Transcript Ultrasound guided Nerve blocks “Seeing is Believing

Dr. Amr Abdulfatah Sayed (M.D.)
Associate prof. of Anesthesia, Chronic Pain Management
Ain Shams Univ. , Cairo , EGYPT
Oct. 2012
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NO clicks
No pops
No paresthesia
No trans-arterial
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Under vision in real
time
How L.A. behaves
How catheter lodge
Reinjection with
inconsistent block
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Mechanical sound energy.
Sinusoidal.
Pulse longitudinal wave
alternating compression
(high pressure) & rarefaction
(low pressure)
P = pressure
T = wave length
F= frequency
distance one peak to other peak
is a wavelength
one peak to other peak is a
wavelength
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electric field is applied to
a piezoelectric crystals.
mechanical distortion of
the crystals
sound waves (i.e.
mechanical energy)
Elect.
impulse
Elect.
image
Mech.
sound
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U/S beam travels through different tissues
Subjected to attenuation (Energy Loss).
1) absorption.
2) reflection.
3) scattering.
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Factors affecting attenuation :
Frequency ( high
 Travel distance
 Tissue nature
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high atten ) ( low
low atten)
The Ultrasound Transducer Source of Energy and
Image
Energy progressively degraded (attenuate) as it enters
deeper tissues
lateral & axial resolution improved with higher
frequency transducers, decrease with increasing tissue
depth
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Structures typically seen as hyperechoic or
echogenic include bone, tendons, pleura, and
nerves below the clavicles.
In contrast, blood, fluids, and nerves above
the clavicles are hypoechoic.
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Generally speaking, a high frequency wave is
subjected to high attenuation thus limiting
tissue penetration
low frequency wave is associated with low
tissue attenuation and deep tissue
penetration.
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receiver amplification is
called the Gain.
Gain increases overall
brightness of the entire
image, including the
background noise.
(TGC) selectively amplify
the weak returning
(attenuated) signals from
deeper structures.
TGC
Gain
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Tissue impedance
resistance of a tissue to
US passage
Strong wave reflection =
hyperechoic (white)
Weak reflection=
hypoechoic (greyish)
No reflection =
anechoic. (black)
Body Tissue
Acoustic Impedance
(106 Rayls)
Air
0.0004
Lung
0.18
Fat
1.34
Liver
1.65
Blood
1.65
Kidney
1.63
Muscle
1.71
Bone
7.8
Isoechoic
Hypoechoic
Hyperechoic
Anechoic
Veins
anechoic (compressible)
Arteries
anechoic (pulsatile)
Fat
hypoechoic with
irregular hyperechoic
lines
Muscles
heterogeneous
(mixture of
hyperechoic lines
within a hypoechoic
tissue
background)
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Bone : High tissue
impedance
Strong reflection
++ hyperechoic lines
with a hypoechoic
shadow underneath
fascicular
or honeycomb appearance
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Reflection is high for air
Air has extremely low
acoustic impedance (0.0004)
acoustic coupling medium
on the transducer surface to
eliminate any air pockets
Otherwise ultrasound waves
will be reflected limiting
tissue penetration.
large dropout artifact.
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deep to hyperechoic
bone outline is a beam
attenuation
Ultrasound beams
subjected to
attenuation by bone,
penetration is severely
impeded.
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Linear array probe
High frequency( >
6MHz)
Superficial structures
Depth max. 6 cm
High clarity
Hokey stick 25mm
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Curved probe
Low frequency (2-5
MHz)
Deep structures > 6cm
Less resolution
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Transducer marker
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Needle probe
orientation
Handling of probe
resting hand on pt.
body
Non dominant hand
More steep angle of
needle = difficult
visualization
IN PLANE (IP)
OUT OF PLANE (OOP)
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Large bore needles (e.g. 17 G)
 Better visualization
 easier to direct.
 Preferred for deep blocks
(e.g. infraclavicular block,
sciatic ) when needle
insertion is steep (> 45
degrees)
Smaller bore needles (e.g. 22
G)
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easily visualized for more
superficial blocks e.g., the
axillary block, when the
angle of needle insertion is
shallow.
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A ( Alignment )
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R ( Rotation)
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T ( Tilting)
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Proper handling the transducer and the needle,
to view the screen, and to position the patient
are essential for block success and to avoid
operator fatigue and body injury.
IMPROPER BODY POSITION
PROPER BODY POSITION
PROPER OPERATOR AND
SCREEN ORIENTATION
IMPROPER OPERATOR AND
SCREEN ORIENTATION
IMPROPER HAND AND ARM
POSITIONS
PROPER HAND AND ARM
POSITION
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Aim to surround the
neural structure
Doughnut sign.
Saline of D5% ( if
PNS) Prior to L.A
Aspirate 1st
doughnut” sign.
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F.A
F.A
Doughnut sign.
Glut. max
Sc. N.
PROPONENTS
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improve success rates
simplify the technical
challenges
decrease performance
times
reduce complications
CRITICS
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lack of controlled trials
High expense
equivocal nature of
images
Requires sustained
training.
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Adults USGRA can be performed in children
Plan @ pre-op visit
Explain for partents ( legal guardian )
Ped. USGRA performed under anesthetized
light sedation ( esp. > 8 yrs , diff. airway ,MH).
EMLA 1 hrs in advance
Small muscle bulk = high f probe (13-6 MHz, “hockeystick,” 26-mm footprint)
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Insulated needle
Epidural 22G for catheter ( long term post op).
In-plane > out off plane
Calculate full dose ( volume 0.3–0.5 mL/kg )
< 5 yrs Bupi. 0.25 %, Ropi. 0.2%, Lido 1%
5 yrs Bupi. 0.375 %, Ropi. 0.5% +epi. (Allison
Ross et al. , A & A July 2000 vol. 91 no. 1 16-26)
Any Questions ?
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Interscalene
Supraclavicular
Infraclavicular
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Axillary
Median N.
Ulnar N.
Radial N.
0.25 -0.5ml /kg
0.25% bupivacaine , 1% lidocaine , 0.25% ropivacaine
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Most cranial approach
Not popular ( Phrenic N.)
Indication : shoulder ,
upper arm, lateral clavicle.
Scanning :
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Medial to lateral survey
 Trace Back Method
Injectate “Perfect Block”=
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0.15-0.3ml /kg
front, in the sheath & behind
medial
SCM
Sc. a
Sc. m
Colour Doppler : to identify vertebral vs &
branches of transverse cervical artery below C6
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Clinical tips
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The usual volume of L.A.
0.3-0.5ml/kg.
(Corner Pocket ) above
the 1st rib, next to
subclavian a. to anesthetize
the lower trunk.
In plane approach is a
must
All U.L
???? Shoulder surgery
2/3 L.A. @ Corner
Local anesthetic injected posterior to the
axillary artery resulting in a U shape spread around the artery
is associated with complete blockade of the arm, forearm and hand.
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Below elbow surgeries
AA
MCN
In Plane
Inject : MCN +12 & 6 O’clock
Inject : MCN + 10 , 2 , 6 O’clock
C
superficial to the Ilio-Psoas Muscle (IPM)
Base touching CFA, extending lateral to it.
Surgery on femur , knee
L4
L3
Dermatomes and osteotomes of the lumbosacral plexus are
illustrated. (Courtesy of Mayo Foundation.)
The American Society of Regional Anesthesia and Pain
Medicine. 2005
Plus femoral : whole LL block
Single for ankle & foot surgery
Technique
Dose (mL/kg)
Usual Volume (mL)
Brachial plexus blocks
0.15-0.3 mL/kg
10 mL
Femoral nerve block
0.2-0.3 mL/kg
10 mL
Sciatic nerve
0.3 -0.5 mL/kg
10-15 ml
Psoas (lumbar block )
0.3 -0.5 mL/kg
10-15 ml
Suggested Dosing for Local Anesthetic Volumes for Common Peripheral Nerve
Blocks (David M. Polaner et al . Regional anesthesia , The Practice of PediatricAnesthesia. 4th ed. 2009)
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Real time
L.A. behaves
Less L.A.
Cath. Fixation
Less vasc. & pleural insults
L.A. Re-deposition @ insufficient block
All benefits of R.As
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Neuronal ( neuritis, neuro – praxia)
L.A. toxicity
Vascular trauma
Pleural
Dr. Amr Abdulfatah Sayed M.D.
[email protected]