Lecture 10 Treatment of Perioperative Hypotension Flashcards

1
Q

Name five true catecholamines.

A

Dopamine, norepinephrine, epinephrine, isoproterenol, dobutamine

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2
Q

Name the two most popular sympathomimetics used for peri-operative hypotension.

A

phenylephrine (direct, hits alpha-1, reflex bradycardia is an issue) and ephedrine (indirect, hits alpha-1 and beta-1, tachyphylaxis is an issue.) Ephedrine should not be used in patients who are taking drugs that inhibit norepinephrine reuptake, such as TCAs, MAO-Is, Cocaine. People who are catecholamine depleted (think Infantry guy after a prolonged firefight or chronic cocaine user) will not respond to ephedrine, since ephedrine requires presence of endogenously produced catecholamines.

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3
Q

What is hypotension used as a surrogate measure for?

A

Cardiac output and tissue perfusion.
-Low BP suggests a potentially compromised global/regional perfusion

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4
Q

Is there a definitive cut off for hypotension for all ages/health statuses?

A

No! Different people handle different BPs differently. The same is true for higher BPs.

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5
Q

How do we treat hypotension (first steps)?

A
  • Determine the cause of the hypotension.
  • Determine the severity of the hypotension
  • Determine what resources you have at your disposal.
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6
Q

What’s the DDx of hypotension? (four categories)

A
  • Hypovolemic hypotension (bleeding out)
  • Distributive hypotension (septic)
  • pump failure (cardiogenic) hypotension (cardiogenic)
  • obstructive hypotension
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7
Q

Are hypotension and shock the same thing?

A

NO! Though they often co-exist.
Shock occurs in the presence of decreased tissue perfusion.

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8
Q

What are some examples of hypovolemic hypotension?

A

bleeding, decreased intake, GI or other losses

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9
Q

What are some examples of distributive hypotension?

A

anaphylaxis, septic shock, neurogenic shock, drug induced (anesthesia inhalation agents)

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10
Q

What are some examples of cardiogenic/pump failure hypotension?

A

MI, myocardial depression

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11
Q

What are some examples of obstructive hypotension?

A

tension pneumothorax, cardiac tamponade, massive PE, intracardiac clot/tumor, HOCM

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12
Q

What steps are there to hypotension therapy?

A
  • Address the underlying cause.
  • Give fluids first
  • Supplement w/ vasopressors for hypovolemic hypotension
  • Add vasopressors and (maybe) fluids for vasodilation/distributive hypotension
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13
Q

What are the two commonly used vasopressors we use?

A

phenylephrine and ephedrine

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14
Q

How are phenylephrine/ephedrine used in ACLS?

A

They really aren’t. Be sure to consider ACLS during your treatment of your patients, both in the OR and out.

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15
Q

Which (phenyl vs ephedrine) is more potent? Does it matter?

A

Phenylephrine is 100X more potent, but it doesn’t really apply to these drugs since they are in different categories. (On a slide, so worth making this just in case it’s tested.)

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16
Q

Which (phenyl vs ephedrine) has a longer duration of action?

A

Ephedrine, provided it is given in its proper dosing.

17
Q

What is phenylephrine’s mechanism of action?

A

Direct vasoconstrictor.

  • Acts as an alpha agonist–>increased vascular tone (venous>arterial)
  • minimal inotropic effects (no beta-1 action)
  • No direct action on HR (but baroreceptors note the increased BP and will prompt reflexive bradycardia)
  • Might increase myocardial work due to greater preload (and myocardial stretch w/ increased afterload)
  • Can improve myocardial O2
18
Q

What is ephedrine’s mechanism of action?

A

Some direct effects, but mostly an indirect vasodilator.

  • Causes endogenous catecholamine release (mostly norepinephrine)
  • Not selective for alpha or beta adrenergic receptors, so they stimulate both.
  • Release beta blockers–>increased HR
  • Increased systolic and diastolic BP, partially due to increased cardiac pumping–>greater cardiac work
  • Myocardial O2 supply-demand relationship could improve or worsen
19
Q

Does phenylephrine improve CO?

A

It can, but not usually.

  • Total SVR increased usually leads to a decreased CO.
  • Dose dependent
  • If myocardial ischemia was the problem, increased perfusion from phenylephrine could improve cardiac function (and CO).
20
Q

What can ephedrine cause in some patients?

A

tachycardia. Concommitant use of phenylephrine can decrease the chances of this happening.

21
Q

What does ephedine do to SVR?

A

It’s unpredictable.
-Released norepinephrine could stimulate alpha receptors more (increased SVR), beta receptors more (decreased SVR), or some other unpredictable combination of different receptors in different vascular beds.

22
Q

What happens when a patient is on a beta blocker and they receive ephedrine?

A
  • HR may decrease or increase
  • SVR will likely increase due to unopposed alpha agonist activity
23
Q

When should you use ephedrine?

A
  • Slow HR
  • No luck w/ phenylephrine
  • Young patient
  • Less concern about myocardial perfusion
24
Q

When should you use phenylephrine?

A
  • HR is faster
  • Ephedrine tried w/o luck
  • Concerned about myocardial perfusion
  • Older pt