Cardiovascular Pharmacology Flashcards
What are the indications for using vasodilators?
angina pectoris
heart failiure
hypertension
What is pre-load?
The volume of blood in the ventricles before they contract
What is after-load?
The force against which the heart has to push the blood (resistance of blood flow)
What term describes the volume of blood in the ventricles before they contract?
pre-load
What term describes the force against which the heart has to push the blood (resistance of blood flow)?
after-load
Explain why blood pressure increases as you get older
As you age, the aorta becomes less pliable (i.e due to natural ageing, muscle thickening etc.) which result in the vessel becoming more rigid and thus unable to dissipate as much of the pressure. Ventricles will have to push harder.
in younger people, where can the majority of the after load be found?
in the arterioles
What are arterioles?
vessels which direct blood into capilleries
In patients with sepsis why might the blood pressure be low?
the arterioles are fully dilated due to toxins in the body causing blood to leak out thus blood pressure
Whe you have heart failiure, what is the usual state of the vessels and why?
vasoconstriction to compensate for low blood pressure.
In older peopd, where is most of the after-load, likely to be found?
on an aortic level
Would you need greater or less force if there is greater pre-load?
greater force
Would you need greater or less force if there is less pre-load?
less force
is a higher pre-load in ischaemic instances good or bad?
bad
Why is it unfavorable to have a high pre-load in ischaemic instances?
in ischaemic situations, there is already high oxygen demand.
A higher pre-load will require more energy/force which will inturn require more oxygen.
the less oxygen being delivered can result in more infarcted tissue
How do vasodilators affect pre-load and how?
vasodilators reduce pre-load by causing blood to pool in the major veins of the body
What is the popular pre-load reducing medication/substance?
organic nitrates.
How do organic nitrates affect pre-load?
They reduce pre-load by relaxing arterial and venous smooth muscle via liberation of nitric oxide.
Do organic nitractes have a cardiac or vascular effect?
vascular effect - no cardiac effect whatsoever
In the case of angina pectoris what are the levels between o2 supply and o2 demand
o2 supply< o2 demand
how much do blood vessels need to be narrowed befor one get’s ischaemia/ ischaemic pain?
75%
in ischaemic instances/ angina pectoris, what medication may be administered to the patient?
organic nitrates to decrease oxygen demand
Describe the mechanism for the decrease in o2 demand when taking nitrates
Nitrates are convert to Nitric oxide - a substance which causes vasodilation of blood vessels
Blood pools peripherally which reduces pre-load in ventricles.
This means less force is required to pump the blood which inturn mean less O2 consumption
What are the hemodynamic effects of nitrates?
venous dilation
- reduced preload
- reduced ventricular size
- reduced vent. wall stress
- reduced o2 demand
coronary vasodilation
- increased mycardial perfusion;redistributes blood flow.
Arterial vasodilation
- decreased afterload –>
- incraesed cardiac output
- decreased blood pressure
Reflex Tachycardia
No direct myocardial action
List examples of typical nitrate vasodilators?
glyceryl trinitrate (nitronol)
isosorbide mononitrate (ismo)
isosorbide dinitrate (angitak)
List some side effects of taking nitrates
Tachycardia
flushing
hypotension
headache
dizziness
what type of proteins in the body convert Nitrates to nitric oxide in the body?
enzymes
How can prolonged use of nitrates affect it’s efficacy?
Nitrates have an agonist affect on the body
body will develop tolerance to it
resulting in decreased efficacy of the drug.
why does Nitrates induce headaches in some patients?
Increases inter-cranial pressure due to vasodilation in the head.
What does the amount of tolerance towards nitrates depend on?
the dose
How can you avoid/minimise patient tolerance towards nitrates?
intermittent administration
use lowest possible dose
intersperse a nitrate-free interval
What is normally done for a patient whose angina pain returns during the nitrate free interval?
A breakthrough drug which has the same action but does not contain nitrates is usually prescribed. This ensures that effects remain within the therapeutic index
How do calcium channel bloockers work?
Blocks calcium channels
prevents the entry of calcium into the cell
which in turn cause the smooth muscle to dilate
How does calcium channels affect afterload?
by preventing calcium entry into smooth muscle sphincters in the arterioles causing them to dilate.
causes blood to pool peripherally in capillaries and reduces BP causing a decrease in after-load.
