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Top Drawer > Vasopressors/Sympathomimetics > Flashcards

Vasopressors/Sympathomimetics Flashcards

1
Q

Vasopressors are NOT a replacemnt for:

A
  • adequate volume (need fluids)
  • blood (need blood)
  • too much anesthesia (lessen your anesthetics)
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2
Q

T/F: vasopressors are used when too much anesthetics are given and cause hypotension

A

false
if this is the consistent cause of hypotension, lighten up on your anesthetics

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3
Q

What two vasopressors are commonly used in anesthesia?

A
  • ephedrine
  • phenylephrine
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4
Q

What is ephedrine?

A

a vasopressor that is a mixed-acting synthetic non-catecholamine sympathomimetic

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5
Q

What are the indirect effects of ephedrine?

A
  • at alpha-1 and beta-1 receptors, it displaces norepi presynaptic vessicles
  • norepi that is released and activates postsynaptic receptors cause vasoconstriction and increased myocardial contraction
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6
Q

What are the direct effects of ephedrine?

A
  • directly stimulates beta-2 receptors
  • increased HR, CO
  • gentle SVR/BP increase
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7
Q

When is ephedrine given?

A
  • low HR/bradycardia
  • low BP/hypotension
  • to increase BP/HR/CO/contractility
  • PONV
  • bronchodilator effect
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8
Q

Explain what alpha receptors do

A
  • alpha 1: vasoconstriction, mydriasis (dilation), urinary retention, ejacuation
  • alpha 2: inhibit presynaptic release of norepi
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9
Q

Explain what beta receptors do

A
  • beta 1: increase CO in heart, increase renin in kidneys
  • beta 2: smooth muscle relaxation (bronchodilator, vasodilation, decreased digestion, decreased urination), increase glucose from liver
  • beta 3: lipolysis of adipose tissue, decreased urination
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10
Q

What happens when ephedrine binds to alpha1 and beta1 receptors?

A

displaces norepinephrine from presynaptic vesicles

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11
Q

What is a difference between ephedrine and epinephrine in their responses to BP?

A
  • epinephrine has stronger increase in BP due to very strong alpha and beta effects
  • ephedrine has gentle increase in BP due to only some SVR increase
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12
Q

Is ephedrine or phenylephrine safer to use in OB?

A

phenylephrine
- ephedrine can cause fetal tachycardia and acidosis, leading to lower umbilical artery pH at delivery

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13
Q

When is ephedrine contraindicated?

A
  • MAOI inhibitors
  • pheochromocytoma
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14
Q

Careful administration of ephedrine in what case?

A

coronary artery disease (CAD)

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15
Q

There is a risk of ______________ with excessive ephedrine administration, which causes decreased response with administration

A

tachyphylaxis
- there is depletion of presynaptic norepinephrine; would need to use different agent in the meantime

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16
Q

Ephedrine Dosing

A

5-10 mg at a time to increase BP/HR

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17
Q

Ephedrine antiemetic dosing

A

25mg of ephedrine/25 mg of vistaril IM, 20 min before the end of surgery

18
Q

What is the concentration of ephedrine in a vial?

A

50 mg/1mL

19
Q

How can we dilute ephedrine for safe administration?

A

1 ml (50mg) + 9 ml of NS = 5 mg/1ml mixture

20
Q

What is the MOA of phenylephrine?

A
  • directly stimulates alpha1 receptors
  • very minimal effect on alpha2 and beta receptors
21
Q

When is phenylephrine used?

A
  • hypotension
  • decreased CO in patients with LV dysfunction
  • good choice if patient is hypotensive with tachycardia
22
Q

What is the vasopressor of choice in OB?

A

phenylephrine

23
Q

In what areas does phenylephrine cause vasoconstriction?

A
  • cutaneous
  • mesenteric
  • splenic
  • renal
24
Q

Phenylephrine Dosing

A

50-100 mcg

25
Q

What is the cardiac effect of phenylephrine?

A

vasoconstriction to increase BP, reflex decrease in HR, increase in coronary blood flow

26
Q

When should phenylephrine not be used?

A

if the patient is bradycardic

27
Q

Which vasopressor would be a better choice in a patient that is hypotensive and bradycardic?

A

ephedrine

28
Q

Which vasopressor would be a better choice in a patient that is hypotensive and tachycardic?

A

phenylephrine

29
Q

What is the concentration of phenylephrine in a vial?

A

10 mg/1 mL (10,000 mcg/1ml)

30
Q

How can phenylephrine be diluted for safe administration?

A

0.1ml (1000mcg) + 9.9 ml NS = 100 mcg/cc

31
Q

Why is phenylephrine the vasopressor of choice in OB?

A
  • good for hypotension post-regional
  • faster onset
  • shorter duration of action
  • maintains fetal pH
  • ephedrine would cause fetal tachycardia and acidosis
32
Q

What are the pros and cons of ephedrine in OB?

A
  • PROS: won’t decrease uterine blood flow; antiemetic property; good for hypotension from regional
  • CONS: can cause fetal tachycardia and acidosis; lowers fetal pH
33
Q

What is an important thing to note when administering a patient phenylephrine, especially in an OB patient?

A
  • make sure the patient is hydrated!!!!
  • if the patient is dehydrated it may cause profound bradycardia to the 20s
34
Q

Dopamine Dosing (low, moderate, and high)

A

Low: < 3mcg/kg/min
Moderate: 3-8 mcg/kg/min
High: 10 mcg/kg/min

35
Q

What is the effect of low dose dopamine?

A
  • low dose: < 3mcg/kg/min
  • activates DA1 receptors which increase renal and splenic blood flow via arterial dilation to these organs
  • reduce norepi release by DA2 receptors
36
Q

Dopamine is a precursor of ______________

A

norepinephrine

37
Q

What is the effect of moderate doses of dopamine?

A
  • moderate dose: 3-8 mcg/kg/min
  • activates a1 and b1 receptors, leading to increased BP and contractility
38
Q

What is the effect of high dose dopamine?

A
  • high doses: 10 mcg/kg/min
  • act primarily on a1 receptors, increasing vasoconstriction
39
Q

Dopamine is used commonly for what type of cardiac patients?

A

patients with acute LV dysfunction needing positive ionotrpic effect

40
Q

Dobutamine Dosing

A

Lower doses: 2.5-5 mcg/kg/min
Higher doses: 5-20 mcg/kg/min

41
Q

What is the mechanism of action of dobutamine?

A
  • activates beta1 receptors, increasing contractility, SV, and CO
  • activates beta-2 receptors, causing arterial vasodilation (slightly lower BP) to preserve preload and afterload

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