Perioperative management - Resection of an infrarenal abdominal aortic aneurysm with interposition of a tube graft

The indication for invasive treatment of an abdominal aortic aneurysm (AAA) is fundamentally derived from weighing the individual rupture risk under the natural course against the operative risk. If the rupture risk under the natural course exceeds the individual operative risk, invasive treatment is generally indicated.

Classification of rupture risk

Indication for surgery

Two procedures are available for the surgical treatment of AAA:

• open replacement of the abdominal aorta with a straight or bifurcated graft (OAR, open aortic repair)
• endovascular implantation of a stent graft (EVAR, endovascular aortic repair)

Laparoscopic aneurysm surgery, usually combined with a mini-laparotomy, is of rather minor importance.

The following recommendations exist for selecting the procedure – OAR or EVAR:

OAR (trans-, retroperitoneal)

• normal life expectancy
• low surgical risk ("fitness")
• anatomy unsuitable for EVAR: landing zone, aneurysm neck (angle, length), iliac vessels (stenoses, elongation, kinking), thrombi, calcification
• Marfan and other connective tissue disorders

EVAR (standard graft, custom-made)

• previous abdominal surgery
• limited life expectancy
• high surgical risk
• anatomy suitable for EVAR (see above)

EVAR requires adequate iliac vessels for access, since the stent graft systems are often large-calibre. Atherosclerotically narrowed, tortuous and kinked, but also aneurysmally dilated iliac vessels are problematic.

In the long term, the endovascular aortic graft is associated with a higher complication rate than open aortic surgery.

The mortality risk for EVAR or OAR in an individual patient can be quickly calculated using the so-called BAR Score Calculator -> www.britishaneurysmrepairscore.com, which can be usefully employed in counselling patients about the risk of an elective procedure with EVAR or OAR.

Video example

Asymptomatic, infrarenal AAA with a diameter of more than 5 cm, unsuitable for EVAR due to angulation of the aneurysm neck beyond 60°.

Contraindications for open aneurysm repair:

• Serious cardiopulmonary risks (e.g. NYHA IV, COPD Gold stage IV)
• Acute or chronic inflammatory abdominal conditions (e.g. florid ulcerative colitis, recurrent sigmoid diverticulitis)
• History of multiple extensive abdominal procedures ("hostile abdomen")
• Cirrhosis of the liver
• Advanced tumour disease
• Compensated renal failure (relative contraindication)

History

• cardiac history
• medication history
• risk factors: smoking, arterial hypertension, coronary artery disease, heart failure, diabetes mellitus, manifest renal insufficiency with/without dialysis dependence, coagulopathies
• walking distance/claudication
• back or flank pain?
• mid- to upper abdominal complaints?

Inspection

• skin changes
• muscular abnormalities
• orthopaedic malalignments
• skin colour
• hair growth
• trophic changes
• swelling, oedema, mycoses, phlegmons, ulcera cruris, etc.

Palpation

• side-to-side comparison of pulse status
• side-to-side comparison of skin temperature
• possibly expansile pulsating mass in the mid-abdomen
• doughy, extensively pulsating, painful abdomen: suspected contained perforation

Side-to-side auscultation of the limb arteries

Ankle-brachial index (ABI)

• ABI = systolic BP posterior tibial artery/systolic BP brachial artery

• An ABI value of < 0.9 is considered diagnostic of relevant PAOD.
• Determination of the ankle-brachial index (ABI) by non-invasive measurement of the Doppler occlusion pressure is a suitable test for detecting PAOD.
• For the diagnosis of PAOD, the ABI value with the lowest ankle artery pressure is decisive.
• A pathological ankle-brachial index is an independent risk indicator for increased cardiovascular morbidity and mortality.

Colour-coded duplex ultrasonography

• carotid, abdominal aorta, limb arteries
• localisation of stenoses and occlusions in almost all vascular regions except the thoracic region
• quantification of the degree of stenosis and assessment of plaque morphology possible
• sensitivity and specificity approximately 90%
• well suited as a screening method

Contrast-enhanced spiral computed tomography (SCTA)

• broad spectrum of indications: traumatic vascular lesion (especially of the trunk), vascular dissection/rupture, aneurysm, arterial thrombosis/embolism, portal/mesenteric vein thrombosis, pulmonary artery embolism, PAOD, vascular tumours
• advantages: quickly performed, detection of relevant comorbidities, visualisation of peripheral arteries, sensitivity and specificity each approximately 90%
• disadvantages: radiation and contrast medium exposure, allergies (approximately 3%), no functional assessment
• aneurysm: three-dimensional visualisation of the entire aorta and its morphology, sufficiently accurate measurement for EVAR, demonstrates wall characteristics with thrombosis and calcification

Angiography (intra-arterial DSA)

• visualisation of the aortic branches (stenoses, renal polar arteries, visceral and iliofemoral arteries)
• dynamic imaging
• disadvantages: limited visualisation of aneurysm morphology (only the perfused lumen), ionising radiation, nephrotoxic contrast medium, invasive

Cardiac check

• resting ECG
• exercise ECG
• echocardiography

Chest radiography

spirometry if required

Laboratory tests

• full blood count
• electrolytes
• coagulation
• renal retention values
• liver enzymes
• blood lipids
• blood group

• Enema the evening before
• Trimming of the hair in the surgical field
• Order packed RBCs
• Foley catheter
• Administer prophylactic perioperative antibiotics 30 min. before beginning surgery (see KRINKO recommendation, Robert Koch Institute)

General surgical risks

• Allergy/intolerance (e.g. latex, medication)
• Wound infection, sepsis
• Thromboembolism
• Skin/tissue/nerve damage due to positioning on the operating table or procedure-related measures
• Keloids

Specific procedural risks

• Bleeding, blood transfusion, risk of infection through allogeneic blood transfusion (hepatitis, HIV)
• Secondary bleeding, possibly requiring surgical management
• Thrombosis of the graft and possibly adjacent vascular segments; hypoperfusion of the legs; gangrene; limb loss/amputation; surgical management
• Injury of adjacent organs (e.g. ureter, urinary bladder, bowel, kidneys, etc.), repeat surgery
• Renal failure in cases of preexisting renal insufficiency or additional interventions on the renal arteries, possibly requiring permanent dialysis
• Nerve injury with dysaesthesia or pain; weakness of the abdominal wall musculature; weakness or partial paralysis of the thigh musculature; each of which may be temporary or permanent
• In men: sexual dysfunction, infertility in case of injury to the vas deferens with a non-functional contralateral vas deferens
• Impaired perfusion of the bowel/ischaemic colitis, possibly requiring resection, temporary or permanent stoma formation
• Spinal ischaemia/paraplegia
• Abdominal compartment syndrome: multi-organ failure, intensive care measures, relaparotomy
• Lymphoedema, temporary or permanent
• Infection-related suture breakage of the graft: bleeding, sepsis, relaparotomy
• Side effects of iodine-containing contrast media
• Anastomotic aneurysm, surgical revision, possibly endovascular
• Incisional hernia
• Intra-abdominal adhesions