Misc. Equipment PDF

Misc. Equipment Clay Freeman, DNP, CRNA Principles II – NRAN80526 1 Objectives Readings: Barash: Chap. 26 Barash: Cha...

Misc. Equipment Clay Freeman, DNP, CRNA Principles II – NRAN80526 1 Objectives Readings: Barash: Chap. 26 Barash: Chap. 10 Barash: Appendix 3 Detail the components of Mapleson systems Discuss the variations and indications for each classification of Mapleson circuits Describe nervous system electrophysiology and how it relates to neuromonitoring modalities Discuss mechanisms, indications, and anesthetic considerations for the various neuromonitoring techniques Detail the types and programming modes of CIEDs Discuss anesthetic considerations for patients with CIEDs 2  History Open Drop anaesthesia Inhalation of anesthetics which are dripped on a permeable mask Spontaneous ventilation only Anesthetic concentration undetermined Lacks visualization of patient’s airway 3 History Draw-Over circuits were created in conjunction with vaporizers that used ambient air as the carrier gas Simplistic and portable when compressed gases and ventilators are not readily available Useful in military and mission trips Could be fitted to provide positive pressure ventilation techniques, passive scavenging, and upstream supplemental O2 4  Innovation Open-drop, Insufflation, and Draw-over anesthesia were inefficient. Poor control of inspired gas concentrations Ergonomics to surgical field Pollution & waste of gases Practitioners developed more sophisticated breathing assemblies which would later be classified as Mapleson Circuits 5 Unicorns Goals of an ideal breathing system: Simple & Inexpensive Accurate delivers intended gas mixture Permits various forms of ventilation (spontaneous, controlled, assisted) Efficient with low fresh gas flows Safety from barotrauma Sturdy but light weight Removes waste gases & CO2 Provides warming/humidification of inspired gases Low resistance and minimal dead space In truth, these arrangements were inefficient at: Economical gas flows Conservation of heat & humidity Consistent scavenging of waste gases 6  Taking All the Credit Mapleson analyzed and defined circuits according to the arrangement of the components The various arrangements demonstrate unique performance characteristics Five original classifications were designated (A-E) The 6th (Mapleson system F) was added later Arrangement of included components: 1) Breathing tubing 2) Fresh gas inlet 3) Adjustable pressure-limiting valve (APL) / Expiratory valve 4) Reservoir bag 7 Taking All the Credit The particular circuit design has implications on the required fresh gas flow to avoid rebreathing of exhaled gases Easiest to group by ❑A ❑B,C ❑D,E,F 8 Clarification The Mapleson breathing circuits are simple & lightweight breathing systems that can be used for both spontaneous and manual ventilation. Mapleson circuits are NOT commonly a part of today’s anesthesia workstation since they are not economical for volatile anesthetic use. They differ from Circle System d/t: Bidirectional gas flow Lacking a CO2 absorber Mapleson circuits depend on high rates of fresh gas inflow to eliminate CO2 and prevent rebreathing BUT there is usually still some rebreathing However, Mapleson systems are still used in pediatrics, patient transport, procedural sedation, T-piece systems, and office-based airway management 9 Semi-Closed Systems 10 Semi-Closed Systems TYPE RESERVOIR REBREATHING OPEN NO NO SEMI-OPEN YES NO SEMI-CLOSED YES PARTIAL CLOSED YES COMPLETE 11 Mapleson A Rarely used The Mapleson A, also known as the “Magill circuit,” Functionally distinct from all the other circuits APL is located near the patient It is the ONLY system where fresh gas flow enters from the distal end of the circuit Disadvantage: Pollution Can’t be used with ventilator 12  Mapleson A Rarely used Drastically different performance when used for spontaneous vs manual ventilation: the Mapleson A design is the Most efficient circuit for spontaneous ventilation if fresh gas flow is equal to minute ventilation - But - Worse efficiency during manual ventilation due to location of APL 13 Mapleson A R3mix Adaptation of Mapleson A is known as the “Lack’s Modification” Was created to facilitate scavenging of gases Added coaxial expiratory limb & Expiratory valve moved near reservoir bag Disadvantage: Increased work of breathing ~ less efficient fresh gas flow than Magill 14 Mapleson B & C Rarely used Mapleson B & C are similar in assembly +/- corrugated tubing o Therefore C has less dead space APL & FGF located proximal to patient Mapleson C sometimes used during emergencies Extremely inefficient in scavenging and high gas flows: Entire system fills with FGF so to prevent rebreathing flow rate must be ~20-25L/min High fire risk due to location of APL 15 Mapleson D Like Mapleson A but the APL and FGF are flipped Most efficient during controlled ventilation since FGF pushes alveolar air toward the APL Is also effective at scavenging of waste gases d/t location of APL away from the patient 16  Mapleson D RE-mix Modification of Mapleson D known as – Bain circuit Coaxially placed FGF warms inspired gases Was used commonly in pediatrics Advantages: Recommend Pethick Test prior to use: Exhaled gases scavenged 1. Occlude pt end Useful in MRI suites 2. Close APL Ease of connecting to ventilator 3. O2 flush to fill circuit 4. Release occlusion → Venturi effect collapses reservoir bag Disadvantage is disconnection & kinks often go unrecognized 17 Mapelson E Modification of Ayre’s T-piece FGF proximal to patient Only circuit that does NOT use a reservoir bag Expired gas pollution FGF required at 2-3x patient minute ventilation during spontaneous respiration 18 Mapleson F / Jackson-Rees Circuit Modification of Mapleson E ✓ Added a reservoir bag Or…”a Mapleson D with the APL moved to the bag” Commonly used for patient transport Easily managed by practitioner Increases ventilatory monitoring 19 Highlights Disadvantages of Mapleson systems to remember why we’ve moved on: High fresh gas flows = high cost High pollution High FGF = less heat/humidification FGF rate difficult to ascertain in correlation to patient minute ventilation Inaccessible components depending on setup Not suitable for patients at risk of MH Exceptions: Mapleson A is only circuit with FGF near the reservoir bag Mapleson C is the only circuit not corrugated Mapleson E is the only circuit without a reservoir bag Bain & Lack have coaxial tubing 20 Resource 21 Resource 22 Manual Resuscitators Nonrebreathing valve Self-Inflating Manual Resuscitators Used consistently during patient transport, emergency resuscitation, or as a back-up supply. Unlike Mapleson circuits, manual resuscitators function in the absence of a gas source AND contain a nonrebreathing valve 23  Manual Resuscitators Nonrebreathing valve Resuscitator components: Self-inflating reservoir bag Nonrebreathing valve (between vent bag & pt) directs gas flow throughout respiratory cycle. Intake valve (between vent & reservoir bag) permits positive pressure ventilation Reservoir valve consists of 2 unidirectional valves Inlet valve permits refilling of the bag with reservoir gas or room air. Outlet valve vents excess FGF ~ APL may be present to limit the PIP o safety standards require resuscitators designed for infants/children have a valve to limit PIP to 45cm Disadvantages: Lacks visual monitoring cue to pt respiratory effort High PIP may be generated – risks barotrauma or gastric insufflation. Significant variability of tidal volume, PIP, and PEEP Nonrebreathing valves generate resistance = increased the work of breathing 24 Nervous System Monitoring 25  ElecroEncephaloGram (EEG) Review: Nervous system is unique in that it functions via electrical activity Neuronal activity generates Extracellular Electrical Potentials composed of postsynaptic potentials & neuronal membrane hyperpolarization This allows for direct assessment of the nervous system by observing for electrical potentials created by neurons Utility of monitoring determined by: Hemodynamic effects on electrophysiology Pharmacologic effects of actional potentials Anesthetics hyperpolarize neurons and affect neurotransmitter release/response at the synapse Presynaptic Glutamate inhibited Postsynaptic GABA potentiated 26  Historical Practice Physiologic responses to noxious stimuli are explained by the nociceptive-medullary-autonomic circuit Spinoreticular tract Brainstem arousal centers Sympathetic/Parasympathetic efferent pathways Traditional physiologic monitors (HR, BP, SpO2) reflect these responses, but only measure supportive parameters of tissue maintenance Anesthetic state of patient is inferred in this manner 27  Updated Theories CNS functions to exchange information via coordinated action potentials are transmitted and Cortical and subcortical structures are critically interconnected Historically, Bottom-up approach to anesthetic effects on neurophysiology was the most widely accepted Dysfunctional communication from thalamus to the cortex created Growing evidence for top-down mechanism Intracortical communication becomes interrupted Likely, a combo of the two theories are responsible for suppression of consciousness under anesthesia 28 EEG Pyramidal cells are highly prevalent within the cerebral cortex The organization of these neurons favors the production of large local field potentials created via extracellular potentials Dendrites of the neurons run parallel with each other Neurons run perpendicular to the cortical surface This geometry creates a biophysical antenna whose potentials can be measured through the scalp Neurons exhibit oscillatory spiking and local field potentials that play a primary role in coordinating and modulating communication 29  EEG Typical mapping involves placement of 10-20 electrodes Placed subdermal w/ conductive gel to reduce impedance EEG activity reflects cerebral metabolism and blood flow Therefore, EEG is a more direct monitor of the function of nervous tissue EEG monitoring is useful when cerebral cortex tissue is vulnerable to ischemia or to guide pharmacologic therapy Clinical Scenarios: Carotid Endarterectomies Cerebral aneurysms Cardiovascular surgery Seizure observation Transcortical assessment (DBS) Observation of physiologic derangements 30  EEG EEG waveforms are a summation of spontaneous postsynaptic potentials Oscilloscope displays Amplitude (5-500 µV) Frequency (Hz) Time Waveforms are classified according to consistent patterns of amplitude and frequency Delta(0.5-4 Hz) Theta (4-8 Hz) Alpha (8-13 Hz) Beta (13-30 Hz) ❑ Gamma (30-80 Hz) 31 EEG Waveforms “Activated” waveforms Beta (13-30 Hz) High Frequency / Low amplitude Frontal region Commonly observed in alert patient with eyes open Alpha (8-12 Hz) Occipital region Awake patient with eyes closed 32 EEG Waveforms “Depressed” waveforms Theta (4-8 Hz) Drowsiness or common in GETA Frontocentral region Replace Alpha waves in early sedation in occipital Delta (1-4 Hz) High Amplitude / Low Frequency Frontocentral region Deep sleep, and anesthesia Or neuronal compromise such as Brain injury Focal dysfunction Generalized encephalopathy 33  EEG Waveforms EEG-based waveforms can be used to track loss of consciousness induced by general anesthesia. Paradoxical excitation: behavioral state at low doses of an anesthetic (increased beta activity) characterized by purposeless movements, incoherent speech,& euphoria/dysphoria Anteriorization: An EEG pattern usually observed in a deep anesthetic state characterized by alpha and delta activity that is greater in the anterior leads relative to the posterior leads loss of the functional connectivity created by propofol/inhaled anesthetic-induced unconsciousness 34 Burst Suppression → Isoelectric During deep anesthesia, a Burst Suppression pattern is eventually produced flat tracings “suppression” interspersed with High-frequency “burst” activity Increased anesthesia doses will increase isoelectric duration Also seen in anoxic coma and certain forms of epilepsy If pharmacologically suppressing cerebral metabolic function, THEN monitoring for ischemia is no longer possible Note: Nitrous oxide does not produce burst suppression 35  EEG Waveforms Isoelectric: An EEG pattern with zero amplitude Seen in [Too] deep states of GETA coma, brain death and during cardiac arrest 36  Interpretation EEG can accurately identify consciousness/unconsciousness, stages of sleep, and coma. Intraop, in the absence of significant changes in anesthetic technique, characteristics of the abnormal EEG can be identified: Patterns that are unpredictable or unexpected o Suggests either anatomic or metabolic alterations of the brain Asymmetry regarding frequency, amplitude, or both when comparing corresponding hemispheres Regional asymmetry is seen with tumors, epilepsy, and cerebral ischemia Epilepsy displays as high-voltage spikes and slow waves 37 Awareness Practitioners across all surgical specialties remain perplexed by the incidence of awareness under anesthesia GETA requires: Unconsciousness, Amnesia, Analgesia, Immobility, Attenuation of autonomic response Consciousness consists of Awareness & Arousal Awareness: Ability to process, integrate, & store information in interaction with the environment lack of awareness is inferred through EEG analysis 38  Processed EEG Manufacturers have developed devices that process reduced channel EEG signals Examines 4 components within the EEG that are associated with the anesthetic state: (1) Low frequency, as found during deep anesthesia (2) High-frequency beta activation found during “light” anesthesia (3) Suppressed EEG waves (4) Burst suppression 39 Various devices: BIS sensor, PSArray, Narcotrend, Entropy Module, Cerebral State Monitor Processed EEG Fourier Transformation: 1) Power analysis converts raw EEG data into a series of sine waves at different frequencies 2) Then power of the signal at each frequency is plotted, allowing for a presentation of EEG activity 3) Signals are further processed for noise reduction in order to decrease artifact 40  EEG-Based Indices Display a dimensionless variable to indicate the level of “wakefulness” created via propriety algorithms GETA induces a change from high values to lower values that indicate states of sedation and unconsciousness BIS index: Range 0-100 Value of 60 suggests reduced probability of consciousness GETA commonly maintained between 45-60 Deleterious effects demonstrated with BIS index ≤ 40 41 EEG Index Disparities Uncertainties exist when using EEG-based indices to define brain states under general anesthesia Different anesthetics act at different molecular targets and neural circuits The different states of altered consciousness demonstrate different EEG signatures These various signatures created by different drugs are readily observed by EEG, but processed EEG indices can confuse or miss certain signals 42 Pharmacology Intravenous hypnotics & Volatile anesthetics produce progressive slowing of EEG until burst suppression Activation of GABA receptors within the cortical & subcortical structures results in inhibition & disorganized communication Characterized with Alpha & Delta oscillations Volatiles: at higher doses Theta bands are present N2O (NMDA & K+ sites of action) demonstrate Beta & Gamma oscillations Synergism exists when combined with other inhalation agents 43  Pharmacology Ketamine creates false excitatory values Dissociative anesthetic o Increases Theta and Beta/Gamma frequencies Dexmedetomidine initially increases Alpha waves o At high doses, primarily Delta waves Opiates decrease Beta, slow Alpha, and increase Delta o Reduces wave variability Vasoactive agents can affect as well 44  Pharmacology Neuromuscular blockade: Overlapping frequencies between EEG & Electromyography (EMG) causes interference in values EMG activity would then increase index values Newer machines are better able to recognize these frequencies and interpret results more accurately 45 Standard of Care ??? Processed EEG Uses: ▪ Depth of anesthesia Deep anesthesia associated with increased delirium and cognitive dysfunction ▪ Awareness with recall Controversial/Unlikely ▪ Another data point to decision-making Processed EEG Issues: Delayed readings (Induction/Emergence) Pharmacologic variances Physiologic disparities with age Electrical interference: Cautery or PNS Electrode impedance Anesthetic Considerations: Recall highest in Trauma, Obstetrics, and Cardiac surgery Recall highest with TIVA anesthetic technique 46 Evoked Potentials 47 Evoked Potentials Evoked potential monitoring utilizes stimulation of a neural pathway to test integrity of the neural pathway This technique can be used for sensory or motor pathways Waveform appearance determined by both the site of stimulation and the site of recording Common Modalities: Somatosensory Evoked Potentials (SSEP) Motor EP (MEP) Brainstem Auditory EP (BAEP) Visual EP (VEP) 48  Somatosensory 1) Electrical stimulus applied to peripheral nerve median, ulnar, posterior tibial 2) Signal transcends the sensory pathway Dorsal root ganglia Dorsal column of the SC 3) Waveform captured at the contralateral cortex Decrease in waveform amplitude or Increased latency indicate neurologic dysfunction Waveforms are low voltage so data is averaged over time (~90 seconds) 49 SSEP SSEPs used in spine, intracranial, endovascular and cardiac surgeries Remember: Dorsal column pathway of the posterior SC is perfused by 2 spinal arteries NOT affected by neuromuscular blockade Possible benefit by suppression of myogenic interference Affected in a dose-dependent fashion to Volatile Anesthetics Wave amplitude is decreased and latency increased N2O should be avoided due to enhancement effect Propofol is ideal for SSEP Mild effects from adjuncts Mild hypothermia increases latency 50 Motor EP Monitors integrity of motor cortex, corticospinal tract, nerve root, and peripheral nerve 1) Motor cortex stimulated 2) Electricity transcends to the anterior horns of the SC 3) Travels from periphery to neuromuscular junction One anterior spinal artery perfuses this corticospinal tract Decreased amplitude of waveform is the most concerning 51 MEP Regularly used in spine and aortic surgery Electrodes placed in scalp overlie the motor cortex Inadvertently activates muscles of mastication o Soft bite blocks placed along molars is crucial Similar anesthetic approach as SSEPs Inhalation doses of 0.5 MAC o Greater concentrations cause a nonlinear and accelerated suppression of MEP amplitude IV anesthetics are more conducive to MEP NO neuromuscular blockade “Prepositioning” baselines are sometimes obtained 52 Combo SSEP & MEP often used in combination to increase sensitivity of monitoring Anatomically distinct from one another Common utilized surgeries: Spinal fusion with instrumentation SC tumor resection Brachial plexus repair Thoracoabdominal aortic aneurysm repair Epilepsy surgery Cerebral tumor resection 53 Brainstem Auditory EP Device is inserted into unilateral ear canal which produces an acoustic stimulus (repetitive click) Order of Transduction: 1) from Ear structures 2) to VIII Cranial nerve 3) to Brainstem Recording electrodes placed near the stimulated ear and at the vertex Used during posterior fossa surgery to assess brainstem function - Or when hearing structures are at risk 54 Anesthetic Strategies Anesthesia considerations Recap Volatiles affect neuromonitoring > IV hypnotics Order of sensitivity: VEP > MEP > SSEP > BAEP Preop benzodiazepines OK except for surgeries involving seizure foci Etomidate and ketamine are exceptions d/t increasing cortical amplitudes which can be used to enhance SSEP & MEP No restrictions on opioids Neuromonitoring affected by physiologic derangements: Blood pressure Ventilation (O2 & CO2) Temperature Anemia Positioning 55 Electromyography EMG monitors responses of motor nerves via evoked action potentials. EMG is recorded from the muscles innervated by cranial or spinal nerves that are at risk during surgery. Monitoring can be either Active or Passive Active or Evoked EMG helps identify intact nerves: Used to identify a nerve or anatomic variances in order to avoid cutting it A stimulator is placed on the nerve of interest, and the result is recorded from the innervated muscle An increase in the latency and/or a reduction in the amplitude may indicate nerve injury. 56 EMG Passive or Spontaneous EMG commonly used in spine surgery to identify nerve irritation before injury EMG triggered by stimulation of malpositioned screws that are too close to nerve roots (Radiculopathy) Cranial nerve monitoring is another form of passive EMG which is utilized during: acoustic neuroma and cerebellopontine angle tumor resections, microvascular decompression, skull base surgeries, thyroid and parotid procedures, and radical neck dissection Only cranial nerves with a motor component can be monitored with EMG (CN III, IV, V, VI, VII, IX, X, XI, and XII) 57 Resource 58 Cardiac Implantable Electronic Devices 59  CIED CIEDs refers to any permanently implanted pacemaker, cardioverter-defibrillator, or cardiac resynchronization therapy devices Utilization is ever increasing due to growing geriatric populations and prevalence of cardiovascular disease Placement of CIEDs provides monitoring and coordinated electrical therapy to regulate heart rhythm in order improve cardiac function 60 Pacemakers Pacemaker placement is indicated for symptomatic bradyarrhythmia and atrioventricular conduction defects likely to progress to complete heart block Have 1-2 leads placed atrial +/- ventricular and a pulse generator Generator transmits electrical pulse through the lead/s in order to depolarize local myocardium Percutaneous vein insertion or directly by a cardiac surgeon Typical lifespan of generator: 10-15 yrs Pacemakers are programmed to maintain normal atrial-ventricular activation regardless of heart rate or responses to metabolic needs 61 Indications Expanded indications for pacemaker implantation include: Sinus node dysfunction Symptomatic bradycardia AV block Cardiomyopathy Heart failure Neurocardiogenic syncope Post heart transplant Terminating tachycardia Congenital heart disease Etc. Sick Sinus Syndrome: describes a multitude of disorders involving irreversible sinus node dysfunction. Results in sinus pause, sinus arrest, or bradycardia d/t inadequate sinus node automaticity. Can result in aberrant atrial tachyarrhythmias (atrial fib/flutter) Pacemaker Dependent: significant symptoms present or cardiac arrest upon pacing cessation 62 Programming Code Pacemaker programming is universally designated according to NASPE/BPEG coding: Revised edition now includes a IV & V position in order to designate mode modulations (when present) Position 1: indicates which chamber is paced; O/ A / V / D Position 2: indicates which chamber is being sensed; O / A / V / D Position 3: indicates the response to sensing; O / I / T / D Inhibited: sensed event causes pacer to withhold an output pulse Triggered: sensed event activates pacer to send output pulse 63  So many options The last two letters of the code (IV & V) are rarely acknowledged in typical nomenclature Position 4: indicates if the device will alter the programmed rate independent of the patient's cardiac activity; O / R Position 5: indicates additional multisite pacing; O / A / V / D Rate modulation: Preserves ventricular function throughout various metabolic needs. Ex) Intrathoracic pressure 64 Programming Overview Atrial pacing: can increase cardiac output ~25%. Utilized to reduce incidence of atrial fibrillation. Requires AV node to be intact. Preserves left ventricular function long term Ventricular pacing: RV pacing alone results in dyssynchronous contraction and potentially deleterious effects. Pacemaker Syndrome AV sequential pacing: Utilized for complete AV block or when ventricular pacing alone cannot maintain cardiac output Triggered: Used when trying to override a tachyarrhythmia. rarely used by itself today. Inhibited: Commonly utilized for concerns of bradyarrhythmia Examples) 1. VOO 2. DVI 3. DDIR 4. DDDRA 65 66 Implantable Cardioverter-defibrillator ICDs consist of a pulse generator and leads for detection of arrythmia and leads to apply treatment Indications: Diagnostic telemetry Antitachycardia pacing Antibradycardia pacing Synchronized cardioversion Nonsynchronized defibrillation All current ICDs are considered pacemakers as well Typical lifespan: 8-12 yrs 67 Indications Prevention of secondary cardiac arrest patients because of V-Tach/Fib V-Tach with structural heart disease Cardiomyopathy w/ EF < 35% Genetic proarrhythmic syndromes or channelopathies Syncope with inducible sustained VT Primary prevention of sudden cardiac death if deemed high risk Etc. 68 ICD programming…similar…but different ICD programming is ALSO universally designated according to NASPE/BPEG coding: Position 1: indicates which chamber is shocked; O/ A / V / D Position 2: indicates Antitachycardia pacing chamber; O / A / V / D Position 3: indicates method of Tachycardia Detection; E / H Position 4: indicates Antibradycardia pacing chambers; O / A / V / D 69 Subcutaneous ICDs Subcutaneous ICDs also exist which do not require venous access BUT these devices are much larger and do NOT provide pacing support or antitachycardia pacing therapy 70 Cardiac Resynchronization Therapy Biventricular pacemaker treatment is used to provide CRT This device includes a third lead placed through the coronary sinus to pace the LV Candidates for implantation in the patient with EF < 35% (CHF) and a QRS duration >120 msec (LBBB) These pts demonstrate marked impairment in LV systolic function and increased myocardial oxygen consumption. The device “resynchronizes” by pacing both the LV septum (RV lead) and LV lateral wall (coronary sinus lead) Patients are considered pacer dependent 71 Intraop Considerations Intraoperative complications r/t CIEDs: Inhibition of pacing Inappropriate antitachycardia therapy “Runaway” pacemaker Reprogramming Rate adaptive pacing interference (minute ventilation changes) Myocardial burns Complete device failure 72  Preoperative Assessment Determine type of device and function ❑ chest x-ray, EKG Determine if pt is pacer dependent & underlying rhythm Determine device response to magnet placement Assure availability of temporary pacing and defibrillation equipment Other relevant cardiac assessments: Echo, Labs, meds 73  EKG Atrial pacing: demonstrated when the atrial impulse can proceed through the AV node (prior to the P-wave) Ventricular Pacing: evident by pacemaker spike preceding QRS complex DDD Pacing: most commonly used pacing mode (A-V sequential pacing). Each atrial and ventricular complex are preceded by a pacemaker spike 74 Anesthesia Considerations Risk Mitigation Strategies: Determine risk of electromagnetic interference (monopolar) Utilize bipolar electrosurgery or ultrasonic scalpel (harmonic) Advise surgeon to use short bursts of cautery (< 5 seconds) Place the return current (grounding) pad so that it avoids crossing the generator. Path from electric scalpel to grounding pad Have rescue equipment: external pacemaker/defibrillator immediately available for all patients with CIED. Activating the electrosurgery in the area of the generator, even if the electrode is not touching the patient, can cause interference 75  Magnet Placement Vs Pacemaker ICD All US devices switch to asynchronous Suspends antitachyarrhythmia pacing mode function AV timing delay and rate varies by each - However, NO pacing mode effect manufacturer Auditory tone can be heard to confirm correct Ex) AAI → AOO, DDD → DOO placement (Medtronic, Boston Scientific) *Caveat: can be programmed to ignore the Some older models do NOT revert back to magnet (St. Jude, Boston Scientific, Biotronik) programmed settings with magnet removal (Boston Scientific) 76 Magnet Placement Position Matters 77 Case Considerations Lithotripsy Oversensing and inhibition possible Avoid activation on R-wave Radiofrequency Ablation ECT Likely not an issue but device should be interrogated postop Cardioversion/Defibrillation Keep pads as far from the CIED generator as possible (Anterior- posterior) Limited CIED access by provider MRI Newer generations allow on a “conditional” basis. Should be evaluated pre- & post-procedure. Risks/Benefits thoroughly discussed 78 Leadless Pacemaker Similar functionality to conventional pacemakers (senses & paces) except it is implanted into the right ventricle Lifespan: 5-7 yrs Does NOT respond to magnets Indications: Single-chamber ventricular pacing, a-fib w/ bundle-branch block, 2nd-degree or 3rd-degree AV block, or sinus bradycardia w/ irregular pauses or unexplained syncope with an abnormal electrophysiological study 79 Implantation May be performed as GETA or as MAC w/ basic monitors Coordination of care dependent on pt underlying etiology and psychosocial Recommended to have emergency medications immediately available: Atropine/Glycopyrrolate Beta-Blocker Antiarrhythmics Complications occur during pacemaker insertion and include: Pneumothorax Pericarditis Lead dislodgment Hematoma Failure to sense, capture or output Pacemaker mediated tachycardia Twiddler syndrome Pacemaker syndrome 80 Additional Resources 81 Additional Resources Miller Chap 38 & 39 Morgan & Mikhail https://www.nejm.org/do/10.1056/NEJMdo004339/full/?requestType=popUp&relatedArticle=10.1056%2F NEJMoa1507192 Isolated Forearm Technique: https://youtu.be/ZEAYsEbkJrw 82