Class 4 Deck 1 Flashcards
Name the 3 sites of actions in which a vasodilator can be classified.
- Arterial dialator (resistance circulation)
- Venodialators (Capacitance circulation)
- Balanced
Give and example of an Arterial dialator, venodialator, and a balanced vasodialator.
- Arterial = Hydralizine, ACE, Nicardipine
- Balanced = Nitroprusside
- Venodialator = Nitroglycerine
Pure arteriole dilator causes minimal effect on what?
-Preload
Balanced vasodilator (SNP) decreases what 2 things?
-Afterload and preload
What drug may be the only pure pulmonary vasodilator?
-Nitrous Oxide
PGE1 is excellent pulmonary vasodilator, but also causes systemic?
Hypotension
What drug may improve coronary circulation?
-NTG
Which drug will increase coronary perfusion pressure?
-Nitroglycerine
In presence of coronary steal, what drug will shunt blood away from ischemic areas and what drug will direct more blood to the ischemic area?
- SNP is bad during MI
- Nitroglycerine is good during MI
How does nitroglycerine treat myocardial ischemia?
- Coronary vasodialtor / Improved collateral flow
- Venodialation decrease venous return and filing pressure
How does CCB treat myocardial ischemia?
- coronary and systemic vasodialators
- Decrease afterload
- Treats coronary vasospasm
Why is SNP non-useful with myocardial ischemia?
- Reduces ventricular filling pressure
- Coronary steal
What 2 drugs use NO, in order to produce their effects? and how do they work?
- SNP (spontaneously generates NO)
- NTG (Requires a cofactor to release NO in smooth muscle)
How does NO (therefore SNP and NTG) produce vasodialation?
- Forms cGMP
- cGMP inhibits calcium entry into smooth muscle cells, which produces vasodialation
What are the effects of NO?
- Vasodilator
- Relax other smooth muscle
- Increase blood flow to the lung
- Decreases pulmonary vascular resistance
What are the clinical applications of NO?
- Hypoxic respiratory failure
- Pulmonary artery HTN
- CPR
What are the adverse effects of NO?
- Reacts w/ O2 to form nitrogen dioxide
- Pulmonary irritant can decrease lung function
- Can induce methemoglobinemia (hemoglobin that doesn’t bind to w/ O2)
What type of drug will prolong the effects of NO?
-phosphodiesterase (PDE) viagra & cialis
What are the effects of SNP?
- Direct action on vascular smooth muscle
- Decrease MAP
- Decrease LA and LV filling pressure
- Decreased afterload promotes forward flow in MR & AI
- Coronary steal
What are the adverse effects of SNP?
- Increase cerebral blood flow and ICP
- Reflex tach and HTN w/ abrupt discontinuation
- Decreased renal blood flow
- Hypotensive efffects w/ spinal or GA
- Worsen intrpulmonary shunt
SNP usage guidelines?
- A-Line
- Can use peripheral line
- Mix in D5W
- Protect from light (breakdown to cyanide)
What are the advantages of SNP?
- Immediate onset
- Short duration
- reduced myocardial O2 demand
Disadvantages of SNP
- Reflex Tach
- Cyanide toxicity ***(photodegredation)
- intrapulmonary shunt
- Methemoglobinemia***
- coronary steal
- Bleeding
- cerebral vasodilator
What is the hyperdynamic response sometime seen with SNP? and how do you treat it?
- Widening of pulse pressure
- Increase GR
- Treat w/ Beta Blocker
Tacyphylaxis in SNP can be a sign of what?
-Cyanide toxicty
How to treat cyanide toxicity?
- Stop SNP
- 100% O2
- Correct acidosis w/ bicarb
- 3% sodium nitrate (oxyhemo to methemo)
- Sodium thiosulfate
- hydroxycobalamin (binds to cyanide)
Thiocynate toxicity tidbits
- Rare
- Cleared by kidneys
- Neurotoxicity
- inhibit uptake of iodine (hypothyroidism possible)
Nitroglycerin (NTG) effects
- Releases NO through a cofactor
- Smooth muscle relaxation
- Affects preload more than afterload
- Dilates vein more than arteries
What does NTG do to Cardiac vasculature?
- relaxes coronary vessels
- Dilates collateral circulation
- Reduces preload and wall tension = ↓ myocardial O2 consumption
- Increased endocardial flow over epicardial flow
