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8362 T&T Exam1 > Mod IV: Regional Anesthesia Part 5 > Flashcards

Mod IV: Regional Anesthesia Part 5 Flashcards

1
Q

Regional Anesthesia - Locating Nerves

How to find what your looking for?

A

Apply that Anatomy

Knowledge of nerve path, surrounding structures, and surface landmarks is of paramount importance

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2
Q

Regional Anesthesia - Locating Nerves

Techniques used to localize nerves

A

Landmarks - Paresthesia - Nerve Stimulator

Ultrasound - Fluoroscopy

CT guided

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3
Q

Regional Anesthesia - Locating Nerves

Nerve localization technique that provides both still and live x-ray views:

A

Fluoroscopy

Used primarily in pain blocks

Expensive

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4
Q

Regional Anesthesia - Locating Nerves

Nerve localization technique that provides still and live Ct images:

A

Ct guided

Used rarely in pain blocks

Extremely expensive!!!

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5
Q

Regional Anesthesia - Locating Nerves

Techniques for locating nerves that use surface landmarks and knowledge of anatomical relationships:

A

Landmark Techniques

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6
Q

Regional Anesthesia - Locating Nerves

Using Landmarks alone can help anesthetized which structures?

A

Ankle

Digits

Cervical plexus

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7
Q

Regional Anesthesia - Locating Nerves

Landmark Techniques can be combined with:

A

Paresthesia

Nerve Stimulator

Ultrasound

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8
Q

Regional Anesthesia - Locating Nerves

The feeling of tingling, tickling, burning, prickling, or buzzing felt is also known as:

A

Paresthesia

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9
Q

Regional Anesthesia - Locating Nerves

What’s the goal of Paresthesia technique?

A

To place the needle in direct contact with the desired nerve to produce a Paresthesia

This tells the practitioner they are very close or in the target nerve, then withdraw slightly until paresthesia stops and inject LA

NEVER inject LA if pt has sharp PAIN or PARESTHESIA!!!

The elicited paresthesia should follow the target nerves distribution

Old technique still used by some practitioners

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10
Q

Regional Anesthesia - Locating Nerves

What are disadvantages of the Paresthesia technique?

A

Risk of neural injury

Higher block failure rates when compared to newer techniques

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11
Q

Regional Anesthesia - Locating Nerves

Nerve localization technique that uses electricity to produce a response of a target nerve:

A

Nerve Stimulator Technique

Used in combination with anatomical and surface landmark knowledge

Motor –Target nerve muscles twitch

Sensory – paresthesia over target nerve distribution

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12
Q

Regional Anesthesia - Locating Nerves

Membrane potentials - What’s Resting MP?

A

– 90 mV

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13
Q

Regional Anesthesia - Locating Nerves - Membrane potentials

What’s Threshold Level? what happens when it’s reached by a stimulus?

A

– 55mV

Depolarization occurs

Propagation of Action potential

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14
Q

Regional Anesthesia - Locating Nerves

How does Nerve Stimulator work?

A

Negative Polarity Impulse

Neutralizes positive current outside nerve dropping MP

Black lead attached to needle

Red positive lead is attached to skin

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15
Q

Regional Anesthesia - Locating Nerves

Which nerves have Lowest Threshold of Ext Stim to generate AP? why?

A

Motor nerves

B/c Highly myelinated nerves

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16
Q

Regional Anesthesia - Locating Nerves

Which nerves have Higher Threshold for External Stim to generate AP? why?

A

Sensory nerves

B/c Unmyelinated nerves – slower

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17
Q

Regional Anesthesia - Locating Nerve - Generating a Action Potential

Which characteristics of a stimulus determine generation of an Action Potential?

A

Stimulus Strength and Duration

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18
Q

Regional Anesthesia - Locating Nerves

Generating a Action Potential - Strength of electrical stimulus is also known as:

A

Current Amplitude

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19
Q

Regional Anesthesia - Locating Nerves

The amount of time a stimulus must be applied to generate an Action Potential is known as:

A

Current Duration

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20
Q

Regional Anesthesia - Locating Nerves

Generating a Action Potential - Impulses of which duration are better discriminator of distance?

A

Short duration impulses

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21
Q

Regional Anesthesia - Locating Nerves

Motor impulse duration:

A

0.1 ms

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22
Q

Regional Anesthesia - Locating Nerves

Sensory impulse duration:

A

0.3 ms

Longer duration needed to reach threshold level

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23
Q

Regional Anesthesia - Locating Nerves

Nerve stimulator - Frequency:

A

1-2 Hz

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24
Q

Regional Anesthesia - Locating Nerves

Nerve stimulator - Duration:

A
  1. 1ms Motor
  2. 3 ms Sensory
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25
Q

Regional Anesthesia - Locating Nerves

Nerve stimulator - Amplitude - Start stimulator at which mA?

A

1-1.5 mA

Position needle => twitch

↓ mA, and adjust needle position …

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26
Q

Regional Anesthesia - Locating Nerves

Nerve stimulator - Amplitude - What’s the goal?

A

Goal is loss of motor response 0.3-0.5mA

Indicates that the tip of the block needle is in correct position

Never inject <0.3mA

(0.2mA by some sources)

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27
Q

Regional Anesthesia - Locating Nerves

Nerve stimulator - Why is Reliability a Problem?

A

74.5% sensitivity for needle to nerve contact

25% NO muscle twitch

even when needle actually touching nerve!!

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28
Q

Regional Anesthesia - Locating Nerves

Nerve stimulator - Reliability is a Problem. However Twitch present at:

A

0.2-0.3mA

ALWAYS INTRANURAL!!

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29
Q

Regional Anesthesia - Nerve stimulator

Technique of Locating Nerves with Series of 3 pulses (3Hz frequency), also known as:

A

Sequential Electrical Nerve Stimulation

(SENSe Mode)

30
Q

Regional Anesthesia - Nerve stimulator

Sequential Electrical Nerve Stimulation aka SENSe Mode - Technique:

A

Series of 3 pulses (3Hz frequency)

2 short: 0.1ms

1 longer: duration increases with Amplitude

0.2ms @ 0.3mA

0.42ms @ 1mA

0.84ms @ 2mA

Longer pulse reaches further in tissue

31
Q

Regional Anesthesia - Nerve stimulator

Use of Sequential Electrical Nerve Stimulation aka SENSe Mode:

A

Single twitch achieved

Needle optimized until 3 twitches present

Goal: current 0.3 – 0.5mA with 3 twitches

32
Q

Regional Anesthesia - Locating Nerves

Stimulating Needles:

A

Insulated

Direct current at the tip for precise nerve location

Blunt Bevel

33
Q

Regional Anesthesia - Locating Nerves

Technique of locating nerves that provides real time imaging of target nerves, related structures, LA injection

A

Ultrasound Guidance

1978 1st case report of using US for regional

34
Q

Regional Anesthesia - Locating Nerves

US guidance has greatly improved as evidenced by:

A

Block success

Speed of onset

Anesthetic quality of block

Becoming the gold standard in block placement!!!

35
Q

Regional Anesthesia - Locating Nerves

What are arguments againts US guidance?

A

Steep learning curve

Adds to much time to blocks

Cost of machine

No need, “…my blocks don’t fail”

36
Q

Regional Anesthesia - Locating Nerves

How is US image generated?

A

Piezoelectric Material in Probe

Electricity => material => sound waves

Sound waves => material => electricity

100 – 300 crystals in a Probe

Send out cyclical pulses of US energy and measures reflected energy that travels back to the probe

Reflected energy produces the US image you see

Probe talks (2%) and listens (98%)

The sum of all the crystals creates the US beam

37
Q

Regional Anesthesia - Locating Nerves

US probe talks (xx%) and listens (yy%)

A

Talks (2%)

Listens (98%)

38
Q

Regional Anesthesia - Locating Nerves - Ultrasound Guidance

When US encounters boundaries some energy is reflected back at the probe and the rest transmitted. What you see is called:

A

Reflection

This is what we see

39
Q

Regional Anesthesia - Locating Nerves - Ultrasound Guidance

Degradation of US by rough surfaces and heterogeneous material is also known as:

A

Scatter

40
Q

Regional Anesthesia - Locating Nerves - Ultrasound Guidance

Conversion of US into heat; This is where majority goes and it is also known as:

A

Absorption

41
Q

Regional Anesthesia - Locating Nerves - Ultrasound Guidance

Does Absorption of US waves using modern US machines poses any risk to pts?

A

There has never been any documented biological risk to Pts

42
Q

Regional Anesthesia - Locating Nerves - Ultrasound Guidance

Degradation of US wave in tissue is also known as:

A

Attenuation

Higher frequency US energy degredates more quickly

43
Q

Regional Anesthesia - Locating Nerves - Ultrasound Guidance

Higher frequency US energy degredates more quickly. What’s the clinical significance of this?

A

Use Higher frequency probes only for superficial structures

Lower Frequency probe are Better for deep structures

44
Q

Regional Anesthesia - Locating Nerves - Ultrasound Guidance

The number of sound waves per sec is also known as:

A

Frequency

2 – 15 MHz commonly used in US

Human ear 20Hz – 20 kHz

45
Q

Regional Anesthesia - Locating Nerves - Ultrasound Guidance

Distance between wave peaks:

A

Wavelength

Inversely related to Frequency

Primary determinant of lateral and axial resolution

Temporal resolution is related to frame rate (typically 30 frames/sec)

46
Q

Regional Anesthesia - Ultrasound Guidance - Probe Selection

Higher Frequency Probes are also known as:

A

Linear Probes

Better resolution of superficial structures

Up to 6 cm deep

For superficial nerve blocks and Vascular access.

IJ line, ISB, Femoral, etc

47
Q

Regional Anesthesia - Ultrasound Guidance - Probe Selection

Lower Frequency probes are also known as:

A

Curvilinear Probes

AKA – Phase Array

Visualize deeper structures

To 14 cm deep

For deeper structure Nerve blocks and Musculoskeletal assessment

Sciatic nerve, TAPs, Neuraxial assessment

48
Q

Regional Anesthesia - Ultrasound Guidance - US Modes

The US mode that displays the 2D imaging we see today is also known as”

A

B-Mode

(Brightness)

What you will typically use

49
Q

Regional Anesthesia - Ultrasound Guidance - US Modes

The US mode that displays Image of Movement over Time is also known as:

A

M-Mode

Useful in assessment of specific tissues

Heart valves, Lung

50
Q

Regional Anesthesia - Ultrasound Guidance - US Modes

The change in sound waves resulting from relative motion between source and receiver is also known as:

A

Doppler Effect

51
Q

Regional Anesthesia - Ultrasound Guidance - Doppler Mode

Red Color indicates flow moving in which direction?

A

Flow coming toward probe

Moving Toward Receiver

Higher Pitch

Useful for Vascular identification

52
Q

Regional Anesthesia - Ultrasound Guidance - Doppler Mode

Blue Color indicates flow moving in which direction?

A

Flow moving Away from probe

Moving Away from receiver

Lower Pitch

Useful for Vascular identification

53
Q

Regional Anesthesia - Ultrasound Machine

Knob that allows for optimal depth adjustment important for focusing image

A

Depth knob

Limited to probe selected

54
Q

Regional Anesthesia - Ultrasound Machine

Knob on Newer machines that can automaticaly focus

A

Focus knob

May have to set depth to focus on

55
Q

Regional Anesthesia - Ultrasound Machine

Knob that allows to adjust Brightness of image on screen

A

Gain knob

Some machines allow for gain to be adjusted at different depths independently

56
Q

Regional Anesthesia - Ultrasound Machine

Knob used to aid in detecting vascular structures

A

Doppler knob

57
Q

Regional Anesthesia - Ultrasound Guidance

What Nerves Look Like? Nerve shapes:

A

Round, oval, triangular

58
Q

Regional Anesthesia - Ultrasound Guidance

Images from US could have which three appearances?

A

Hyper-echoic

Hypo-echoic

Honeycomb

59
Q

Regional Anesthesia - Ultrasound Guidance

What are possible US Image Artifacts?

A

Shadowing

Enhancement

Reverberation

Mirror image

Velocity Error

60
Q

Regional Anesthesia - Ultrasound Guidance - Image Artifact

A significant reduction of image below solid objects is known as:

A

Shadowing

61
Q

Regional Anesthesia - Ultrasound Guidance - Image Artifact

Overly intense echogenicity behind an object (Blood vessel, cyst) is known as:

A

Enhancement

62
Q

Regional Anesthesia - Ultrasound Guidance - Image Artifact

Equally spaced bright linear echoes below an object is known as:

A

Reverberation

63
Q

Regional Anesthesia - Ultrasound Guidance - Image Artifact

Objects appearing on both sides of a highly reflective interface represents which artifact?

A

Mirror image

64
Q

Regional Anesthesia - Ultrasound Guidance - Image Artifact

Visual displacement of interface due to difference in actual US velocity versus celebrated speed (1540 m/sec) is known as:

A

Velocity Error

65
Q

Regional Anesthesia - Ultrasound Guidance

What are the two axial options for maping a structure?

A

Short Axis

Long Axis

66
Q

Regional Anesthesia - Ultrasound Guidance - Imaging a structure

A Cross sectional or Transverse view represents which axis?

A

Short Axis view

67
Q

Regional Anesthesia - Ultrasound Guidance - Imaging a structure

A Longitudinal view represents which axial view?

A

Long Axis view

68
Q

Regional Anesthesia - Ultrasound Guidance

Needle Approaches:

A

In Plane

Out of Plane

69
Q

Regional Anesthesia - Ultrasound Guidance

Professor’s Practice using US - Nerve Block:

A

Short axis View

Needle In Plane

Injection of LA under direct visualization

Placement of Catheter directly visualized

70
Q

Regional Anesthesia - Ultrasound Guidance

Professor’s Practice using US - Vascular Access:

A

Short Axis

Out of Plane

8362 T&T Exam1 (16 decks)

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