Page 83 - Medicine and Surgery

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Chapter 2: Hypertension and vascular diseases 79

define the anatomy prior to deciding on surgical man- even if patients survive to surgery mortality is 50%.
agement. Suprarenal aneurysms have a much poorer prognosis
with a high risk of renal impairment. Many patients have
Management concomitant ischaemic heart disease or cerebrovascular
Ruptured abdominal aortic aneurysm is a surgical disease, which affects outcome.

emergency.
Careful resuscitation is required, maximal systolic

blood pressure should be 80–90 mmHg to main- Thoracic aortic aneurysms and
tain renal and cerebral perfusion without exacerba- aortic dissection
ting the leakage. O negative blood may be required
untilbloodiscross-matched,asbloodlosscanbemas- Definition
sive. Aortic dissection is defined as splitting through the en-
Surgery at a specialist centre gives the best outcome,
dothelium and intima allowing the passage of blood into
but patients may not be fit for transfer. the aortic media.
The aneurysm is cross-clamped, partially excised and

replaced with a Dacron graft. If the aneurysm is too Aetiology
low, or when the iliac and femoral arteries are ei- Predisposingfactorstothoracicaorticaneurysms,which
ther aneurysmal or too diseased with atherosclerosis, may dissect include hypertension, atherosclerosis, bicus-
a‘trouser’ bifurcation graft is used to anastomose to pid aortic valve, pregnancy, increasing age and Marfan’s
the iliac or femoral arteries. syndrome. In all cases there is degeneration of collagen
Asymptomatic small aneurysms should be managed
and elastic fibres of the media, known as ‘cystic me-
conservatively with aggressive management of hyper- dial necrosis’. Trauma, including insertion of an arterial
tension and other risk factors for atherosclerosis and catheter, is also a cause.
yearly ultrasound scans to monitor progress.
Abdominal aortic aneurysms over 5 cm should be
Pathophysiology
treated electively. Whilst surgical techniques remain There is an intimal tear, then blood forces into the aortic
wall, it can then extend the split further along the wall
the standard treatment, increasingly endovascular
stenting techniques are being used that can be per- of the vessel.
formed under local anaesthetic. TypeAdissectionsinvolvetheascendingaorta(seeFig.
2.16), and in these cases the major risk is of dissection
Prognosis tracking back towards the heart, causing haemoperi-
Mortality rate in elective surgery is 5% or less. In rup- cardium and tamponade. These are further subdi-
tured abdominal aortic aneurysms only 20% survive, vided depending on whether the dissection extends

Left common
carotid artery
Brachiocephalic
Left subclavian
trunk
artery

Aortic valve
Type I Type II Type III
TYPE A TYPE B
Figure 2.16 Types of aortic dissection.