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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 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)

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Elect. impulse Mech. sound Elect. image

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U/S beam travels through different tissues attenuation Subjected to attenuation (Energy Loss). 1) absorption. 2) reflection. 3) scattering. Factors affecting attenuation : Frequency ( high high atten ) ( low low atten) Travel distance Tissue nature

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a)absorption b)reflection c)scattering d) refraction

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Lateral Resolution ( side-by-side) : to visualize two structures @ same plane & perpendicular to U/S beam improved by increasing F or transducer diameter Axial Resolution : ( above the other) : @ different tissue depths Improved by higher frequencies

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Lat. Axial

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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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Frequency is expressed in MHz number of compressions peaks /sec. ( Pr. Peaks ) High frequency = less tissue penetration = high attenuation) Low frequency = high 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. Gain TGC

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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 (10 6 Rayls) Air0.0004 Lung0.18 Fat1.34 Liver1.65 Blood1.65 Kidney1.63 Muscle1.71 Bone7.8

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Isoechoic Hypoechoic Hyperechoic Anechoic

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Veinsanechoic (compressible) Arteriesanechoic (pulsatile)

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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

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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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hyperechoic region, deep to a fluid filled structure (e.g., a vessel beam passes from area of low attenuation to higher attenuation coefficient.

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twice Reverberation artifacts U/S/waves striking a surface twice that is close to perpendicular commonly seen with highly attenuating wide-bore needles

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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 Curved probe Low frequency (2-5 MHz) Deep structures > 6cm Less resolution Hokey stick 25mm

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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) 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 ) R ( Rotation) 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.

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PROPER BODY POSITION IMPROPER BODY POSITION

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IMPROPER OPERATOR AND SCREEN ORIENTATION PROPER OPERATOR AND SCREEN ORIENTATION

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IMPROPER HAND AND ARM POSITIONS PROPER HAND AND ARM POSITION

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Transverse View (short axis view) for nerves e.g. Brachial plexus

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Aim to surround the neural structure Doughnut sign. Saline of D5% ( if PNS) Prior to L.A Aspirate 1 st

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doughnut sign. Doughnut sign. F.A

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Glut. max Sc. N.

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PROPONENTSCRITICS improve success rates simplify the technical challenges decrease performance times reduce complications 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 f Small muscle bulk = high f probe (13-6 MHz, hockey- stick, 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 0.30.5 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)

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Any Questions ?

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Interscalene Supraclavicular Infraclavicular 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 : Medial to lateral survey Trace Back Method Injectate Perfect Block = 0.15-0.3ml /kg front, in the sheath & behind

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Colour Doppler : to identify vertebral vs & branches of transverse cervical artery below C6 SCM Sc. a Sc. m medial

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Clinical tips The usual volume of L.A. 0.3-0.5ml/kg. (Corner Pocket ) above the 1 st 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

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Groove Coracoid lateral Pectoralis Maj medial Calvicle superior Better catheter insertion

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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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In Plane MCN Inject : MCN +12 & 6 Oclock Inject : MCN + 10, 2, 6 Oclock AA Below elbow surgeries

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superficial to the Ilio-Psoas Muscle (IPM) Base touching CFA, extending lateral to it. C

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Surgery on femur, knee

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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

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6-8 cm Pect

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Plus femoral : whole LL block Single for ankle & foot surgery

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TAP Thoracic Paravetebral Block Psoas Block

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TechniqueDose (mL/kg)Usual Volume (mL) Brachial plexus blocks0.15-0.3 mL/kg10 mL Femoral nerve block0.2-0.3 mL/kg10 mL Sciatic nerve0.3 -0.5 mL/kg10-15 ml Psoas (lumbar block )0.3 -0.5 mL/kg10-15 ml (David M. Polaner et al. Regional anesthesia, The Practice of PediatricAnesthesia. 4 th ed. 2009) Suggested Dosing for Local Anesthetic Volumes for Common Peripheral Nerve Blocks (David M. Polaner et al. Regional anesthesia, The Practice of PediatricAnesthesia. 4 th 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

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Dr. Amr Abdulfatah Sayed M.D. dramr2001@gmail.com