues, releasing the tamponade effect on bleeding and exacerbating the loss of vascular tone, potentially leading to haemodynamic instability38. Therefore, the use of LA should be encouraged, especially because LA has been associated with a relative mortality rate reduction of 38%39. Ultrasound-guided percutaneous access should be chosen compared to femoral artery cutdown. As previous studies have shown that approximately 30% of patients undergoing rEVAR become haemodynamically unstable, proximal aortic control may be attempted by compliant aortic balloon occlusion (ABO) in the supracoeliac abdominal aorta40,41. However, the existing evidence on ABO is weak, with no definite reduction in bleeding-related deaths. This is an area where further prospective research is needed to assess the potential benefit and safety of ABO in rAAA42,43. A critical factor in performing rEVAR is the extent of stent graft oversizing, as hypovolaemia-induced hypotension may lead to an aortic diameter decrease. In order to prevent type Ia or Ib endoleaks, 30% stent graft oversizing is recommended in patients who have undergone imaging in the setting of permissive hypotension44. The choice of endograft for rEVAR is fully determined by aortoiliac morphology as there is no proven superiority of one manufacturer over another. An aorto-uni-iliac stent graft with a femoro-femoral cross-over bypass can be chosen for significant unilateral iliac occlusive disease or tortuosity, or if the contralateral femoral artery cannot be accessed (Figure 3). Intraoperative angiogram after ruptured endovascular aneurysm repair (rEVAR) When rEVAR cannot be performed due to unavailability of facilities and devices, or due to unsuitable anatomy (short or angulated landing zone, excessive thrombus, multiple large accessory renal arteries, problems in ilio-femoral access), OSR is the only surgical option (Figure 4). Open rAAA repair can be performed by a transperitoneal or retroperitoneal approach. Transperitoneal approach offers rapid access to the infrarenal aorta and is ideal in emergencies but should not be used in a hostile abdomen due to prior abdominal surgery. In suprarenal AAA, a retroperitoneal approach may be used as the exposure can be extended into the thoracic aorta, especially when encountering a thoracoabdominal aortic aneurysm20. If there are conditions mandating upper proximal abdominal aorta control like pararenal or short neck infrarenal, supracoeliac aortic clamping can be used. For exposure, dissection is done separately from the primary inframesocolic exposure, by dividing the lesser omentum or gastrohepatic ligament, and supracoeliac. Although supracoeliac clamping offers several advantages, such as potentially less-extensive atherosclerotic disease and the avoidance of extensive mobilization of the left renal vein for control, it also induces ischaemia of the abdominal visceral organs45. Intraoperative images Clamping should be placed in the most distal location and should be done time-efficiently as clamping induces ischaemic injuries to the distal abdominal organs from the clamping area. Moreover, the clamping and unclamping procedure requires coordination with the anaesthesiologist to avoid sudden changes in blood pressure and haemodynamic stability. After clamping, the aortic neck is dissected, and the diseased segment of the aorta is replaced with a graft, followed by bilateral iliac anastomosis. Because rAAA carries a significant risk of severe haemorrhagic shock, several strategies should be employed to minimize blood loss. These include permissive hypotension, rapid patient transfer, preparation of plasma and platelet products, prioritizing rEVAR over OSR, and favouring percutaneous access over open femoral cutdown. Additionally, the use of cell salvage may reduce the overall need for blood transfusion, thereby improving survival outcomes46. Some advocate using tranexamic acid intraoperatively. Four RCTs comparing rEVAR and OSR have been conducted to date, all finding no statistical differences in perioperative mortality rates8–11. When summarizing the existing evidence on this topic, a notable contradiction emerges between the pooled results of observational studies, registries, and RCTs. Evidence from observational studies indicate that rEVAR improves short-term survival, whereas pooled RCTs (ECAR, IMPROVE, AJAX) fail to demonstrate a similar advantage12,47. Regarding long-term survival, pooled data from IMPROVE, AJAX, and ECAR indicated a consistent, albeit statistically non-significant, trend favouring rEVAR48. Similarly, three large cohort studies from Sweden49 and the USA50,51, as well as a meta-analysis involving 31 383 patients, demonstrated a significant long-term survival advantage for rEVAR12. In summary, both large population-based studies and RCTs support a survival benefit of rEVAR. When combined with considerations such as cost-effectiveness, improved quality of life, and shorter hospital stays50, rEVAR is currently recommended as the preferred treatment option for anatomically suitable patients. Patients should be admitted to the intensive care unit post surgery for close monitoring, as potential complications may affect multiple organ systems. Serial intra-abdominal pressure (IAP) monitoring should be performed as intra-abdominal hypertension or abdominal compartment syndrome (ACS) can occur. It is defined as when there is sustained or repeated elevation of IAP >12 mmHg, or >20 mmHg with new onset of organ dysfunction or failure for the latter. A serious complication of both rEVAR and OAR is bowel ischaemia, with a pooled analysis of 101 studies showing a prevalence of clinically relevant bowel ischaemia of nearly 10% in rAAA patients52. In patients with suspected colonic ischaemia, serial clinical assessments, IAP monitoring and early sigmoidoscopy and exploratory laparotomy are recommended. Deep venous thrombosis can occur post surgery; therefore, a prophylactic dose of anticoagulant should be initiated within 24–48 h after surgery. If there is ongoing bleeding or significant coagulopathy, mechanical prophylaxis using compression devices can be used until anticoagulant contraindication subsides53. Other common perioperative complications are myocardial infarction, acute kidney injury, respiratory complications, and acute lower limb ischaemia. rAAAs pose a significant challenge, with high mortality rates and complex clinical presentations and treatment. EVAR has emerged as the preferred treatment strategy for many patients due to its minimally invasive nature and reduced recovery time compared to open surgical repair. However, anatomical limitations necessitate careful selection of treatment strategies. Standardized protocols, clear communication, and interdisciplinary training are essential to optimize outcomes. The authors have no funding to declare. The authors declare no conflict of interest.