LECTURE 7 (Cannulation)

Question 1

What is a cannula?

Answer 1

A flexible tube containing a needle (stylet) which may be inserted into a blood vessel

Question 2

What are the main factors prior to inserting a peripheral cannula?

Answer 2

• Location of sitting
• Condition of the vein
• Purpose of the device

Question 3

What are the properties of the Cephalic vein?

Answer 3

• Size + position -> excellent for transfusions
• Accommodates a large-gauge cannula
• Provides a natural splint

Question 4

What are the properties of the Basilic vein?

Answer 4

• A large vessel
• Ulnar border or hand and forearm

Question 5

What are the properties of the Digital veins?

Answer 5

• Small
• Can accommodate a small-gauze needle
• Last resort for fluid administration

Question 6

What are the properties of Metacarpal veins?

Answer 6

• Accessible
• Easily visualised and palpated
• Well suited for cannulation

Question 7

What are the Indications for cannulas?

Answer 7

• Short-term therapy (less than a week)
• Bolus injections/short infusions in the outpatient/day unit setting

Question 8

What are the Contraindications for cannulas?

Answer 8

• Long-term intravenous therapy
• Longer/continuous infusions of medications that are vesicant or those that have a pH > 9

Question 9

What does application of the tourniquet promote?

Answer 9

Venous distension

Question 10

What is the difference between the Direct method and the Indirect method?

Answer 10

Direct method = when the device enters through skin and immediately enters the vein

Indirect method = When the device is inserted through the skin and vein is relocated and device is advanced into the vessel

Question 11

Why shouldn’t the stylet be reintroduced after unsuccessful cannulation?

Answer 11

Could result in
- catheter fragmentation
- embolism

Question 12

What is the measurement used for needles and cannulas?

Answer 12

Standard wire gauge

Measures the internal diameter (the smaller the gauze size, the larger the diameter)

Question 13

How do you prepare the skin?

Answer 13

An antiseptic solution (e.g 2% chlorhexidine solution or 70% alcohol) should be applied with repeated back-and-forth strokes with friction for 30-60 seconds for an area of 4-5cm

Question 14

When should cannulas be resited?

Answer 14

48-72 hours

Question 15

What are the complications of Cannula insertion?

Answer 15

• Pain
• Hematoma
• Phlebitis
• Irritation/damage due to large cannulas or movement
• Chemical irritation from drugs
• Bacterial infection

Question 16

What is Phlebitis?

Answer 16

Inflammation of the intima of the vein

CHARACTERISED BY:
- pain and tenderness along cannulated vein
- erythema
- warmth and streak formation with/without palpable cord

Question 17

What are the three types of Phlebitis?

Answer 17

• Mechanical
• Chemical
• Bacterial

Question 18

What are Arterial cannulas?

Answer 18

Plastic tube inserted and secured in a peripheral or central artery

Question 19

Where are Arterial cannulas most commonly used?

Answer 19

In intensive care units and during surgery to
- Provide a means for continuous intra-arterial pressure monitoring
- Facilitate frequent blood sampling for blood gas and lab analysis

Question 20

What are safest and most common sites for arterial cannulation?

Answer 20

• Radial artery
• Dorsalis pedis

Question 21

Where is the central site of choice if peripheral arterial cannulation is not possible?

Answer 21

Femoral cannulation

Question 22

What are the Indications for Arterial cannulation?

Answer 22

• During/following major anaesthesia
• Monitoring of acid/base balance and respiratory status in: acute respiratory failure, mechanical ventilation, during and after CPR, critically ill patients, severe sepsis and shock conditions

Question 23

What are the Contraindications for Arterial cannulation?

Answer 23

• Previous upper extremity surgery
• Previous axillary clearance
• Peripheral vascular disease
• Raynaud’s disease (decreased blood flow to fingers)
• Diabetes
• Collagen vascular disease
• Active upper or lower limb infection