Reasons For Arterial Cannulation

Question 0

5 sites for arterial cannulation

Answer 0

Radial artery site of choice good collateral supply from ulna artery
Femoral artery used in severely hypotensive patients
Dorsalis pedis (very small and cant mobilise patient
axillary artery
brachial artery. short term, last resort, End artery so thrombosis could lead to complete ischaemia

Question 1

List 5 reasons for arterial Cannulation

Answer 1

1. Continuous monitoring of blood pressure (provides best to beat systolic, diastolic and mean arterial bp)
2. Frequent arterial blood sampling
3. When BP needs to be precisely controlled (eg neurosurgery, middle air surgery)
4. When NIBP is impractical
5. Transport of critically ill patients

Question 2

Factors involved in choosing an arterial cannulation site

Answer 2

Must be good collateral supply to limb
Easily visible and accessible
In area not prone to infection or near wound
Not in a limb with a vascular prosthesis or AV fistula

Question 3

Complications of arterial cannulation

Answer 3

Severe bleeding from disconnection
Haematoma 
thrombosis
infection
inadvertent intra arterial injection
distal ischaemia
intimal damage (damage to artery wall)
aneurysim formation
pain
nerve damage

Question 4

Consequences of inadvertent arterial injection?

Answer 4

arterial spam
tissue destruction by drug (thiopentone)
chemical artetitis
vasoconstriction
causes distal vascular occlusion which leads to limbs ischemia which results in gangrene

Question 5

Ways of avoiding inadvertent arterial injection

Answer 5

label the line

put arterial set on a separate drip stand

Question 6

Equipment for A Line

Answer 6

1. Arterial cannula usual size 20 or 22G so smaller than venous cannula
2. Giving set :
   * flushing mechanism 3-4 mls an hours prevents clotting and back flow and keeps line open
   * Non compliant manometer tubing
   * 3way tap for zeroing
3. Normal saline pressurised to 300mmHg
4. Transducer

Question 7

What is a transducer

Answer 7

A device that changes energy from one form to another. In the case of A line it changes movement energy into electrical energy

Question 8

When should the line be zeroed

Answer 8

1. When the transducer is initially connected

2. Whenever the patient is moved

Question 9

Practical considerations for A line

Answer 9

No air in line
runt through before pressuring bag
transducer should be level with right atrium
Zero line when first connected to transducer and whenever patient is moved
Observe site for bleeding and distal Ischaemia
Investigate any blood on floor - has 3 way tap been left open or line become disconnected

Question 10

Mean Arterial Pressure normal range

Answer 10

70 - 105 mmHg

Question 11

MAP =

Answer 11

MAP = systolic + (diastolic x2) /3

Question 12

Mean arterial pressure is directly related to —–?

Answer 12

perfusion of vital body organs

Question 13

Describe an arterial wave form

Answer 13

1Rapid upstroke reflects blood ejected from ventricles into aorta i.e reflects myocardial contractility

2. Dicrotic notch (closure of aortic valve, end of T wave)
3. Downward slope/End diastolic (lowest pressure before next cardiac cycle indicates resistance to outflow from hear)

Question 14

What does a slow upstroke on an arterial wave form indicate

Answer 14

need for inotropic support

Question 15

Arterial wave form - how to calculate stroke volume

Answer 15

Measure area from beginning of upstroke to dicrotic notch

CO=Stroke Vol x HR

Question 16

Arterial waveform- The position of the dicrotic notch on the down stroke reflects

Answer 16

Peripheral vascular resistance

Question 17

The dicrotic notch will be —– in vasoconstricted patients and —- in patients who are vasodilated or in hypovolaemic patients

Answer 17

higher

lower