Antidysrhythmics Flashcards Preview

Anesthesia Pharmacology > Antidysrhythmics > Flashcards

Flashcards in Antidysrhythmics Deck (90)
2

What are the 2 major mechanisms that cause ectopic cardiac dysrhythmias?

Automaticity

Reentry

3

What is automaticity in the myocardium?

The ability of the cardiac muscles to depolarize spontaneously without electrical stimulation from the nervous system.

4

The discharge rate of normal or abnormal pacemaker activity may be accelerated by what: (4)

  • Drugs
  • Various forms of cardiac disease
  • Reduced potassium
  • Alterations of autonomic nervous system tone

5

What does enhanced normal automaticity result in?

What does abnormal automaticity result in?

Sinus tachycardia

Accelerated idioventricular rhythm

6

Reentry is responsible for most of the clinically important arrhythmias, including a-fib, a-flutter, AV nodal reentry, AV reentry involving a bypass tract, ventricular tachycardia after MI, and v-fib.  True or false?

True.

7

What are other underlying mechanisms that can cause dysrhythmias? (7)

Myocardial Ischemia
Hypoxemia
Bradycardia-->ventricular dysrhythmias
Hypokalemia, hypomagnesemia-->ventricular dysrhy.
Volatile agents and other drugs
Acid-Base Changes-->alkalosis 
ANS Changes

8

What are the following antidysrhythmic classes?

Class I
II
III
IV

I. Membrane stabilizers

II. Beta blockers

III. Prolong repolarization

IV: Ca channel blockers

9

How do Class I agents work? (3)

Decrease automaticity

Decrease conduction through bypass tracts by blocking "fast" Na channels

Decrease Phase 0 depolarization

 

10

What is Phase 0?

Rapid depolarization via Na channels

Gates close when 0 mV reached

11

What is Phase 1?

Partial repolarization (K moves out the cell)

12

What is Phase 2?

Plateau (slow Ca movement into cell to neutralize K out)

13

What is Phase 3?

Rapid repolarization

(Ca channel close and K continues to move out unopposed)

14

What is Phase 4?

Resting phase, repolarization

15

The Class I drugs are the membrane stabilizers that block _______ channels thereby inhibiting Phase ___ .

Sodium

0

16

What do Class IA drugs do? (3)

Depress Phase 0 depolarization

Prolong action potential duration

Slow conduction velocity

17

What are the Class IA drugs? (3)

Procainamide

Disopyramide

Quinidine

18

When is QUINIDINE indicated? (3)

What class drug is it?

  • A-fib
  • WPW
  • PVC's

Class IA

19

What do Class IB drugs do? (2)

Shorten AP conduction

Have little effect on Phase 0

20

What are the Class IB drugs? (3)

Phenytoin

Lidocaine

Tocainide

21

What do Class IC drugs do? (3)

Greatly depress Phase 0 depolarization

Minimally affect AP duration

Slow conduction

22

What class of agents bind most rapidly to the receptors?

What class of agents have the slowest binding and dissociation from the receptor?

Class IB

Class IC

23

What % of patients with a-fib taking quinidine, procainamide, and disopyramide will convert to NSR?

25%

24

Class IA drugs can be given IM and are preferred to be given IV? True or false?

False

Not IM because of pain.

Limited via IV because of vasodilation and myocardial depression can result.

25

What drug is effective in the treatment of acute and chronic supraventricular dysrhythmias?

Quinidine

26

What are the side effects of quinidine? (5)

  • Prolonged QT
  • Syncope or sudden death
  • Hypotension
  • Allergic reaction (itch, hives)
  • Diarrhea

27

We use quinidine in the OR.  True or false?

False.

28

What EKG changes will indicate that quinidine should be discontinued or the dose should be decreased?

50% increase in QRS duration or heart block will ensue

29

What pts should not be prescibed quinidine? (2)

prolonged QT interval

AV heart block

30

What are the indications for procainamide? (3)

  • PVT
  • PVC
  • Ventricular dysrhythmias

Note: Not as effective in treating atrial tachydysrhythmias as quinidine.

31

What are the side effects of procainamide? (5)

  • Myocardial depression
  • Hypotension (by direct myocardial depression)
  • Asystole or v-fib (heart block or high conc. of drug)
  • Lupus-like symptoms (SLE-like syndrome)
  • Rash

Note: SLE is systemic lupus erythematasous

Also, incidence of side effects are high!

32

What are the indications for disopyramide?

Atrial and ventricular tachydysrhythmias

33

What is the adminiatration for disopyramide?

Oral

34

What is the mechanism of disopyramide?

When is the peak effect?

Simiar to quinidine, membrane stabilizing

2 hours

35

What are the side effects of disopyramide? (3)

Direct myocardial depression--precipitating CHF, hypotension

Anticholinergic activity--dry mouth, urinary hesitancy

Prolonged QT and paradoxical VT

 

36

What are the indications for lidocaine relating to dysrhythmias? (2)

PVC

V-tach

Note: Minimal atrial effects!

37

Lidocaine has significant 1st pass metabolism.  True of false?

True.

38

What is the dose for lidocaine? 

IV
IM
IV infusion rate

2 mg/kg 

4 - 5 mg/kg

1 - 4 mg/min

39

What is the mechanism of lidocaine? (2)

Delays the rate of Phase 4 depolarization

Blocks Na channels in depolarized tissues

Note: Not able to alter rate of atrial cells so not good for atrial tach.

40

What are the side effects of lidocaine? (3)

> 5 mcg/ml (in plasma)
5-10 mcg/ml
> 10 mcg/ml

Stimulation of CNS

Seizures, hypotension

CNS depression, apnea, cardiac arrest

41

What are the indications for phenytoin? (3)

Paradoxical VT

Torsade de Pointes

Digitalis toxicity

42

How can phenytoin be administered?

What is the IV dose?

What is the max dose?

PO, IV

1.5 mg/kg q5 min or 10-15 mg/kg

1 gram

43

What is the mechanism of phenytoin? (2)

Shortens QT interval

Improved conduction through the AV node

Note: Similar effects are lidocaine, but more profound.

44

What drug shortens the QT interval more than any other drug?

Phenytoin

45

What are the side effects of phenytoin? (4)

Bone marrow suppression

Increased blood sugar

CNS disturbances: cerebellar symptoms

Hypotension

46

What is the indication for MEXILETINE and TOCAINIDE?

V-tach

47

What is the mechanism of MEXILETINE and TOCAINIDE?

Similar to lidocaine

48

What are the side effects of MEXILETINE and TOCAINIDE? (2)

Epigastric burning

Neurologic effects

49

ON BOARDS

What are rare effects of TOCAINIDE? (2)

Bone marrow depression 

Pulmonary fibrosis

50

When is FLECAINIDE indicated? (3)

Atrial tachdysrhythmias

WPW

Ventricular premature beats (sometimes)

51

What is the mechanism of FLECAINIDE? (2)

AV conduction block

Decreased SA node function

52

What are the side effects of FLECAINIDE? (4)

Moderate negative inotropic effect

Prodysrhythmic effect

Vertigo

Visual accomadation problems

53

What drug is most effective at suppressing premature ventricular beats and v-tach?

FLECAINIDE

54

What are the indications for beta blockers? (4)

A-fib

A-flutter

Paroxysmal AT

Digitalis induced ventricular dysrhythmias

55

What are the common beta blockers? (3)

Propanolol

Metoprolol

Esmolol

56

What is the mechanism of Class II (beta blocking) drugs? (3) 

Block sympathetic activity

Decreased rate of Phase 4 depolarization

Decreased rate of SA node discharge

57

What are the side effects of beta blockers? (5)

  • Allergic rash
  • Bradycardia
  • Bronchospasm
  • CHF (worsen)
  • Mental depression, fatigue

58

What is a Class III drug?

Amiodarone

59

What is the indication for amiodarone? (2)

Refractory supraventricular / V tach

WPW

60

Amiodarone is not very effective for atrial tach.  True or false?

True.

61

What is the dose of amiodarone?

initial IV dose
IV infusion rate

150 mg/ 10 min

1 mg/min

62

What is the mechanism of amiodarone? 

Prolongs refractory period in all cardiac tissue

63

What must you do when giving amiodarone?

Give slowly because it can cause hypotension.

64

What are the side effects of amiodarone? (3)

Pulmonary toxicity

Ventricular tachydysrhythmias

Hypotension

65

If the daily dose of amiodarone exceeds 400mg, what side effect is likely to occur?

What is the course of treatment?

Pulmonary alveolitis

Decrease FiO2 at lowest possible to maintain adequate oxygenation because of increased production of free oxygen radicals.

66

What are other side effects from chronic use of amiodarone? (10)

  • Bradycardia (resistance to atropine)
  • Heart block
  • Neurologic abnormalities like muscle weakness, ataxia
  • Pulmonary fibrosis
  • Hypo/hyper thyroidism
  • Corneal deposits
  • Phytosensitivity
  • Cyanotic discoloarion of the face
  • Increased plasma transaminase
  • Displacement of digoxin from binding sites

67

What are the Class IV drugs? (2)

Verapamil

Diltaizem

68

What are known as the supraventricular antidysrhythmics?

Class IV, Ca channel blockers

69

What are the indications for calcium channel blockers? (3)

Paroxysmal SVT

Afib

A-flutter

70

What drug may decrease the response to catecholamines and sympathetic stimulation which may manifest as sinus arrest, AV heart block, and result in low CO?

AMIODARONE

71

The use of what drug may indicate the potential need for a temporary pacemaker?

AMIODARONE

72

What is the dose of verapamil?

PO
IV

80 - 120 mg PO q 6-8 hours

5 - 10 mg IV

73

What is the dose of diltiazem?

IV

20 mg IV

Note: This is 2nd line drug to be used in beta blocker doesn't work.

74

What is the mechanism of action of Class IV drugs? (2)

Decrease phase 4

Depresses AV node

75

What is the metabolism and excretion of Class IV drugs?

Hepatic metabolism

Renal excretion

 

76

What are the side effects of Class IV drugs? (3)

Hypotension

AV block

Direct myocardial depression (usually with chronic therapy)

77

What class of drug increases:

effective refractory period
action potential duration
QT duration

Class IA

Quinidine, Procainamide, Disopyramide

78

What class of drug decreases:

depolarization rate
conduction velocity

Class IA 

79

What class of drug decrease:

effective refractory period
action potential duration

Class IB

Lidocaine, Phenytoin, Mexiletine, Tocainide

80

What class of drug:

decrease depolarization rate and conduction velocity
increase PR, QRS, and QT duration

Class IC

Flecainide

81

What class of drug decrease:

conduction velocity
automaticity
QT duration

Class II

Beta blockers

82

What class of drug:

decrease conduction
decrease automaticity
increase refractory period
increase PR duration
increase QT

Class III

Amiodarone

83

What class of drug decreases action potential duration?

Class IV

Verapamil, Diltiazem

84

What are the indications for digitalis? (2)

Atrial tachydysrhythmias

Heart failure

85

What is the oral dose of digitalis?

0.5 - 1 mg over 12-24 hours

86

What is the mechanism of digitalis?

Increase phase 4 slope

Increased AV node refractoriness

87

What are the side effects of digitalis? (5)

  • Digitalis toxicity
  • EKG changes--digitalis effect
  • Cardiac dysrhythmias
  • Nausea
  • Disturbance of cognitive function

88

When is adenosine indicated? (2)

PSVT (atrial tach)

WPW

89

What is the dose of adenosine IV?

6 mg 

Repeat in 3 min with 6-12 mg

90

What is the mechanism of adenosine? (2)

Similar to Ca blocker

Hyperpolarize the cell

Note: Will see flat line on ECG!

91

What are the side effects of adenosine? (5)

  • Headache
  • Facial flushing 
  • Bronchospasm
  • Dyspnea
  • Transient AV block