Neuroanesthesia Monitoring

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Questions and Answers

What is the primary goal of neuro anesthesia as it relates to brain function?

  • Induce complete anesthesia without any cerebral activity
  • Provide adequate oxygen and glucose to meet metabolic demands (correct)
  • Minimize muscle relaxation during procedures
  • Reduce blood flow to the brain

Which methods are used specifically for monitoring blood flow to the brain (CBF and ICP)?

  • Laser doppler blood flow (correct)
  • Nitrous oxide wash-in (correct)
  • Radioactive xenon clearance (correct)
  • ICP monitors (e.g. intraventricular catheters) (correct)

What type of monitoring would directly assess the metabolic state of brain tissue?

  • Electroencephalography
  • Jugular venous oximetry (correct)
  • Intracranial pressure monitoring
  • Evoked potentials

Which of the following techniques are primarily used for monitoring brain function during anesthesia? (select all that apply)

<p>Electroencephalography (EEG) (C), Evoked potentials (B), Electromyography (D)</p> Signup and view all the answers

What are beta waves characterized by in terms of frequency and amplitude when a person is awake?

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

Which statement best describes the relationship between EEG activity and metabolic conditions?

<p>EEG activity reflects brain's wakefulness and can diminish with decreased blood flow. (C)</p> Signup and view all the answers

In the International 10-20 system, odd-numbered electrodes are positioned in which hemisphere?

<p>Left hemisphere (B)</p> Signup and view all the answers

Which type of brainwave is associated with children during normal sleep and not associated with adults?

<p>Theta waves - low frequency (D)</p> Signup and view all the answers

What happens to beta wave activity in response to hypoxia or ischemia?

<p>Beta activity transiently increases as a compensatory mechanism for blood flow. (A)</p> Signup and view all the answers

Which of the following are the 3 categories of neurophysiologic monitoring? (Select all that apply)

<p>Function (A), Blood Flow (B), Metabolism (C)</p> Signup and view all the answers

Which of the following devices are used for monitoring cerebral metabolism? (Select all that apply)

<p>Intercerebral PO2 electrode (A), Cerebral oximetry (B), Jugular vein oximetry (C)</p> Signup and view all the answers

Which of the following are NOT recorded by EEG? (Select all that apply)

<p>Subcortical structures (A), Spine (B), Cranial nerves (C), Peripheral nerves (D)</p> Signup and view all the answers

Which cells are primarily responsible for producing the electrical activity that is detected by an EEG?

<p>Pyramidal cells in the cerebral cortex (A)</p> Signup and view all the answers

What comprises the electrical activity recorded by EEG?

<p>Excitatory and inhibitory postsynaptic potentials of pyramidal cells (B)</p> Signup and view all the answers

What is the nasion?

<p>The depressed area between the eyes (B)</p> Signup and view all the answers

What is the inion?

<p>The lowest point of the skull (A)</p> Signup and view all the answers

When are the medium frequency, higher amplitude alpha waves typically seen?

<p>When awake but restful (C)</p> Signup and view all the answers

Which waves are associated with deep coma, anesthesia, and hypoxia?

<p>Delta waves (C)</p> Signup and view all the answers

What type of wave activity is primarily observed in awake EEG recordings?

<p>Beta waves (D)</p> Signup and view all the answers

What can cause EEG depression? (Select all that apply)

<p>Decrease in blood flow (A), Decrease in oxygen (B), Decrease in glucose (C)</p> Signup and view all the answers

What are epileptiform patterns and spikes indicative of on an EEG?

<p>Epilepsy (B)</p> Signup and view all the answers

What is burst suppression in EEG patterns characterized by?

<p>Periods of high voltage electrical activity alternating with periods of no brain activity (A)</p> Signup and view all the answers

What are causes of burst suppression? (Select all that apply)

<p>Anesthesia (A), Hypothermia (B), Cardiopulmonary bypass (C), Hypoxic-ischemic insult (D)</p> Signup and view all the answers

What does unilateral burst suppression indicate?

<p>Cerebral ischemia (A)</p> Signup and view all the answers

What is the gold standard for EEG monitoring that is rarely achieved in the OR?

<p>16 channels (B)</p> Signup and view all the answers

What occurs to the EEG as the level of anesthesia deepens?

<p>The EEG waveforms decrease in frequency and have a higher amplitude (i.e., slower and taller) (A)</p> Signup and view all the answers

What occurs as a result of most IV anesthetics and inhalation agents?

<p>Dose-dependent EEG depression and burst suppression (C)</p> Signup and view all the answers

How does hypothermia alter EEG readings?

<p>It leads to burst suppression patterns due to decreased CMRO2 (B)</p> Signup and view all the answers

How does ketamine affect EEG readings?

<p>Increased cortical activity that causes an underestimation of anesthetic depth (D)</p> Signup and view all the answers

Which agent does not reduce BIS when used as a sole agent?

<p>Nitrous Oxide (N2O) (B)</p> Signup and view all the answers

Which agent is known to cause increased beta wave activity?

<p>Nitrous Oxide (N2O) (A)</p> Signup and view all the answers

Which of the following brain wave patterns are prevalent during general anesthesia? (Select all that apply)

<p>Theta waves (A), Delta waves (B)</p> Signup and view all the answers

During which stages of anesthesia is increased beta wave activity observed?

<p>Induction and light anesthesia (C)</p> Signup and view all the answers

At what minimum alveolar concentration (MAC) is brain isoelectric activity observed?

<p>1.5-2 (B)</p> Signup and view all the answers

Which of the following drugs is characterized by epileptiform activity?

<p>Sevoflurane (A)</p> Signup and view all the answers

Which drug is characterized by myoclonus with no epileptiform activity?

<p>Etomidate (A)</p> Signup and view all the answers

The development of new ___ waves during anesthesia maintenance indicates a risk for ischemia.

<p>delta (C)</p> Signup and view all the answers

Which of the following are considered mimics for cerebral ischemia? (Select all that apply)

<p>Deep anesthesia (A), Hypothermia (B), Hypocarbia (C)</p> Signup and view all the answers

20-30 sec lag time between EEG measurement and BIS value

<p>True (A)</p> Signup and view all the answers

Which of the following factors impair the accuracy of bispectral index (BIS) monitoring? (Select all that apply)

<p>Hypothermia (A), Encephalopathy (B), Electromyographic interference (C)</p> Signup and view all the answers

Which agents decrease bispectral index (BIS) without a sedative effect?

<p>Neuromuscular blocking agents (B)</p> Signup and view all the answers

What are somatosensory evoked potentials? (select 2)

<p>Electrical signals measured from the periphery to the brain brain in response to tactile stimuli (A), measures the nerve pathways responsible for feeling pressure, touch, temperature, and pain (D)</p> Signup and view all the answers

What is the best anesthetic technique for SSEP monitoring?

<p>Total Intravenous Anesthesia (TIVA) (A)</p> Signup and view all the answers

Which agents should be avoided in SSEP monitoring? (select 3)

<p>Ketamine - increase (A), Combination of N2O and inhalation agents - synergistic decrease (C), Inhalation agents - dose-dependent decrease (D)</p> Signup and view all the answers

What are the three types of sensory evoked potentials?

<p>Somatosensory Evoked Potentials (SSEP) (A), Visual Evoked Potentials (VEP) (B), Brainstem Auditory Evoked Potentials (BAEP) (C)</p> Signup and view all the answers

What is the preferred anesthetic when monitoring Visual Evoked Potentials (VEPs)?

<p>TIVA (A)</p> Signup and view all the answers

Which sensory evoked potential is unique in its resistance to the influence of anesthetic agents?

<p>Brainstem auditory evoked potentials (B)</p> Signup and view all the answers

You note a 50% decrease in amplitude during evoked potential monitoring during surgery. What is this indicative of?

<p>Impending nerve damage (A)</p> Signup and view all the answers

What are the peaks and troughs of waveforms called in evoked potentials?

<p>Polarity and latency (A)</p> Signup and view all the answers

A BAEP with increased latency of __ mS is a significant finding

<p>greater than 2 (C)</p> Signup and view all the answers

Where are MEPs recorded in response to depolarization of the motor cortex?

<p>Over muscles in the hand (A), Over muscles in the foot (B)</p> Signup and view all the answers

What is the preferred anesthetic management for monitoring motor evoked potentials (MEPs)?

<p>TIVA with no NMBDs (A)</p> Signup and view all the answers

What is the difference between the SEP and EEG response to inhaled anesthetics? (select 2)

<p>SEPs are recordable with inhaled anesthetics (A), EEGs are abolished by high dose IV and inhaled anesthetics (B)</p> Signup and view all the answers

What is the difference between the amplitude of waves in Somatosensory Evoked Potentials (SEPs) and Electroencephalography (EEG)?

<p>EEG waves typically have a larger amplitude than SEP waves. (A)</p> Signup and view all the answers

Which cranial nerves can be monitored via EMG? (Select all that apply)

<p>All except I, II, VIII (A)</p> Signup and view all the answers

What is the normal range of cerebral blood flow (CBF) in mL/100g?

<p>50-65 mL/100g (B)</p> Signup and view all the answers

Match the following CBF limits (ml/100g/min) with their corresponding conditions:

<p>50 = Acidosis 40 = Impaired protein synthesis &lt;30 = Edema &lt;20 = Critically low CBF</p> Signup and view all the answers

Match the Cerebral Perfusion Pressure (CPP) values with their corresponding events:

<p>30-40 = Ischemia &lt; 30 = Critical CPP &lt; 25 = Irreversible brain damage 80-100 = Normal</p> Signup and view all the answers

What is the critical PaO2 level considered to be?

<p>&lt;50 mmHg (A)</p> Signup and view all the answers

What is the critical level of paCO2 considered to be hazardous?

<p>Less than 20 mmHg (A)</p> Signup and view all the answers

What factors determine cerebral blood flow (CBF)?

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

What are NIM (Nerve Integrity Monitors) ETTs used for?

<p>Assessing nerve function during surgical procedures involving the airway (B)</p> Signup and view all the answers

What can EEG be used to monitor in neuroanesthesia?

<p>Ischemia/perfusion (A)</p> Signup and view all the answers

What are the limitations of laser Doppler flowmetry in measuring cerebral blood flow (CBF)? select 2

<p>It only measures local CBF. (B), Itvrequires a burr hole. (C)</p> Signup and view all the answers

What are the limitations of transcranial Doppler ultrasonography? (Select all that apply)

<p>Requires a fixation device (A), Transmission is limited by skull thickness (B), Cannot measure absolute CBF (C), Failure rate is 5-20% (D)</p> Signup and view all the answers

What is transcranial Doppler ultrasonography used to measure?

<p>Intracranial pressure (ICP) (A), Cerebral autoregulation (B), CO2 reactivity (C), CPP (D)</p> Signup and view all the answers

What is the primary purpose of microdialysis catheters in neuroanesthesia?

<p>To semi-quantitatively assess vessel patency and flow in the aneurysmal sac (B)</p> Signup and view all the answers

What is Indocyanine green video angiography used to measure during aneurysm surgery?

<p>Cerebral blood flow (A)</p> Signup and view all the answers

Where are supratentorial pressures measured?

<p>Lateral ventricle and subarachnoid space over the convexity of the cerebral cortex (A)</p> Signup and view all the answers

What is the jugular bulb?

<p>A dilated region of the internal jugular vein that collects blood from the brain with negligible contamination (A)</p> Signup and view all the answers

What is the purpose of jugular venous oxygen saturation?

<p>Estimation of global balance between cerebral O2 demand and supply via the jugular bulb (A)</p> Signup and view all the answers

What are the limitations of jugular venous oxygen saturation measurement? select 2

<p>It cannot detect focal cerebral ischemia. (A), CMRO2 must remain constant for valid measurements. (B)</p> Signup and view all the answers

What is near infrared spectroscopy in the context of cerebral oximetry?

<p>A technique to measure tissue oxygen saturation (A)</p> Signup and view all the answers

What are the limitations of cerebral oximetry? (Select all that apply)

<p>Intersubject variability (A), Lack of definable threshold (B), Contamination from extracranial blood (C)</p> Signup and view all the answers

What are precordial Dopplers used to detect?

<p>Venous air embolism (A)</p> Signup and view all the answers

Which of the following monitors are used to monitor intracranial pressure (ICP)? (Select all that apply)

<p>Intraventricular catheter (A), Fiberoptic parenchymal catheter (B), Sub-arachnoid bolt (C), Epidural catheter (D)</p> Signup and view all the answers

Which anesthetic is known to cause non-rapid eye movement sleep patterns on the EEG?

<p>Dexmedetomidine (B)</p> Signup and view all the answers

What is characteristic of the EEG pattern of propofol?

<p>Early beta waves progressing to synchronous alpha waves (A)</p> Signup and view all the answers

What is a limitation of the Bispectral Index (BIS)?

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

Which types of operations have a high potential for damaging cranial nerves? (Select all that apply)

<p>Posterior fossa (A), Lower brain stem (B)</p> Signup and view all the answers

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Study Notes

Neuroanesthesia Goals

  • Overall Goal: Ensure brain receives sufficient oxygen and glucose
  • Perioperative Goals:
    • Maintain favorable blood and oxygen supply
    • Prevent brain herniation
    • Facilitate muscle relaxation

Risks

  • Patients with neurological disease undergoing surgery are at higher risk of brain hypoxia and ischemia

Intraoperative Monitoring

  • Goal: Improve patient outcomes via early detection of issues and adjusting anesthetic/surgical procedures
  • Standard Monitors: EKG, BP, SPO2, ETCO2, temperature, precordial or esophageal stethoscope
  • Expanded Monitors: Art line, CVP, PA, precordial doppler

Categories of Neurophysiologic Monitoring

  • Function: EEG, evoked potentials, electromyography
  • Blood Flow: CBF, ICP
    • CBF Measurement Methods:
      • Nitrous oxide wash-in
      • Radioactive xenon clearance
      • Laser Doppler blood flow
    • ICP Measurement Methods:
      • Intraventricular catheter
      • Sub-arachnoid bolt
      • Epidural catheter
      • Fiberoptic parenchymal catheter
  • Metabolism:
    • Invasive: Intercerebral PO2 electrode
    • Non-invasive: Transcranial cerebral oximetry and jugular venous oximetry

EEG

  • Definition: Recording of brain's electrical activity from the cerebral cortex
  • Source: Pyramidal cells in the cerebral cortex
    • Result of summation of excitatory and inhibitory postsynaptic potentials
  • Primarily records cortical activity: Limited recording of subcortical structures, spinal cord, cranial nerves, and peripheral nerves
  • Oxygen and Glucose Dependency: EEG is significantly impacted by oxygen and glucose supply
  • Monitoring Locations:
    • Scalp: Electrically neutral area
      • Electrodes can be taped or use small needles
    • International 10-20 System: Standardized electrode placement
      • 10 or 20% of skull circumference between electrodes
      • Even numbers: Right Hemisphere
      • Odd numbers: Left Hemisphere
      • Landmarks:
        • Nasion: Depressed area between eyes
        • Inion: Lowest point of the skull
  • EEG Wave Patterns:
    • Beta waves: High frequency, low amplitude (awake)
    • Alpha waves: Medium frequency, higher amplitude (awake and relaxed)
    • Theta waves: Low frequency (children during sleep)
    • Delta waves: Low frequency, high amplitude (deep coma, anesthesia, hypoxia)
  • EEG Reflects: Brain wakefulness and metabolic activity
  • EEG Depression Causes
    • Decreased blood flow
    • Reduced oxygen supply
    • Insufficient glucose
  • Awake EEG: Dominated by high frequency, low amplitude beta waves
  • Hypoxia/Ischemia EEG Changes:
    • Initial increase in beta activity (compensation mechanism)
    • Slow theta waves
    • Disappearance of beta waves
    • Low amplitude delta waves

Abnormal EEG Patterns

  • Generalized slowing: Slowed activity
  • Focal or localized slow activity: Slow activity in a specific area
  • Periodic patterns: Recurring patterns

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