Ruptured Abdominal Aortic Aneurysm

Overview

Ruptured abdominal aortic aneurysm (rAAA) represents one of the most time-critical vascular emergencies, with overall mortality rates of 65-85% including pre-hospital deaths. [1,2] The condition occurs when an infrarenal aortic aneurysm exceeds the tensile strength of the vessel wall, leading to extravasation of blood into the retroperitoneum or free peritoneal cavity. The classic clinical triad of sudden severe abdominal or back pain, hypotension, and palpable pulsatile abdominal mass is present in only 25-50% of patients, necessitating a high index of suspicion in any elderly patient presenting with collapse and abdominal symptoms. [3]

Immediate recognition and urgent transfer to a vascular centre for emergency repair represent the only chance of survival. The management paradigm has evolved significantly with the introduction of endovascular aneurysm repair (EVAR) for ruptured aneurysms and the adoption of permissive hypotension strategies during resuscitation. Contemporary evidence from the IMPROVE trial demonstrates that an EVAR-first strategy in anatomically suitable patients offers equivalent 30-day mortality to open repair with improved quality of life outcomes. [4]

Time to definitive surgical intervention remains the single most important determinant of survival, with every hour of delay associated with increased mortality. The combination of rapid diagnosis, judicious resuscitation avoiding aggressive fluid administration, and immediate vascular surgical involvement forms the cornerstone of optimal management. For patients who survive to hospital discharge, long-term outcomes depend heavily on management of comorbidities and secondary prevention of cardiovascular events. [5]

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Epidemiology

Incidence and Prevalence

The annual incidence of ruptured AAA in developed countries ranges from 4 to 10 per 100,000 population, representing approximately 1-2% of all deaths in men over 65 years. [6] In the United Kingdom, approximately 6,000-8,000 ruptured AAA cases occur annually, with around 2,000 patients surviving to hospital discharge. [7] The implementation of national AAA screening programmes has led to a reduction in rupture rates by detecting and electively repairing aneurysms before rupture.

Population-based screening data from the UK NHS AAA Screening Programme demonstrates a prevalence of AAA (diameter ≥3.0 cm) of 1.5% in 65-year-old men. [8] Of detected aneurysms, the annual rupture risk is stratified by diameter: less than 1% for aneurysms 3.0-4.4 cm, 1-3% for 4.5-5.4 cm, 3-15% for 5.5-6.9 cm, and over 20% for aneurysms ≥7.0 cm. [9]

Demographics

Risk Factors for Rupture

Major Risk Factors:

• Aneurysm diameter (most important modifiable factor) [9]
• Female sex (rupture at smaller diameters, higher mortality) [10]
• Smoking (current smokers have 3-5× higher risk) [12]
• Hypertension (especially systolic > 160 mmHg) [13]
• Chronic obstructive pulmonary disease [14]
• Family history of AAA (first-degree relative) [15]

Minor Risk Factors:

• Rapid aneurysm expansion (> 5 mm in 6 months)
• Cardiac transplant recipients (high rupture risk)
• High wall stress on biomechanical imaging [16]

Impact of Screening Programmes

The UK NHS AAA Screening Programme, offering one-time ultrasound screening to all men at age 65, has demonstrated a 42% reduction in AAA-related mortality in the screened population. [8] Similar programmes in Sweden, Australia, and the United States have shown comparable benefits. Women are not routinely screened due to lower prevalence (0.5% in 65-year-old women), but selective screening is recommended for women with strong cardiovascular risk factors or family history.

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Aetiology and Pathophysiology

Molecular Pathogenesis

Exam Detail: Abdominal aortic aneurysm formation represents a multifactorial degenerative process characterized by:

1. Extracellular Matrix Degradation

• Increased activity of matrix metalloproteinases (MMP-2, MMP-9) [17]
• Reduced tissue inhibitors of metalloproteinases (TIMPs)
• Progressive elastin fragmentation and collagen breakdown
• Loss of structural integrity in the media and adventitia

2. Chronic Inflammatory Infiltration

• Macrophage and T-lymphocyte infiltration of vessel wall
• Release of pro-inflammatory cytokines (IL-6, TNF-α, IL-1β)
• Oxidative stress and free radical production
• Neovascularization of the aneurysm wall [17]

3. Vascular Smooth Muscle Cell Dysfunction

• Apoptosis and depletion of medial smooth muscle cells
• Phenotypic switching from contractile to synthetic state
• Impaired extracellular matrix synthesis
• Loss of normal vessel wall architecture

4. Biomechanical Factors

• LaPlace's law: Wall tension = (Pressure × Radius) / Wall thickness
• Larger diameter aneurysms experience exponentially higher wall stress
• Turbulent flow and increased shear stress
• Intraluminal thrombus formation (protective or pathologic remains debated)

Rupture Mechanism

Rupture occurs when wall stress exceeds the tensile strength of the diseased aortic wall. The relationship follows LaPlace's law, where wall tension increases proportionally with aneurysm radius and transmural pressure. Critical biomechanical studies demonstrate that peak wall stress, rather than diameter alone, more accurately predicts rupture risk. [16]

Classification of Rupture Patterns

The retroperitoneum can accommodate 2-4 litres of blood before tamponade effect is lost. This "contained rupture" provides a crucial therapeutic window but remains unstable and can progress to free rupture at any moment. Approximately 25% of contained ruptures will progress to free rupture within 24 hours if not surgically treated. [3]

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Clinical Presentation

Classic Triad (Present in Only 25-50%)

The traditional teaching emphasizes three cardinal features, but their absence does not exclude the diagnosis:

All three features together are present in only 25-50% of cases, particularly in unstable patients. [3] The absence of the full triad should never be used to exclude ruptured AAA in the appropriate clinical context.

Typical Presentation Patterns

Catastrophic Presentation (Free Rupture):

• Sudden onset of severe, tearing abdominal or back pain
• Rapid progression to cardiovascular collapse
• Pallor, diaphoresis, altered consciousness
• Profound hypotension (SBP less than 90 mmHg)
• Abdominal distension with peritonism
• Often moribund on arrival

Contained Rupture Presentation:

• Severe constant abdominal or back pain (may wax and wane)
• Pain radiating to flanks, groin, or legs
• Patient may be relatively stable initially
• Tachycardia disproportionate to blood pressure
• Abdominal tenderness, guarding
• Grey Turner's sign (flank ecchymosis) - late finding

Atypical/Misleading Presentations: Ruptured AAA is frequently misdiagnosed initially, with common alternative diagnoses including:

Red Flag Combinations:

• Age > 50 + collapse + abdominal/back pain = rAAA until proven otherwise
• Known AAA + new abdominal pain = assume rupture
• Syncope + back pain in elderly patient = urgent AAA evaluation
• Renal colic presentation without haematuria in patient > 65 = consider AAA

Physical Examination Findings

General Appearance:

• Pallor, diaphoresis, distress
• Altered mental status (confusion, agitation, drowsiness)
• Position of comfort (often still, unlike renal colic)

Vital Signs:

• Tachycardia (HR > 100 bpm in 80%)
• Hypotension (variable - may be normotensive with contained rupture)
• Tachypnoea
• Pulse pressure may be widened in chronic AAA

Abdominal Examination:

• Pulsatile expansile mass (epigastric/periumbilical)
  • Expansile quality (expands laterally, not just pulsates)
  • Size often underestimated or not detectable (sensitivity 30-50%)
  • More difficult in obese patients (BMI > 30)
• Abdominal tenderness (diffuse or localized)
• Abdominal distension (intraperitoneal blood)
• Peritonism (guarding, rigidity, rebound) suggests free rupture
• Absent bowel sounds

Peripheral Examination:

• Cool, mottled extremities
• Delayed capillary refill
• Femoral pulses usually present (absence suggests aortoiliac occlusion)
• Lower limb ischaemia (rare, suggests embolization)

Special Signs:

• Grey Turner's sign (flank ecchymosis) - late, rarely seen acutely
• Cullen's sign (periumbilical ecchymosis) - rare
• Femoral vein distension (suggests aortocaval fistula)

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Differential Diagnosis

Life-Threatening Differentials ("Must Not Miss")

Ruptured AAA must be distinguished from other acute abdominal catastrophes:

Common Mimics

Clinical Pearls for Differentiation:

• Age > 65 with abdominal pain + haemodynamic instability = rAAA first
• Absence of haematuria in "renal colic" over age 60 = rAAA
• Known AAA + any new abdominal symptoms = assume rupture
• Consider bedside ultrasound to rapidly exclude/confirm AAA

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Investigations

Haemodynamically Unstable Patient

DO NOT DELAY SURGERY FOR IMAGING

In patients with high clinical suspicion of ruptured AAA and haemodynamic instability:

1. Activate vascular team immediately - do not wait for confirmation
2. Bedside ultrasound (if immediately available, less than 2 minutes):
   • Confirms presence of AAA (sensitivity 95% for AAA ≥3 cm)
   • Cannot reliably diagnose rupture (limited by retroperitoneal location)
   • Positive finding (AAA) + unstable patient = proceed to theatre
3. Essential bloods during resuscitation (do not delay theatre):
   • Group and crossmatch 10 units RBC
   • FBC (baseline Hb may be normal acutely)
   • Coagulation (INR, APTT, fibrinogen)
   • U&E, creatinine (baseline renal function)
   • Lactate, ABG/VBG (assess tissue perfusion)
   • Troponin (concurrent MI)

Unstable patient with confirmed/suspected rAAA → direct to theatre without CT

Haemodynamically Stable Patient (Contained Rupture Suspected)

A minority of patients (15-30%) present with contained rupture and relative haemodynamic stability (SBP > 90 mmHg sustained). These patients benefit from rapid CT imaging to confirm diagnosis and plan intervention.

CT Angiogram Findings in rAAA:

• Aneurysm diameter (usually > 5.5 cm, but rupture can occur in smaller aneurysms)
• Retroperitoneal haematoma (high-attenuation blood surrounding aorta)
• Active contrast extravasation (active bleeding, poor prognostic sign)
• Discontinuity of aortic wall calcification
• Loss of fat planes around aorta
• Draped aorta sign (posterior wall conforming to vertebral body)
• Free intraperitoneal blood (suggests free rupture)

EVAR Anatomical Suitability Assessment on CT:

• Proximal neck length ≥10-15 mm below lowest renal artery
• Proximal neck diameter ≤32 mm
• Proximal neck angulation less than 60°
• Iliac artery diameter ≥7 mm (access)
• Iliac tortuosity manageable
• Approximately 60-70% of ruptured AAA are anatomically suitable for EVAR [4]

Laboratory Investigations

Point-of-Care Ultrasound (POCUS)

Emergency physicians and vascular surgeons increasingly use POCUS to rapidly assess for AAA:

Technique:

• Curvilinear probe (2-5 MHz)
• Scan in transverse and longitudinal planes
• Measure maximum AP and transverse diameter (outer wall to outer wall)
• Assess for free fluid in abdomen (FAST exam)

Interpretation:

• Normal aorta: less than 3.0 cm diameter
• AAA: ≥3.0 cm diameter
• Rupture: Cannot be directly visualized (retroperitoneal), but presence of AAA + instability = assume rupture
• Free fluid + AAA = likely free intraperitoneal rupture (very poor prognosis)

Limitations:

• Operator-dependent
• Difficult in obese patients
• Cannot reliably diagnose rupture (only presence of AAA)
• Cannot assess EVAR suitability

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Classification and Staging

Haemodynamic Classification

Hardman Index (Mortality Prediction)

The Hardman Index predicts perioperative mortality and aids in patient selection and family counselling. [18]

Score Interpretation:

• 0-1 points: Mortality ~20-30%, proceed with surgery
• 2 points: Mortality ~50%, surgery reasonable but high risk
• ≥3 points: Mortality 80-90%, consider futility and goals of care discussion [18]

Limitations:

• Derived from open repair era; EVAR may offer survival benefit even in high-risk patients
• Not a contraindication to surgery but informs prognostication
• Shared decision-making essential with patient/family

Glasgow Aneurysm Score (GAS)

Alternative prognostic tool incorporating age, shock, myocardial disease, cerebrovascular disease, and renal disease. Scores > 85 associated with mortality > 65%. Less commonly used than Hardman Index.

Anatomical Classification for EVAR

Approximately 60-70% of ruptured AAAs have anatomy suitable for EVAR. [4] The remaining 30-40% require open repair.

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Management

The management of ruptured AAA requires coordinated multidisciplinary care involving emergency physicians, vascular surgeons, anaesthetists, and intensive care teams. Time to definitive repair is the most critical determinant of survival.

Pre-Hospital and Emergency Department Resuscitation

Immediate Actions (First 15 Minutes):

1. Activate Major Haemorrhage Protocol and Vascular Team

   • Direct notification to on-call vascular surgeon
   • Activate operating theatre and hybrid theatre if available
   • Notify anaesthetics, ICU, blood bank

2. Airway and Breathing

   • High-flow oxygen (15 L/min via non-rebreather)
   • Avoid intubation if possible (hypotension on induction can precipitate arrest)
   • If intubation required: senior anaesthetist, prepare for immediate decompensation
   • Avoid positive pressure ventilation initially (increases intra-abdominal pressure)

3. Circulation - Permissive Hypotension Strategy

Critical Concept: Permissive Hypotension

Traditional aggressive fluid resuscitation is CONTRAINDICATED in ruptured AAA. [19]

Rationale:

• Increasing blood pressure can disrupt clot tamponade in contained rupture
• Fluid resuscitation dilutes clotting factors and reduces blood viscosity
• Hypothermia from rapid infusion worsens coagulopathy
• Target: Maintain cerebral perfusion while minimizing haemorrhage

Permissive Hypotension Targets: [19]

• SBP 70-90 mmHg (conscious patient with palpable radial pulse)
• SBP 50-70 mmHg if unconscious (MAP > 50 mmHg)
• Avoid SBP > 100 mmHg until aortic control achieved

Resuscitation Protocol:

• Two large-bore IV cannulae (14-16G)
• Minimal crystalloid (500 mL bolus only if SBP less than 70 mmHg)
• Initiate massive transfusion protocol
• Ratio-based transfusion: RBC:FFP:Platelets = 1:1:1 [20]
• Target Hb > 70 g/L (not higher)
• Tranexamic acid 1g IV over 10 minutes (within 3 hours of bleeding onset) [21]
• Calcium chloride 10 mmol IV (citrate toxicity from massive transfusion)
• Warm fluids and patient (prevent hypothermia)

4. Monitoring

   • Continuous ECG, SpO₂, blood pressure (arterial line if time permits)
   • Urinary catheter (monitor urine output, decompress bladder)
   • Temperature monitoring

5. Analgesia

   • Small doses IV morphine (2-5 mg) if SBP permits
   • Avoid sedation (obscures neurological assessment and drops BP)

DO NOT:

• Give aggressive fluid boluses to normalize blood pressure
• Wait for investigations before notifying vascular team
• Transfer unstable patient to CT scanner
• Delay theatre for "optimization"

Surgical Repair Options

Two main surgical strategies exist: endovascular aneurysm repair (EVAR) and open surgical repair (OSR). The choice depends on patient haemodynamic status, anatomical suitability, and local expertise.

Endovascular Aneurysm Repair (EVAR) for Ruptured AAA

Indications:

• Suitable infrarenal aortic neck anatomy
• Adequate iliac artery access
• Availability of appropriate stent-graft
• Hybrid theatre or endovascular suite available
• Expertise in emergency EVAR

IMPROVE Trial Evidence: [4] The landmark IMPROVE randomized controlled trial (2014) compared EVAR-first strategy vs. open repair for ruptured AAA:

• 30-day mortality: No significant difference (35.4% EVAR vs 37.4% open, p=0.62)
• Women: Lower mortality with EVAR strategy (OR 0.67)
• Quality of life: Better with EVAR at 3 months
• Cost-effectiveness: EVAR cost-effective at UK thresholds

Conclusion: Offer EVAR to all patients with ruptured AAA if aortic morphology is suitable. [4]

EVAR Technique for rAAA:

1. Local or general anaesthesia (GA may precipitate haemodynamic collapse)
2. Percutaneous or open femoral artery access
3. Aortic balloon occlusion (if haemodynamically unstable) - temporary control
4. Rapid deployment of aorto-bi-iliac stent-graft
5. Confirm seal and no endoleak on completion angiography

Advantages of EVAR:

• Reduced physiological stress (especially in high-risk patients)
• Lower perioperative mortality in some subgroups (women, contained rupture)
• Faster recovery, shorter ICU stay
• Less fluid/blood product requirement
• Reduced risk of abdominal compartment syndrome

Disadvantages:

• Only 60-70% anatomically suitable
• Risk of endoleak (Type I or III requires immediate conversion to open)
• Requires specialized equipment and expertise
• Longer-term surveillance required

Open Surgical Repair

Indications:

• Unsuitable anatomy for EVAR (hostile neck, inadequate iliac access)
• No EVAR capability available
• EVAR failure/complication requiring conversion
• Aortoenteric fistula or aortocaval fistula (relative)

Open Repair Technique:

1. Incision: Midline laparotomy (xiphoid to pubis)

2. Proximal Control:

   • Supracoeliac aortic clamping (if patient unstable, clamp first before exploring)
   • Evacuate haematoma and identify neck of aneurysm
   • Infrarenal clamp (if anatomy permits)

3. Aneurysm Sac Management:

   • Open sac, evacuate thrombus
   • Control back-bleeding from lumbar and IMA
   • Assess need for IMA reimplantation (if large, back-bleeding significant)

4. Graft Insertion:

   • Dacron tube graft (if iliac arteries normal)
   • Bifurcated graft (if iliac aneurysmal or occlusive disease)
   • End-to-end proximal anastomosis
   • Distal anastomosis to aorta or iliac arteries

5. Closure:

   • Close aneurysm sac over graft (reduce infection risk)
   • Mass closure of abdomen or leave open (if abdominal compartment syndrome risk)

Damage Control Surgery Approach:

In the most unstable patients (Class III), consider damage control principles:

• Rapid aortic control
• Graft insertion
• Minimal intra-abdominal dissection
• No bowel inspection initially
• Temporary abdominal closure
• Resuscitation in ICU
• Planned re-laparotomy at 24-48 hours

Complications of Open Repair:

• Immediate: haemorrhage, cardiac arrest, coagulopathy
• Early: ischaemic colitis (5-10%), acute kidney injury (30-50%), abdominal compartment syndrome (10-15%)
• Late: incisional hernia (20-30%), graft infection (less than 1%), erectile dysfunction (25%)

Comparison: EVAR vs Open Repair for rAAA

Meta-Analysis Evidence:

Multiple meta-analyses demonstrate:

• Similar 30-day mortality between EVAR and open repair in anatomically suitable patients [22]
• EVAR associated with reduced morbidity (renal failure, cardiac events)
• Open repair durable long-term; EVAR requires ongoing surveillance
• Women may have survival benefit with EVAR [4]
• Hostile anatomy treated with EVAR has higher mortality than friendly anatomy [22]

Post-Operative Care

All patients surviving operative repair require intensive care unit admission.

First 24 Hours Priorities:

1. Manage Lethal Triad (Hypothermia, Acidosis, Coagulopathy)

   • Rewarm patient (target core temperature > 36°C)
   • Correct acidosis (pH > 7.25) with haemostatic resuscitation and ventilation
   • Correct coagulopathy:
     • Target fibrinogen > 1.5 g/L (cryoprecipitate or fibrinogen concentrate)
     • Platelets > 75 × 10⁹/L
     • INR less than 1.5
   • Thromboelastography (ROTEM/TEG) guided transfusion if available [20]

2. Cardiovascular Support

   • Invasive arterial and central venous monitoring
   • Aim euvolaemia (avoid over-resuscitation)
   • Vasopressors (noradrenaline) to maintain MAP > 65 mmHg
   • Inotropes if myocardial dysfunction (dobutamine)
   • Echocardiography to assess cardiac function

3. Renal Protection

   • High risk of AKI (30-50% post-operatively) [11]
   • Ensure adequate renal perfusion (MAP > 65 mmHg, euvolaemia)
   • Avoid nephrotoxins
   • Monitor urine output (target > 0.5 mL/kg/hr)
   • Early renal replacement therapy if anuric or severe metabolic acidosis/hyperkalaemia

4. Monitor for Abdominal Compartment Syndrome (ACS)

   • Risk factors: massive transfusion, prolonged hypotension, open repair
   • Measure bladder pressure (> 20 mmHg = intra-abdominal hypertension)
   • ACS defined as sustained bladder pressure > 20 mmHg with organ dysfunction
   • Treatment: decompressive laparotomy [11]

5. Assess Bowel Viability (Ischaemic Colitis Risk)

   • Most common after open repair (5-10%)
   • Due to inferior mesenteric artery (IMA) sacrifice and hypoperfusion
   • Clinical signs: bloody diarrhoea, abdominal distension, metabolic acidosis
   • Diagnosis: sigmoidoscopy (mucosal ischaemia), CT (bowel wall thickening, pneumatosis)
   • Management: resuscitation and bowel rest (mild), laparotomy and resection (transmural necrosis)

6. Respiratory Support

   • Most patients require mechanical ventilation 24-72 hours
   • Lung-protective ventilation (tidal volume 6-8 mL/kg)
   • Early extubation when haemodynamically stable

7. Thromboprophylaxis

   • High VTE risk but bleeding risk initially
   • Mechanical prophylaxis (intermittent pneumatic compression) from day 1
   • Pharmacological prophylaxis (LMWH) when bleeding controlled (usually day 2-3)

Ongoing ICU Management:

• Daily assessment of organ function (renal, cardiac, respiratory, neurological)
• Early enteral nutrition (within 48 hours if bowel viable)
• Glycaemic control (target 6-10 mmol/L)
• Delirium prevention and management
• Early mobilization when stable
• Surveillance for complications (MI, stroke, infection)

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Complications

Immediate (Intra-Operative and First 24 Hours)

Early Post-Operative (First 30 Days)

Ischaemic Colitis - Important Complication:

Ischaemic colitis occurs due to hypoperfusion of the colon (especially sigmoid and splenic flexure) compounded by IMA ligation during aneurysm repair.

Risk Factors:

• Prolonged hypotension
• IMA ligation without adequate collaterals
• Concurrent inferior mesenteric vein thrombosis
• Hypogastric artery occlusion

Clinical Presentation:

• Bloody diarrhoea (within 48 hours post-op)
• Abdominal pain and distension
• Metabolic acidosis, rising lactate
• Sepsis if transmural necrosis

Diagnosis:

• Sigmoidoscopy (gold standard) - mucosal ischaemia, ulceration
• CT abdomen (bowel wall thickening, pneumatosis, portal venous gas)

Grading:

• Grade I (mucosal ischaemia): Conservative management, resolves
• Grade II (full-thickness ischaemia, reversible): Observation, supportive care
• Grade III (transmural necrosis): Requires laparotomy, colon resection, stoma

Mortality with transmural necrosis: 50-90% despite intervention.

Long-Term Complications (> 30 Days)

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Prognosis and Outcomes

Mortality Statistics

Ruptured AAA has among the highest mortality rates of any surgical emergency:

Factors Associated with Mortality:

Favourable Prognostic Factors:

• Contained rupture (vs. free intraperitoneal)
• Haemodynamic stability (SBP > 90 mmHg)
• Younger age (less than 75 years)
• Absence of cardiac disease
• Normal renal function
• Low Hardman Index score (0-1)
• Rapid time to surgical intervention

Poor Prognostic Factors:

• Free rupture into peritoneal cavity
• Profound hypotension (SBP less than 70 mmHg)
• Loss of consciousness
• Cardiac arrest pre-operatively
• Age > 80 years
• Severe cardiac or renal comorbidity
• Hardman Index ≥3 [18]

Long-Term Survival (Survivors to Hospital Discharge)

Among patients who survive the initial hospitalization:

• 1-year survival: 70-80%
• 5-year survival: 40-60% [5]
• 10-year survival: 20-30%

Long-term survival is determined primarily by cardiovascular comorbidities (coronary disease, stroke) rather than aneurysm-related factors. Secondary prevention (statin, antiplatelet, smoking cessation, hypertension control) is essential. [5]

Futility Considerations and Ethical Decision-Making

The extremely high mortality of ruptured AAA, especially in patients with multiple adverse prognostic factors, raises important questions about surgical futility.

When to Consider Goals of Care Discussion:

• Hardman Index ≥3 (mortality 80-90%) [18]
• Cardiac arrest requiring prolonged CPR
• Prolonged severe hypotension (> 30 minutes with SBP less than 50 mmHg)
• Significant pre-morbid frailty or limited life expectancy
• Patient advance directive against aggressive intervention

Approach:

• Emergency surgery is default for most patients
• Rapid shared decision-making with family if patient unable
• Explain extremely high mortality but emphasize surgery is only chance
• Respect patient autonomy and advance directives
• Palliative care involvement if non-operative management chosen

Non-Operative Management: For patients declining surgery or deemed unsuitable:

• Comfort-focused care
• IV morphine for pain control
• Anxiolytics (midazolam) for distress
• Allow family presence
• Death usually occurs within hours

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Prevention and Screening

Primary Prevention

Modifiable Risk Factors:

• Smoking cessation: Most important modifiable factor; smoking increases AAA growth rate and rupture risk 3-5 fold [12]
• Blood pressure control: Target BP less than 140/90 mmHg (lower if possible); reduces rupture risk [13]
• Lipid management: Statins may slow AAA growth and reduce cardiovascular mortality [5]
• Exercise: Regular moderate exercise associated with slower AAA growth
• Avoid heavy lifting: Sudden increases in intra-abdominal pressure theoretically increase rupture risk

Non-Modifiable Risk Factors:

• Male sex, age > 65, family history, connective tissue disorders

Screening Programmes

UK NHS AAA Screening Programme: [8]

• One-time ultrasound screening offered to all men at age 65
• Men > 65 can self-refer if not previously screened
• Women not routinely screened (lower prevalence 0.5%)

Screening Protocol:

• Abdominal ultrasound measuring maximal AP diameter
• Normal (less than 3.0 cm): discharge, no further screening
• Small AAA (3.0-4.4 cm): annual surveillance ultrasound
• Medium AAA (4.5-5.4 cm): 3-monthly surveillance ultrasound
• Large AAA (≥5.5 cm): refer to vascular surgery for consideration of elective repair

Effectiveness:

• 42% reduction in AAA-related mortality in screened population [8]
• Prevents approximately 1,000 deaths annually in UK
• Cost-effective intervention
• Similar programmes exist in Sweden, Australia, United States

Selective Screening Recommendations: Consider screening in:

• Women with family history of AAA
• Women with cardiovascular risk factors (smoking, hypertension)
• First-degree relatives of AAA patients (earlier screening at age 50-55)

Surveillance of Known AAA

For patients with known AAA below surgical threshold:

Indications for Elective Repair:

• Diameter ≥5.5 cm (men) or ≥5.0 cm (women) [9]
• Rapid expansion (> 1 cm per year or > 5 mm in 6 months)
• Symptomatic AAA (abdominal/back pain even without rupture)
• Saccular morphology (higher rupture risk)

Elective AAA repair (open or EVAR) has 30-day mortality less than 5%, vastly better than emergency repair for rupture. [9]

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Key Guidelines and Evidence

Major Guidelines

1. European Society for Vascular Surgery (ESVS) Guidelines 2019 [9]

   • Comprehensive AAA management recommendations
   • Threshold for intervention: ≥5.5 cm (men), ≥5.0 cm (women)
   • EVAR-first strategy for ruptured AAA if anatomically suitable
   • Permissive hypotension during resuscitation

2. Society for Vascular Surgery (SVS) Guidelines 2018

   • Similar recommendations to ESVS
   • Emphasize importance of rapid diagnosis and transfer to vascular centre
   • Recommend consideration of EVAR for ruptured AAA

3. UK NHS AAA Screening Programme [8]

   • Population screening for men at age 65
   • Surveillance protocols for detected aneurysms
   • Referral pathways for surgical intervention

Landmark Trials

1. IMPROVE Trial (2014) [4]

   • Multicentre RCT comparing EVAR strategy vs. open repair for ruptured AAA
   • 613 patients randomized
   • Primary outcome: 30-day mortality (no significant difference, 35.4% vs 37.4%)
   • Women had lower mortality with EVAR strategy
   • EVAR associated with better quality of life at 3 months
   • Conclusion: Endovascular strategy should be considered for all patients with ruptured AAA

2. EVAR-1 Trial (2005)

   • Elective AAA repair: EVAR vs. open repair
   • Lower 30-day mortality with EVAR (1.7% vs 4.7%)
   • No long-term survival difference (higher re-intervention rate with EVAR)

3. UK Small Aneurysm Trial (2002)

   • Surveillance vs. early surgery for AAA 4.0-5.5 cm
   • No survival benefit from early surgery
   • Established 5.5 cm threshold for intervention

High-Impact Publications

4. Hardman DT, et al. J Vasc Surg 1996 [18]

   • Derived Hardman Index for mortality prediction in ruptured AAA
   • Validated prognostic tool still used today

5. Sweeting MJ, et al. BMJ 2012

   • Meta-analysis of rupture risk by AAA diameter
   • Informed current surveillance protocols

6. Powell JT, et al. Lancet 2014

   • IMPROVE trial cost-effectiveness analysis
   • EVAR strategy cost-effective at UK thresholds

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Common Exam Questions and Viva Preparation

Viva Point: Opening Statement:

"Ruptured abdominal aortic aneurysm is a life-threatening vascular emergency characterized by failure of the aneurysm wall integrity leading to retroperitoneal or intraperitoneal haemorrhage. It carries an overall mortality of 65-85% including pre-hospital deaths. The classic triad of sudden abdominal or back pain, hypotension, and palpable pulsatile mass is present in only 25-50% of patients. Immediate recognition, permissive hypotension resuscitation, and urgent surgical repair represent the only chance of survival."

Key Facts to Quote:

• Overall mortality 65-85%; operative mortality 35-50% (open), 25-40% (EVAR) [1,2,4]
• 50-65% die pre-hospital [1,2]
• Rupture risk by diameter: less than 1% (less than 5.5 cm), 5-15% (5.5-6.9 cm), > 20% (≥7 cm) [9]
• IMPROVE trial: No difference in 30-day mortality between EVAR and open (35.4% vs 37.4%) [4]
• Permissive hypotension target: SBP 70-90 mmHg [19]
• Hardman Index ≥3: mortality 80-90% [18]
• UK screening reduces AAA mortality by 42% [8]

Commonly Asked Questions

Q1: How would you manage a 75-year-old man presenting with sudden onset back pain, BP 85/60 mmHg, and a pulsatile abdominal mass?

A: "This patient has a ruptured AAA until proven otherwise. My immediate management would be:

1. Call for senior help and activate the vascular team urgently
2. Resuscitate using permissive hypotension strategy - target SBP 70-90 mmHg, avoid aggressive fluids
3. Two large-bore IV access, crossmatch 10 units RBC
4. Activate massive transfusion protocol
5. High-flow oxygen
6. Do NOT delay for imaging if unstable - proceed directly to theatre

If the patient is relatively stable (sustained SBP > 90), I would arrange urgent CT angiography to confirm diagnosis and assess EVAR suitability, but only if this does not delay definitive management.

Definitive treatment is emergency surgical repair, either EVAR if anatomically suitable or open repair. Based on the IMPROVE trial, an EVAR-first approach should be considered if anatomy permits."

Q2: What is permissive hypotension and what is the evidence for it?

A: "Permissive hypotension is a resuscitation strategy that accepts lower blood pressure targets (SBP 70-90 mmHg) to maintain cerebral perfusion while minimizing ongoing haemorrhage. The rationale is that aggressive fluid resuscitation can:

• Disrupt haemostatic clot in contained rupture
• Dilute clotting factors and cause coagulopathy
• Induce hypothermia
• Increase bleeding before definitive surgical control

The target is a conscious patient with palpable radial pulse (SBP ~80-90 mmHg). This approach is supported by trauma literature and vascular surgery consensus, though ruptured AAA-specific RCT evidence is limited due to ethical constraints. Once aortic control is achieved surgically, normal resuscitation targets apply."

Q3: What are the findings on CT that confirm ruptured AAA?

A: "CT angiography is the gold standard for diagnosing ruptured AAA in haemodynamically stable patients. Key findings include:

• Abdominal aortic aneurysm (diameter typically > 5.5 cm, but can rupture smaller)
• Retroperitoneal haematoma (high-attenuation blood around aorta)
• Active contrast extravasation (active bleeding - poor prognostic sign)
• Discontinuity of aortic wall calcification
• Draped aorta sign (posterior wall conforming to vertebral body)
• Free intraperitoneal blood (suggests free rupture, very poor prognosis)

The scan also assesses EVAR anatomical suitability by evaluating proximal neck length, diameter, angulation, and iliac access. Approximately 60-70% of ruptured AAAs are suitable for EVAR."

Q4: What are the major complications after ruptured AAA repair?

A: "Complications can be divided into immediate, early, and late:

Immediate (first 24 hours):

• Death (35-50%)
• Massive haemorrhage
• Coagulopathy (lethal triad: hypothermia, acidosis, coagulopathy)
• Cardiac arrest, myocardial infarction

Early (first 30 days):

• Acute kidney injury (30-50%) - due to hypoperfusion, suprarenal clamping
• Ischaemic colitis (5-10%) - from IMA ligation and hypoperfusion; presents with bloody diarrhoea
• Abdominal compartment syndrome (10-15% open repair) - requires decompressive laparotomy
• Multi-organ failure
• Respiratory failure
• Lower limb ischaemia (embolization)

Late (> 30 days):

• EVAR-specific: endoleak (10-15%), sac expansion
• Graft infection (less than 1% but catastrophic)
• Incisional hernia (20-30% after open repair)
• Sexual dysfunction (25% after open repair)

The most feared early complication is ischaemic colitis with transmural necrosis, which carries 50-90% mortality despite intervention."

Q5: When would you consider surgery futile in ruptured AAA?

A: "This is a difficult ethical question. While emergency surgery is the default for most patients, there are situations where mortality is so high that futility should be discussed:

Consider goals of care discussion when:

• Hardman Index ≥3 (mortality 80-90%)
• Cardiac arrest requiring prolonged CPR
• Prolonged severe hypotension (> 30 minutes with SBP less than 50 mmHg)
• Significant pre-morbid frailty or very limited life expectancy
• Patient advance directive against aggressive intervention

However, I emphasize that surgery is still offered in most cases as it is the only chance of survival. The decision requires rapid shared decision-making with the patient (if conscious) or family, explaining the extremely high mortality while acknowledging surgery is the only option for survival. I would involve senior vascular surgery and critical care colleagues in this discussion and respect patient autonomy and advance directives."

Common Mistakes

❌ Mistakes that fail candidates:

1. Aggressive fluid resuscitation - Normalizing BP before surgical control worsens bleeding
2. Delaying theatre for investigations in unstable patient - CT is for stable patients only
3. Missing the diagnosis - Low threshold in elderly patient with collapse + abdominal pain
4. Not activating vascular team immediately - Time to surgery is critical
5. Quoting outdated mortality figures - Know contemporary IMPROVE trial data
6. Stating EVAR is always better - Similar 30-day mortality; depends on anatomy
7. Not mentioning permissive hypotension - Fundamental resuscitation principle
8. Forgetting ischaemic colitis - Important post-operative complication with high mortality

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Patient and Family Information

What is a Ruptured Abdominal Aortic Aneurysm?

An abdominal aortic aneurysm (AAA) is a bulge or swelling in the main blood vessel (aorta) that carries blood from your heart through your abdomen. When this bulge bursts or tears (ruptures), it causes life-threatening internal bleeding. This is a medical emergency that requires immediate surgery.

Warning Signs

• Sudden, severe pain in the tummy or back
• Collapse, fainting, or feeling extremely unwell
• Feeling sweaty, cold, and faint
• A pulsating feeling in the abdomen (though this may not always be noticeable)

If you or someone experiences these symptoms, especially if you are over 65, male, or a smoker, call 999 immediately.

Emergency Treatment

Treatment involves emergency surgery to repair the torn blood vessel. There are two main types:

1. Keyhole surgery (EVAR) - A stent-graft is inserted through small cuts in the groin
2. Open surgery - The surgeon makes a large cut in the abdomen to repair the aorta with a graft

The surgeon will choose the best option based on your anatomy and how stable you are. Both operations carry high risks, but surgery is the only chance of survival.

What to Expect

Ruptured AAA is extremely serious:

• Many patients do not survive despite surgery (survival is around 40-60% with surgery)
• Recovery requires intensive care for several days
• Complications are common (kidney problems, bowel issues)
• Full recovery takes 3-6 months

Screening

In the UK, all men are offered a free one-time ultrasound scan at age 65 to check for AAA. This screening can detect aneurysms before they rupture, allowing planned (elective) surgery which is much safer than emergency surgery.

If you are over 65 and male and have not been screened, ask your GP about AAA screening.

Resources

• NHS AAA Screening Programme
• NHS: Abdominal Aortic Aneurysm
• Circulation Foundation Patient Information

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References

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