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24 Principles of Anesthesia II > Test 1: Radiology/ Laser Safety (Andy's Cards) > Flashcards

Test 1: Radiology/ Laser Safety (Andy's Cards) Flashcards

1
Q

Who/when discovered X-ray therapy and how?

A
  • Wilhelm Roentgen (1895)
  • While experimenting with currents in a glass tube noticed that a fluorescent screen in the lab began to glow.
  • Placed objects between the screen and the tube –> called “x” ray = something unknown
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2
Q

What are the four types of radiation?

A
  1. Electromagnetic = from motion of atoms (combined with electricity and magnetism)
  2. Mechanical = travel through substances
  3. Nuclear (neutron) = unstable atom nuclei
  4. Cosmic (beta) = electrons only; travels at almost speed of light (ex: sunlight)
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3
Q

What is non-ionizing radiation?

A
  • Radiation that cannot knock electrons off atoms and doesn’t break molecular bonds
  • Only harmful from heat energy (ex: radiowaves or microwaves)
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4
Q

What is ionizing radiation?

A
  • These types of radiation knock off electrons
  • When electrons are knocked off atoms, they create ions
  • Ion electrical charge causes intracellular chemical changes (cell apoptosis, cancer, defects)
  • Risk can be additive (can add up)
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5
Q

What are the negative effects of ionizing radiation?

A
  1. Break DNA chains = cell apoptosis
  2. Mutate DNA chain = cancer
  3. Mutated sperm or egg cell = birth defects
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6
Q

What are the similarities of x-rays to visible light rays?
What is the difference?

A

Similar:
- Both are electromagnetic energy
- Carried by particles called photons

Difference in energy levels (wavelengths)

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7
Q

X-rays have _______ wavelengths and _________ energy.

Radio waves have _______ wavelengths and ________ energy.

A
  • X-rays have shorter wavelengths and higher energy.
  • Radio waves have longer wavelengths and lower energy.
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8
Q

How is light emitted?

A
  • Caused by the movement of electrons in an atom
    1. Moving particles excite atoms (when heated)
    2. Electron “jumps” to a higher energy level (orbit)
    3. To fall back to the original orbit, it must release energy (photon or light)
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9
Q

How do smaller atoms affect the amount of photons released?

A
  • Electron orbitals are by low jumps in energy
  • Less likely to absorb X-ray photons
  • This will show up as a greyish color on the X-ray image

Ex: soft tissue

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10
Q

How do larger atoms affect the amount of photons released?

A
  • Greater energy difference between orbitals d/t orbits being further apart
  • More likely to absorb photons
  • This will show up as a whiter or brighter color on the X-ray image

ex: bones

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11
Q

What makes up an electrode pair of an X-ray machine?

A
  • Cathode
  • Anode
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12
Q

What is a cathode?

A
  • A filament (in the center) shape that is heated up as machine charges.
  • The heat filament current causes electrons to fly off of filament
  • Negative charged side of the x-ray tube
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13
Q

What is an anode?

A
  • A positively charged metal disc of tungsten that will attract electrons across the tube from the cathode
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14
Q

Components of the x-ray machine

A
  • Thick shield surrounds the entire machine
  • The window in the shield allows a narrow beam of photons to escape
  • A camera is on the opposite side of the tube that records the patterns of the X-ray photons
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15
Q

What does the camera of the x-ray machine do?
What can effect it?

A
  • Produces a chemical reaction on the film
  • Ambient light can darken or lighten
  • Intensity changes to photon beam (over/under exposure) alter appearance
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16
Q

What do we use medical x-rays for?

A

Diagnostics

Radiography
- bone fractures, tube placement, foreign objects

Mammography

Computed Tomography (CT)
- 3D image generated when x-ray combines with computer processing

Fluoroscopy
- real-time image (with/without contrast)

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17
Q

Can x-rays be used theraputically?

A
  • YES, as radiation therapy
  • At higher doses, radiation can damage the cancer cell’s DNA
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18
Q

What is the most common side effect of radiation therapy?

A

Fatigue

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19
Q

Annual allowable radiation dose:

  • Whole body in 1 year
  • Extremities
  • Eye lens
  • Pregnancy
A

Whole body in 1 year = 5,000 mrem
Extremities = 50,000 mrem
Eye lens = 15,000 mrem
Pregnancy (after 2nd/3rd) Trimester = 500 mrem

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20
Q

What is Rem?

A
  • Radiation dose times a weighting factors
  • Nearly equivalent to Rad
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21
Q

What is known as the direct sources of radiation?

A
  • Primary X-ray beam
  • Leaking from other sites within the equipment
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22
Q

Amount of Rem exposure from the following sources:

CXR
Coronary angiogram
Angioplasty
CT

A
  • CXR: 5-10 mrem
  • Coronary angiogram: 1,500 mrem
  • Angioplasty: 5,700 mrem
  • CT: 5,000 mrem
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23
Q

What are indirect sources of radiation?

A
  • Scattered radiation
  • This is radiation that reflect off tables, patients, and other surfaces
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24
Q

What are three factors that affect scatter radiation?

A
  • Collimation (width of the beam; wider collimation has more radiation scatter)
  • Object thickness (thicker patients will result in more radiation scatter)
  • Air Gap (distance between patient and cassette; the greater the distance, the more radiation scatter)

*Clarified by Dr. Kane

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25
Q

How much rem will cause transient erythema?

A
  • 200,000 mrem
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26
Q

What is ALARA?

A
  • As Low As Reasonably Achievable
  • Radiation protection
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27
Q

What are the 3 things to reduce radiation?

A
  1. Limit time spent near beam entry
  2. Distance
    - direct source: double distance from beam = 1/4 the exposure rate
    - indirect source: scatter = > 6 ft from patient
  3. Shielding
    - lead aprons, portable shields, thyroid, lead glasses
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28
Q

How do you wear the dosimeters?

A

Two badges:
1. Outside the apron on the collar
2. Inside the apron on the waist

29
Q

What are the 3 “Don’t” to dosimeters?

A
  1. Don’t mix up
  2. Don’t share dosimeter with others
  3. Don’t leave in the car on the dashboard/seat
30
Q

The principles of MRI are based on interactions between what two things?

A
  • Based on the interaction between the static magnetic field and individual atom nuclei.
31
Q

The magnetic field of the MRI is used to orient the nuclei of _______ molecules to north-south poles.

A
  • Hydrogen
32
Q

How does the MRI create an image?

A
  • Radio wave pulses change the orientation of specific atoms, which radiates energy to create an image.
33
Q

How is contrast generated?

A
  • Contrast is generated by time til tissue relaxation when the radio frequency is turned off.
  • When the radio frequency is turned off, protons realign with the magnetic field releasing electromagnetic energy.
34
Q

What factors affect the contrast generated?

A
  • Various densities of hydrogen nuclei in tissues
  • Different chemical and physical properties of the tissues
35
Q

What are the two contrast images for MRI?

A
  • T1 contrast/ view
  • T2 contrast/ view
36
Q

Describe a T1 contrast/view.

A
  • Relaxation of the magnetic vector
  • Radio frequency is off and not trying to move the orientation of the atom
  • Provides a good grey-white matter contrast
  • Good for viewing anatomy
37
Q

How do fat and water appear on a T1 weighted image?

A

Fat appears bright
Water appears dark

38
Q

Describe a T2 contrast/view.

A
  • Axial spin relaxes
  • Radio frequency turned on
  • Great for identifying tissue edema
  • Good for viewing pathology
39
Q

How do fat and water appear on a T2 weighted image?

A

Fat is darker
Water is lighter

40
Q

What is the most common contrast material used for MRI?

A
  • Gadolinium
41
Q

How does Gadolinium enhance the equality of MRI images?

A
  • Gadolinium dye alters the magnetic properties of nearby water molecules, enhancing the quality of MRI images.
42
Q

What are the side effects of Gadolinium?
How is it cleared from the body and how quickly?

A
  • Mild side effects: itching, rash, abnormal skin sensation
  • Cleared with normal GFR in 24 hours.
43
Q

Is the magnetic field always on?

A

YES

44
Q

Risks in MRI?

A
  • Projectile risk
  • Radiofrequency energy causes tissue/device heating
  • Electromagnetic interference causes artifacts such as the interpretation of ECG
  • Acoustic noise up to 125 dB == wear hearing protectors (CRNA and patient)
45
Q

What are the AANA Standards of Care for MRI?

A
  • EKG, pulse ox, BP, capnography q 15 minutes when providing anesthetics
  • Airway (cannula, mask, ETT vs. LMA)
  • Suction
  • Spontaneous ventilation vs. ventilator
  • Minimize movement (versed comes in handy)
  • Complications (ex. airway access)
  • MRI-compatible infusion pumps…. vs long, long, IV tubing
  • Laryngoscope handles, blades…induction may occur in a separate room
46
Q

Things to know about patient positioning for MRI?

A
  • Head and neck scans will result in an inaccessible airway.
  • Abdominal scans will have the patient’s arms over their head. This can lead to brachial plexus injuries.
47
Q

What objects could be in the patient that can be effected or affect the MRI scan?

A
  • Pacemakers
  • AICDs
  • Implanted insulin pumps
  • New generations of these devices are MRI-compatible
48
Q

What objects are considered MRI-compatible?

A
  • Heart valves safe
  • Endovascular and biliary stents are usually embedded after eight weeks
  • Coronary stents OK immediately
  • Vascular ports and IVC filters are safe
  • Any Orthopedic implants…titanium, safe; screws are made of lead and securely in bone.
49
Q

What happens if you move too quickly toward an MRI field (ie: running into the MRI room)?

A
  • Rapid movement toward the field (> 1m/sec) will result in dizziness, HA, light flashes, nausea
  • Move calmly in the MRI room.
50
Q

What does L.A.S.E.R. stand for?

A
  • Light Amplification by Stimulated Emission of Radiation
51
Q

What is ordinary light vs laser light?

A
  • Ordinary light contains many wavelengths that spread out in many directs
  • Laser has a specific wavelength with a focused narrow beam and high intensity
52
Q

The unexcited state electrons orbit the nucleus at the _________ energy.

A
  • lowest
53
Q

In the unexcited state, electrons occupy orbits _________ to the nucleus.

A
  • closest
54
Q

How is radiation produced?

A
  • As the electrons absorb energy, they become excited and move to a higher orbit
  • Upon return from an excited state to ground state, they spontaneously emit photons of energy (electromagnetic radiation)
55
Q

Properties of Laser Radiation?

A
  • Monochromatic: All photons in the laser beam are the same wavelength
  • Coherence: Travel of photons is synchronized in time and space (no random movement)
  • Collimation: Laser beam photons are parallel (allow the beam to focus on a small area)
56
Q

What gives a type of laser its name?

A
  • The Lasing Medium
57
Q

What are the 3 lasing mediums?

A
  • Argon
  • Carbon dioxide
  • Nd:YAG
58
Q

What should be known about Argon lasers?

A
  • Used in dermatology
  • Modest tissue penetration (0.05-2 mm)
59
Q

What should be known about CO₂ lasers?

A
  • Used in vocal cords, oropharynx
  • Scatter is minimal
  • Surrounding tissue damage is negligible and absorbed by water/disperse little heat
60
Q

What should be known about Nd:YAG lasers?

A
  • Most powerful laser
  • Used for tumor debulking (prostate, bladder tumors)
  • Deeper tissue penetration (2-6 mm)
61
Q

What are the 5 hazards of laser?

What are the two hazards CRNAs are most concerned with for lasers?

A
  • Atmospheric contamination (most concern)
  • Airway fire (most concern)
  • Perforation of a vessel or structure
  • Embolism
  • Inappropriate energy transfer
62
Q

What is a Laser Plume?

A
  • Fine particulates produced d/t vaporization of tissue
  • Laser Plume can result in HA, nausea after inhalation
  • Laser Plumes could cause interstitial pneumonia, bronchiolitis, emphysema
  • Laser Plumes could be carcinogenic
63
Q

What makes up the fire triad?

A
  • Ignition source (aka Laser)
  • Fuel (drapes, ET Tube, nasal cannula)
  • Oxidizer (oxygen)
64
Q

What are the two major sources for OR fires?

A
  • ESU (Electrosurgical units aka “Bovie”)
  • Laser
65
Q

What are some scenarios for endotracheal fire discussed in the lecture?

A
  • Surgeon is lasering airway through the ETT and burns through PVC tube…
  • Surgeon is completing tonsillectomy in a pediatric patient with an uncuffed tube…
  • Surgeon uses bovie to “cut” through trachea for a tracheotomy…
66
Q

How to prevent Airway fire?

A
  • Laser-resistant ETTs
  • Low-inspired (21% if possible) O2
  • Wet pledgets around the ETT
  • Methylene blue in the ETT cuff (visual)
  • Use scissors to cut into trachea instead of bouvie
  • Remove ETT during laser procedure and reinsert ETT prn sats
67
Q

Anesthesia Plan for the patient undergoing Laser therapy.

A
  • Preoperative evaluation of airway (stridor, flow volume loops, CT, fiberoptic eval)
  • Mutual planning with surgeon) Intermittent apneic oxygenation, jet ventilation)
  • Total IV anesthesia (Propofol, remifentanil, Xylocaine spray)
68
Q

Anesthesia plan to prevent airway fire:

A
  • Methylene blue in cuff
  • Saline gauze protection of airway/face
  • Short, repeated pulses of laser instead of long continuous mode
  • Keep O2 < 30%, avoid nitrous
  • Communicate and monitor video camera for signs of airway fire

24 Principles of Anesthesia II (23 decks)

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