L10: Vessels of the Lower Limb Flashcards
Describe the arterial tree of the lower limb.
The abdominal aorta bifurcates at L5 into the left and right common iliac arteries. These further divide into external and internal iliac arteries. The internal iliac artery heads into the pelvis to give rise to the arteries to supply the viscera and the superior and inferior gluteal arteries (leave through the greater sciatic foremen and emerge around the piriformis) and he obturator artery which travels through the obturator canal to supply the medial compartment muscles.
The external iliac heads out deep to the inguinal ligament continuing into the thigh as the femoral artery. In the anterior thigh it gives rise to the medial and lateral circumflex artery, the profunda femoris (PF) and form the PF arises 3/4 perforating arteries to supply the posterior thigh. The PF is the prime supply to the anterior thigh. Themedial and lateral circumflex femoral arteriesarise soon after the origin of theprofunda femoris artery, although they branchout fromthe commonfemoral artery at the level of bifurcation in 20% of patients. These important vesselscanflow in either direction. The femoral artery travels through the adductor hiatus into the popliteal fossa. The popliteal artery continues as the posterior tibial after it have given of the anterior tibial. The anterior tibial travels through the aperture in the IOM to supply the anterior thigh. The posterior branch gives rise to the fibular artery which supplies the lateral aspect of the leg.
The anterior tibial travels onto the dorsum of the foot, once there it continues as the dorsalis pedis artery. This is palpable on the dorsum.
On the dorsum there is the dorsalis pedis artery travel down which gives rise to the deep plantar which travels deep into the foot and will anastomose with vessels in the foot. On the sole of the foot, the posterior tibial artery which travels behind the medial malleolus, emerges into the foot and divides into the medial and lateral plantar arteries. This forms a plantar arch. There is an anastomoses with the deep plantar artery from the dorsum.
What is the clinical importance of the femoral artery?
The femoral vessels lie relatively superficially and so are vulnerable to injury. They can be accessed to obtain an ABG in emergencies if there is poor peripheral perfusion and pulses. It can also be used in minimally invasive procedures. In these procedures a catheter is placed into the femoral artery which can then be advanced up the arterial tree to the target organ. Procedures include:
- Coronary angiography
- Coronary angioplasty
Embolization of cerebral aneurysms.
Define ischaemia.
Perfusion fails to meet the demand of the tissues; tissue hypoxia and anaerobic metabolism results leading to tissue damage and death if adequate perfusion is not restored (infraction).
What is a common cause fo chronic limb ischaemia?
ower limb ischaemia is most commonly caused by atherosclerotic disease.
What are risk factors for atherosclerosis?
Atheroma formation is a natural process that happens with age. Certain risk factors greatly accelerate atherosclerosis: - Smoking - Hypertension - Hyperlipidaemia (diet and genetics) - Genetic predisposition - Being male Diabetes
Where does atherosclerosis commonly occur?
Atherosclerosis occur in large and medium sized arteries. We often see atherosclerotic plaque at bifurcation points due to turbulence of blood follow. This is why hypertension is a risk factor. HTN causes micro-trauma to the lining of the blood vessels increasing the chance of atherosclerotic disease. In the absence of HTN we have more turbulence at these bifurcation points. They typically effect coronary arteries, the carotid arteries, the lower limb arteries and the aorta itself.
What is the Fontaine classification of limb Ischaemia?
The stages of chronic limb ischemia;
1. Asymptomatic 2. Intermittent claudication 3. Ischemic rest pain 4. Ulceration/gangrene (critical ischemia)
How can critical ischaemia present?
Gangrene - Can be wet or dry. Wet gangrene is necrosis with infection, dry gangrene is necrosis without infection.
Other examples include ulceration and pain at rest.
Give causes of acute limb ischaemia.
Usually happens in a previously “normal” limb
- Most often caused by a plaque rupture, resulting in complete occlusion of there artery by a thrombus in situ, or giving rise to an embolus that travel down the arterial tree until it becomes stuck in a distal vessel and occludes it - Can also be caused by an emboli from somewhere else such as the heart in a patient with AF - Patients who have undergone recent LL angioplasty or grafting of an occlusion may also present with acute limb ischaemia
What are the signs and symptoms of limb ischaemia?
The 6P’s
- Pain
- Perishingly Cold
- Pallor
- Paraesthesia
- Paralysis
- Pulseless
How is acute limb ischaemia investigated and managed?
- Do not delay and refer to the vascular surgeons for urgent revascularisation
Following this;- Investigations into the cause if unknown
- Searching for and treating vascular disease elsewhere e.g. coronary arteries, carotid doppler
- Initiating/optimising the treatment of risk factors such as diabetes, HTN and hyperlipidaemia
- Lifestyle modification and education - diet, smoking cessation
Other aspects depend on the patient
Describe the venous supply to the lower limbs.
In the venous system there is a system of deep and superficial veins. The deep venous system follows the arterial system.
In terms of the superficial veins we can see the dorsal venous arch. These give rise to two major superficial veins: the greater saphenous vein and the small saphenous vein. The small saphenous vein is seen on the posterior aspect of the leg. The great saphenous vein is seen on the medial leg and the thigh. It ascends anterior to the medial malleolus up, the medial aspect of the lower limb, the leg and the thigh and meets the femoral vein in the femoral triangle. The small saphenous vein travels up the leg, posterior to the lateral malleolus. It meets the popliteal vein the popliteal fossa.
When can the femoral vein be accessed in a clinical setting?
The femoral vein can be accessed for emergency IV access and for temporary IV access such as in:
- Trauma
- Burns
- Difficult IV access such as in circulatory shock, intravenous drug users (the veins become thrombosed over time), peripheral veins, obesity
- Can be used for venepuncture (and VBG) in emergencies
Central lines are preferred into the large veins is the internal jugular vein as it is considered a cleaner site.
Where do we access major superficial veins of the lower limb?
We can also access major superficial veins. The great saphenous vin can be accessed anterior to the medial malleolus - it is fairly consistent here. This site can be used in emergencies. You can cannulate in the veins on the dorsum of the foot - it is not ideal but sometimes it is necessary.
What are varicose veins?
In varicose veins is increased pressure in the saphenous veins and can be caused by proximal venous obstruction e.g. pregnancy or a pelvic tumour. The veins lose there elasticity and become dilated. The valves then no longer oppose each other and help to keep blood flow in one direction. This means since the valves no longer meet and we get stasis of the blood and bulging of the wall.
