Principles of Anesthesia II Unit I Flashcards
Lesions located where are rarely diagnosed/picked up on physical exam?
Mediastinum, interstitium and in the center of the lung
What is the relationship of acute vs chronic illness to the effectiveness of a physical exam vs CXR?
Physical exam is good for acute illness, CXR is better for chronic illness
What is under vs overexposure in an xray?
Over = the film is very dark
Under = the film is very bright
If the film is overexposed, what structures are easier to identify?
The T-spine, mediastinal structures and retrocardiac structures
Small nodules and fine structure cannot be seen if the film is overexposed
If the film is underexposed, what structures are easier to identify?
The small pulmonary blood vessels are more prominent
The downside here is d/t the underexposure it may give the appearance of there being infiltrates when none are present
Excessive breast tissue can cause what problem during a CXR?
The breast tissue absorbs some of the x-ray beam causing underexposure
What is the interpretative difference of a PA vs AP x-ray?
The heart will be magnified on an AP projection
This occurs because the heart is farther from the film and the x-ray beam diverges as it goes farther from the tube
When is PA projection of an x-ray commonly done? AP?
PA = generally done on ambulatory patients standing up
AP = on patients lying down, what we commonly did in the ICU
Why do we instruct patients to inspire for a CXR?
To push the liver and abdominal contents down. If not done, the pulmonary vessels can become crowded and the heart will appear larger
What do you need to be aware of if the domes of the diaphragm are at the seventh posterior ribs on x-ray?
The chest should be considered hypo-inflated and the diagnosis of basilar PNA or cardiomegaly should be done with extreme care
What are the 2 acronyms given to help standardize how you read a CXR?
ATMIB and Are There Many Lung Lesions
Both guide you to go; Abdomen first, then thorax, mediastinum, the individual lungs, then both lungs
On a CXR, how many anterior ribs are visible? Posterior?
A = 10
P = 6
What is the order, per lecture, to systematically read a CXR?
Start with the bony framework, then evaluate soft tissues, then the lung fields/Hila, diaphragm and pleural spaces, mediastinum and heart then the abdomen/neck
What structures are you examining when you inspect the bony framework?
You should be able to count and number the ribs, inspect the capulae, humeri and shoulders, and clavicles, and see the diaphragms overlying the posterior aspects of the 10th or 11th ribs (in a normal adult)> The spine and sternum are generally difficult to visualize in detail on standard PA films due to overlying shadows.
What are the soft tissues you are examining on CXR?
Breast shadows, supraclavicular areas and tissues along the sides of the chest
What creates the hilum (lung root) on a CXR?
The shadow of the pulmonary artery and vein that are adjacent to the heart shadow
What borders the right heart/mediastinal border? Left?
Right = IVC, RA, ascending aorta and SVC
Left = LV, LA, pulmonary artery, aortic arch and subclavian artery/vein
What are the 3 main pitfalls to x-ray interpretation?
Poor inspiration, over/under penetration and rotation
Which view of the lungs has extensive overlap?
The PA view
Which lung has more lobes?
R = 3 lobes
L = 2 lobes
The RUL is adjacent to what ribs?
The first 3 - 5 ribs posteriorly, anteriorly, it can extend as far as the 4th rib (more obvious on a lateral view)
The RLL is adjacent to what internal structures on x-ray?
The 6th thoracic vertebral body and extends to the diaphragm
What do the fissures in the R. Lung seperate?
Minor fissure (horizontal) separates the the RUL and the RML, the major fissure (oblique) separates the RLL from the others
Why are fissures not a reliable marker to use when examining a CXR?
They are not always easily identifiable and in some people they may not be completely formed or may even be completely absent on CXR
What areas are you examining with a lateral view?
Oblique fissure, horizontal fissure, thoracic spine, retrocardiac space and retrosternal space
What structures can you identify with a PA view?
Aortic arch
Pulmonary trunk
Left atrial appendage
Left ventricle
Right ventricle
Superior vena cava
Right hemidiaphragm
Left hemidiaphragm
Horizontal fissure
What is the silhouette sign?
Something is coming into contact with the border of the heart/aorta which obscures the normal border
What is the air bronchogram sign?
We can visualize the bronchi now (normally it is obscured by alveoli) which generally indicates some sort of consolidation (this consolidation of non-air material allows us to see the bronchi)
Most disease states replace _____ with a pathological process that creates the visual change on xray?
Air
A consolidation radiologically transcribes to what?
A density corresponding to a segment or lobe, air bronchogram and no significant loss of lung volume
What are the radiologic criteria for absorptive atelectasis?
- A density corresponding to a segment or lobe
- significant signs of loss of volume
- compensatory hyperinflation of normal lung(s)
What are the steps in evaluating an abnormality on CXR?
- Identification of abnormal shadows
- Localization of lesion
- Identification of pathological process
- Identification of etiology
- Confirmation of clinical suspension
Where should a CVC tip lie?
lie between the most proximal venous valves of the subclavian or jugular veins and the right atrium
The loss of what generally indicates a pleural effusion/accumulation of fluid outside the lung?
Loss of the costo-phrenic angle
How can you differentiate RLL vs RML lobe PNA on CXR?
They occupy almost the same position on an CXR, the easy way to identify the difference is RLL PNA will occupy most/all of the costo-phrenic angle, RML should leave that angle intact
What is a Gohn complex?
A lesion caused by TB that consists of a calcified focus of infection and an associated lymph node
What type of radiation comes from the motion of atoms and combine electricity and magnetism?
Electromagnetic
What type of radiation only travels through substances?
Mechanical
What type of radiation is the result of unstable atomic nuclei?
Nuclear
What type of radiation is composed of electrons only and is frequently emitted from the sun?
Cosmic (beta) waves
What type of radiation does a CXR utilize?
Electromagnetic
What category of radiation does not knock off electrons, doesn’t break molecular bonds and is only harmful from it’s ability to produce heat?
Non-ionizing
What process creates ionizing radiation?
Some stimulus (the exact stimulus is not important for this class) causes a particle to lose an electron, as the ion is created energy/radiation is produced
What category of radiation are you most likely to encounter in patient care areas?
Ionizing
non-ionizing dominates the break room though
Of the EMS spectrum, what rays are not part of the visible spectrum?
Radio waves and gamma rays
X-rays are most similar to what other ray?
Light rays
both are electromagnetic energy and carried by photons
What is the relationship of wavelength to energy of a ray?
As wavelength shortens, energy drastically increases
Describe how light is emitted (same process as creating a photon)?
An external stimulus causes an electron to become excited and jump to a higher orbital. This state is energetically unfavorable; and so the electron will eventually go back to a lower energy orbital. When this occurs, energy is released as a photon
What type of tissue is more likely to be made of small atoms? Large atoms?
Small = soft tissue
Large = bones
Why are bones bright on an x-ray?
Because they are larger atoms they absorb more photons making them appear brighter. Smaller atoms, like soft tissue, absorb less making them grey. Since air has very little to no capability to absorb photons the pulmonary space has a tendency to appear black
Describe the basics of how an x-ray machine works
A filament in a cathode heats up, this energy causes electrons to leave the filament. An anode made of tungsten is positively charged and attracts the photons across the tube. As the photons leave this tube, they hit tissues and reflect to create the image.
What environmental factor can alter a CXR’s appearance?
Ambient light
What is the basic difference between a CT and a CXR?
Both use x-rays to create an image, a CT however uses x-rays along with computer processing to create a 3D image
What is a non-image related use for medical x-rays?
Radiation therapy for cancer
What s/e of radiation therapy is common across all anatomic locations?
Fatigue
What is the most common s/e of radiation therapy above the abdomen? Most common s/e of the abdomen and below?
Above = hair loss
Abdomen and below = diarrhea
What areas of the body when exposed to radiation therapy can cause N/V?
Brain, pelvis and abdomen
What anatomic areas when exposed to radiation therapy can cause urinary changes?
Abdomen, rectum and pelvis
What is the allowable radiation dose for the whole body?
5,000 mrem
What is the allowable radiation dose for the extremities?
50,000 mrem
What is the allowable radiation dose for lens of the eye?
15,000 mrem
What is the allowable radiation dose for pregnancy?
500 mrem
How many mrem’s are released from a CXR?
5-10 mrem
How many mrem’s are released during a coronary angiogram?
1,500 mrem
How many mrem’s are released during an angioplasty?
5,700 mrem
How many mrem’s are released from a CT?
5,000 mrem
What 3 factors can affect radiation scatter?
Collimation - the “size” of the window that radiation is allowed to escape
Object thickness - the thicker the object, the more the radiation will scatter (this is partially why imaging on obese patients can be of poor quality)
Air gap - fairly straightforward; the longer the distance to travel, the more opportunity there is for scatter to occur
At what dose of mrem does transient erythema occur?
200,000 mrem
What dose of mrem is unlikely to cause fetal s/e after 20 weeks of gestation?
Less than 10,000 mrem
With a direct source of radiation, what is the relationship of distance to exposure rate?
For every doubling of distance (or factor increase by 2) you will decrease exposure rate by 1/4
(if you go from 2 to 8 feet, and starting mrem is say 100 mrem/min, you have doubled your starting distance 3 times, 2 -> 4 -> 6 -> 8, be VERY careful when doing this math and be comfortable with the difference between factor increases, which is what this is, and standard multiplication. So, you have 3 factor increases of distance, so you will multiply 100 by 0.25 3 times) -> 100 x 0.25 = 25 mrem/minute (first factor), 25 x 0.25 = 6.25 mrem/minute (2nd factor), 6.25 x 0.25 = 1.5626 mrem/minute (3rd factor). This illustrates why distance is so valuable in reducing radiation exposure
You are 3 feet away from a radiation source and receiving 750 mrem/min of radiation, you move away from the radiation source to 15 feet. What is your new exposure rate?
2.93 mrem/minute (remember, this is factor multiplication, for each doubling of the distance you reduce radiation exposure by 1/4 and in this scenario you have doubled the distance 4 times)
What occurs is you leave a dosimeter on your car dashboard?
Because it is being exposed to cosmic (beta) radiation it can falsely elevate/trip the dosimeter
The interactions between what create the images of an MRI?
The interactions between the static magnetic field and the individual atom nuclei
Why is MRI, in general, a safer option than a CT?
Because an MRI does not use ionizing radiation there are less cell death/damage risks
Describe how an MRI orients molecules/atoms to create images
The magnetic field orients the nuclei of hydrogen molecules to north/south poles and radio wave pulses change the orientation of specific atoms which radiates energy
What property allows MRI to create detailed pictures?
Each atom/molecule “resonates” at a unique frequency, and when exposed to the properties used in an MRI machine, each atom creates an image unique to that atom. So hydrogen will look different than iron
What is a T1 MRI image most useful in identifying?
Due to the good grey-white matter contrast, it is good to examine anatomy.
fat appears bright, water appears dark in T1
What is a T2 MRI image most useful in identifying?
Because of it’s ability to identify tissue edema, it is very useful in identifying tissue pathologies
How does fat and water appear on T1 vs T2 MRI images?
T1 = Fat is bright, water is dark
T2 = Fat is darker than water
What is the most common contrast medium used in MRI?
Gadolinium
How does gadolinium work?
It Alters the magnetic properties of nearby water molecules which enhances the quality of MRI images.
What pieces of equipment, in general, should not be introduced in a room with MRI?
Oxygen/nitrous oxide tanks
Anesthesia machine
Monitors
Infusion pumps
Stretchers
Crash carts
Most of these items are generally located just outside
What is the primary danger/risk of MRI?
Projectile risk. Another concern is heating, particularly of metal components that have been implanted in someone
Dr. Mordecai gave an example of how she had the LINX procedure for acid reflux, and because of that she isn’t safe in an MRI room
Do the AANA standards of care have any changes/accommodations for a patient in MRI?
No, these standards apply regardless of the patient care setting
What type of MRI scans (think region of the body being scanned) have a high incidence rate of brachial plexus injury?
Abdominal scans - because you have to place the arms over the head to get them out of the way of the scan
What s/sx can occur if you approach the MRI field rapidly?
dizziness, HA, light flashes, nausea
What implantable devices should warrant caution before being exposed to an MRI? Which are generally safe?
Caution/may not be safe = Pacemakers, AICDs and insulin pumps
Generally safe = Heart valves, endovascular and biliary stents after the 8 week mark, coronary stents, vascular ports, IVC filters and most orthopedic implants
What type of stent is immediately safe for MRI (no waiting period necessary to allow for healing/attachment to native vessel)?
Coronary stents
What differences are present between normal light vs a laser?
A laser has a specific wavelength, a focused narrow beam and high intensity
Normal light = many/varying wavelengths and spreads out in many directions
What type of radiation does a laser make use of?
Electromagnetic
What are the 3 properties listed on the powerpoint that describe the behavior of lasers?
Monochromatic - all photons of a laser are of the same wavelength
Coherence - the travel of the photons is synchronous; they do NOT move randomly
Collimation - the laser beam photons are nearly perfectly parallel which allows for a very focused beam
What are the 3 primary lasers used in medicene?
Argon, CO2 and Nd:YAG lasers
What laser has minimal scatter/minimal damage to surrounding tissue making it preferable for vocal cord/oropharynx surgery?
CO2 laser
What laser has modest penetration (0.05 - 2mm) and is commonly used for dermatology?
Argon lasers
Why does a CO2 laser cause minimal to no to surrounding tissue?
The CO2 laser is well absorbed by water, meaning it disperses very little heat
What is the most powerful laser with deeper penetration of 2 - 6mm and useful in tumor debulking?
Nd:YAG lasers
What are the 2 primary risks we are concerned with when lasers are in use?
Atmospheric contamination (think condyloma surgery) and airway fire
What are the 5 hazards listed in lecture of laser use?
Atmospheric contamination, perforation of a vessel/structure, embolism (think air embolism from a hole in a vessel), inappropriate energy transfer and airway fire
Why are we so concerned about atmospheric contamination from laser procedures?
The plume of smoke can transmit particulates that can be carcinogenic in nature
What are the basic/generic safety considerations with laser use?
Laser glasses for provider
Laser glasses for patient with eyes taped
Windows covered
Laser plume masks for vaporized viruses and particulates
Appropriate suction
Water/saline irrigation on back table
Don’t tent drapes/have pockets of oxygen
What is the fire triad?
An ignition source, fuel (oxygen) and an oxidizer
What are the 2 major sources of OR fires?
ESU (electrical surgical units, think cautery devices) and lasers
What are some interventions you can use to help maintain airway fire safety?
Laser-resistant ETTs
Low-inspired (21% if possible) O2
Wet pledgets around the ETT
Methylene blue in the ETT cuff
Use scissors to cut into trachea instead of bouvie
Remove ETT during laser procedure and reinsert ETT prn sats
Why must TIVA be a backup if there are planned apneic periods during surgery due to airway fire concerns?
If you are apneic, you aren’t breathing in any volatile; you want to prevent surgical awareness, so you can use TIVA to help maintain anesthesia
What should be included in the anesthesia care plan if airway fire is of concern?
Methylene blue ETT cuff, saline gauze protection of face/airway, try to convince the surgeon that short repeated pulses of a laser is better instead of long/continuous, avoid O2 concentration of greater than 30%, avoid nitrous and communicate
What type of radiation does not travel through the air?
Mechanical