Inotropes and vasopressors

Question 1

What do dromotropes do?

Answer 1

Increase conduction speed in AV node

Question 2

What do lusitropes do?

Answer 2

Promote diastolic relaxation (calcium mediated)

Question 3

What do bathmotropes do?

Answer 3

Make myocardium easier to depolarise (bring resting membrane potential and depolarisation threshold closer together)

Question 4

What effect does alpha 1 agonism have?

Answer 4

SM contraction

Vasoconstriction

Question 5

What effect does alpha 2 agonism have?

Answer 5

Reduces brainstem vasomotor centre-mediated CNS activation
Lowers BP
Reduces HR

Question 6

What effect does beta 1 agonism have?

Answer 6

Inotropic
Dromotropic
Chronotropic

Question 7

What effect does beta 2 agonism have?

Answer 7

SM relaxation

Question 8

What effect does beta 3 agonism have?

Answer 8

Lipolysis

Bladder relaxation

Question 9

What effect does dopamine agonism have on vasculature?

Answer 9

SM relaxation, particularly renal arteries - promote diuresis

Question 10

What are the effects of phenylephrine?

Answer 10

Peripheral vasoconstriction by stimulation of alpha 1 receptors and reflexive bradycardia as BP increases

Question 11

What is the mechanism of action of noradrenaline?

Answer 11

Potent alpha 1 agonist with mild beta adrenergic agonism

Question 12

Adrenaline at lower concentrations?

Answer 12

beta adrenergic effects predominate, causing raised HR and contractility via beta 1 and SM relaxation from beta 2

Question 13

Adrenaline at higher concentrations?

Answer 13

More alpha 1 agonism, leading to vasoconstriction

Question 14

How does dobutamine work?

Answer 14

Beta agonist, preferentially activating beta 1 receptors
Mild effect on beta 2 receptors and alpha receptors
Overall: inotropy, mild chronotropy and mild vasodilatory

Question 15

How does isoproterenol work?

Answer 15

Synthetic, non-selective beta agonist
Inotropy
With more profound chronotropy and vasodilatory effect than dobutamine

Question 16

How does dopamine have its main haemodynamic effects?

Answer 16

Via conversion to noradrenaline and adrenaline

Question 17

How does ephedrine work?

Answer 17

Increases activity of noradrenaline at adrenergic receptors

Question 18

Where is vasopressin made?

Answer 18

Synthesised as a prohormone in the hypothalamus

Travels down axon of that cell which terminates in the posterior pituitary

Question 19

When is vasopressin released?

Answer 19

In response to extracellular fluid hypertonicity (hyperosmality)+

Question 20

How does vasopressin affect the kidneys?

Answer 20

Increased transcription and insertion of aquaporin 2 channels in collecting tubules, allowing for water resorption

Question 21

What are the advantages of vasopressin over other pressors?

Answer 21

• Not pH dependent (catecholamines have diminshed response in acidic environment)
• Promotes platelet activity (e.g. in bleeding patient)
• Does not cause pulmonary vasoconstriction (and therefore does not increase RV afterload)