Misc Equip

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Questions and Answers

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?

A valve to limit the peak inspiratory pressure to 45cm Signup and view all the answers

What is a disadvantage of using manual resuscitators?

Lack visual monitoring cues to patient respiratory effort Signup and view all the answers

What is a potential risk of using manual resuscitators?

Barotrauma or gastric insufflation Signup and view all the answers

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

They are not economical for volatile anesthetic use. Signup and view all the answers

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

Bidirectional gas flow Signup and view all the answers

In which type of system is rebreathing completely prevented?

Closed system Signup and view all the answers

What is the unique feature of the Mapleson A circuit?

Fresh gas flow enters from the distal end of the circuit Signup and view all the answers

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

Location of the APL Signup and view all the answers

What is the Mapleson A R3mix circuit adapted for?

Scavenging of gases Signup and view all the answers

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

All of the above Signup and view all the answers

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

FGF pushes alveolar air toward the APL Signup and view all the answers

What is the primary way the nervous system functions?

Via electrical activity Signup and view all the answers

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

Bain circuit Signup and view all the answers

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

Pethick Test Signup and view all the answers

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

To directly assess the nervous system by observing electrical potentials Signup and view all the answers

What is the effect of anesthetics on neurons?

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

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

Anatomic or metabolic alterations of the brain Signup and view all the answers

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

Bottom-up approach Signup and view all the answers

What is a characteristic of regional asymmetry in the EEG?

Tumors, epilepsy, and cerebral ischemia Signup and view all the answers

What are the components of consciousness?

Awareness and Arousal Signup and view all the answers

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

To directly assess the function of nervous tissue Signup and view all the answers

What is the classification of EEG waveforms based on?

Amplitude and frequency Signup and view all the answers

What is the purpose of Fourier Transformation in processed EEG?

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

What is the characteristic of Beta waves in EEG?

High frequency, low amplitude Signup and view all the answers

What is the range of the BIS index?

0-100 Signup and view all the answers

What is the effect of Ketamine on EEG frequencies?

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

What is the characteristic of Delta waves in EEG?

High amplitude, low frequency Signup and view all the answers

What is the effect of Opiates on EEG frequencies?

Decreases Beta, slows Alpha, and increases Delta Signup and view all the answers

What is the purpose of EEG in clinical scenarios?

To guide pharmacologic therapy and monitor for cerebral ischemia Signup and view all the answers

What is the effect of anesthesia on EEG waveforms?

It decreases the frequency and amplitude of EEG waveforms Signup and view all the answers

What is the effect of Neuromuscular blockade on EEG indices?

Increases index values due to overlapping frequencies with EMG Signup and view all the answers

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

Epilepsy Signup and view all the answers

What is the purpose of processed EEG?

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

What should be immediately available for all patients with CIED?

External pacemaker/defibrillator Signup and view all the answers

What happens when a magnet is placed on a pacemaker?

It switches to asynchronous pacing mode Signup and view all the answers

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

It can interfere with the CIED's function Signup and view all the answers

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

Keep the pads as far from the CIED generator as possible Signup and view all the answers

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

Oversensing and inhibition Signup and view all the answers

What is a consideration for patients with CIED undergoing MRI?

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

What is a characteristic of some older ICD models?

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

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

The CIED should be interrogated postoperatively Signup and view all the answers

A pacemaker can cause myocardial burns during surgery.

True Signup and view all the answers

DDD pacing is a type of atrial pacing.

False Signup and view all the answers

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

True Signup and view all the answers

Bipolar electrosurgery can cause electromagnetic interference with pacemakers.

False Signup and view all the answers

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

False 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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