module 5

Question 1

Preload is

Answer 1

directly related to the venous return to the heart and reflects end-diastolic volume (EDV) which is the resting volume of the heart.

Question 2

This is known as the Frank-Starling Law

Answer 2

When the diastolic filling of the heart is increased or decreased with a given volume, the displacement of the heart is also altered. In other words, when preload is increased, stroke volume is increased and vice versa.

Question 3

What is compliance

Answer 3

‘distensibility of the ventricle … the change in ventricular volume for a given change in pressure’.

Question 4

Contractility

Answer 4

refers to the strength and efficiency of myocardial contraction.

Question 5

Afterload

Answer 5

represents the impedance to blood leaving the heart.

Question 6

ejection pressure:

Answer 6

end-systolic pressure opposing the vascular resistance

Question 7

• stroke volume:

Answer 7

the volume of blood ejected from the heart at each contraction

Question 8

• intrinsic factors:

Answer 8

functional characteristics of heart

Question 9

• extrinsic factors:

Answer 9

neural or hormonal control

Question 10

Shock

Answer 10

is an acute process in which the mechanisms to maintain cardiovascular homeostasis are disrupted resulting in an imbalance between cellular oxygen supply and cellular oxygen demand. Adequate cellular perfusion depends on a functioning cardiorespiratory system as well as adequate vascular tone and intravascular volume.

Question 11

compensatory mechanisms of shock

Answer 11

• activation of the sympathetic nervous system
• release of antidiuretic hormone (ADH)
• stimulation of the renin-aldosterone-angiotensin (RAA) system
or
• Increased HR
• Vasoconstriction – including decrease peripheral perfusion and peripheral temperature
• Decreased urine output
• Maintenance of BP

Question 12

Congestive heart failure (CHF) is described by many authors as

Answer 12

insufficient oxygen delivery to meet the metabolic demands caused from inadequate cardiac function or circulation.

Question 13

drugs that support cardiac function (contractility):

Answer 13

ace inhibitors
beta blockers
inotropes

Question 14

drugs that decrease volume load (preload/congestion):

Answer 14

diuretics

Question 15

drugs that reduce resistance to emptying (afterload):

Answer 15

vasodilators

Question 16

Frusemide

Answer 16

is effective to decrease circulating volume and reduce preload, thereby relieving dilatation of the ventricles and pulmonary congestion.

Question 17

ACE inhibitors (angiotensin converting enzyme)

Answer 17

cause vasodilation. Used for reduction of afterload and ↓ ventricular wall stress. Captopril is a commonly used ACE inhibitor

Question 18

• Digoxin:

Answer 18

cardiac glycoside that blocks myocardial cellular sodium-potassium pump causing an increase in the uptake of calcium thereby increasing the efficiency of contraction. Digoxin also has antiarrhythmic properties and prevents sympathetic over stimulation.

Question 19

• Beta blockers:

Answer 19

block the release of the stress hormones adrenaline and noradrenaline in certain parts of the body. This results in a slowing of the heart rate and reduces the force at which blood is pumped around your body.
They can also block your kidneys from producing angiotensin II, this results in lowering your blood pressure.

Propranolol, atenolol, carvedilol are beta blockers.

Question 20

• Aldosterone antagonists:

Answer 20

preventing sodium/water reabsorption and decreasing potassium loss. Spironolactone is an aldosterone antagonist.

Question 21

ECG tracing explanation

Answer 21

The SA node impulse depolarizes the right and left atria by contiguous spread, producing the P wave.
• When the atrial impulse arrives at the atrioventricular (AV) node, it passes through the node at a much slower velocity than any other part of the heart, producing the PR interval.
• Once the electrical impulse reaches the Bundle of His, the conduction velocity becomes very fast and spreads simultaneously down the left and right bundle branches to the ventricular muscle,
through the Purkinje fibres, producing the QRS complex.
The repolarization of the ventricle produces the T wave, but the repolarization of the atria is not usually visible on the ECG tracing

Question 22

• The P wave reflects

Answer 22

atrial depolarization (contraction)

Question 23

• The QRS complex represents

Answer 23

the onset of ventricular depolarization

Question 24

• The T wave indicates

Answer 24

ventricular repolarization: occurs just before ventricles start to relax
T wave is wider than the QRS complex because relaxation occurs more slowly

Question 25

Hypokalaemia –

Answer 25

defined as serum potassium less than 3.5 mmol/L • Decreased extracellular potassium causes myocardial hyperexcitability which may result in action potentials to fire prematurely & disrupting the normal cardiac cycle • Commonly caused be excessive GI losses • ECG findings include a flattened T wave

Question 26

Hyperkalaemia –

Answer 26

defined as serum potassium greater than 5.0 mmol/L - Often caused by increased intake of K+ supplements (i.e. parenteral additives/ oral supplements) or transfusions of packed red blood cells - ECG findings include a peaked T wave with hyperkalaemia

Question 27

Sinus arrhythmia

Answer 27

• Variation in regularity in heart rate originating from the sinus node (p wave) • Usually a benign rhythm and occurs in paediatrics often during sleep. HR will increase with inspiration and decrease with expiration

Question 28

Superventricular tachycardia

Answer 28

Most common non-arrest arrhythmia in childhood and most common to cause cardiovascular instability in infancy. • Generally, rates in infants are 250 to 300 beats/min; in children up to 250 beats/min; in adolescents 150- 220 beats/min.

Question 29

Ventricular tachycardia

Answer 29

* Less common in children. * Potentially life threatening arrhythmia, always requiring prompt intervention. * Wide complex tachycardia which originates in the ventricle * Patients may have a pulse with minimal to severe haemodynamic effects * If the patient is pulseless the treatment is CPR and defibrillation.

Question 30

Pulseless electrical activity

Answer 30

Absence of palpable pulse or other signs of circulation despite the presence of a rhythm on the monitor

Question 31

Adrenaline

Answer 31

increase myocardial contractility and rate by stimulating the ß1 receptors, as well as increasing blood pressure through increasing vascular tone by stimulating the α1 receptors.1

Question 32

Adrenaline is the first line drug for:

Answer 32

``` pulseless ventricular tachycardia ventricular fibrillation pulseless electrical activity bradycardia asystole ```

Question 33

Adenosine

Answer 33

Used in supraventricular tachycardia to temporarily block abnormal conduction and slow the heart rate.

Question 34

Amiodarone

Answer 34

Used to treat tachyarrhythmias, such as VT, or refractory VT/VF if unresponsive to defibrillation and adrenaline.

Question 35

Atropine

Answer 35

Used in bradycardia caused by vagal stimulation. | Sedative and amnesic actions.

Question 36

Midazolam

Answer 36

Used to sedate patient prior to the administration of muscle relaxants.

Question 37

Suxamethonium

Answer 37

Fast acting neuromuscular blocking agent. Used for muscle paralysis to assist with intubation.

Question 38

Vecuronium

Answer 38

Neuromuscular blocking agent with a longer action. Used for muscle paralysis for the control of ventilation and to assist with intubation.