Applied anatomy of arteries and veins of limbs
Understand the concepts and associated principles, functional and clinical applications of:
1. The ideal sites of: (i) radial artery puncture; (ii) brachial artery puncture
Arterial puncture may be peformed to provide a sample of arterial blood for analysis of blood gases.
The radial artery is commonly chosen and is readily palpable between skin and bone at the distal
end of the radius on the front of the wrist (palpate between brachioradialis muscle and flexor carpi
radialis tendon).
The brachial artery is an alternative – palpable in the cubital fossa (medial to the tendon of biceps).
2. The potential danger of a “superficial” ulnar artery
The ulnar artery normally passes deep to the common origin of the forearm flexor muscles.
However, it may pass superficial to them (about 3%), particularly if associated with a high division of
the brachial artery.
A superficial ulnar artery can be endangered by inadvertent injection (as it tends to be mistaken for
a superficial vein). Intra-arterial injection of certain drugs may cause vasoconstriction causing death
of the forearm and hand musculature. For this reason, anaesthetic agents should not be injected
into the cubital fossa.
3. Why adrenaline should not be used in digital nerve blocks
A nerve block involves infiltrating local anaesthetic around a nerve to interrupt conduction. Although
anaesthesia may be achieved by infiltration directly around certain structures, eg in a wound, much
more local anaesthetic agent is required than with a nerve block. Directly injecting certain areas eg
the palm or sole, may be painful and injecting into tight, confined compartments may raise pressure
in the compartment, compromising vascular supply.
Appropriate sites for access to nerves are determined by relationships to anatomical landmarks and
potential hazards eg accompanying vessels and neighbouring vital organs.
The area anaesthetised by a nerve block corresponds to the sensory distribution of the nerve (distal
to the site of infiltration) minus the area of overlap from adjacent nerves.
For a digital nerve block, each of the four digital nerves at the base of a finger (supplied by a palmar
digital and dorsal digital nerve on each side) may be blocked. An alternative approach is to infiltrate
around the common palmar digital nerve in a web space (often necessary to block more than one).
Use of vasoconstrictors with nerve blocks – adrenaline
Conditions that increase blood supply (inflammation, exercise) decrease duration of action so
vasoconstrictor drugs (eg adrenaline) may be used to prolong the action of a local anaesthetic.
Adrenaline should not be injected into terminal parts, particularly digits or the penis because they
are supplied by end arteries.
4. The common sites of venepuncture and intravenous cannulation
Venepuncture:
The procedure is best performed on a distended vein, and it is far more convenient to choose a
superficial vein of the upper limb. In emergencies, the femoral vein may be used because more
peripheral veins may be difficult to access (particularly with shocked, obese or very young patients).
Superficial veins are highly variable. Although any prominent vein in the upper limb may be used, the
cubital fossa is the most satisfactory site because large superficial veins meet in the roof of this
region. A median cubital vein typically connects the cephalic vein to the basilica vein in the
subcutaneous tissue. However, a median cephalic vein and a median basilic vein may be present
instead.
Intravenous Cannulation:
Performed to infuse fluid, transfuse blood and administer drugs. Typically a peripheral vein is
chosen, but a central vein – eg internal jugular or subclavian – is used to monitor CVP, infuse certain
drugs or supply parental nutrition.
It is far better to choose a superficial vein of the upper limb (to avoid risk of thrombosis in the lower
limb). The chosen vein should be as distal as possible along the limb (preferably the non-dominant
limb). Indwelling canulae should not overlie a joint (to avoid kinking).
The veins are distended by application of a tourniquet proximal to the selected site. Ideal sites are at
an inverted V junction point or where a vein pierces deep fascia. Veins tend to be more fixed at
these sites.
5. The lymph drainage of the breast (noting its significance in tumour spread)
The lymphatic drainage of the breast is important because of its role in the metastasis of cancer
cells.
Lymph passes from the nipple, areola, and lobules of the gland to the subareolar lymphatic plexus.
From this plexus:
 >75% lymph, especially from the lateral breast quadrants, drains to the axillary lymph
nodes, initially to the anterior or pectoral nodes. However some may drain directly to other
axillary nodes or interpectoral, deltopectoral, supraclavicular, or inferior deep cervical
nodes
 Most of the remaining lymph, particularly from the medial breast quadrants, drains to the
parasternal nodes or to the opposite breast
 Lymph from the inferior quadrants may pass deeply to abdominal nodes
6. Why swelling of the upper limb was a common sequel to a “radical mastectomy”
Simple mastectomy – the breast is removed down to the retromammary space
Radical mastectomy – removal of the breast, pectoral muscles, fat, fascia, and as many lymph nodes
as possible in the axilla and pectoral region.
Lymphatics normally take up fluid that has leaked from capillaries which would otherwise
accumulate in the interstitial compartment. Surgical removal of lymphatics may cause lymphoedema
as there is no removal of this fluid.
7. The effects and diagnosis of a sudden occlusion of the femoral artery
The six P’s:
Painful, Pale, Paralysed, Paraesthesia, Pulselessness, Perishingly Cold
8. The effects and diagnosis of long standing peripheral vascular disease of the femoral artery
Palpation of the posterior tibial pulses (between the posterior surface of the medial malleolus and
the medial border of the calcaneal tendon) is essential for examining patients with occlusive
peripheral arterial disease.
Intermittent claudication, characterised by leg pain and cramps, develops during walking and
disappears after rest. These conditions result in ischaemia of the leg muscles caused by narrowing or
occlusion of the leg arteries (eg femoral artery).
Other effects:
 Skin colour changes from white → blue → black
 Decubitus ulcers (pressure sores)
 Ischaemia/gangrene and tissue loss
 Hair loss
9. The site of: (i) great saphenous vein ‘cut-down’ (noting the structure endangered); (ii) femoral
artery and femoral vein punctures
(i) Saphenous cutdown – even when it is not visible (ie in infants, obese people or patients in shock
whose veins are collapsed), the great saphenous vein can always be located by making a skin incision
anterior to the medial malleolus. This is performed to insert a cannula for prolonged administration
of blood, plasma expanders, electrolytes or drugs.
Care should be taken to avoid laceration of the saphenous nerve which accompanies the vein
(patient will complain of pain or numbness along the medial border of the foot)
(ii) NAVY!
Femoral artery puncture – palpable in the femoral triangle (below the mid-inguinal point).
Femoral vein cannulation – locate femoral artery by palpation, the vein is just medial. Insert the
needle just medially to pulse, remembering that the vein may also be posterior to the artery.
10. The sites, diagnosis and effects of: (i) varicose veins (noting the significance of incompetence of
the valves of the perforating veins); (ii) deep vein thrombosis
(i) Varicose veins – abnormally swollen, twisted veins, most often seen in the legs (great saphenous,
short saphenous or dorsal venous arch). When the walls of veins lose their elasticity, they become
weak. A weakened vein dilates under the pressure of supporting a column of blood against gravity.
Varicose veins have a greater calibre than normal, and their valve cusps do not meet or have been
destroyed by inflammation. These incompetent valves mean the column of blood ascending towards
the heart is unbroken, placing increased pressure on the weakened walls, further exacerbating the
problem.
Incompetent valves of perforating veins are significant because the muscular venous pump shunts
blood from deep to superficial veins where blood pools.
Varicose veins may cause valvular incompetence OR valvular incompetence may cause varicose veins
(ii) Deep vein thrombosis (DVT) – of one or more of the deep veins of the lower limb is characterised
by swelling, warmth and erythema (redness caused by inflammation and infection).
Venous stasis is an important cause of thrombus formation. This can be caused by:
 Incompetent, loose fascia that fails to resist muscle expansion, diminishing the effectiveness
of the musculovenous pump
 External pressure on the veins from bedding during a prolonged hospital stay or from a tight
cast or bandage
 Muscular inactivity (eg overseas flight)
Thrombophlebitis – DVT with inflammation around the involved veins
11. How an infection of a toe may produce painful swelling in the ‘groin’
Lymph nodes enlarge when disease. Abrasions and minor sepsis, caused by pathogenic
microorganisms or their toxins in the blood or other tissues, may produce moderate enlargement of
the superficial inguinal lymph nodes (lymphadenopathy) in otherwise healthy people. Because the
enlarged nodes are located in the subcutaneous tissue, they are usually easy to palpate.
Field of drainage of the inguinal lymph nodes – the trunk inferior to the umbilicus, including the
perineum, as well as the entire lower limb. Thus an infection in any of these areas (including the
toes) may cause enlargement.
12. The structures involved in the differential diagnosis of a “lump” in the femoral triangle
 Enlarged inguinal lymph nodes – infection, metastasis
 Inguinal hernia
 Undescended (cryptorchid) testis
 Muscles – Sartorius, adductor magnus, iliopsoas, rectus femoris, pectineus
 Femoral vein, artery or nerve