Chapter 46: vasodilators Flashcards
Agents that act primarily on the arterioles are called what?
Resistance vessels
Agents that act primarily on veins are what?
Capacitance vessels
What determines its hemodynamic effects and is a major determinant factor r/t both therapeutic and undesired effects?
Selectivity
What effect do arterioles have on afterload & cardiac workload
decrease in cardiac afterload & cardiac workload
What effects do arterioles have on cardiac output and tissue perfusion?
Increase in CO & tissue perfusion
What are some primary therapeutic uses of vasodialtors?
-Systemic & pulmonary HTN
-hypertensive crisis/pheochromocytoma
-angina pectoris/MI
-HF
-Peripheral vascular disease
What are 3 ADRs r/t vasodilation
-postural hypotension
-reflex tachycardia
-expansion of blood volume (w/ prolonged use)
Why would someone get postural hypotension r/t vasodilation
-relaxation of smooth muscle in the veins. gravity causes blood to pool. further decreases venous return. Decrease in CO & BP. Decreased ventricular pressure
Why would someone develop reflex tachycardia r/t vasodilation?
- direct reduction in arterial pressure.
-reduces CO. - can be due to arterial or venous dilation
What can you pretreat reflect tachycardia with?
Cardioselective beta blocker
What should pt use vasodilators with to prevent therapeutic effects from being cancelled out?
diuretics
What drug is a selective dilation of arterioles?
Hydralazine
if a person is takin hydralazine what would you notice about their arterial BP & peripheral resistance?
It falls
On hydralazine, a pts HR and contractility would do what?
Increase
What drug would you want to take with hydralazine to help with the cardiac effects?
Cardioselective beta-blocker (metoprolol)
hydralazine is inactivated by a metabolic process known as what?
Acetylation (rate is genetically determined)
What are 3 ADRs for hydralazine?
- reflex tachycardia
-increased blood volume
-systemic lupus erythematosus-like syndrome
What 2 drugs can hydralazine be combined with?
-diuretics
-beta-blockers
A pt comes in and is complaining of fever, muscle and joint pain, and has nephritis, pericarditis, and positive rheumatoid antibodies. What syndrome do they have and what should you do if they are taking hydralazine?
Systemic lupus erythematosus-like syndrome
Discontinue drug
if a pt is a slow acetylator, what should you do to the dose?
Lower the dose
(they may not be inactivating the drug, so it may become toxic)
If a pt is a rapid acetylator, what should you do to the dosage?
Increase dose
(They may need more of the drug d/t a fast metabolization of the drug)
Which vasodilator produces significantly more selective dilation of the arterioles than hydralazine?
minoxidil
Why would you give minoxidil?
For Pt with sever HTN & have not responded effectively w/ safer drugs
What must minoxidil be metabolized to?
Minoxidil sulfate
Minoxidil sulfate causes potassium channels to open resulting in what?
Efflux of potassium ions out of the cell
Reducing their ability to contract is caused by what?
Hyperpolarization of the VSM
What are 4 ADRs of minoxidil
-reflex tachycardia
-sodium and water retention
-hypertrichosis
-Pericardial effusion
What is the main reason many pt stop taking minoxidil?
Hypertrichosis
What adverse effect from minoxidil can lead to cardiac tamponade?
Pericardial effusion
What diuretic can you not take with minoxidil and why?
potassium sparing because of hyperkalemia
If loop diuretics is ineffective with the ADR of sodium and water retention from minoxidil what should you do?
Start dialysis or discontinue drug
What is hypertrichosis and how many people develop it >4 weeks within taking minoxidil?
-excessive growth of hair
-specific pattern beginning on face then arms,legs,back
-80% of people develop
-caused by proliferation of epithelial cells at hair follicle base
What is the drug of choice for hypertension emergencies?
Sodium Nitroprusside
How is sodium nitroprusside administered?
IV infusion only
Does sodium nitroprusside have a short or long duration of action?
Short
What is given with sodium nitroprusside concurrently?
Oral antihypertensives
Does sodium nitroprusside cause dilation on venous, arteriole, or both
both
What is the most potent and fast-acting vasodilator available?
Sodium Nitroprusside
What would you give to someone experiencing sodium & water retention while on Sodium Nitroprusside?
Loop diuretics
What is the active component of sodium nitroprusside?
Nitric Oxide
What does nitric oxide activate?
an enzyme present in VSM
Cyanide groups will be converted to thiocyanate via what organ?
Liver
What is the cofactor?
Thiosulfate.
How is thiosulfate excreted?
Kidneys
What are 3 ADRs of Sodium Nitroprusside?
-excessive hypotension
- cyanide poisoning
-thiocyanate toxicity
Thiocyanate toxicity can occur if drug is given longer then what?
3 days
Thiocyanate toxicity can cause sever CNS ADRs such as:
-disoriented, hallucinations, delusions
If cyanide poisoning occurs, what should you do?
Discontinue nitroprusside and co-administer thiosulfate
Thiocyanate levels need to be:
below 0.1 mg/ml
