Inotropes + vasopressors

Question 1

Adrenaline actions

Answer 1

Non- selective agonist at all adrenergic receptors
Low dose infusion has inotropic B effects but increasing the dose increases alpha action
B2 linked peripheral vasodilation can cause diastolic blood pressure to fall

Question 2

Which isomer of adrenaline is more potent?

Answer 2

L isomer- 15x more potent than dextro isomer

Question 3

Dopamine adrenergic effect?

Answer 3

Low dose infusion has mainly B1 action, higher doses increase a action
Increases atrioventricular conduction
Can cause tachycardia at higher doses (esp with inadequate preload)
Stimulates NA release

Question 4

Dopamine effects (not via adrenoreceptors)

Answer 4

N + V- D2 receptors in the ChemoreceptorTZ
Inhibits prolactin secretion
PEripheral D1 activation causes vasodilation of renal + mesenteric beds
Does NOT cross BBB

Question 5

Dobutamine adrenergic effects

Answer 5

Primarily B1 receptors with some B2 and a1 action
Decreases preload due to peripheral b2 activation- dilation reduces return + svr

Question 6

Isoprenaline adrenergic action

Answer 6

Potent B1 + B2 receptor agonist, increases CO but SVR can drop due to peripheral B2 action
Commonly used for bradyarrhythmias

Question 7

Dopexamine adrenergic affects

Answer 7

ANalogue of dopamine- has action on B2 and D1 receptos with minimal B1 and no a1
Causes inotropy via cardiac B2 but reduces peripheral vascular resistance

Question 8

Protein kinase actions inside cardiac cells?

Answer 8

Phosphorylation of L type calcium channels to increase calcium influx during action potential
INcreases the release of calcium from sarcoplasmic reticulum
(overall increases force of myocardial contraction)

Question 9

HOw do PDE inhibitors increase inotropy?

Answer 9

PDE cause breakdown of cAMP (which activates protein kinase A)
INhibition increases cAMP and therefore calcium

Question 10

Examples of PDE III inhibitors?

Answer 10

Enoximone + milrinone- both inodilators

Question 11

How does aminophylline have a positive inotropic effect?

Answer 11

Non selective PDE inhibitor

Question 12

WHich PDE isoenzymes work in the myocardium?

Answer 12

3+4

Question 13

How does levosimendan work and when is it used

Answer 13

Increases myocyte sensitivity to Calcium by binding to troponin C_ increases contractility without increasing intracellular calcium
Used in cases of severe acute cardiac failure
Also relaxes vascular smooth muscle by opening ATP sensitive K+ channels causing peripheral vasodilation

Question 14

How does digoxin increase inotropy

Answer 14

INhibits the sodium-potassium atpase pump- increasing intracellular sodium
Decreases the inwards movement of sodium via the sodium calcium exchange pump, decreases the movement of calcium out of cells
INcreases intracellular calcium

Question 15

How does glucagon increase inotropy?

Answer 15

Gs protein linked and so activation increases intracellular cAMP

Question 16

Where are a1 adrenoreceptors found

Answer 16

Smooth muscle of the peripheral vasculature

Question 17

Norad actions?

Answer 17

A1 adrenoreceptor activation, some B1 action
Minor inotropic action but this is offset by the baroreceptor reflex vagal response to the increaswed blood pressure

Question 18

Ephidrine actions?

Answer 18

Mixed A + B adrenergic stimulation
Works directly and indirectly by displacing norad from storage granules

Question 19

Ephedrine causes tachyphylaxis because

Answer 19

Noradrenaline store are depleted

Question 20

Phenylephrine actions

Answer 20

Potent and pure a1 agonist
Causes reflex bradycardia due to the baroreceptor response

Question 21

Metaraminol actions

Answer 21

Mainly a1 with some b1
Direct + indirect actions by causing norad release

Question 22

WHat type of receptor are V1 receptors?

Answer 22

G1 protein coupled. Stimulation by ADH causes peripheral vasoconstriction