Misc Equip
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What is a key difference between Mapleson circuits and manual resuscitators?

  • The presence of a reservoir valve
  • The ability to monitor respiratory effort
  • The presence of a gas source
  • The use of a nonrebreathing valve (correct)

    • What is the primary function of the intake valve in a manual resuscitator?

  • To permit positive pressure ventilation
  • To permit refilling of the bag with reservoir gas or room air (correct)
  • To vent excess fresh gas flow
  • To direct gas flow throughout the respiratory cycle

    • What is the purpose of the outlet valve in a manual resuscitator?

  • To limit the peak inspiratory pressure
  • To direct gas flow throughout the respiratory cycle
  • To permit refilling of the bag with reservoir gas or room air
  • To vent excess fresh gas flow (correct)

    • What is a safety feature required in manual resuscitators designed for infants and children?

    <p>A valve to limit the peak inspiratory pressure to 45cm</p> Signup and view all the answers

    What is a disadvantage of using manual resuscitators?

    <p>Lack visual monitoring cues to patient respiratory effort</p> Signup and view all the answers

    What is a potential risk of using manual resuscitators?

    <p>Barotrauma or gastric insufflation</p> Signup and view all the answers

    What is the main reason why Mapleson circuits are not commonly used in today's anesthesia workstation?

    <p>They are not economical for volatile anesthetic use.</p> Signup and view all the answers

    What is the key difference between Mapleson circuits and Circle Systems?

    <p>Bidirectional gas flow</p> Signup and view all the answers

    In which type of system is rebreathing completely prevented?

    <p>Closed system</p> Signup and view all the answers

    What is the unique feature of the Mapleson A circuit?

    <p>Fresh gas flow enters from the distal end of the circuit</p> Signup and view all the answers

    What is the disadvantage of the Mapleson A circuit during manual ventilation?

    <p>Location of the APL</p> Signup and view all the answers

    What is the Mapleson A R3mix circuit adapted for?

    <p>Scavenging of gases</p> Signup and view all the answers

    What is the main disadvantage of the Mapleson B and C circuits?

    <p>All of the above</p> Signup and view all the answers

    What is the advantage of the Mapleson D circuit during controlled ventilation?

    <p>FGF pushes alveolar air toward the APL</p> Signup and view all the answers

    What is the primary way the nervous system functions?

    <p>Via electrical activity</p> Signup and view all the answers

    What is the modification of the Mapleson D circuit known as?

    <p>Bain circuit</p> Signup and view all the answers

    What is recommended to be performed prior to using the Bain circuit?

    <p>Pethick Test</p> Signup and view all the answers

    What is the main reason for using EEG in monitoring the nervous system?

    <p>To directly assess the nervous system by observing electrical potentials</p> Signup and view all the answers

    What is the effect of anesthetics on neurons?

    <p>They hyperpolarize neurons and affect neurotransmitter release/response</p> Signup and view all the answers

    What does a pattern that is unpredictable or unexpected in the EEG suggest?

    <p>Anatomic or metabolic alterations of the brain</p> Signup and view all the answers

    What is the traditional approach to understanding anesthetic effects on neurophysiology?

    <p>Bottom-up approach</p> Signup and view all the answers

    What is a characteristic of regional asymmetry in the EEG?

    <p>Tumors, epilepsy, and cerebral ischemia</p> Signup and view all the answers

    What are the components of consciousness?

    <p>Awareness and Arousal</p> Signup and view all the answers

    What is the purpose of EEG in monitoring the nervous system?

    <p>To directly assess the function of nervous tissue</p> Signup and view all the answers

    What is the classification of EEG waveforms based on?

    <p>Amplitude and frequency</p> Signup and view all the answers

    What is the purpose of Fourier Transformation in processed EEG?

    <p>To convert raw EEG data into a series of sine waves at different frequencies</p> Signup and view all the answers

    What is the characteristic of Beta waves in EEG?

    <p>High frequency, low amplitude</p> Signup and view all the answers

    What is the range of the BIS index?

    <p>0-100</p> Signup and view all the answers

    What is the effect of Ketamine on EEG frequencies?

    <p>Increases Theta and Beta/Gamma frequencies</p> Signup and view all the answers

    What is the characteristic of Delta waves in EEG?

    <p>High amplitude, low frequency</p> Signup and view all the answers

    What is the effect of Opiates on EEG frequencies?

    <p>Decreases Beta, slows Alpha, and increases Delta</p> Signup and view all the answers

    What is the purpose of EEG in clinical scenarios?

    <p>To guide pharmacologic therapy and monitor for cerebral ischemia</p> Signup and view all the answers

    What is the effect of anesthesia on EEG waveforms?

    <p>It decreases the frequency and amplitude of EEG waveforms</p> Signup and view all the answers

    What is the effect of Neuromuscular blockade on EEG indices?

    <p>Increases index values due to overlapping frequencies with EMG</p> Signup and view all the answers

    What is a characteristic of high-voltage spikes and slow waves in the EEG?

    <p>Epilepsy</p> Signup and view all the answers

    What is the purpose of processed EEG?

    <p>To examine 4 components within the EEG associated with the anesthetic state</p> Signup and view all the answers

    What should be immediately available for all patients with CIED?

    <p>External pacemaker/defibrillator</p> Signup and view all the answers

    What happens when a magnet is placed on a pacemaker?

    <p>It switches to asynchronous pacing mode</p> Signup and view all the answers

    Why is it important to avoid activating electrosurgery near a CIED?

    <p>It can interfere with the CIED's function</p> Signup and view all the answers

    What should be done during cardioversion/defibrillation for a patient with a CIED?

    <p>Keep the pads as far from the CIED generator as possible</p> Signup and view all the answers

    What is a concern during lithotripsy for a patient with a CIED?

    <p>Oversensing and inhibition</p> Signup and view all the answers

    What is a consideration for patients with CIED undergoing MRI?

    <p>Newer generations of CIED allow MRI on a conditional basis</p> Signup and view all the answers

    What is a characteristic of some older ICD models?

    <p>They do not revert back to programmed settings with magnet removal</p> Signup and view all the answers

    What should be done for a patient with a CIED undergoing ECT?

    <p>The CIED should be interrogated postoperatively</p> Signup and view all the answers

    A pacemaker can cause myocardial burns during surgery.

    <p>True</p> Signup and view all the answers

    DDD pacing is a type of atrial pacing.

    <p>False</p> Signup and view all the answers

    Temporary pacing and defibrillation equipment should be available for patients with a pacemaker.

    <p>True</p> Signup and view all the answers

    Bipolar electrosurgery can cause electromagnetic interference with pacemakers.

    <p>False</p> Signup and view all the answers

    A patient with a pacemaker is considered pacer dependent if they have a normal underlying rhythm.

    <p>False</p> Signup and view all the answers

    Study Notes

    Mapleson Circuits

    • Not commonly used in modern anesthesia workstations due to economic reasons for volatile anesthetic use
    • Differ from Circle Systems in two ways:
      • Bidirectional gas flow
      • No CO2 absorber
    • Depend on high fresh gas flow rates to eliminate CO2 and prevent rebreathing
    • Still used in pediatrics, patient transport, procedural sedation, T-piece systems, and office-based airway management

    Semi-Closed Systems

    • Classification based on reservoir and rebreathing characteristics:
      • Open: No reservoir, no rebreathing
      • Semi-Open: Reservoir present, no rebreathing
      • Semi-Closed: Reservoir present, partial rebreathing
      • Closed: Reservoir present, complete rebreathing

    Mapleson A (Magill Circuit)

    • Functionally distinct from other circuits
    • APL located near the patient
    • Fresh gas flow enters from the distal end of the circuit
    • Disadvantages:
      • Pollution
      • Can't be used with a ventilator
    • Most efficient circuit for spontaneous ventilation if fresh gas flow equals minute ventilation
    • Worse efficiency during manual ventilation due to APL location

    Mapleson A (R3mix/Lack's Modification)

    • Adaptation of Mapleson A to facilitate scavenging of gases
    • Added coaxial expiratory limb and expiratory valve moved near the reservoir bag
    • Disadvantages:
      • Increased work of breathing
      • Less efficient fresh gas flow than Magill

    Mapleson B & C

    • Rarely used
    • Similar in assembly, with C having less dead space
    • APL and FGF located proximal to the patient
    • Extremely inefficient in scavenging and high gas flows
    • High fire risk due to APL location

    Mapleson D

    • Like Mapleson A, but with APL and FGF flipped
    • Most efficient during controlled ventilation since FGF pushes alveolar air toward the APL
    • Effective at scavenging waste gases due to APL location away from the patient

    Mapleson D (RE-mix/Bain Circuit)

    • Modification of Mapleson D
    • Coaxially placed FGF warms inspired gases
    • Used commonly in pediatrics
    • Advantages:
      • Exhaled gases scavenged
      • Recommend Pethick Test prior to use

    Manual Resuscitators

    • Nonrebreathing valve
    • Components:
      • Self-inflating reservoir bag
      • Nonrebreathing valve (between vent bag and patient)
      • Intake valve (between vent and reservoir bag)
      • Reservoir valve (with 2 unidirectional valves)
    • Disadvantages:
      • Lacks visual monitoring cue to patient respiratory effort
      • High PIP may be generated, risking barotrauma or gastric insufflation
      • Significant variability of tidal volume, PIP, and PEEP
      • Nonrebreathing valves generate resistance, increasing the work of breathing

    Electroencephalogram (EEG)

    • Direct assessment of nervous system function via extracellular electrical potentials
    • Utility determined by:
      • Hemodynamic effects on electrophysiology
      • Pharmacologic effects on action potentials
    • Anesthetics hyperpolarize neurons and affect neurotransmitter release/response at the synapse
    • Presynaptic glutamate is inhibited, while postsynaptic GABA is potentiated

    Nervous System Monitoring

    • Historical practice: Physiologic responses to noxious stimuli are explained by the nociceptive-medullary-autonomic circuit
    • Traditional physiologic monitors (HR, BP, SpO2) reflect supportive parameters of tissue maintenance
    • Anesthetic state of the patient is inferred in this manner

    Updated Theories

    • CNS functions to exchange information via coordinated action potentials
    • Cortical and subcortical structures are critically interconnected
    • Growing evidence for top-down mechanism: Intracortical communication becomes interrupted
    • Likely, a combination of top-down and bottom-up mechanisms is responsible for suppression of consciousness under anesthesia

    EEG

    • Pyramidal cells in the cerebral cortex produce large local field potentials via extracellular potentials
    • Geometry of neurons 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
    • Typical mapping involves placement of 10-20 electrodes
    • EEG activity reflects cerebral metabolism and blood flow
    • EEG monitoring is useful when cerebral cortex tissue is vulnerable to ischemia or to guide pharmacologic therapy

    EEG Waveforms

    • 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)
    • "Activated" waveforms:
      • Beta (13-30 Hz)
      • Alpha (8-12 Hz)
    • "Depressed" waveforms:
      • Theta (4-8 Hz)
      • Delta (1-4 Hz)

    EEG-Based Indices

    • Display a dimensionless variable to indicate the level of "wakefulness" created via proprietary algorithms
    • GETA induces a change from high values to lower values that indicate states of sedation and unconsciousness
    • BIS index: Range 0-100, with values of 60 suggesting reduced probability of consciousness
    • GETA is commonly maintained between 45-60

    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

    Pharmacology

    • Intravenous hypnotics and volatile anesthetics produce progressive slowing of EEG until burst suppression
    • Activation of GABA receptors within the cortical and subcortical structures results in inhibition and disorganized communication
    • Characterized by Alpha and Delta oscillations
    • Volatiles: at higher doses, Theta bands are present
    • N2O (NMDA and K+ sites of action) demonstrate Beta and Gamma oscillations, with synergism existing when combined with other inhalation agents

    Miscellaneous

    • Neuromuscular blockade: Overlapping frequencies between EEG and Electromyography (EMG) cause interference in values
    • Vasoactive agents can affect EEG values
    • Standard of care for patients with cardiac implantable electronic devices (CIEDs) undergoing magnet placement:
      • Have rescue equipment immediately available
      • Avoid activating electrosurgery in the area of the generator
      • Magnet placement: Position matters, with varying effects on pacemakers and ICDs

    Anesthesia Circuits

    • Occlude PT end: useful in MRI suites, allows for ease of connecting to ventilator, and O2 flush to fill circuit
    • Disadvantages: disconnection and kinks often go unrecognized

    Mapelson Circuits

    • Mapelson E: modification of Ayre's T-piece, FGF proximal to patient, no reservoir bag, high fresh gas flows required
    • Mapelson F/Jackson-Rees Circuit: modification of Mapelson E, added reservoir bag, commonly used for patient transport

    Disadvantages of Mapelson Systems

    • 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

    • Mapelson A: only circuit with FGF near the reservoir bag
    • Mapelson C: only circuit not corrugated
    • Mapelson E: only circuit without a reservoir bag
    • Bain & Lack: coaxial tubing

    Manual Resuscitators

    • Nonrebreathing valve: used consistently during patient transport, emergency resuscitation, or as a back-up supply

    EEG

    • Anteriorization: EEG pattern in deep anesthetic state, characterized by alpha and delta activity greater in anterior leads
    • Burst Suppression: EEG pattern in deep anesthesia, characterized by high-frequency "burst" activity interspersed with flat "suppression" tracings
    • Isoelectric: EEG pattern with zero amplitude, seen in deep states of GETA, coma, brain death, and cardiac arrest
    • EEG-Based Indices: display a dimensionless variable to indicate level of "wakefulness", commonly used in BIS index

    EEG Interpretation

    • Accurately identifies consciousness/unconsciousness, stages of sleep, and coma
    • Intraop, suggests anatomic or metabolic alterations of the brain
    • Regional asymmetry seen with tumors, epilepsy, and cerebral ischemia

    Awareness

    • GETA requires: Unconsciousness, Amnesia, Analgesia, Immobility, Attenuation of autonomic response
    • Awareness: ability to process, integrate, and store information in interaction with the environment
    • Lack of awareness is inferred through EEG analysis

    Processed EEG

    • Manufactures devices that process reduced channel EEG signals
    • Examines 4 components within the EEG associated with the anesthetic state
    • Various devices: BIS sensor, PSArray, Narcotrend, Entropy Module, Cerebral State Monitor

    Pharmacology

    • Intravenous hypnotics & Volatile anesthetics produce progressive slowing of EEG until burst suppression
    • Ketamine: creates false excitatory values, increases Theta and Beta/Gamma frequencies
    • Dexmedetomidine: initially increases Alpha waves, at high doses, primarily Delta waves
    • Opiates: decrease Beta, slow Alpha, and increase Delta, reduce wave variability

    EMG

    • Active or Evoked EMG: helps identify intact nerves, used to identify a nerve or anatomic variances in order to avoid cutting it
    • Passive or Spontaneous EMG: commonly used in spine surgery to identify nerve irritation before injury

    Cardiac Implantable Electronic Devices (CIEDs)

    • Refers to any permanently implanted pacemaker, cardioverter-defibrillator, or cardiac resynchronization therapy devices
    • Utilization is increasing due to growing geriatric populations and prevalence of cardiovascular disease

    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 to depolarize local myocardium

    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

    Intraop Considerations

    • Intraoperative complications related to CIEDs:
      • Inhibition of pacing
      • Inappropriate antitachycardia therapy
      • "Runaway" pacemaker
      • Reprogramming
      • Rate adaptive pacing interference
      • Myocardial burns
      • Complete device failure

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