(A) - CV Support

Question 1

What four factors determine overall cardiac output and cardiac function?

Answer 1

Preload
Afterload
Contractility
Heart rate

Question 2

What is preload?

Answer 2

Filling pressure

Stretch of ventricular muscle at end diastole just before contraction
Related to end diastolic volume
Higher preload usually increases stroke volume up to a limit

Question 3

What is afterload?

Answer 3

Pressure the LV has to overcome to pump blood into circulation

MAP is the largest contributor
Increases with hypertension
Increases with aortic stenosis
High afterload reduces stroke volume

Question 4

What is contractility?

Answer 4

Intrinsic strength of myocardial contraction
Improves stroke volume at a given preload
Reduced in heart failure or after myocardial infarction

Question 5

What is systemic vascular resistance (SVR)?

Answer 5

Resistance in the systemic circulation that the heart pumps against
Major determinant of afterload and mean arterial pressure

Question 6

What is mean arterial pressure (MAP)?

Answer 6

Average arterial pressure across systole and diastole
Reflects adequacy of tissue perfusion
Depends on cardiac output and systemic vascular resistance

Question 7

What does low MAP cause at tissue level?

Answer 7

Tissue hypoperfusion
Hypoxia
Anaerobic metabolism
Lactate rise
Organ dysfunction

Question 8

What is basic non invasive monitoring of cardiac function?

Answer 8

Heart rate
Non invasive blood pressure
Oxygen saturations
Continuous ECG monitoring

Question 9

What monitoring does an arterial line provide?

Answer 9

Continuous invasive blood pressure monitoring
Access for arterial blood gases
Useful in unstable patients on ICU

Question 10

What does central venous pressure measure and where is it measured?

Answer 10

Estimates right sided filling pressure as a surrogate of preload
Measured via a central venous catheter in the vena cava or right atrium

Question 11

What is central venous oxygen saturation and what does it suggest?

Answer 11

Oxygen saturation of venous blood returning to the heart
Low values suggest increased oxygen extraction
Can indicate low cardiac output or high metabolic demand

Question 12

What is pulmonary artery wedge pressure and what does it reflect?

Answer 12

Pressure measured when a pulmonary artery catheter is wedged
Reflects left atrial pressure
Used rarely in specialist settings

Question 13

What echocardiography options are used in ICU and what do they assess?

Answer 13

Transthoracic echo assesses function non invasively

Transoesophageal echo gives detailed views in ventilated or difficult windows
Assesses ventricular function
Volume status
Valves
Pericardial effusion

Question 14

What is PiCCO monitoring and how does it estimate cardiac output?

Answer 14

Pulse contour cardiac output monitoring
Uses a central venous line
Uses a thermodilution arterial line
Provides continuous cardiac output estimates and volume status trends

Question 15

What is an oesophageal Doppler monitor used for?

Answer 15

Measures blood flow in the thoracic aorta
Estimates stroke volume and cardiac output
Used to guide fluid therapy perioperatively and in ICU

Question 16

Why is fluid status optimisation the first step in haemodynamic support?

Answer 16

Many patients have low preload from hypovolaemia
Improving preload can improve stroke volume and cardiac output
Avoids unnecessary inotropes and vasopressors

Question 17

How does low central venous pressure affect cardiac output?

Answer 17

Suggests reduced preload
Less ventricular filling
Lower stroke volume
Reduced cardiac output

Question 18

How do IV fluids improve cardiac output in hypovolaemia?

Answer 18

Increase preload
Increase end diastolic volume
Increase stroke volume via Frank Starling mechanism
Can raise cardiac output and MAP

Question 19

Why is excessive IV fluid harmful in ICU?

Answer 19

Causes fluid overload
Leads to pulmonary oedema
Worsens heart failure congestion
Associated with increased mortality

Question 20

What are inotropes?

Answer 20

Drugs that change myocardial contractility
Positive inotropes increase contractility
Negative inotropes reduce contractility

Question 21

When are positive inotropes used?

Answer 21

Low cardiac output states
Heart failure
Post myocardial infarction
Post cardiac surgery

Question 22

How do catecholamine inotropes work?

Answer 22

Stimulate sympathetic receptors
Beta receptor effects increase contractility and heart rate
Alpha receptor effects increase vasoconstriction depending on drug

Question 23

Name common catecholamine positive inotropes used in ICU

Answer 23

Adrenaline
Dobutamine
Isoprenaline
Noradrenaline
Dopamine

Question 24

Why is noradrenaline described as mainly a vasopressor?

Answer 24

Strong alpha mediated vasoconstriction raises SVR and MAP
Only weak beta inotropic effect

Question 25

What are non catecholamine positive inotropes and how do they work?

Answer 25

Milrinone is a phosphodiesterase 3 inhibitor increasing contractility and vasodilation Levosimendan increases calcium sensitivity of myocardium improving contraction

Question 26

Why are inotropes usually given via a central line in ICU?

Answer 26

Risk of extravasation causing tissue injury if given peripherally Allows reliable infusion Patients require close monitoring and titration

Question 27

What are examples of negative inotropes?

Answer 27

Beta blockers Calcium channel blockers Flecainide

Question 28

What are vasopressors and what do they do to MAP?

Answer 28

Drugs causing vasoconstriction Increase systemic vascular resistance Increase mean arterial pressure Improve tissue perfusion pressure

Question 29

When are vasopressors commonly used in ICU?

Answer 29

Vasodilatory shock Severe sepsis Perioperative hypotension Cardiac arrest resuscitation support

Question 30

Name common vasopressors

Answer 30

Noradrenaline Vasopressin Adrenaline Metaraminol Ephedrine Phenylephrine

Question 31

What is vasopressin and how does it work as a vasopressor?

Answer 31

Antidiuretic hormone Causes vasoconstriction via smooth muscle contraction Increases water reabsorption in collecting ducts

Question 32

What is glycopyrronium and when is it used?

Answer 32

Antimuscarinic drug Treats bradycardia during anaesthesia Blocks acetylcholine at muscarinic receptors

Question 33

What is an intra aortic balloon pump used for?

Answer 33

Temporary haemodynamic support in cardiogenic shock Support in acute coronary syndrome Support after cardiac surgery

Question 34

Where is an intra aortic balloon pump placed and how is it driven?

Answer 34

Catheter inserted via femoral artery into descending thoracic aorta Balloon inflates and deflates in sync with cardiac cycle Helium used to inflate balloon rapidly

Question 35

How does an intra aortic balloon pump improve coronary perfusion?

Answer 35

Inflates during diastole Augments diastolic pressure Pushes blood into coronary arteries

Question 36

How does an intra aortic balloon pump reduce afterload?

Answer 36

Deflates just before systole Reduces resistance to ejection Increases cardiac output

Question 37

What are the key overall effects of an intra aortic balloon pump?

Answer 37

Increases coronary blood flow Reduces afterload Increases cardiac output