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Principles II > implantable cardiac rhythm management devices: anesthesia implications > Flashcards

implantable cardiac rhythm management devices: anesthesia implications Flashcards

1
Q

what does the pacemaker system consist of ?

A
  • pulse generator: power source or battery
  • leads or wires
  • cathode/anode electrodes
  • body tissue
  • pulse generator and leads are the things we need to be able to identify and sometime manipulate
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2
Q

what is the cathode?

A

negative electrode; refers to a pathway

*“cathode current departs”, or leaves device/battery

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3
Q

what is the anode?

A

positive electrode;

*current returns to device/battery

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4
Q

what is opposite of cathode and anode?

A

cation = positively charged
anion = negatively charger
*cathode and anode are the currents that transmit these

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5
Q

what is a bipolar pacemaker system?

A
  • the body tissue is part of the circuit

* impedes

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6
Q

what is unipolar pacemaker system?

A

body tissue contact is essential for grounding

*if contact not made, grounding does not occur so pacing does not occur

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7
Q

describe the pulse generator

A
  • contains a battery that provides energy for sending electrical impulses to the heart
  • houses the circuitry that controls pacemaker operations
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8
Q

describe the anatomy of the pacemaker

A
  • connector: top portion; contains the atrial and ventricular connector; where atrial and ventricular wires, leads connect
  • hybrid: center; merges connector and battery; “brain” of the pacemaker; holds the resistors, defibrillation protection, output capacitors, clock, and reed switch (most of pacemaker components in the hybrid)
  • battery: bottom portion
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9
Q

describe the leads of the pacemaker

A
  • insulated wires
  • deliver electrical impulses from the pulse generator to the heart
  • **sense cardiac depolarization
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10
Q

describe the pacing lead components

A
  • conductor
  • connector pin: connects into the top connection portion of the pacemaker
  • insulation
  • electrode (tip): prongs around here hold into the wall of the heart muscle
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11
Q

when was the first pacemaker implanted?

A
  • 1958

- asynchronous single-chamber

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12
Q

when was the first implantable cardioverter-defibrillator (ICD) implanted?

A

1980

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13
Q

what was significant about pacemakers and defibrillators in the US in 2003?

A
  • 325,800 pacemakers implanted

- 127,300 defibrillators implanted

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14
Q

what are indications for a pacemaker?

A
  • chronic atrioventricular (AV) heart block
  • chronic bifascicular and trifascicular block
  • *AV heart block after acute MI (damaged tissue, so section doesn’t receive signal well)
  • *Sinus node dysfunction
  • hypersensitive carotid sinus and neutrally mediated syndromes (neurogenic syncope)
  • children and adolescents with bradycardias
  • *dilated cardiomyopathy
  • *cardiac transplantation (disconnect b/w host and implant)
  • *heart failure, a fib
  • termination of tachydysrhythmias
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15
Q

where are endocardial leads placed?

A

inserted intravenously through a major vessel

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16
Q

where are epicardial or myocardial leads placed?

A

inserted subcostally; embedded either above the cardium or in the myocardium

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17
Q

where are transvenous leads placed?

A

inserted via a large vein, distal to the heart

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18
Q

describe unipolar pacing

A

placement of negative electrode in the atrium or ventricle and the positive (ground) electrode distant from the heart (metallic portion of the pulse generator acts as the ground of positive electrode and is placed in Sub Q tissue)

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19
Q

describe bipolar pacing

A

placement of both the negative and positive electrodes in the cardiac chamber being paced

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20
Q

describe atrioventricular timing

A

timing that is preset in the pacemaker of a dual chamber pacing b/w atria and ventricles

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21
Q

what activates rate adaptive pacing?

A
  • increase in respiratory rate or minute ventilation (runners)
  • increase in body movement
  • shortened QT interval
  • increased atrial rate
  • rise in central venous temperature
  • decrease in venous blood pH
  • increase in RV stroke volume
  • increase in ventricular pump action
  • not all pacemakers are rate adaptive; depends upon how active and/or if frequent changes in hemodynamics
22
Q

describe biventricular pacing

A

allows both ventricles to contract and allows maximum volume

  • used for functional hemodynamic abnormalities with asynchronous ventricular contraction r/t conduction delays and leading to prolonged isovolumetric time, compromised diastolic filling time, and ineffective atrial contraction
  • *moderate-severe CHF
23
Q

describe the NASPE classification of pacing

A

I) chamber paced: V- ventricle, A- atrium, D- dual, O- none, S- A or V
II) chamber sensed: V, A, D, O, S
III) response to sensing: T- triggers pacing, I- inhibits pacing, D- dual (T & I), O- none
IV) programmable functions; rate modulation: P- programmable rate &/or output; M- multiprogrammability of rate, output, sensitivity, etc.; C- communicating functions (telemetry); R-rate modulation; O-none
V) antitachyarrhythmia functions: P- pacing, S- shock, D- dual (P & S), O- none

24
Q

what are indications for ICDs?

A
  • cardiac arrest d/t V tach or V fib
  • drug resistant VT with hemodynamic impact causing syncope
  • patients with coronary artery disease and a history of sudden death with documented sustained VT
  • prevention for patients with coronary artery disease and nonsustained VT
25
Q

what are functions of ICDs?

A
  • antitachycardia pacing
  • antibradycardia pacing
  • cardioversion and defibrillation
26
Q

how does a defibrillator usually work?

A

-typically detects VT or fibrillation and terminates by overdrive pacing and delivering high energy shock

27
Q

what are ICD generator, rate-sensing leads?

A

electrodes to deliver high energy shocks via wire mesh patch electrodes applied directly to the epicardial surface of the heart

28
Q

where are normal placements of ICDs?

A
  • upper chest or lower abdomen
  • defibrillators are bigger so seen more often in abdominal area where there is more sub q fat for placement
  • need to know placement to consider bovie pad placement
29
Q

what questions should be asked during a pre op eval concerning ICDs?

A
  • is there a device?
  • why was the device implanted?
  • what type of device?
  • is the patient dependent on the device?
  • what is the device’s function?
  • when was the last visit to the doctor
  • when was the last time you called in to have device checked? how often?
  • last time battery was changed?
  • any issues with the devices? if so, what?
  • vertigo or syncope?
30
Q

what could vertigo or syncope indicate with ICDs?

A

pacemaker dysfunction

*if rate has 10% decrease in asynchronous rate (usu. set at 70 or 72), may indicate battery dysfunction

31
Q

what may an irregular HR indicate with ICDs?

A

pulse generator failure to sense R waves or competition with own intrinsic pacer

32
Q

how should the type of pacemaker device be investigated?

A
  • explore old resources: old records
  • manufacturer’s ID card from the patient (probably wont have)
  • CXR: confirms and evaluates the intactness of pacer electrodes
  • EKG: evaluates one to one capture; not diagnostic for patients in which intrinsic HR is > preset pacemaker setting so use magnet to convert to asynchronous mode
33
Q

how can you determine the dependency of the pt. on the pacemaker?

A
  • verbal history or written medical record of syncope from a bradyarrhythmia requiring device
  • history of AV node ablation requiring device (this affects the rhythm of the EKG so get a pre op EKG to look for changes during surgery)
  • device evaluation that shows no spontaneous ventricular activity
34
Q

how can device function be assessed?

A

interrogate the device

  • consult from cardiologist or pacemaker clinic
  • do if pt. knows nothing about pacemaker or an issue is suspected (syncope, vertigo, SOB, irregular pulse, “not feeling well”)
35
Q

describe management of anesthesia with ICDs

A
  • monitor EKG
  • monitor peripheral pulse (SaO2) to indicate circulation
  • defibrillator present
  • magnet available
  • atropine, epi, isoproterenol (chemical pacemaker) in the room and available!
  • *be prepared for pacer failure!
36
Q

what is electromagnetic interference (EMI)?

A

-signals from other sources which the pacemaker or ICD senses (artifact)

37
Q

what is the most common source of EMI?

A

electrocautery

*unipolar cautery worse then bipolar

38
Q

what are other sources of EMI?

A
  • AC power supplies
  • microwaves
  • ventilators
  • monitors
  • radio frequency ablation
  • MRI
  • radiation therapy
  • peripheral nerve stimulator (use most distal site, not face)
39
Q

what is the risk of endocardial leads have been placed within 4 weeks?

A
  • at risk for dislodgement
  • scarring has not occurred to hold leads in place
  • is PA catheter placement feasible?
40
Q

what factors determine the EMI’s effect on the implanted cardiac device?

A
  • strength of the source
  • distance of the source from the leads and pulse generator
  • frequency of the signal
41
Q

what is the pacemaker’s response to EMI?

A
  • inhibition d/t ventricular oversensing (in VVI, oversenses rate than what it actually is and inhibits pacing; causes brady)
  • paces asynchronously
  • triggers atrial or ventricular fibrillation
  • burns myocardium at lead site
  • energy damages pulse generator circuit or battery or reprograms it
42
Q

what is the defibrillator’s response to EMI?

A
  • inappropriate shock delivery
  • failure to deliver shock
  • reprogrammed
  • burns myocardium at lead site
  • energy damages pulse generator circuit
43
Q

what are methods to minimize EMI effects?

A
  • suggest bipolar or harmonic scalpel
  • ensure cautery grounding pad is as far from pulse generator as possible
  • ensure pulse generator and leads are not located between the operative site and the grounding pad (serious burns and problems)
  • utilize short bursts of cautery with the lowest strength
  • make sure a programmer is readily available
  • monitor for arrhythmias and be prepared to treat
  • if defibrillation is necessary, use the anterior-posterior placement of paddles (not across the body) and lowest effective dose of electrical energy possible
  • determine if reprogramming to asynchronous or disabling rate adaptive function is necessary
  • disable antitachyarrhythmia function
44
Q

what happens if defibrillation is necessary with an ICD?

A

there will be an acute increase in stimulation threshold, causing a loss of capture and the need for prompt insertion of a transvenous pacer or transcutaneous pacer

45
Q

what is the function of the magnet with the pacemaker?

A
  • activates the reed switch within the pulse generator to STOP SENSING capabilities, thus pacemaker paces asynchronously
  • magnet rate 70-72 (a much lower rate indicates low battery)
  • may be vulnerable to reprogramming
  • watch magnetic instrument mat used in surgery by OR techs to hold instruments (can act like a reed switch); do not place on chest or upper abdomen depending on where pulse generator is located
46
Q

what is the function of the magnet on defibrillators?

A
  • disables detection of tachyarrhythmias, thus no shock can be delivered
  • pacing ability remains intact
  • variability in reaction to removal of magnet depending on brand (Medtronic reactivates; Guidant remain inactivated and beeps to be reset)
47
Q

describe post op care for ICDs

A
  • continue to monitor cardiac rhythm
  • interrogate and possibly restore function of pacemaker or ICD
  • special attention to restoration of antiarrhythmia functions (call the rep)
48
Q

what does dual pacing provide?

A

atrioventricular (AV) synchrony where atrial pacing will take place in the “inhibited” mode and the pacing device will ensure that a ventricular event follows

49
Q

what does inhibited response to sensing do?

A

the appropriate chamber is paced unless intrinsic electrical activity is detected during the pacing interval

50
Q

what does the triggered response to sensing do?

A

the pacing device will emit a pulse only in response to a sensed event

51
Q

what can magnets be used for?

A

applied over the pacemaker to avoid inhibition by EMI

Principles II (18 decks)

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