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Methods of Anesthesia > Pacemakers > Flashcards

Pacemakers Flashcards

1
Q

Methods for temporary cardiac pacing

A
  1. Transcutaneous
  2. Transesophageal
  3. Transvenous
  4. Epicardial
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2
Q

Preferred pacing method in an emergency

A

Transcutaneous

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3
Q

Disadvantages to transcutaneous pacing

A
  1. It’s painful
  2. Least effective capture (40-80 mA)
  3. Ventricular only pacing
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4
Q

Placement options for transesophageal pacing

A
  1. Have pt swallow pill electrode that is connected to a pacing wire
  2. Insert a flexible catheter connected to a pacing wire
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5
Q

Disadvantages to transesophageal pacing

A
  1. Only paces the atria
  2. Requires relatively high current for capture (>20mA)
  3. Is uncomfortable and requires sedation if possible
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6
Q

Advantage of transesophageal pacing

A

No need for x-rays or cath lab

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7
Q

When is temporary transvenous pacing indicated?

A

If a patient is stable or if transcutaneous pacing isn’t working

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8
Q

How is the pacing function of the temporary transvenous pacing controlled?

A

Through an external pacemaker box

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9
Q

Why does temporary transvenous pacing take longer?

A

It requires central line placement and leads to be placed through the central line

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10
Q

Advantages to temporary transvenous placement

A
  1. A provider can place atrial and ventricular leads
  2. Provides more effective capture
  3. Does not require as much energy for capture (1.5-3mA)
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11
Q

Disadvantages to temporary transvenous placement

A
  1. More time consuming

2. Requires expert placement

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12
Q

What is epicardial pacing?

A
  • Leads are sewn into myocardium when chest is open during cardiac surgery
  • Pacing is controlled through external pacemaker box
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13
Q

Permanent pacemaker consisting of a pulse generator that is connected to pacing wires that have been inserted into the heart via the subclavian vein

A

Cardiovascular implantable electronic device (CIED)

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14
Q

3 types of CIEDs

A
  1. Pacemakers
  2. Automated implantable cardioverter defibrillators (ICDs)
  3. Chronic resynchronization therapy (CRT or biventricular pacemakers)
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15
Q

2 primary reasons for a patient to receive a pacemaker

A
  1. To pace patients with slow heart rates

2. To improve the timing of atrial and ventricular beats in patients with complete heart block

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16
Q

Can provide pacing, synchronized cardioversion and antitachycardia pacing in addition to defibrillation

A

Intravascular ICDs

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17
Q

Indicated only for defibrillation

A

Subcutaneous ICDs

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18
Q

Improves ventricular synchrony in pts with HF with 2 ventricular leads

A

Biventricular pacemakers (CRT)

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19
Q

What should you do when they test the ICD?

A

Give a small propofol bolus prior to shock

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20
Q

Refers to cardiac cells responding to pacemaker stimulation

A

Capture

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21
Q

Refers to minimum current level at which capture is observed

A

Pacing threshold

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22
Q

Normal capture for transvenous/epicardial approach

A

1.5-3mA

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23
Q

Normal capture for transcutaneous approach

A

40-80 mA

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24
Q

Current at which the pacemaker maintains capture

A

Maintenance threshold

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25
Q

How do you determine the maintenance threshold?

A

At least 10% higher than the pacing threshold

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26
Q

How sensitive the pacemaker is to sensing electrical activity within the heart

A

Sensitivity threshold

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27
Q

If pacemaker sensitivity is too high,

A

it may not pace as much as it should

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28
Q

If pacemaker sensitivity is too low,

A

it may pace when it is not supposed to

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29
Q

Pace at which the pacemaker is typically programmed

A

60 bpm

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30
Q

How can you tell if a heart beat comes from a pacemaker?

A

If there is a pacer spike prior to a P wave or QRS complex

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31
Q

True/false. If a patient has a pacemaker, the SA node can still initiate heart beats

A

True

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32
Q

Why is it dangerous to have 2 potential sources of heart beats?

A

If the R wave occurs during the time that a T wave should occur (R on T phenomenon), it can lead to vfib/vtach

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33
Q

Pacing mode that ensures only one source is providing current to the heart at a given time through sensing

A

Demand mode

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34
Q

When does the pacemaker initiate heart beats in demand mode?

A

If the HR is too low

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35
Q

What happens to a demand pacemaker during cautery?

A

It will stop pacing as it senses surgical cautery to be electrical activity of the heart

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36
Q

When is a patient pacemaker dependent?

A

If the rely on their pacemaker to have normal cardiac output

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37
Q

When the pacemaker cannot sense anything, and is therefore constantly pacing

A

Asynchronous mode

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38
Q

Advantage of asynchronous mode

A

The pacemaker will not stop pacing during cautery, preventing cautery induced bradycardia

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39
Q

Disadvantage of asynchronous mode

A

Can lead to R on T phenomenon if the paced rate is slower than the intrinsic rate

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40
Q

How to prevent R on T phenomenon with asynchronous mode

A

Ensure the paced rate is greater than the intrinsic rate

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41
Q

How can the anesthetist ensure the pt’s intrinsic rate is slower than what the asynchronous rate would be?

A

Give beta blockers

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42
Q

When should the pacemaker be converted to asynchronous mode?

A

If the pt was experiencing clinically significant and prolonged cautery induced bradycardia

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43
Q

How does the pacemaker get converted to asynchronous mode?

A

The anesthetist can place a magnet over it or the pacemaker rep can reprogram it prior to surgery

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44
Q

Programmed to increase the paced HR whenever it senses increases in movement and/or minute ventilation

A

Rate modulation

45
Q

Terminates tachycardia by pacing faster than the intrinsic rate

A

Antitachycardia pacing

46
Q

When is antitachycardia pacing effective?

A

For afib, aflutter, SVT and monomorphic vtach

47
Q

When does the pacemaker shock the heart with antitachycardia pacing?

A

If several attempts at ATP prove ineffective

48
Q

Indications for a pacemaker

A
  1. Sinus bradycardia
  2. Sick sinus syndrome (malfunctioning SA node where SA node speeds up and slows down)
  3. 3rd degree AV block
  4. Mobitz Type II heart block
  5. Afib with slow ventricular response
49
Q

What type of pacemaker should be used for a patient with chronic bradycardia and/or sick sinus syndrome?

A

Atrial

50
Q

What type of pacemaker should be used for a patient with afib with slow ventricular response?

A

Ventricular

51
Q

What type of pacemaker should be used for a patient with complete heart block?

A

Dual chamber

52
Q

A dual chamber pacemaker can fix complete heart block if:

A
  1. The atrial lead senses when the atria contracts

2. The ventricular lead is programmed to pace 120-200 msec after the atria contracts

53
Q

Significance of single chamber pacemaker for complete heart block

A

Sensing portion in R atrium and pacing portion in ventricle

-No atrial pacing spikes because there is no atrial lead

54
Q

Where is the L ventricular lead inserted for the biventricular pacemaker?

A

Via the coronary sinus with the aid of fluoroscopy

55
Q

Why is an additional lead in the L ventricle helpful?

A

In advanced HF, RBBB, LBBB, the R and L ventricles can be out of sync when they contract, leading to decreased CO

  • Improves SV and CO
  • Decreased myocardial oxygen demand
56
Q

Why are ICDs dangerous?

A

They can be inappropriately triggered to shock whenever cautery is used

57
Q

Energy used to shock arrhythmias with ICDs

A

15-35J

58
Q

How to prevent accidental shock from an ICD during surgery

A
  1. Disable the shock function of the ICD, either with pacemaker rep or place a magnet over it in the OR
  2. Keep electrical current away from the ICD (use harmonic scalpel or bipolar cautery)
59
Q

Advantages to harmonic scalpel

A
  1. Cuts thicker tissue than bovie
  2. Less smoke
  3. Less thermal damage
60
Q

Disadvantages to harmonic scalpel

A
  1. Takes longer to cut and coagulate tissue

2. Can only coagulate as it cuts

61
Q

How does a magnet affect ICDs

A
  1. It disables the shock function only

2. Does not convert to asynchronous mode

62
Q

Can cautery induced bradycardia still occur in pacemaker dependent patients despite magnet placement?

A

Yes, if they have an ICD

63
Q

When does the shock function NOT have to be disabled?

A

If the surgical site is below the umbilicus

64
Q

Advantages to subcutaneous ICD

A
  • Less risk compared to intravascular leads

- Effective as standard transvenous devices

65
Q

Disadvantages to subcutaneous ICD

A
  1. Not indicated in pts who require anti-bradycardia pacing, cardiac resynchronization therapy or antitachycardia pacing
  2. Increased energy requirements
  3. Not designed to treat ventricular arrhythmias at rates lower than 170 bpm
66
Q

15 minute procedure that checks the function and battery life of a pacemaker

A

Pacemaker interrogation

67
Q

How often should pacemakers be checked?

A

Every year

68
Q

How often should ICDs be checked?

A

Every 6 months

69
Q

What should you know preop about pacemakers?

A
  1. What type of device (pacemaker vs ICD)
  2. What is the programmability of the device?
  3. Underlying rhythm?
  4. Pacemaker dependent?
  5. Rate modulation?
  6. Capture effectively?
  7. Magnet response?
  8. Adequate battery life? (>3-6 months)
  9. Manufacturer’s perioperative recommendations
70
Q

Supplies to be readily available if a patient has a pacemaker or ICD

A
  1. External pacemaker with pacing pads
  2. Magnet
  3. Anti-bradycardia drugs
71
Q

True/false. Devices should be interrogated and/or reprogrammed to original function after surgery

A

True, pts should not be discharged without their devices being interrogated

72
Q

First letter of pacemaker classification

A

Which chambers have pacing leads

A, V, D

73
Q

Second letter of pacemaker classification

A

Which chambers can “sense” electrical activity

A, V, D, O (O= none)

74
Q

Third letter of pacemaker classification

A

How a pacemaker responds after it senses electrical activity

I, D, T, O

75
Q

Fourth letter of pacemaker classification

A

Programmability

76
Q

Fifth letter of pacemaker classification

A

Antitachyarrhythmia function

77
Q

What does the “I” mean in the third letter

A

The pacemaker will inhibit itself from pacing whenever it senses intrinsic/electrical activity in the heart (it is in demand mode)

78
Q

What does the “T” mean in the 3rd letter?

A

The ventricular lead will be triggered to pace when it senses intrinsic/electrical activity (good in complete heart block or with biventricular pacemaker)

79
Q

When the 2nd pacemaker letter is “O”, the 3rd letter will always be:

A

O

80
Q

3 letter pacemaker code for sinus bradycardia

A

AAI

81
Q

3 letter pacemaker code for slow afib/a flutter

A

VVI

82
Q

3 letter pacemaker code for AV block, normal sinus node

A

DDD or VDD

83
Q

3 letter pacemaker code for AV block and sinus bradycardia

A

DDD

84
Q

3 letter pacemaker code for sinus bradycardia with a magnet placed

A

AOO

85
Q

What is contraindicated with CIED patients?

A

MRI

86
Q

How do you avoid damage to the CIED during radiation?

A

Shield it as much as possible

87
Q

Are ICDs or pacemakers more sensitive to radiation therapy interference?

A

ICDs

88
Q

Precautions with radiofrequency ablation?

A

May be acceptable under direction of the attending physician

89
Q

Precautions with emergency defibrillation

A

Place pads away from pacemaker

90
Q

Precautions with transcutaneous electrical nerve stimulation

A

Can interfere with ICD resulting in inappropriate shock

91
Q

Cardiovascular effects of ECT

A

After/during the shock, there is an initial parasympathetic discharge (10-15 sec) followed by a sympathetic response (3-5 min) where HR, BP and myocardial oxygen consumption all increase

92
Q

Cerebral effects of ECT

A

Cerebral oxygen consumption, blood flow, and ICP increase

93
Q

Anesthetics used for ECT

A
  • Etomidate or Brevital
  • Methohexital (not used commonly)
  • Propofol
  • Ketamine
94
Q

Significance of etomidate for ECT

A

Longer seizure duration, but does not blunt the sympathetic response

95
Q

Significance of propofol for ECT

A

Decreases seizure duration but does blunt the sympathetic response

96
Q

Significance of ketamine for ECT

A

Long seizure duration when compared to barbiturates and propofol. ICP increases and can be concerning

97
Q

Airway management for ECT

A
  • Intubation is not required unless risk for reflux
  • Ventilation can be assisted with face mask
  • Hyperventilation lowers seizure threshold and prolongs seizure duration
98
Q

Significance of NMBs for ECT

A

They reduce muscle convulsions and decrease risk of serious injury (succs is commonly used)

99
Q

CIED implications for ECT

A
  • Can be triggered by skeletal muscle potentials during seizures (low risk)
  • Regular demand pacemakers should be converted to asynchronous mode if pt is pacemaker dependent
  • Shock function of ICDs should be deactivated prior to therapy
100
Q

Synchronized litho shock delivery

A

Triggered by R wave on EKG, delivered in refractory period

101
Q

Advantage of synchronized litho shocks

A

Lower risk of causing PVCs/arrhythmias

102
Q

Disadvantage of synchronized litho shocks

A

Procedure goes slower because it can only shock as fast as the heart rate

103
Q

Advantage of non-synchronized litho shocks

A

Procedure goes faster

104
Q

Disadvantage of non-synchronized litho shocks

A

More likely to cause PVCs/arrhythmias

105
Q

Implications of CIEDs with lithotripsy

A
  1. Can interpret shock same way as cautery is interpreted
  2. In atrial paced patients with synchronized shocks, litho can perceive an atrial pacing spike as an R wave and deliver a shock prior to the R wave, causing arrhythmias
106
Q

Management of lithotripsy in atrial paced patients

A

Avoid synchronized shocks

107
Q

Management of lithotripsy in regular demand pacemakers

A

Place pacemaker in asynchronous mode

108
Q

Management of lithotripsy in ICDs

A

Disable the shock function at minimum, but AHA recommends ESWL be avoided in these patients

Methods of Anesthesia (20 decks)

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