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Related Subjects: Renal Colic |Acute Cholecystitis |Acute Appendicitis |Chronic Peritonitis |Abdominal Aortic Aneurysm |Ectopic Pregnancy |Acute Cholangitis |Acute Abdominal Pain/Peritonitis |Assessing Abdominal Pain |Penetrating Abdominal Trauma

Abdominal Aortic Aneurysms greater than 5.5 cm need surgical repair. The mortality risk of elective surgery is 6% and emergency surgery 50%. pain. AAA are common in those over 60 and should be considered in any presentation of back or abdominal pain.

About

• An aneurysm is defined as a 50% (x 1.5) increase in blood vessel diameter
• An Abdominal Aorta would be aneurysmal at 3 cm.
• Those greater than 5.5 cm need to be assessed for surgical repair
• Most begin below the renal arteries and extend down as far as the iliac arteries

Aetiology

• Chronic inflammatory process with loss of smooth muscle
• May be a genetic basis leading to a weakness in the wall.
• A reduction in elastin and collagen is seen and may be a factor
• Shape can be fusiform or saccular
• Wall tension increases with increasing radius so increasing risk of rupture as it gets bigger
• The retroperitoneum may tamponade a bleed which can be stable until you give too many fluids and raise BP or dilute clotting factors.

Risk factors

• Smoking - now or in past, Increasing Age, Male x 5-10, COPD
• Increased height, Increased BMI
• Connective tissue disorders
• A family history is a risk factor
• Risk factors for rupture: Female x3, Smoking, Low FEV1

Clinical

• Sudden onset Abdominal Pain + Hypotension
• Presence of a Pulsatile expansile mass = Leaking AAA
• Gastrointestinal bleeds can be seen with aorto-enteral fistulas
• Leaking AAA is a Surgical emergency
• Tender abdominal mass is suggestive of symptomatic aneurysm
• Classically an elderly male with severe back or abdominal pain which may radiate to groin.
• Small bleeds may cause abdominal/back pain and hypotension
• Distal clot embolisation leading to limb ischaemia
• Unusual presentations
  • Atheroembolism to lower extremities
  • Thrombosis (sudden severe ischaemia of legs)
  • High output CHF from aortocaval fistula
  • GI bleeding from primary aorto-enteric fistula

Investigations

• FBC, U&E, LFTs, Lactate, Crossmatch, ABG if needed
• Depending on urgency CXR, ECG, ABG
• Emergency USS: can be done in resus and shows aorta. If normal in size then a leaking AAA is unlikely. If diameter is 6 cm it could be a leaking AAA. Emergency ultrasound helpful only if aorta is clearly seen and completely normal often not helpful due to bowel gas and patient discomfort cannot rule out a leak from AAA
• CT Aortogram: can aid the decision for surgery quickly. It can help plan surgery. Is the patient a candidate for an emergency EVAR or straight to the OR for operative repair? However, delays can lead to deaths in the scanner. CT scan is the best test for aneurysms being considered for repair. Can help define associated iliac aneurysms, eligibility for endovascular repair, possible suprarenal extension
• Conventional MRI has no advantage over CT for AAA

Comments

• Most AAAs rupture into the retroperitoneal cavity, which results in the classical triad of pain, hypotension, and a pulsatile mass.
• However, this triad is seen in only 25-50% of patients, and many patients with ruptured AAA are misdiagnosed
• Surgery is a CEPOD category 1 emergency and the patient should go straight for surgery. Ensure consented and massive transfusion protocol activated and that the anaesthetic team aware and ITU have a bed.
• Note that anaesthetic induction can cause hypotension so is not started until the moment that the procedure is about to begin.

Differentials

• Appendicitis (associated GI symptoms)
• Diverticulitis (fevers, GI symptoms, focal left sided tenderness)
• Aortic dissection (ripping pain, extends into chest and upper back)
• Incarcerated hernia (physical exam, CT scan if exam inconclusive)
• Renal colic

Management:Emergency

• ABC, Oxygen, IV fluids and if suggested that the aneurysm is leaking then urgent resuscitation is needed. Urinary catheter.
• IV access + if needed get 2 units O negative blood and Group and cross match 6-8 units. Contact vascular surgeons and transfer if fit enough.
• Target is to transfuse to systolic pressure 90-120 mmHg. Monitor renal output with a urinary catheter. Intraarterial monitoring. Do not aim for normal BP.
• Transfer: Transfer to a specialist vascular centre should occur within 30 minutes of diagnosis. Patients who remain haemodynamically stable should be transferred to either an Resuscitation area or local equivalent. Patients who are unstable may need rapid transfer to theatres. Contraindications to transfer and cases where survival unlikely and where consultant to consultant discussion helpful.
  • Cardiac arrest in the current admission;
  • Patients requiring intubation due to acute deterioration;
  • Patients requiring inotropic support (vasoactive drugs), except in certain rare situations.
• Prepare theatre (Operating room) Inform nurses. Needs Emergency repair - prognosis is poor. Abdominal muscles contract splints aneurysm. This is reversed with anaesthesia with subsequent hypotension.
• Open Surgical repair: Emergency Laparotomy done and aorta cross clamped and aneurysm replaced with a Dacron graft. If the aneurysm is too low, or if iliac/femoral arteries involved a 'trouser' bifurcation graft is used to anastomose to the iliac or femoral arteries. Ruptured abdominal aortic aneurysm (AAA) has an overall mortality rate of 90%. Mortality and complications including MI, Renal failure, coagulopathy are common
• EVAR: Consider endovascular aneurysm repair (EVAR) or open surgical repair for people with a ruptured infrarenal abdominal aortic aneurysm (AAA). Be aware that EVAR provides more benefit than open surgical repair for most people, especially men over 70 and women of any age open surgical repair is likely to provide a better balance of benefits and harms in men under 70. Consider open surgical repair for people with a ruptured AAA if standard EVAR is unsuitable. Do not offer complex EVAR to people with a ruptured AAA if open surgical repair is suitable, except as part of a randomised controlled trial comparing complex EVAR with open surgical repair.

Elective Management

• Endovascular Aneurysm Repair (EVAR) avoids a laparotomy and cross-clamping can be done on selective cases via the femoral artery. It can be done in a catheterisation laboratory and regional or local anaesthesia. Endovascular instruments inserted via the femoral artery. A stent graft will be inserted through the femoral artery and advanced up into the aorta to the site of the aneurysm. A stent graft is a long cylinder-like tube made of a thin metal framework (stent), while the graft portion is made of various materials such as Dacron or polytetrafluoroethylene (PTFE) and may cover the stent. The stent helps to hold the graft in place. The stent graft is inserted into the aorta in a collapsed position and placed at the aneurysm site. Once in place, the stent-graft will be expanded (in a spring-like fashion), attaching to the wall of the aorta to support the wall of the aorta. The aneurysm will eventually shrink down onto the stent graft.
• Elective open surgery shows no survival benefits for electively operating with stable AAA < 5.5 cm. Midline incision, aortic cross clamped, Heparinised. Dacron graft used. May be a trouser graft if the iliac arteries are included. Enclosed is an aneurysmal sac. AAA > 5.5 cm have an almost 10% 1-year risk of rupture.
• Frailty considerations: Patients age >85 years or with severe systemic disease or severe frailty will benefit from a consultant to consultant discussion prior to transfer to a vascular unit. Impaired mental capacity in itself is not a contraindication to assessment and transfer.

High risk individuals

• In some cases an operative procedure may not be appropriate.
• Poor prognostic indicators include age >76 years
• Creatinine (Cr) >190
• Hb <9.0 g/dL
• Loss of consciousness
• ECG evidence of ischaemia (3 or more = 100% mortality).
• Therefore, palliation may be more appropriate

References

• Abdominal aortic aneurysm: diagnosis and management NICE Guideline, No. 156
• Management and Transfer of Patients with a Diagnosis of Ruptured Abdominal Aortic Aneurysm to a Specialist Vascular Centre January 2019

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