Vasodilators

Question 1

alpha 2 receptor subtypes

Answer 1

alpha 2A: sedation, analgesia, sympatholysis
alpha 2B: vasoconstriction, antishivering
alpha 2C: startle response

Question 2

Most common SE produces by clonodine

Answer 2

sedation and xerostomia

Question 3

Alpha 2 agonists produce sedation in what area of the brainstem?

Answer 3

the locus ceruleus

Question 4

Where to alpha 2 agonists produce analgesia? What does neuraxial placement inhibit?

Answer 4

Site of analgesia is the spinal cord. Substance P and nociceptive neuron firing are inhibited.

Question 5

alpha 2 agonists decrease anesthetic requirements by how much?

Answer 5

50%

Question 6

1. What can occur with abrupt discontinuation of clonidine therapy?
2. What will exaggerate this response and why?
3. What would be appropriate intraoperative management?

Answer 6

1. rebound hypertension (as soon as 8 hours).
2. Will be exaggerated in patients also on beta-blocker: beta 2 is blocked causing vasoconstriction and alpha receptors are unopposed.
3. labetalol and clonidine patch

Question 7

What are the three classes of calcium channel blockers (what is each one most selective for)?

Answer 7

phenylalkylamines: verapamil (AV node), benzothiazepines: cardizem (AV node), dihydropyridines: all the -pines (arteriolar beds)

Question 8

MOA of CCBs

Answer 8

blockade of Ca2+ influx through L-type (L for long-lasting) voltage-gated Ca2+ channels in myocardial and vascular smooth muscle cells. Dihydropyridines work EXTRACELLULARLY, phenylalkylamines work INTRACELLULARLY, and benzothiazipines has unknown Ca2+ channel mechanism but may also work on Na-K pump, decreasing intracellular Na available to exchange with Ca2+.

Question 9

Phenylalklyamines and benzothiazepines should not be given in what type of patients?

Answer 9

Patients with heart failure, severe bradycardia, sinus node dysfunction, or AV node block.

Question 10

Good combination for coronary artery vasopasm

Answer 10

nitrates and calcium channel blockers

Question 11

Which CCB has the greatest vasodilating effect?

Answer 11

Nicardipine

Question 12

CCB overdose may be partially reversed by what agents?

Answer 12

IV administration of calcium or dopamine

Question 13

Drug interactions with CCB

Answer 13

May increase digoxin levels and enhance neuromuscular blocking agents and impair reversal of blockade (calcium is required for presynaptic release of Ach).

Question 14

First line therapy for HTN, CHF, and mitral regurgitation

Answer 14

ACE inhibitor therapy

Question 15

Refractory hypotension (not responsive to fluids or administration of phenylephrine) secondary to ACE inhibitor therapy prior to surgery may be treated with which agents?

Answer 15

Vasopression (V1 and V2 receptors) and methylene blue (inhibits production of nitric oxide)

Question 16

SE of ACE inhibitors

Answer 16

Cough d/t bradykinin, angioedema, hyperkalemia r/t decreased aldosterone secretion, increased insulin sensitivity causing hypoglycemia.

Question 17

What do phosphodiesterase inhibitors do?

Answer 17

Inhibit the breakdown of cAMP and cGMP causing smooth muscle relaxation

Question 18

Treatment for cyanide toxicity

Answer 18

100% O2. treat acidosis, and administer THIOSULFATE 150 mg/kg IV over 15 minutes (acts as sulfur donor to convert cyanide to thiocyanate)

Question 19

Sodium nitroprusside metabolism

Answer 19

In liver and kidney to thiocyanate and cyanomethohemoglobin

Question 20

Contraindications for nitroglycerin

Answer 20

severe aortic stenosis and hypertrophic obstructive cardiomyopathy

Question 21

What do high doses of nitroglycerin produce? What is the treatment?

Answer 21

methemoglobinemia, especially in patients with hepatic dysfunction. Methylene blue 1% 1-2 mg/kg over 5 minutes.

Question 22

Hydralazine

Answer 22

Systemic ARTERIAL vasodilator. Used to treat HTN associated with pregnancy and outpatient CHF (in combo with nitrates).

Question 23

What is responsible for the vasodilating effect of sodium nitroprusside?

Answer 23

Nitric oxide (NO), which activates guanylate cyclase present in vascular smooth muscle resulting in increased intracellular concentrations of cGMP.

Question 24

How does sodium nitroprusside (SNP) generate NO? What byproduct accumulates with doses > 2 mcg/kg/min?

Answer 24

SNP interacts with oxyhemoglobin, dissociating immediately and forming methemoglobin while releasing cyanide and NO. The risk of cyanide toxicity increases with doses > 2mcg/kg/min precipitating anaerobic respiration, lactic acidosis, tissue anoxia, and increased mixed venous O2.

Question 25

SNP infusion rates > 3 mcg/kg/min results in

Answer 25

heme-platelet aggregation inhibition and increased bleeding time

Question 26

What vasodilator is contraindicated in patients with glaucoma?

Answer 26

Fenaldopam

Question 27

Fenaldopam MOA

Answer 27

Dopamine type 1 receptor agonist. Increases cAMP causing arterial vasodilation. Increases renal blood flow and urine output.

Question 28

cerebral effects of SNP

Answer 28

increased blood flow and cerebral blood volume. May increase ICP in patients with decreased intracranial compliance. Patients with known inadequate cerebral blood flow associated with increased ICP or carotid artery stenosis should not be treated with SNP.

Question 29

Nitric oxide MOA

Answer 29

endogenous vasodilator. Produces relaxation of pulmonary arterial system (administered by inhalation) by increasing cGMP concentrations. It dilates vessels at the alveolar levels, improving V/Q matching and oxygenation.

Question 30

Clinical uses for nitric oxide

Answer 30

Pediatric lung injury and persistent pulmonary HTN of the newborn. Also used off-label in adults for heart-to-lung transplant candidates for pulmonary HTN.

Question 31

What happens with discontinuation of NO?

Answer 31

A drop in SpO2 occurs. Life-threatening rebound arterial hypoxemia and pulmonary HTN may occur. WEAN OFF.

Question 32

Sildenafil, vardenafil, and tadalafil

Answer 32

PDE5 inhibitors. Effective pulmonary vasodilators, great for pulmonary HTN. Also used to treat erectile dysfunction.