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NU 600

Exam 4 - Vasodilators and Antidysrhythmics

What are the 4 uses of peripheral vasodilators? Tx HTN, hypotensive technique, increase stroke volume, reduce preload
Nitro- based vasodilators produce their effects by producing what substance? nitric oxide
What does nitric oxide stimulate? guanylate cyclase
What does guanylate cyclase increase? Intracellular concentrations of cGMP
What is the effect of cGMP? Vascular relaxation
What are 6 roles of NO? 1)chemical messenger 2)vascular homeostasis 3)platelet regulation 4)CNS neurotransmitter 5)GI relaxation 6)immune response
Where does NO synthesis occur? Endothelial cells
NO is produced in endothelial cells from _________ by the enzyme _________. L-Arginine; NO synthase
In the presence of decreased tissue oxygenation, endothelial cells (increase/decrease) NO production. increase
NO has (negative/positive) inotropic and chronotropic effects. Negative
What does the inhibition of NO suggest? CV system is continuously exposed to NO dependent vasodilator tone
Where in the lungs are the bronchodilatory effects of NO achieved? Areas of pulmonary circulation which supply blood to ventilated areas
How does NO influence platelets? Inhibits platelet actiivty, aggregation, and adhesions
How does NO inhibit adhesions? Activates guanylate cyclase, which increases cGMP, and decreases intracellular calcium
Stimulation of the _______ receptor leads to the release of NO. NMDA
What are two neurologic functions that NO is involved in? Memory, antinociception
What effect does NO have in the GI tract? Causes relaxation of the peripheral nerves in the GI tract
Essential hypertension is a reflection of decreased levels of ________. NO
What amino acid decreases BP in patients with essential hypertension? L-arginine
What class of anti-hypertensives stimulate the production of NO? ACE inhibitors
What inactivates NO? Hemoglobin in systemic circulation
NMDA is an (inhibitory/excitatory) neurotransmitter. excitatory
What effect do VAAs have on NO? Suppress NO formation, resulting in decreased neurotransmission and increasing GABA
What class of medications can be used to decrease MAC requirements? Nitric oxide synthase inhibitors
What nitric oxide synthase inhibitor can be purchased OTC? L-arginine
The effects of NO are rapidly terminated by binding to what blood product? Hgb
In what scenarios is NO given through vent delivery systems? After bypass, newborn hypertension, prematurity w/respiratory distress
NO toxicity leads to what three conditions? Methemoglobinemia, rebound pulmonary hypertension, NO2 toxicity
What is Silo Filler’s disease? Occupational lung disease associated w/the inhalation of toxic gas (NO2)
How does Silo Filler’s Disease present? ARDS, pulmonary edema,
What are the 3 clinical uses for peripheral vasodilators? 1)Tx of HTN 2)controlled HTN 3)Increase LV SV w/regurgitation
What are 3 clinical uses for nitro-based vasodilators? 1)Tx symptomatic LV dysfxn 2)decrease preload 3)decrease effects of peripheral vasoconstrictors
What are three meds that produce direct vasodilation? Sodium nitroprusside, nitroglycerin, hydralazine
Identify which Rx produces vasodilation of arteries, veins, or both: Nipride, nitroglycerin, hydralazine. Nipride=both, nitroglycerin=veins, hydralazine=arteries
What is the primary mechanism of action of nipride, nitroglycerin, and hydralazine? Production of nitric oxide
What is the composition of nipride? Ferrous ion center w/5 cyanide and 1 nitrosyl sodium group
What blood product does SNP interact with? Oxyhemoglobin
What occurs when SNP interacts w/oxyhemoglobin? Dissociates to form methemoglobin along with releasing cyanide and NO.
What enzyme does NO inhibit and what does this result in? Inhibits adenylate cyclase and increases cGMP (vasodilation)
What enzyme does NO activate? Guanylate cyclase
What is the mechanism of action of cGMP? Inhibits calcium entry into vascular smooth muscle cells and increases calcium uptake into the endoplasmic reticulum (vasodilation)
What initially occurs in the metabolism of SNP? An electron is transferred from the iron of oxyhemoglobin to yield methemoglobin and an unstable SNP radical
What occurs with breakdown of the unstable SNP radical? All 5 cyanide ions are released
What happens to the 5 cyanide ions that are released w/SNP metabolism? 1 ion reacts with methemoglobin to form cyanomethemoglobin; the remaining 4 ions are catalyzed by rhodanese to form thiocyanate
Cyanomethemoglobin is (toxic/non-toxic). Non-toxic
What type of toxicity results from the use of SNP? Cyanide toxicity
Increased concentrations of what product is found with high rates of SNP infusions? Thiocyanate
Cyanide toxicity with SNP occurs with rates greater than ____________. 2mcg/kg/min
Increase tissue cyanide produces what effects? Anoxia, anaerobic metabolism, lactic acidosis
When should cyanide toxicity be suspected? When hypotension exists despite treatment
What are 4 medications utilized in the treatment of cyanide toxicity? Sodium bicarbonate, sodium thiosulfate, sodium nitrate, hydroxocobalamin (Vit B12a)
Besides administering medications, what are two immediate actions to take with cyanide toxicity? D/c gtt and give 100% O2
Why is sodium bicarbonate given in cyanide toxicity? Tx the metabolic acidosis
How does sodium thiosulfate work to treat cyanide toxicity? Converts cyanide to thiocyanate
What is the dose of sodium thiosulfate for cyanide toxicity? 150mg/kg over 15min
Thiocyanate is (more/less) potent than cyanide in its harmful effects. More
How does sodium nitrate work to treat cyanide toxicity? Converts hemoglobin to methemoglobin, and methemoglobin acts as an antidote to convert cyanide to cyanomethemoglobin
What is the dose of sodium nitrate in the treatment of cyanide toxicity? 5mg/kg
How does hydroxocobalamin work to treat cyanide toxicity? Binds cyanide to form cyanocobalamin (Vit B12)
What is the dose of hydroxocobalamin for cyanide toxicity? 25mg/hr up to 100mg
What is the infusion rate of SNP? 0.3-20mcg/kg/min
What is the maximum amount of time you can infuse SNP at a max rate of 20mcg/kg/min. 10min
_______ accounts for a decrease in SVR, while _______ accounts for a decrease in venous return. Arterial vasodilation; venodilation
What receptors respond to venous pooling and decreased R atrial pressure as seen w/Nipride? Baroreceptor reflexes respond and cause tachycardia
The administration of Nipride results in a net (increase/decrease) in CO. Increase
Why is there an increase in CO w/Nipride? Increase in peripheral SNS tone combined w/decreased ventricular resistance
What negative effect can SNP have on the heart in regards to blood flow. May cause intracoronary steal, diverting blood away from ischemic areas to areas that are perfused
SNP (increases/decreases) CBF and blood volume. Increases
Created by: philip.truong
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