Sympathomimetics Flashcards Preview

Anesthesia Pharmacology > Sympathomimetics > Flashcards

Flashcards in Sympathomimetics Deck (36)
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1
Q

which type of drug should you give if the pt has a “pipe” problem? Pump?

A

pipe-vasopressor
pump-inotrope

Before deciding ask yoursef Is there a perfusing rhythm and does the pt have adequate volume

2
Q

what are the effects of inotropes?

A

Improve contractility
improve CO
treat pump problem

3
Q

What are the effects of vasopressors?

A

INcrease vascular tone
Increase SVR
treat pipe problem

4
Q

What role does calcium play in muscle contraction?

A

Actin wants to interact with myosin, but tropomysin is blocking it. Calcium binds to troponin which moves tropomysin out of the way so actin and myosin can form cross bridges.

5
Q

define the following in terms of calcium: inotropy, chronotropy, and lusitropy

A

ionotropy–quantity of Ca in cell, maximum tension developed
Chronotropy-Rate of Ca delivery, rate of contraction
Lusitropy–removal of Ca, rate of relaxation

6
Q

_______ is an important second messenger. By increasing it in the cardiac myocyte, you will increase Ca++ which will increase contractiliy

A

cAMP

7
Q

how do B agonists increase cAMP?

A

Indirectly by stimulating adenyl cyclase which converts ATP into cAMP

8
Q

How do phosphodiesterase inhibits increase cAMP?

A

prevents breakdown of cAMP

9
Q

B1 receptors increase _______ and _______. B2 receptors increase _____________.

A

Inotropy and chronotropy

ionotroy

10
Q

HOw do norepi, epi, dopamine, dobutamine and isoproteranol affect a, B1 and B2?

A

NOrepi, B1 with even stronger a
Epi- equal a, B@ and B2
Dopamine a is strongest , B1 and 2 are equal
Dobutamine-mostly B1 with some B2. + or - with a
Iso pure B (strong on both)

11
Q

What are adverse effects of epi and norepi?

A

Epi-Arrythmogenic, can cause Vtach

Norepi–Intense SVR may decrease CO

12
Q

What are adverse effects of dopamine, dobutamine and isoproteronol?

A

Dopamine–largely indirect acting
Dobutamine–tachycardia
Isopro–significant tachycardia, arrhythmias and and decreased SVR

13
Q

What are the effects of cyclic nucleotides as second messengers?

A

activate protein kinases

open ion channels

14
Q

Which family of PDEs are used for CV system?

A

IIIA

15
Q

What are the actions of PDEIII in cardiac myocytes and vasculature?

A

Cardiac=increase cAMP->Ca++, increase Ca+++->contractility

Vascular tissue: INcrease cyclic nucleotide->smooth muscle relaxation. decreases PA pressures and SVR

16
Q

What is loading dose and infusion rate for milrinone?

A

0.05mg/kg lasts 30 minutes

Infusion rate 0.5mcg/kg/min

17
Q

Why is norepi the first line inotrope? What would you add if you had poor systolic function?

A

NOrepi provides positive inotropy (B1) and maintains perfusion pressure (a1). If systolic function is poor add dobutamine, epi or a PDE3 inhibitor

18
Q

The second messenger in vasculature is cAMP? t or f

A

f

The end result still comes from an increase in calcium

19
Q

Increasing dose of catecholamines increase _______ effects.

A

alpha

20
Q

What is onset and duration of phenylephrine?

A

Onset 30 seconds

duration 2-3 minutes

21
Q

what is the dose for an infusion of phenylephrine?

A

25-100 mcg/min

22
Q

what is methoxamine?

A

a pure direct a1 agonist.
bolus 5-10 mg
onset 1 min
duration 5-10 min

23
Q

how is ephedrine metabolized and eliminated?

A

Inactivated by MAO in liver (if pt is on MAOIs duration may be prolonged to 20-30 min)
40% is exreted unchanged in urine

24
Q

how does ephedrine affect uterine vascular resistance?

A

minimally

25
Q

How does vasopressin exert its effect on SVR?

A

Activates V1 receptor which utilizes the same second messenger system as alpha agonists. Ca++ is increased and muscular contraction happens

26
Q

Name 2 other vasopressin receptors (besides V1) and give their function

A

V2-kidney
Dilation of renal endothelium, increases water permeability
V3-pituitary
Neurotransmitter that increases ACTH release

27
Q

The principle role of vasopressin is regulating vascular tone. T/F

A

F

28
Q

What are physiologic levels of vasopressin?

A

5-10 pmol/L

29
Q

Onset of sepsis_____ AVP levels

A

increases, but in time it will decrease these levels to 1/3 of normal

30
Q

Vasopressin replacement therapy may be needed after ______________

A

cardiopulmonary bypass

4-6 units/hour

31
Q

What are side effects of vasopressin?

A
Intense vasoconstriction
-Myocardial ischemia
-decreased CO
-Mesenteric ischemia
-Digital necrosis
However it may be beneficial for pulmonary HTN
32
Q

What are potential advantages of calcium sensitizers?

A

Less arrhythmogenic
Do not increase O2 consumption
Since they use a different mechanism of action they may be synergist with conventional inotropes

33
Q

Primobendon and levosimendon are examples of _______ _________

A

calcium sensitizers

34
Q

how does methyline blue affect vasodilation?

A

blocks activation of guanlylate cyclase by NO.-> less cGMP = less vasodilation
Should only be used as a rescue drug in refractory vasodilation when MAP < 50 mmHg and Norepi>35mcg/min

35
Q

What is dose, of methylene blue for vasodilation?

A

1.5-2mcg/kg over 10-60 min. Repeat doses have been given

36
Q

What side effect may methyline blue have in doses >2mg/kg?

A

hyperbilirubinemia and hemolytic anemia

under 2-transient decrease in spo2 and discoloration of skin and urine