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Anesthesia MM/TL > Hypotensive Agents > Flashcards

Hypotensive Agents Flashcards

1
Q

Why is there widened pulse pressure in the elderly?

A

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

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2
Q

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

A

Postop renal dysfunction

Increased risk of cerebral events.

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3
Q

How does nitrates work?

A

Release nitric oxide which activates guanylyl cyclase to synthesize cGMP

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4
Q

What is inhaled nitric oxide used for?

A

Reversible pulmonary hypertension

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5
Q

What is the onset of nitroprusside?

A

1-2 minutes

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6
Q

What is the infusion rate of nitroprusside?

A

0.5-10 mcg/kg/min

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7
Q

Why must nitroprusside infusions be protected from light?

A

Because of photodegradation

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8
Q

How does nitroprusside work?

A

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

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9
Q

What does Cyanide bind to?

A

Methemoglobin

Cytochrome oxidase

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10
Q

What is the first sign of acute cyanide toxicity?

A

Resistance to hypotension agents (tachyphylaxis)

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11
Q

What are the signs of cyanide toxicity?

A

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

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12
Q

When does cyanide toxicity occur?

A

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

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13
Q

How should cyanide toxicity be treated?

A 
Mechanical ventilation with FiO2 of 100%
Sodium thiosulfate (150mg/kg over 15 minutes)
3% Sodium nitrate (5 mg/kg over 5 minutes)
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14
Q

How does sodium nitrate work?

A

Oxidizes methemoglobin to hemoglobin

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15
Q

What can happen with the accumulation of thiocyanate?

A 
Thyroid dysfunction
Muscle weakness
Psychosis
Hypoxia
Nausea
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16
Q

Does renal failure increase your risk of cyanide toxicity?

A

No

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17
Q

How do you treat methemoglobinemia?

A

Methylene blue

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18
Q

What are the CV effects of nitroprusside

A

Reflex tachycardia and increased contractility

Coronary steal

19
Q

What are the cerebral effects of nitroprusside

A

Dilation of cerebral vessels –> increased ICP

20
Q

What are the pulmonary effects of nitroprusside

A

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

21
Q

How does nitroprusside cause release of catecholamines and renin?

A

By a decrease in ABP

22
Q

How does nitroprusside cause prolonged neuromuscular blockade?

A

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

23
Q

What vessels does nitroglycerin work better on?

A

Venules

24
Q

Why does nitroglycerin have to in special tubing?

A

It adsorbs to polyvinylchloride

25
Q

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

A
  1. Reduces preload
  2. Reduces after load
  3. Redistribution of blood flow to the sub endocardium
  4. Relief of coronary artery spasm
26
Q

What is the infusion rate?

A

0.5-10 mcg/kg/min

27
Q

What are the CNS effects of nitroglycerin?

A

Same as nitroprusside

28
Q

What are the pulmonary effects of nitroglycerin?

A

Dilation of vessels

Bronchodilation

29
Q

What other useful properties does nitroglycerin have?

A

Decreases platelet aggregation

Decreases uterine contraction (can use if retained products)

30
Q

What is the onset of hydralazine?

A

15 minutes

31
Q

What is the duration of hydralazine?

A

2-4 hours

32
Q

How is hydralazine metabolized?

A

Acetylation and hydroxylation in the liver

33
Q

How is nitroglycerin metabolized?

A

Rapid reduction in the liver and blood by glutathione nitrate reductase

34
Q

How is hydralazine helpful in heart failure?

A

Decreases afterload

35
Q

What are the CNS effects of hydralazine

A

Same as nitroprusside and nitroglycerin

36
Q

What is the mechanism of action of fenoldopam?

A

Activation of D1 –> rapid vasodilation

37
Q

What are the CV effects of fenoldopam?

A

Reduces systolic and diastolic BP

reflex tachycardia

38
Q

What does fenoldopam do to intraocular pressure?

A

Increases it

39
Q

What does fenoldopam do to the kidneys?

A

Increases RBF

Increases UOP, creatinine clearance, sodium extraction

40
Q

How do dihydropyridine calcium channel blockers work?

A

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

41
Q

What are the dihydropyridine calcium channel blockers?

A

Nicardipine

Clevidipine

42
Q

What are the CV effects?

A

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

43
Q

What is the infusion rate of nicardipine?

A

5-15 mg/h

44
Q

Why is the skin flushed in cyanide poisoning

A

Due to elevated cyanide-hemoglobin complexes

Anesthesia MM/TL (36 decks)

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