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POCUS > POCUS (EDE Manual) > Flashcards

POCUS (EDE Manual) Flashcards

1
Q

What does “echogenic” mean?

A

A material that produces echoes (ie. U/S waves bounce off) -the more echogenic a substance is, the whiter the image it produces on the screen

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2
Q

What does “echolucent” mean?

A

A material tha does not produce echoes (ie. U/S waves pass through it) -the more echolucent a substance is, the blacker the image it produces on the screen

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3
Q

What does “hyperechoic” mean?

A

Hyperechoic = more white than the substances surrounding it

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4
Q

What does “hypoechoic” mean?

A

Hypoechoic = more black than the substances surrounding it

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5
Q

What does “anechoic” mean?

A

Completely black - produces no echoes at all

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6
Q

What does “near field” mean?

A

The TOP HALF of the U/S screen -represents that part of the body CLOSEST to the probe

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7
Q

What does “far field” mean?

A

The BOTTOM HALF of the U/S screen -represents that part of the body FARTHEST AWAY from the probe

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8
Q

What is “penetration”, “attenuation” and “reflection”?

A

Ultrasound waves, depending on the amount of energy they possess, will PENETRATE (ie. pass through) a medium. -As they penetrate the tissues, they continually lose some of their energy to the tissues through which they pass, a process called ATTENUATION -The rest of the waves’ energy is REFLECTED back towards the waves’ original source (ie. the ultrasound probe)

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9
Q

What does “resistance” mean?

A

A medium through which it is difficult for waves to travel through -aka impedence

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10
Q

What are examples of tissues with low resistance vs. high resistance?

A

Low resistance = ie. ultrasound waves can pass through very well and thus the image is DARKER (less waves bouncing back) –> liquid (blood/urine) -medium resistance = ie ultrasound waves can pass through moderately well –> solid organs (liver/spleen) -high resistance = ie. ultrasound waves can’t pass through at all and thus the image is WHITER (all waves bouncing back to probe) –> bone

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11
Q

What is “scatter”?

A

When ultrasound waves have no problem passing through a substance but the waves are immediately deflected in all directions instead of directly back towards the probe so you get a blurry image -ie. this is what you see with GAS!

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12
Q

What are “acoustic windows”? -what serves well as acoustic windows?

A

Acoustic windows = substances you can use to allow U/S waves to penetrate deeper into the body without interference from bowel gas -good acoustic windows = solid organs (ie. liver, spleen, full bladder)

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13
Q

What substances reflects 100% of the ultrasound waves that hit it?

A

Bone

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14
Q

Why do you have to use U/S gel?

A

Because U/S gel creates a liquid medium for ultrasound waves to penetrate through! -if you don’t use U/S gel, then you will have air trapped between the probe and the skin surface and all your waves will be deflected/scattered in all directions giving you a blurry image

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15
Q

What does “interface” mean?

A

Two different tissues against each other -ie. blood against a solid organ, blood between two different organs (between kidney and liver, between kidney and spleen, blood between myocardium and pericardium)

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16
Q

What are the different types of modes on an ultrasound machine?

A

B mode = brightness mode = THIS IS WHAT WE USE THE VAST MAJORITY OF THE TIME A mode = amplitude mode M mode = motion mode D mode = doppler mode

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17
Q

What is axial resolution?

A

The ability of the waves to distinguish between two objects at different depths -ability of the scan to determine whether a big echogenic blob is actually two smaller echogenic blobs ONE ON TOP OF THE OTHER! (ie. different depths) -improves as frequency increases

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18
Q

What is the relationship between frequency and penetration? -what is the relationship between frequency and resolution?

A

Frequency and penetration are INVERSELY RELATED -as frequency increases, penetration decreases -as frequency decreases, penetration increases Frequency and resolution are DIRECTLY RELATED -as frequency increases, resolution increases -as frequency decreases, resolution decreases

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19
Q

What is the benefit of a low frequency probe vs. a high frequency probe?

A

Low frequency probe = allows you to look at DEEP structures since the penetration is high = for chest and abdomen (ie. the 3.5 MHz prob) High frequency probe = allows you to look at SUPERFICIAL structures since the penetration is low but resolution is high = for soft tissue

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20
Q

What is a transducer?

A

Ultrasound probe :)

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21
Q

What does “format” mean? -two types?

A

Field of view produced by the probe -Two types: 1. Linear format = produces rectangular field of view –> used for viewing objects close to the surface 2. Sector format = produces pie shaped wedge field of view –> used for objects deeper to the surface

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22
Q

What does “array” mean?

A

Array = refers to the way the crystals (the elements that vibrate to produce the ultrasound waves) are arranged -can be phased or linear

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23
Q

Define: -longitudinal view -transverse view

A

Longitudinal view: probe placed along a line running from head-to-toe (ie. along the body) -wedge-shaped section of the body with the left side of the screen corresponding to the cephalad direction -ie. in RUQ view, you hold the probe in longitudinal view and thus you see the patient’s lungs in on the left side of the screen because it’s cephalad and the patient’s liver on the right side of the screen because it’s caudal Transverse view: probe placed along a line running from left to right (ie. across the body) -produces a CT image = as you look at the screen, the patient’s head is away from you, the patient’s feet are towards you, and the patient’s right side corresponds to the screen’s left side and the patient’s left side corresponds to the screen’s right side -when you are in the transverse view, the LEFT side of the screen will correspond to the patient’s RIGHT! ***REMEMBER THAT THE PART OF THE BODY CLOSEST TO THE PROBE WILL ALWAYS BE AT THE TOP OF THE SCREEN NO MATTER WHAT VIEW YOU ARE IN!!!!! -get in the habit of thinking in terms of “near field” vs. “far field|

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24
Q

How should you always orient the probe?

A

With the small knob or bar TOWARDS THE PATIENT’S HEAD (in longitudinal view) or TOWARDS THEIR RIGHT side (in transverse view) -if the machine doesn’t have a knob, then gently tap the probe on one side of the probe head and your finger should appear on the left side of the screen and should be oriented towards the patient’s head or their right side

25
Q

Fill in the blanks: 1. In the longitudinal view, to move the area of interest to the right, move the probe _____. 2. In the longitudinal view, to move the area of interest to the left, move the probe _____. 3. In the transverse view, to move the area of interest to the right, move the probe to the patient’s ____. 4. In the transverse view, to move the area of interest to the left, move the probe to the patient’s ____.

A
  1. Cephalad 2. Caudad 3. Right 4. Left
26
Q

How does depth and magnification relate to each other on an ultrasound machine? -how can you tell how deep you are when looking at an image?

A

Depth = the greater the depth, the less the magnification; the lesser the depth, the greater the magnification -can tell how deep you are by looking at the centimeter marks on the side of the screen (the more centimeter markings there are, the greater the depth)

27
Q

What does gain mean?

A

Gain = allows you to modulate the strength of the signal returning to the probe -as more energy returns to the probe, the brighter the image

28
Q

How do you make an echogenic structure stand out? What about an anechoic structure?

A

Echogenic structure = one that reflects a lot of energy back to the probe so turn up the gain to increase the strength of the signal returning to the probe Anechoic structure = one that absorbs all the energy so will be black on the screen = turn down the gain to decrease the strength of the signal returning to the probe to enhance dark structures

29
Q

What are the 3 types of artifact in POCUS?

A
  1. Refraction 2. Shadowing 3. Enhancement
30
Q

What is refraction/edge artifact?

A

When the U/S waves are deflected from their original path by passing close to a large, curved, fluid filled structure (ie. bladder or gall bladder) = this can cause a shadow-like image that seems to project from the edges of the curved structure and can look like free fluid but it’s not! -usually you can see refraction artifact on either or both sides of the fluid filled structure

31
Q

What is shadowing/acoustic shadowing?

A

When U/S waves hit something that blocks their path (ie. bone), everything behind the blocking structure appears black and we could be tricked into thinking it was free fluid -but it looks like a shadow!

32
Q

What two artifacts in POCUS can mimic free fluid?

A
  1. Refraction/edge artifact 2. Acoustic shadowing
33
Q

What is enhancement?

A

Enhancement = opposite of shadowing: when U/S waves go through an area of low resistance (ie. fluid), the tissues on the far side of the area glow more brightly than the tissues beside them -the bladder, gall bladder or any fluid filled structure can do this -the waves go through the fluid without any difficulty and then when they hit different tissue on the far side of the structure, the excess energy is then bounced back to the probe making the far side look brighter

34
Q

In subxiphoid view of the heart, what structures will you see in the NEAR field? -what structures will you see in the FAR field?

A

Remember that near field (top of screen) = what is closest to your probe and far field (bottom of screen) = what is farthest away from your probe -since you are subxiphoid, in the near field, you will see the liver, LV and RV (the inferior structures). In the far field, you will see the LA and RA (the superior structures)

35
Q

How can you ensure you see an adequate view of the pericardium in a subxiphoid view? (2)

A
  1. Turn UP the gain! The pericardium is a thick fibrous structure that is echogenic 2. Ensure you obtain the “7” = this is the ventricular septum that tells you that you have the right subxiphoid view
36
Q

What are the two key questions of cardiac EDE? -purpose of these questions?

A
  1. Is there vigorous global cardiac activity? 2. Is there a pericardial effusion? -purpose of these questions: eliminate potentially correctible causes of shock
37
Q

You do a cardiac EDE in a resuscitation and the heart is not beating. Management plan?

A

Stop resuscitation - this is cardiac standstill. Unless there is a defibrillatable rhythm on the monitor (ie. VF, VT, SVT), the patient is dead. -in pediatrics, ensure that the patient is well-oxygenated and normothermic before stopping resuscitations

38
Q

In a patient with unexplained hypotension, you perform a cardiac EDE and find that the heart is beating vigorously. What is your brief differential and next management steps?

A

Think HYPOVOLEMIA or tension pneumothorax! Give fluids fluids fluids, consider needle decompression to rule out pneumothorax. Also consider unsuspected blood loss (do FAST)

39
Q

You perform a cardiac EDE and see that the heart is beating but not vigorously as you would expect….what is your ddx and what do you label the scan?

A

Ddx: 1. Ischemic hypokinesis 2. Primary cardiac issue 3. Electrolyte abnormalities: hyperkalemia especially 4. Severe metabolic acidosis -the test must be declared INDETERMINATE

40
Q

How much fluid accumulation is required to see on cardiac POCUS?

A

At least 100 ml! -100 ml = will see posteriorly, only in systole -100-300 ml = will see posteriorly, throughout the entire cardiac cycle ->300 ml = will see anteriorly and posteriorly -looks like an extra black area inside the pericardium which does NOT change in shape when you sweep

41
Q

How much fluid can the normal pericardium accommodate until hemodynamic compromise occurs if the fluid build up is acute?

A

Only 100-200 ml of fluid (if accumulating rapidly) -if this is the case, you need to perform an emergent pericardiocentesis -if accumulates over time, then can tolerate much much more

42
Q

You are performing a cardiac EDE and you’re having trouble bringing the heart into view. What are 3 things you can do to improve your image generation?

A
  1. Get the patient to take a big deep breath and hold it - will work if the heart is too high in the chest and breathing in will drop the diaphragm and also the heart, bringing it closer to the probe 2. If a patient has a protuberant abdomen, ask the patient to flex their legs to relax the abdominal muscles 3. Use the liver as an acoustic window (look from the patient’s right side)
43
Q

What can be a potential source of a false positive on the subxiphoid view of a cardiac EDE?

A

Epicardial fat = will appear ANTERIORLY first as opposed to effusions which will appear POSTERIORLY first due to gravity (and NEVER only anteriorly)

44
Q

What is your management plan for the following scenarios: -FAST positive, patient unstable -FAST positive, patient stable -FAST negative, patient unstable -FAST negative, patient stable

A

-FAST positive, patient unstable: you’re done! Call Gen Surg and get patient to OR ASAP -FAST positive, patient stable: CT Scan -FAST negative, patient unstable: clinical judgement ALWAYS takes precedence! Never allow a negative EDE to reassure you if there is something worrisome about the patient’s presentation! Call Gen Surg and get a consult, may need to go to OR directly OR CT with full resusc gear -FAST negative, patient stable: can do serial FAST exams and if still negative over a few hours, then this is very reassuring!

45
Q

Which is the most important part of the abdominal scan?

A

RUQ!!!! -Hepatorenal space (Morrison’s pouch) is the second lowest part of the supine abdomen, next to the pelvis! -but the pelvis as such little volume that any clinically significant intraperitoneal bleed will quickly overflow into the RUQ via the right paracolic gutter -bleeding in the LUQ will also be diverted directly to the RUQ by the phrenicolic ligament and the mesentery of the transverse colon

46
Q

Fill in the blank: The hepatorenal view alone will detect hemoperitoneum in more than _____% of clinically significant intraabdominal bleeding.

A

80%! -EDE can reliably detect over 500 mL of free fluid in the abdomen

47
Q

What is the Morrison’s pouch?

A

Space between the liver and the kidney = hepatorenal space

48
Q

Why is the LUQ scan more technically difficult than the RUQ scan?

A
  1. Spleen is smaller than the liver and more difficult to visualize 2. Spleen is more mobile than the liver so fluid can accumulate on either side and not just in the splenorenal space 3. The splenorenal interface is HIGHER than the hepatorenal interface so ribs are more of an obstacle in addition to bowel gas
49
Q

What are sources of false positives in a FAST scan?

A
  1. Perinephric fat: usually symmetrical and roughly same size so make sure you compare RUQ and LUQ if you see this 2. Intraluminal bowel gas: can figure this out because of peristalsis presence 3. Imitators of free blood: ascites, fluid from a ruptured ovarian cyst, urine from a ruptured bladder, etc. ****Remember that if your scan is positive in a stable patient, use your clinical judgement! May require a CT abdo
50
Q

What are sources of false negatives in a FAST scan?

A
  1. Adhesions from previous abdominal surgery: these can prevent free fluid from accumulating in the expected places! So never trust a negative scan in a person who has had previous abdominal surgery 2. Variable LUQ: because of the spleen being freely mobile and small, the fluid won’t JUST accumulate in the splenorenal interface! Can also accumulate cephalad to the spleen so need to make sure you can visualize the diaphragm up to the 9’oclock position 3. Delayed presentation: patients presenting 12-24 hours after a bleed may have blood clots in the abdomen which may just look grey or white and difficult to detect
51
Q

What are some tricks to get the best images from your RUQ and LUQ scans?

A
  1. Make sure your probe is in the true longitudinal plane and you are at maximum depth! Can zoom in for details after you see all of your desired structures 2. Place the patient in 5-10 degrees of trendelenburg position for 15-20 minutes to help deliver free fluid to the RUQ and LUQ 3. Ask the patient to hold their breath either at end expiration or end inspiration if you’re having trouble seeing in between the ribs 4. When in doubt, RESCAN!!! Patients who have a negative FAST and who won’t be CT scanned should, at a minimum, receive a second EDE before discharge.
52
Q

What are you trying to visualize in the pelvic scan? -in men -in women

A

In men: rectovesicular pouch (space between bladder and rectum) In women: rectouterine pouch (Pouch of Douglas) ***Remember that your bladder is in the near-field/top of screen since it is the closest thing to your probe and you are looking specifically in the far field/bottom of screen for any black/fluid = this will be free fluid in the space between the bladder/uterus and the rectum -Turn down the gain if you need to in order to visualize black fluid better, especially since the bladder will give you a lot of enhancement artifact (ie. everything behind the bladder will look a lot brighter since the ultrasound waves travel right through the bladder, then bounce back to your probe from the tissues behind the bladder)

53
Q

What can you do to optimize your pelvic view of the FAST prior to scanning?

A

Could consider putting in a urinary catheter and instill 250 cc of NS into the bladder and clamp the catheter -this gives you a perfect acoustic window through the bladder to peer deep behind the bladder for free fluid

54
Q

What are the sex specific false positives in the pelvic view?

A

Women: -can have physiologic free fluid in the rectouterine pouch Men: -the prostate can look quite hypoechoic (ie. black) and be mistaken for free fluid -can have someone do a DRE and push on the prostate while you are looking with your probe and if the thing you’re looking at moves, then it’s the prostate

55
Q

What does free fluid in the pelvis look like in: -men -women

A

-Men: the rectum is retroperitoneal in males so fluid can ONLY appear anterior to the rectum in the “mickey mouse ears”! -Women: the uterus is free floating in the pelvis so free fluid can appear in BOTH “mickey mouse ears” and around his “bowtie”

56
Q

How do you perform lung ultrasound to rule out pneumothorax in E-FAST? -in B mode, what three things are you looking for to ensure that there is NO pneumothorax? -in M mode, what are you looking for?

A

Place your probe longitudinally to capture the rib space -B mode: Signs of normal lung function (ie. no pneumothorax) 1. Lung sliding with respirations 2. Comet tails with respirations 3. Lung pulse. This is evidence of movement between the visceral pleura and the parietal pleura! -if you see no lung sliding and no comet tails, then this is POSITIVE for pneumothorax! -M mode: things to look for: 1. Seashore sign = this is what lung sliding looks like in motion mode 2. Stratosphere sign/bar code sign = pneumothorax (no lung sliding) 3. Lung Point sign

57
Q

What is lung sliding?

A

The movement between the visceral pleura and parietal pleura

58
Q

What are comet tails?

A

Comet tails are vertical reverberation artifacts arising from the pleural line

59
Q

What is the lung point?

A

The lung point is the transition between collapsed and normally expanded lung. Although difficult to locate, the lung point is reportedly 100% specific for pneumothorax when present -seen in M mode and is a hallmark sign of a pneumothorax

POCUS (7 decks)

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