Week 3- Venous and arterial access

Question 1

Where are superficial veins located?

Answer 1

Superficial veins are located in the subcutaneous tissues (fat with loose connective tissue).

Note in the picture the external jugular vein sat just under platysma muscle in the neck. View of the left neck with just skin and superficial fat removed.

Question 2

What vein is shown?

What structure does it drain into?

Answer 2

The external jugular vein is shown, draining into the subclavian vein.

External jugular vein can be cannulated for central venous access in the case that you cannot access the internal jugular vein.

Question 3

What does the subcutanous location of veins mean in practice?

Answer 3

Subcutaneous location of veins means that they move freely with the skin.

For clinical procedures you need to make sure you stabilise the vein by holding the skin.

Question 4

What muscles are shown?

What vein can be accessed between these muscles?

Answer 4

Note the two heads of sternocleidomastoid, with sternal head and clavicular head.

The internal jugular vein can be accessed between the two heads of sternocleidomastoid.

Question 5

Define phlebotomy

Where is the preferred site?

Which veins are usually accessed?

Answer 5

Phlebotomy = the sampling of blood usually from superficial veins

Preferred site usually upper limb over the cubital fossa

Cephalic, basilic or median cubital veins are accessed.

Question 6

What are the major borders and contents of the cubital fossa?

Answer 6

Cubital fossa borders:

Superior border = hypothetical line between epicondyles of the humerus

lateral border = medial border of bracioradialis muscle

medial border = lateral border of pronator teres

Contents:

Radial nerve

Biceps tendon

Brachial artery

Median nerve

Veins:

Cephalic

Basilic

medican cubital vein

Question 7

What should you be careful of if you go through the deep fascia within the cubital fossa?

Answer 7

Median nerve and brachial artery sit directly beneath deep fascia

If the brachial artery is punctured it can bleed profusely under the deep fascia.

Question 8

Which vein should ideally be used for phlebotomy?

Answer 8

Ideally the cephalic vein should be used as it is the safest.

Due to the fact that median nerve and brachial artery sit medially, whereas cephalic vein sits laterally.

The cutaneous nerves of the skin also tend to sit away from the lateral side of the cubital fossa.

Question 9

What is key to phlebotomy?

Answer 9

Stabilise the skin and approach through the skin at a shallow angle.

Question 10

What are the two muscles shown?

Answer 10

• Brachoradialis
• pronator teres

Question 11

What are the indications for cannulation?

How long can a cannula stay in place?

Answer 11

• For intravenous infusion –> fluid, blood, drugs
• Repeated venous sampling
• Measuring central venous pressure
• Short term venous access (duration varies)
• Can stay in place for days if not infected
• For longer term use, need a central venous line

Question 12

What are the contraindications for venous cannulation?

Answer 12

• Regional infection
• oedematous
• Inflamed tissue
• burns
• Vascular damage or trauma
• regional pain or trauma

Question 13

What are the complications of cannulation?

Answer 13

• Infection
• Sepsis
• Venous inflammation
• thrombosis
• thrombophlebitis
• Embolus
• Tissue infusion

Question 14

What are common locations for superficial vein cannulation?

Answer 14

• Cubital fossa
• Dorsal hand
• anatomical snuffbox
• medial ankle venous cut down –> uncommon but need to know

Question 15

Label the image

What two structures do the superficial veins of the cubital fossa sit near?

Answer 15

Cephalic vein

basilic vein

median cubital vein

Superifical veins sit close to the medial cutaneous nerve and lateral cutaneous nerve of the forearm.

Question 16

What can damage to the cutaneous nerves of the forearm cause?

Answer 16

Damage to the cutaneous nerves of the forearm can cause:

Pain

paraesthesia

Sensory loss

Question 17

What structures are highlighted in yellow?

Answer 17

Question 18

What is the purpose of the tourniquet?

Why is the dorsal hand a good site for cannulation?

Answer 18

Tourniquet application occludes venous return and aids superficial vein identification.

Dorsal venous nertwork of the hand provides classic easy access route for cannulation. Multiple mobile veins sit on the dorsal hand just under thin mobile skin. They are easily seen/ palpated.

Question 19

Which superficial vein can be a target for cannulation in the anatomical snuffbox?

What other structures should you be careful of in this region?

What are the boundaries of the anatomical snuffbox?

Answer 19

The cephalic/ houseman’s vein passes over the roof of the anatomical snuffbox from the lateral side of the dorsal venous network.

It passes superficially to snuffbox tendons.

Also passes in close proximity to the superficial cutaneous branch of the radial nerve which can be damaged.

Boundaries of the anatomical snuffbox:

Medially –> extensor pollicis longus

laterally –> extensory pollicis brevis and abductor pollicis longus

Question 20

Where will a patient report paraesthesia if the superficial branch of the nerve is compressed?

Answer 20

The superificial portion of the radial nerve innervates the first dorsal webspace –> patient will feel pain/ tingling here.

Question 21

Label the image

Answer 21

Question 22

Label the structures shown

Answer 22

Tendons –> extensor pollicis longus, extensor pollicis brevis, abductor pollicis longus

Overlying the tendons = extensor retinaculum

Vein running over is the cephalic vein

Next to this is the superificial radial nerve

deeper within the anatomical snuffbox = radial artery

Question 23

what are the indications for venous cutdown?

Answer 23

Venous cutdown is indicated when percutaneous venous acces s unsuccessful. Also in:

1) Children/ infants/ adults in shock
2) iv drug abusers
3) Burned or scarred patients
4) Distorted anatomy
5) Cardiac arrest without palpable femoral pulse
6) individuals in which IV line cannot be quickly obtained

Question 24

What vein passes superficial to the medial malleolus?

What nerve is associated with this vein?

How can you locate this vein for venous cut down?

Describe venous cut down procedure

Answer 24

Great saphenous vein passes around 1-2 cm anterior from the medial malleolus.

The saphenous nerve passes with the great saphenous vein and supplies the medial side of the leg and foot. (also gives branches to the knee joint and contributes to the patellar and subsartorial plexus.)

How to identify:

• Identify the medial malleolus
• Identify the great saphenous vein via palpation around 1-2 cm anterior to medial malleolus
• Measure 1-1.5 cm anterior and superior to the medial malleolus
• perform a transverse incision of up to 2.5cm from the anterior toward the posterior border of the tibia
• A cannula can be directly inserted under the skin

Question 25

Where would you cannulate a neonate/ young child?

Answer 25

central venous cannulation, veins on the scalp (especially babies), cubital fossa, dorsum of hand, external juglar vein, and venous cut down --\> saphenous, basilic Or intraosseous infusion --\> long bones such as femur, tibia, proximal humerus

Question 26

What is intraosseous infusion?

Answer 26

Intraosseous infusion = process of injecting directly into the marrow of a bone. This provides a non-collapsible entry point into the systemic venous system technique is used to provide fluids and medication when intravenous access is not available or not feasible. Intraosseous infusions allow for the administered medications and fluids to go directly into the vascular system.

Question 27

Why is intraosseous infusion feasible / useful?

Answer 27

Bones contain an extensive vascular network. Intraosseous/ medullary space pressure is generally greater than systemic venous pressure, meaning any fluid/ medication introduced here will quickly pass into the venous system. A network of venous sinusoids exist in the medullary cavity which drain into the venous circulation

Question 28

Why in intraosseous infusion do we aim for the proximal/ distal end of the bone?

Answer 28

Aim for proximal/ distal ends due to the thickness of the bone in the centre of the bone which is the weight bearing portion (diaphysis).

Question 29

What are two common sites for intraosseous infusions? Does the dose/ rate of drug introduction change? are there any pharmocokinetic differences between intraosseous and intravenous lines?

Answer 29

1) proximal humerus (greater tubercle) 2) anterior proximal tibia Fluids/ drugs can be administerd at the same dose and rate as the intravenous route No pharmacokinetic differences exist between intravenous and intraosseous lines.

Question 30

What bony feature is shown? What muscle has been reflected back? What nerve must be avoided?

Answer 30

The greater tubercle of the proximal humerus The deltoid has been reflected back The axillary nerve must be avoided.

Question 31

What are the indications for central venous system catheterisation? What are the two sites for central venous catheters?

Answer 31

Indications: Required for long term venous access Chemotherapeutic drug administration Right heart access option if peripheral veins inaccessible central venous pressure measurement Sites: 1) internal jugular vein line 2) subclavian line

Question 32

What are the complications of central venous catheterisation?

Answer 32

* infection * heamorrhage * catheter occlusion * pneumothorax * air embolus * displacement and tissue infiltration * iatrogenic nerve/ arterial injury

Question 33

Which muscle is shown? label the two bellies and the fossa shown why is this a useful landmark? what vein can be accessed? What are the two access routes?

Answer 33

Sternocleidomastoid is shown with its sternal head and clavicular head. Inbetween the two muscle bellies = lesser supraclavicular fossa, The internal jugular vein can be accessed here for central venous catheterisation. Access routes: superior apex of the lesser supraclavicular fossa posterior border of sternocleidomastoid

Question 34

Why is central venous catheterisation preferentially done on the right vs the left?

Answer 34

Due to the relatively straight line of the Right IJV into the SVC

Question 35

Why is an xray done after central venous catheterisation?

Answer 35

Position of the IJV central venous line can be checked via radiography Also check for pneumothorax

Question 36

What is the surface anatomy of the EJV?

Answer 36

The EJV passes from the angle of the mandible to the lateral edge of the SCM clavicular head

Question 37

Label the image

Answer 37

Top arrow points to the accessory nerve Then the external jugular vein Then the cutaneous nerve point of the neck where the cervical plexus cutaneous portion emerges in posterior triangle of the neck deep to sternocleidomastoid. Bottom arrow points to sternocleidomastoid.

Question 38

What is the cervical plexus? nerve roots? What are its two portions and what do they innnervate?

Answer 38

Cervical plexus --\> anterior rami of of C1-C4, arises lateral to the transverse processes, located deep to sternocleidomastoid in the neck, emerge at the nerve point in the posterior triangle of the neck. Has two types of branches: muscular and cutaneous Cutaneous (4 branches): Lesser occipital - innervates the skin and the scalp posterosuperior to the auricle (C2) Great auricular nerve - innervates skin near concha auricle (outer ear) and external acoustic meatus (ear canal) (C2&C3) Transverse cervical nerve - innervates anterior region of neck (C2&C3) Supraclavicular nerves - innervate the skin above and below the clavicle (C3,C4) Muscular: Ansa cervicalis (This is a loop formed from C1-C3 which supplies the four infrahyoid aka strap muscles), etc. (thyrohyoid (C1 only), sternothyroid, sternohyoid, omohyoid) Phrenic (C3-C5 (primarily C4))-innervates diaphragm and the pericardium Segmental branches (C1-C4)- innervates anterior and middle scalenes

Question 39

What venous route can be accessed in the neonate?

Answer 39

The dural venous sinuses in the cranium can be accessed in the neonate. The superior sagittal sinus passes deep to the anterior and posterior fontanelles Can be used for emergency venous access.

Question 40

What are the indications for arterial blood sampling?

Answer 40

Acid base and blood gas sampling

Question 41

What are the complications of arterial blood sampling/ access?

Answer 41

Complications: 1) haematoma 2) arterial spasm --\> causing ischaemia 3) retrograde embolism 4) traumatic aneurysm 5) infection/ sepsis

Question 42

Where is the femoral artery located? What can it be used for? what should you take care of in this region?

Answer 42

Femoral artery located at the midinguinal point around 1.5 cm medial/ lateral to it. The femoral nerve sits around 1cm lateral to the femoral artery, care should be taken not to hit the nerve during arterial access.

Question 43

Where can the radial artery be accessed for cannulation? Which tendon may mark its location?

Answer 43

The radial artery is accessible near the wrist as a pulse point or for cannulation Marked by the tendon of flexor carpi radialis, radial artery is lateral to this. This tendon is useful as you can approach the artery laterally, which pushes it against the tendon and stops the artery moving around.

Question 44

Why should you not cannulate the ulnar artery?

Answer 44

Ulnar artery and ulnar nerve are very closely related, high chance of damage to the ulnar nerve during this procedure.

Question 45

What are the uses of the radial artery?

Answer 45

Radial artery: can be harvested for grafts a radiocephalic fistula can be used for haemodialysis (radial artery connected to cephalic vein) the radial artery can be cannulated

Question 46

What test should always be done prior to accessing the radial artery?

Answer 46

Allen's test should always be done prior to access to ensure there is collateral circulation via the ulnar artery and to prevent necrosis of tissue in the hand.

Question 47

What must you do during radial artery cannulation?

Answer 47

Confirm collateral supply using allens test use a preheparinised syringe approach vessel at 45 or 90 degrees