Vascular Drugs

Question 1

What is the formula for mean blood pressure?

Answer 1

BP = Cardiac output * Systemic Vascular Resistance

Question 2

What is the formula for cardiac output?

Answer 2

CO = Heart rate * stroke volume

Question 3

What is the formula for O2 delivery?

Answer 3

O2 Delivery = Cardiac Output * Arterial O2 Content

Question 4

How much O2 is delivered and consumed per minute at rest?

Answer 4

Delivery = 1000 ml/min
Consumption = 250 ml/min

Remaining = 750 ml/min

Question 5

What are the factors affecting Stroke volume?

Answer 5

Preload (the end pDiastolic that stretches the ventricles) = filling

Contractility

Afterload (end load of tension in ventricle walls before it ejects) = resistance

Question 6

What do vascular dilator drugs do?

Answer 6

Relax vascular smooth muscle

Can act on arterial and/or venous sites

Dose dependent, i.e. GTN

Can act on other tissue such as cardiac muscle

Question 7

How do arterial dilators work?

Answer 7

Decrease BP by decreasing systemic vascular resistance, therefore Cardiac output increased

Question 8

How do veno dilators work?

Answer 8

Stroke volume decreases, i.e. CO decreased => decrease in BP

Question 9

What are the indications of vascular dilators?

Answer 9

Hypertension

• essential HT
• hypertensive crisis
• pre-eclampsia
• pulmonary HT

Preload reduction or afterload reduction
- cardiac failure / cardiogenic shock

Question 10

What groups of drugs cause dilation?

Answer 10

Generalist:

• ACEI
• Beta blockers
• Ca2+ blockers
• Nitrates
• alpha-1 blockers
• others

Specialist

• PDEI
• Mg2+
• alpha-2 agonists
• Nitroprusside
• Dobutamine
• Hydralazine
• Others

Question 11

What is the final common pathway of vascular dilator drugs?

Answer 11

Nitric oxide which cause calcium reduction and vascular smooth muscle relaxation

Question 12

What is the purpose of the drug adrenaline?

Answer 12

Vasopressor and +ve ionotrope.chronotrope

Question 13

What is adrenaline’s mechanism of action?

Answer 13

Binds non-selectively to all adrenergic receptors

Question 14

How does adrenaline affect alpha-1 receptors?

Answer 14

increases peripheral resistance via vasoconstriction therefore increasing BP

Question 15

How does adrenaline affect beta-1 receptors?

Answer 15

Increases HR (+ve chronotropic action)
Increases cardiac contractility (+ve ionotropi action)

Both increase cardiac output

Question 16

How does adrenaline affect beta-2 receptors?

Answer 16

Increases bronchodilation and respiratory rate

Question 17

What undesired affect may adrenaline have?

Answer 17

It may decrease BP if CO increases more rapidly than peripheral resistance resulting in a low venous return

Question 18

What situations is adrenaline used in?

Answer 18

Cardiac arrest - increases peripheral resistance and CO therefore increases cardiac perfusion

Shock and anapylaxis - increases CO and periph. resistance therefore increase perfuson, also helps breating in anaphylaxis

Question 19

How can adrenaline be administered?

Answer 19

IV bolus 1mg
IM/SC Injection
IV infusion 0.1-1mcg/kg/min

Question 20

What is the purpose of the drug noradrenaline?

Answer 20

Similar to adrenaline

i.e. vasopressor and +ve ionotrope/chronotrope

Question 21

What is noradrenaline’s mechanism of action?

Answer 21

Similar to adrenaline

i.e. non-selective activation of adrenergic receptors

Question 22

When is noradrenaline used?

Answer 22

To increase blood pressure in severely vasodilated (shocked) patients

Question 23

When should caution be taken when giving noradrenaline?

Answer 23

In patients without severe maldistributive shock, may be nephrotoxic by cutting of renal blood supply

Question 24

How many noradrenaline be administered?

Answer 24

IV infusion 0.1-1 mcg/kg/min

Never as a bolus

Question 25

What is the purpose of the drug dopamine?

Answer 25

Renal failure - Low doses increase renal perfusion

Shock & heart failure - medium dose increase CO

Maldistributive/vasodilated shock - high dose increases peripheral resistance

Question 26

How does low dose dopamine have effect?

Answer 26

Binds to D1 receptors

• vasodilating effect in renal, mesenteric and coronary arteries
• incr. renal perfusion and diuretic effect

Question 27

How does intermediate dose dopamine have effect?

Answer 27

Dopamine is a noradrenaline precursor

Broken down into noradrenaline which binds to beta-1 receptors

• +ve ionotropic and chronotropic effects
• increased CO and increased BP

Question 28

How does high dose dopamine have effect?

Answer 28

Broken down to noradrenaline which binds to alpha-1 receptors

• vasopressor effect
• increases peripheral resistance

Question 29

What is the main mechanism of vasoconstrictors?

Answer 29

To increase Ca2+

Question 30

What is an inodilator?

Answer 30

A drug which has both vasoconstricting (+ve inotropic) and vasodilating effects

Question 31

Give examples of inodilators

Answer 31

cAMP

Steroids

Question 32

How do steroids work as inodilators?

Answer 32

Inhibit vasoconstriction of vascular beds in organds therefore preventing organ ischaemia
- inhibition of adrenergic receptors and Ca2+ uptake

Inhibit systemic inflammatory response therefore may decrease vasodilation and increase paucity of vasculature

Question 33

What is cushing’s reflex?

Answer 33

Increased systolic/diastolic BP, bradycardia, and irregular breathing due to increased pressure within the skull.