Week 3- Venous and arterial access Flashcards
Where are superficial veins located?
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.
What vein is shown?
What structure does it drain into?
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.
What does the subcutanous location of veins mean in practice?
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.
What muscles are shown?
What vein can be accessed between these muscles?
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.
Define phlebotomy
Where is the preferred site?
Which veins are usually accessed?
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.
What are the major borders and contents of the cubital fossa?
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
What should you be careful of if you go through the deep fascia within the cubital fossa?
Median nerve and brachial artery sit directly beneath deep fascia
If the brachial artery is punctured it can bleed profusely under the deep fascia.
Which vein should ideally be used for phlebotomy?
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.
What is key to phlebotomy?
Stabilise the skin and approach through the skin at a shallow angle.
What are the two muscles shown?
- Brachoradialis
- pronator teres
What are the indications for cannulation?
How long can a cannula stay in place?
- 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
What are the contraindications for venous cannulation?
- Regional infection
- oedematous
- Inflamed tissue
- burns
- Vascular damage or trauma
- regional pain or trauma
What are the complications of cannulation?
- Infection
- Sepsis
- Venous inflammation
- thrombosis
- thrombophlebitis
- Embolus
- Tissue infusion
What are common locations for superficial vein cannulation?
- Cubital fossa
- Dorsal hand
- anatomical snuffbox
- medial ankle venous cut down –> uncommon but need to know
Label the image
What two structures do the superficial veins of the cubital fossa sit near?
Cephalic vein
basilic vein
median cubital vein
Superifical veins sit close to the medial cutaneous nerve and lateral cutaneous nerve of the forearm.
What can damage to the cutaneous nerves of the forearm cause?
Damage to the cutaneous nerves of the forearm can cause:
Pain
paraesthesia
Sensory loss
What structures are highlighted in yellow?
What is the purpose of the tourniquet?
Why is the dorsal hand a good site for cannulation?
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.
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?
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
Where will a patient report paraesthesia if the superficial branch of the nerve is compressed?
The superificial portion of the radial nerve innervates the first dorsal webspace –> patient will feel pain/ tingling here.
Label the image
Label the structures shown
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
what are the indications for venous cutdown?
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
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
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
Where would you cannulate a neonate/ young child?
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
What is intraosseous infusion?
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.
Why is intraosseous infusion feasible / useful?
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
Why in intraosseous infusion do we aim for the proximal/ distal end of the bone?
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).
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?
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.
What bony feature is shown?
What muscle has been reflected back?
What nerve must be avoided?
The greater tubercle of the proximal humerus
The deltoid has been reflected back
The axillary nerve must be avoided.
What are the indications for central venous system catheterisation?
What are the two sites for central venous catheters?
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
What are the complications of central venous catheterisation?
- infection
- heamorrhage
- catheter occlusion
- pneumothorax
- air embolus
- displacement and tissue infiltration
- iatrogenic nerve/ arterial injury
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?
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
Why is central venous catheterisation preferentially done on the right vs the left?
Due to the relatively straight line of the Right IJV into the SVC
Why is an xray done after central venous catheterisation?
Position of the IJV central venous line can be checked via radiography
Also check for pneumothorax
What is the surface anatomy of the EJV?
The EJV passes from the angle of the mandible to the lateral edge of the SCM clavicular head
Label the image
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.
What is the cervical plexus? nerve roots?
What are its two portions and what do they innnervate?
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
What venous route can be accessed in the neonate?
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.
What are the indications for arterial blood sampling?
Acid base and blood gas sampling
What are the complications of arterial blood sampling/ access?
Complications:
1) haematoma
2) arterial spasm –> causing ischaemia
3) retrograde embolism
4) traumatic aneurysm
5) infection/ sepsis
Where is the femoral artery located?
What can it be used for?
what should you take care of in this region?
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.
Where can the radial artery be accessed for cannulation?
Which tendon may mark its location?
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.
Why should you not cannulate the ulnar artery?
Ulnar artery and ulnar nerve are very closely related, high chance of damage to the ulnar nerve during this procedure.
What are the uses of the radial artery?
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
What test should always be done prior to accessing the radial artery?
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.
What must you do during radial artery cannulation?
Confirm collateral supply using allens test
use a preheparinised syringe
approach vessel at 45 or 90 degrees
