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Emergency Medicine - BT > EDE Exam > Flashcards

EDE Exam Flashcards

1
Q

What is wave attenuation?

A

When waves pass through mediums, they lose energy to the tissues through which they pass (this is converted to negligible heat)

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2
Q

What determines how well ultrasound waves travel?

Compare blood, solid organs, bone and gas

A 
Resistance (or impedance) of tissues
Blood: low resistance
Solid organs: mod
Bone: reflects 100% of US waves (high resistance)
Gas: causes scatter - deflects waves
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3
Q

What is the relationship between energy and brightness on US?

A

Higher energy reflected = brighter image on screen

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4
Q

Name 5 tissue interfaces of interest in EDE

A 
Kidney/liver 
Kidney/spleen
Myocardium/pericardium
Between thick fibrous aortic wall
Gestational sac in uterus
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5
Q

What are 4 modes of transmission on the US machine and which do we use most?

A

**B (brightness) mode
A (amplitude)
M (motion)
D (doppler)

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6
Q

What is axial resolution? What is determined by?

A

The ability of waves to distinguish between two different objects at different depths.
Determined by frequency of the probe

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7
Q

What is lateral resolution? What is it determined by?

A

The ability of waves to distinguish between two objects at the same depth (right-left axis). Determined by focus

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8
Q

What is the relationship between frequency and penetration?

A

INVERSE
As frequency increases, penetration decreases (finer, more detailed images - cannot seem as far down)
As frequency decreases, penetration increases

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9
Q

What is the relationship between frequency and resolution?

A

DIRECT
As frequency increases, resolution increases
As frequency decreases, resolution decreases

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10
Q

What is the general EDE probe frequency?

A

3.5 MHz

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11
Q

What is the format of a probe?

What is the array of a probe?

A

Format: field of view produced by probe - linear (vascular) vs. sector (abdo - curved)
Array refers to crystal organization of the probe - flat linear vs. cured linear

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12
Q

Describe the orientation of the probe vs. screen in

  1. longitudinal view
  2. transverse view
A
  1. Longitudinal - left side of screen is cephalad
  2. Transverse - left side of screen is patient’s right
    * exception: echocardiography - left side of probe = patient’s left
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13
Q

How do you centre the image in:

  1. longitudinal view
  2. transverse view
A

Longitudinal - to move area of interest right, move probe cephalad, to move area of interest left, move probe caudad
Transverse - to move area of interest right, move probe to patient’s right, to move left, move probe to patient’s left

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14
Q

What are 2 image modulation knobs to use on the machine?

A

Depth

Gain

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15
Q

What is the relationship between depth and magnification?

A

The less the depth, the greater the magnification

*set the depth to maximum when beginning a scan

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16
Q

What does changing gain control?

A

Increases the sensitivity of the probe which modifies the apparent strength of the ultrasound wave return
changes screen to be whiter or darker
To make an echogenic structure stand out, increase the gain
To make an anechoic structure stand out, decrease the gain

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17
Q

What does focus do?

A

Improves lateral resoultion - turn it off if your machine has one

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18
Q

What are 3 types of artifact?

A

Refraction: when US waves are deflected by passing close to a large, curved, fluid filled structure - get a shadow like image projecting from edge of structure = edge artifact

Shadowing: when US waves hit an area of high resistance that blocks their path - everything behind that structure appears black (ie. vertebral body)

Enhancement: When US waves go through area of low resistance (fluid), tissues on the far side glow more brightly (ie. gallbladder, bladder)

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19
Q

Which types of artifact can mimic free fluid

A

Refraction

Shadowing

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20
Q

What is the dead zone?

A

First few centimetres of screen - cannot use any information here

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21
Q

What are 5 structures you should see in the subxiphoid view of cardiac EDE?

A 
liver
pericardium
RV
LV
pericardium
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22
Q

In cardiac EDE, what is the orientation of the

  1. near field images
  2. far field images
A
  1. inferior structures

2. superior structures

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23
Q

What are 2 questions addressed by cardiac EDE

A
  1. is there vigorous global cardiac activity
  2. is there a pericardial effusion
    (goal to differentiate causes of shock)
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24
Q

What are the two options in evaluating cardiac activity? What is one exception?

A
  1. heart not beating - stop resus
    * exception - pediatric hypoxic arrest (and hypothermia)
  2. heart beating vigorously
    * look for hypovolemia, tension PTX, unsuspected blood loss
    * if you cannot call one of these 2 things should call the scan INDETERMINATE
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25
Q

How much fluid does a normal pericardium contain?

A

50 mL

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26
Q

With a patient in supine position, how much fluid needs to accumulate before you see:

  1. posterior effusion in systole only
  2. posterior effusion throughout cycle
  3. anterior and posterior effusion
A
  1. 100 mL
  2. 100-300 mL
  3. > 300 mL
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27
Q

How do you make the diagnosis of tamponade?

A

CLINICAL diagnosis - pericardial effusion with hypotension or pulsus paradoxus

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28
Q

How much fluid can a pericardium accomodate acutely before hemodynamic compromise?

A

100-200 mL

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29
Q

What are 3 ways to improve your cardiac EDE?

A
  1. patient holds breath (drops diaphragm down)
  2. flex the legs
  3. cheat over to patient’s right to get a better acoustic window
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30
Q

What are false positives of pericardial effusion on EDE?

A

abdominal free fluid
pleural effusion
epicardial fat

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31
Q

How to differentiate epicardial fat pad from pericardial effusion?

A

Echolucent stripe, can be thick

appears anteriorly first (effusions appear posteriorly)

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32
Q

What are 10 causes of acute pericarditis/

A

Post MI (Dressler’s)
Myxedema
Radiation induced
Infection - viral, bacterial, fungal, parasitic
Collagen disease (RA, RF, PAN, SLE, scleroderma, dermatomyositis)
Amyloid
Aneurysm
Anticoagulation
Renal failure (uremia)
Drugs - penicillin, procainamide, phenytoin, hydralazine, pulmonary INH
ITP
Trauma/Surgical procedures
Tumors - leiomyofibroma, rhadomyosarcoma, teratoma
Metastatic - leukemia, lymphoma, lung, breast, melanoma
Endocarditis with valve ring abscess
Sarcoidosis

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33
Q

What are 5 viral causes of pericarditis?

5 bacterial causes?

A

Coxsackie, echovirus, adenovirus, EBM/mono, influenza

Staph, GAS, S. pneumo, N. meningidites, TB

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34
Q

What are 4 steps in emergency pericardiocentesis from the paraxiphoid approach?

A
  1. Assemble equipment - 18 gauge 10 cm spinal needle, stopcock, 20 cc syringe
  2. Attach lead V2 to needle
  3. Advance needle towards left scapula tip
  4. Aspirate till cavity entered
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35
Q

When do you stop a pericardiocentesis?

A
  1. blood obtained (>20 mL easily = RV)
  2. pulsations felt
  3. ECG changes = ST elevation is the current of injury
36
Q

What plane of view is aortic EDE done in? What is the first landmark

A

transverse

vertebral spine

37
Q

What are 3 defining features of the aorta?

A
  1. thick walled
  2. non compressible
  3. lack of respiratory variability
    * sniff test will be negative when R sided pressures are high
38
Q

What are 2 pitfalls of identifying the aorta?

A
  1. pulsatility
  2. sidedness
    common for IVC to be undetectable, can identify aorta without seeing IVC
    textbooks say 10% of aorta’s are on patient’s right
39
Q

How do you diagnose AAA?

A

transverse view has aortic diameter or > 3 cm in any viewuntil the iliac bifurcation
outer wall to outer wall
don’t need to see bifurcation if this is seen >3 cm

40
Q

What is the object of interest in aortic ede?

A

echogenic aortic vessel wall

*increase gain

41
Q

Can you determine AAA rupture on EDE?

A

NO, only AAA presence
Need to do a FAST afterwards to r/o free fluid
Often ruptures retroperitoneal

42
Q

What percentage of AAA’s are fusiform?

A

95%

95% are infrarenal

43
Q

What percentage of aortas will you see successfully in the beginning? What about when you are more experienced?

A

50% vs. 80%

44
Q

What are 2 ways to overcome bowel gas on aortic EDE?

A
  1. Push and wait
  2. Move probe off centre then angle to keep the spine centred
  3. Scan quickly looking for true positive
45
Q

What are 4 possible outcomes with abdominal EDE?

A
  1. Unstable patient, positive FAST –> OR
  2. Stable patient, positive FAST –> CT or rescan EDE
  3. Suspicious patient, EDE negative –> use clinical judgement
  4. Stable, benigin patient, EDE negative –> serial EDE’s
46
Q

What are the 3 main views of abdominal EDE?

A

RUQ
LUQ
pelvis

47
Q

What is visualized in the RUQ view?

A 
Hepatorenal space (Morrison's pouch) 
second lowest part of abdomen, will collect overflow from pelvis via R paracolic gutter
bleeding in LUQ will traverse via phrenicolic ligament and mesentery of transverse colon
48
Q

How often will hepatorenal view detect hemoperitoneum?

A

80% of clinically significant cases

49
Q

When can EDE detect abdominal free fluid?

A

reliable if >500 cc

~250 cc if very careful

50
Q

Where should you place the probe for upper abodminal EDE?

A

think posterior axillary line

use kidney as a reference to find interface

51
Q

Why is the LUQ scan more difficult?

A

smaller than liver - smaller target
more mobile than liver - fluid can accumulate on either side of splenorenal space
*splenorenal interface is higher, more restricted by ribs and gas shadowing

52
Q

How do you troubleshoot the LUQ view?

A

Find best possible view and tilt the probe 30 degrees cephalad towards the be to avoid the ribs
*will reduce the apparent size of the target area
scan through 2 adjacent rib spaces - if significant overlap is seen on images

53
Q

What are 3 imitators of abdominal free fluid?

A 
Ascites
Peritoneal dialysis fluid
Fluid from ruptured ovarian cyst
Fluid from ruptured bladder 
Intraluminal bowel fluid
54
Q

What is an important false positive on the RUQ/LUQ view?

A

Perinephric fat
Distinguish because more echogenic
Often bilateral, symmetrical
Direct relationship with body habitus

55
Q

What are 3 false negatives of abdominal free fluid?

A 
Adhesions
Delayed presentations (blood has clotted) - may appear echogenic
LUQ variability - may accumulate medial or superior beyond splenorenal interace
56
Q

What do you need to image in the LUQ view?

A

Diaphragm - from 6 to 9 o clock position

57
Q

What are tips to improve your abdominal scans?

A
  1. Scan in true longitudinal plane with maximal depth
  2. 5-10 degrees of trendelenburg for 15-20 min * can decrease by 1/3 the amount of fluid needed to visualize for ED sonographer
  3. hold breath
  4. rescan
58
Q

What does the pelvic view visualizes in

  1. males
  2. females
A
  1. rectovesicular pouch

2. rectouterine pouch (pouch of douglas)

59
Q

How can you improve this view?

A

instill 250 cc of NS into bladder to make an acoustic window
*decrease gain - looking for dark fluid
may get enhancement artifact if full bladder

60
Q

What are 5 contraindications to placement of urinary catheter?

A 
high riding/absent prostate
blood at meatus
scrotal hematoma
perineal ecchymosis
unstable pelvic fracture
61
Q

What are 2 false positives for abdominal free fluid in the pelvis?

A
  1. Females - physiologic fluid

2. Males - prostate can look hypoechoic - distinguish by pushing on prostate

62
Q

Where does pelvic fluid accumulate in males? in females?

A
  1. Anterior to rectum (a retroperitoneal structure) - Mickey’s ears
  2. Anterior or posterior to uterus - Mickey’s ears and bow tie
63
Q

What is the goal of obstetrical EDE?

A

Rule in a benign condition - IUP

64
Q

What is the rate of ectopic pregnancy?

A

1 in 80
40% are misdiagnosed at first contact
second leading cause of maternal death (10%)

65
Q

What is a false positive of adnexal mass on exam?

A

Corpus luteum

66
Q

What is the rate of heterotopic pregnancy?

A

1 in 30,000
1 in 4,000 in areas with endemic chlamydia
1 in 100 in fertility treatments

67
Q

What probes are used in obstetrical EDE?

A
  1. Transabdominal - 3.5 MHz probe + needs full bladder
  2. Transvaginal - 5-7.5 MHz endocavitary probes, higher frequency
    gives better axial resolution with no real cost of penetration because you no longer need an acoustic window
    Need EMPTY bladder
68
Q

What is the area of interest in obstetrical EDE?

A

endometrial stripe - echogenic, white line

69
Q

What is the contraindication of TV EDE?

A

Recent gynecologic survery

70
Q

How do you prep the TV probe?

A

gel, condom, muko

get rid of all air bubbles

71
Q

What 3 structures are required to diagnose an IUP?

A
  1. decidual reaction - thick, echogenic white lining
  2. gestational sac - anechoic black area
  3. yolk sac - thick, echogenic layer within gestational sac
    double ring sign is earliest sign of definitive IUP (when sac is 10 mm by TV and 20 mm by TA - seen @ 5 weeks by TV, 6-7 weeks by TA)
72
Q

When should you see fetal cardiac activity?

A

TV: fetal pole >5 mm (6 weeks)
TA: fetal pole >10 mm (7-8 weeks)
Presence of fetal pole trumps 3 criteria

73
Q

When do you see live IUP?

A

TV: 6 weeks
TA: 7-8 weeks
HR >100 for good fetal outcome - do not test with Doppler
ensure rhythmic activity is within gestational sac, far away from uterine wall

74
Q

What is the gestational sac made of?

A

Amnion and chronion cavities
May not always see the amnion
Yolk sac will be obliterated at 12 weeks when amnion fuses with chorion

75
Q

What are 2 important false positives in obstetrical EDE?

A
  1. empty gestational sac (in ectopic, pseudogestational sac)
    NO YOLK SAC
  2. extrauterine pregnancy +/- fetal cardiac activity
    RECOGNIZE UTERINE TISSUE
76
Q

Why do we measure the myometrium in obstetrical EDE?

A

To assess for interstitial/corneal pregnancies
Ectopic equivalent but intrauterine
Will hemorrhage
Myometrial mantle > 5 mm (8 mm if generous)
Will appear off centre

77
Q

What are other diagnostic possibilities on obstetrical EDE?

A

Incomplete abortion
Complete abortion
Blighted ovum (empty gestational sac >25 mm without yolk sac, suspect if >20 mm)
Molar pregnancies (snowstorm pattern, small fluid filled black holes)

78
Q

How do patients with molar pregnancies present?

A 
Very high BHCG
Hyperemesis gravidarum
Hyperthyroidism features
Uterus large for dates
Anemia
79
Q

What are the discriminatory values for BHCG in TV and TA views

A

TV: 1500 mIU/mL
TA: 3000 mIU/mL
Always do an EDE and use clinical judgement
Empty uterus and BHCG above discriminatory threshold should be strong evidence of ectopic

80
Q

What can we use crown rump length for in obstetrical EDE?

A

> 5 mm without fetal cardiac activity - unlikely to progress successfully

81
Q

When to use the obstetrical EDE algorithm?

A

Women of childbearing age with any one of:

  1. pelvic pain
  2. abdominal pain
  3. vaginal bleeding
  4. unexplained hypotension
82
Q

What are 8 risk factors for ectopic pregnancy?

A 
Endometriosis
Tumors
PID *7 fold risk
Previous ectopic
Previous pelvic surgery
Previous induced abortions
Infertility
DES exposure in utero
83
Q

What are the 10 commandments of EDE?

A
  1. Nothing replaces clinical skills
  2. Call it a negative study when it is incontrivably so
  3. Do not hesistate to call a study inconclusive
  4. Only use EE in appropriate clinical situations
  5. Redo EDE if scan initially negative and clinically suspicious
  6. Be slow and deliberate
  7. Be methodical
  8. Don’t drop the probe
  9. Communicate with patients (including limitations)
  10. Nothing shall replace the primacy of your clinical skills
84
Q

What are the 2 views of the TV obstetrical EDE?

A
  1. Sagittal - reference mark to ceiling, sweep L and R (uterus longitudinal)
  2. Coronal - reference mark 90 degrees CCW, sweep ant/post (uterus circular)
85
Q

What is the spatial orientation of TV EDE?

A

near field = caudal

far field = cephalad

Emergency Medicine - BT (16 decks)

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