Hypotensive Agents

Question 1

Why is there widened pulse pressure in the elderly?

Answer 1

Because the non compliant vessels conduct blood back to the heart during late systole, causing more cardiac workload and less diastolic filling (pressure)

Question 2

What is widened pulse pressure associated with in cardiac surgery patients?

Answer 2

Postop renal dysfunction

Increased risk of cerebral events.

Question 3

How does nitrates work?

Answer 3

Release nitric oxide which activates guanylyl cyclase to synthesize cGMP

Question 4

What is inhaled nitric oxide used for?

Answer 4

Reversible pulmonary hypertension

Question 5

What is the onset of nitroprusside?

Answer 5

1-2 minutes

Question 6

What is the infusion rate of nitroprusside?

Answer 6

0.5-10 mcg/kg/min

Question 7

Why must nitroprusside infusions be protected from light?

Answer 7

Because of photodegradation

Question 8

How does nitroprusside work?

Answer 8

It enters RBCs where it receives an electron from iron forming methemoglobin (Fe3), nitro group and 5 cyanide molecules

Question 9

What does Cyanide bind to?

Answer 9

Methemoglobin

Cytochrome oxidase

Question 10

What is the first sign of acute cyanide toxicity?

Answer 10

Resistance to hypotension agents (tachyphylaxis)

Question 11

What are the signs of cyanide toxicity?

Answer 11

Metabolic acidosis
Cardiac arrhythmias
Increased venous oxygen content (decreased utilization)

Question 12

When does cyanide toxicity occur?

Answer 12

When given over 500 mcg/kg at an infusion rate over 2 mcg/kg/min

Question 13

How should cyanide toxicity be treated?

Answer 13

Mechanical ventilation with FiO2 of 100%
Sodium thiosulfate (150mg/kg over 15 minutes)
3% Sodium nitrate (5 mg/kg over 5 minutes)

Question 14

How does sodium nitrate work?

Answer 14

Oxidizes methemoglobin to hemoglobin

Question 15

What can happen with the accumulation of thiocyanate?

Answer 15

Thyroid dysfunction
Muscle weakness
Psychosis
Hypoxia
Nausea

Question 16

Does renal failure increase your risk of cyanide toxicity?

Answer 16

No

Question 17

How do you treat methemoglobinemia?

Answer 17

Methylene blue

Question 18

What are the CV effects of nitroprusside

Answer 18

Reflex tachycardia and increased contractility

Coronary steal

Question 19

What are the cerebral effects of nitroprusside

Answer 19

Dilation of cerebral vessels –> increased ICP

Question 20

What are the pulmonary effects of nitroprusside

Answer 20

Dilation of vessels –> abolished hypoxic vasoconstriction response and less perfusion to some normally ventilated alveoli –> increased physiological dead space and V/Q mismatch

Question 21

How does nitroprusside cause release of catecholamines and renin?

Answer 21

By a decrease in ABP

Question 22

How does nitroprusside cause prolonged neuromuscular blockade?

Answer 22

Because of a decrease in muscle blood flow so delayed onset and reversal due to decreased delivery

Question 23

What vessels does nitroglycerin work better on?

Answer 23

Venules

Question 24

Why does nitroglycerin have to in special tubing?

Answer 24

It adsorbs to polyvinylchloride

Question 25

How does nitroglycerin reduces myocardial oxygen demand and increase oxygen supply?

Answer 25

1. Reduces preload 2. Reduces after load 3. Redistribution of blood flow to the sub endocardium 4. Relief of coronary artery spasm

Question 26

What is the infusion rate?

Answer 26

0.5-10 mcg/kg/min

Question 27

What are the CNS effects of nitroglycerin?

Answer 27

Same as nitroprusside

Question 28

What are the pulmonary effects of nitroglycerin?

Answer 28

Dilation of vessels | Bronchodilation

Question 29

What other useful properties does nitroglycerin have?

Answer 29

Decreases platelet aggregation | Decreases uterine contraction (can use if retained products)

Question 30

What is the onset of hydralazine?

Answer 30

15 minutes

Question 31

What is the duration of hydralazine?

Answer 31

2-4 hours

Question 32

How is hydralazine metabolized?

Answer 32

Acetylation and hydroxylation in the liver

Question 33

How is nitroglycerin metabolized?

Answer 33

Rapid reduction in the liver and blood by glutathione nitrate reductase

Question 34

How is hydralazine helpful in heart failure?

Answer 34

Decreases afterload

Question 35

What are the CNS effects of hydralazine

Answer 35

Same as nitroprusside and nitroglycerin

Question 36

What is the mechanism of action of fenoldopam?

Answer 36

Activation of D1 --> rapid vasodilation

Question 37

What are the CV effects of fenoldopam?

Answer 37

Reduces systolic and diastolic BP | reflex tachycardia

Question 38

What does fenoldopam do to intraocular pressure?

Answer 38

Increases it

Question 39

What does fenoldopam do to the kidneys?

Answer 39

Increases RBF | Increases UOP, creatinine clearance, sodium extraction

Question 40

How do dihydropyridine calcium channel blockers work?

Answer 40

By blocking the L-type calcium channels on arterioles which normally allow calcium into the cells

Question 41

What are the dihydropyridine calcium channel blockers?

Answer 41

Nicardipine | Clevidipine

Question 42

What are the CV effects?

Answer 42

Vasodilation > venodilation so maintain preload while decreasing systemic afterload thereby increasing CO

Question 43

What is the infusion rate of nicardipine?

Answer 43

5-15 mg/h

Question 44

Why is the skin flushed in cyanide poisoning

Answer 44

Due to elevated cyanide-hemoglobin complexes