Basics  of  Ultrasound  Guided  Nerve  Blocks  

Dr  Shiv  Kumar  Singh  Consultant  Anaesthesia    

Royal  Liverpool  University  Hospitals  shvkmrsngh@aol.com  

www.anaesthesiaworld.com    

Know  your  machine  

             Probes:  Frequency  and  ResoluJon  

Curvilinear Probe: Low frequency , deeper structure

Linear Probe: High Frequency, superficial structures

High (8–12 MHz), Medium (6–10 MHz), and Low (2–5 MHz)

Transducer  selecJon  

•  Where  is  the  area  of  interest?  

•  Deep/superficial  

•  Size  of  scanning  window  

•  Size  of  paJent?                                                                                                                        

Frequency  vs  resoluJon  

• Higher  frequency  =  beRer  resoluJon  

•  Decreased  penetraJon  

•  Superficial  scanning  

Aspect  markers  

Aspect  Marker  

The  aspect  marker  (green    dot)  on  the  screen  corresponds    to  the  NOTCH  on  this  probe    NOT  THE  DOT    

                 Important  Knobs  on  the  machine  

                   Preset  Knob:  Most  Important  

Press patient button and once the screen appears, use track pad to move the arrow and then press select

Nerve  Preset  

•  Set  of  sophisJcated  algorithms  that  the  machine  uses  automaJcally,  appropriate  to  what  you  are  doing  

•  Gives  the  machine  some  idea  of  what  you  want  to  do!  

•  Correct  preset,  a  great  starJng  point  

Gain  Knobs  

Increase  gain  =  Brighter  image  

Decrease  gain  =  darker  image  

Adjust  gain  unJl  same  level  of  brightness  displayed  regardless  of  depth  

Gain  se\ngs  

Too  dark  

Balanced  

Too  bright  

             Auto  gain:  Similar  to  preset  

Micro Maxx

M Turbo

Depth  Knobs  

Adjusts  displayed  data  

Start  deep  to  see  all  anatomy  

Adjust  to  fill  display  with  area  of  interest    

Depth  Too  

shallow  Too    deep  

Correct    depth  

As  you  increase  the  depth  the  widow  will  become  narrower  

This  

This  to  

AdjusJng  the  frequency  

These  are  called  RESoluJon,  GENeral  and  PENetraJon  

Use  highest  resoluJon  you  can  without  compromising  far  field  echoes  and  without  impacJng  frame  rate  

Frequency  buRons  

Colour  Doppler  

Flow toward transducer = RED

Flow away from transducer = BLUE

     For  the  machine:                                            Keep  it  simple  

Get  used  to  working  with:-­‐  

•  PRESET  

•  DEPTH  

•  GAIN  

•  FREQUENCY  

•  COLOUR  DOPPLER  

A`er  you  know  the  machine;  know  your  anatomy  

Landmarks  are  sJll  important  

Know  your  anatomy  

Can’t  see  anything!!!  

apply  PART(S)  

What  is  PART(S)  

•  Pressure  

•  Alignment  by  

•  RotaJon    and  

•  Tilt  and  Slide  

PART  

Apply little pressure and tilt the probe so that it is perpendicular and parallel to the structure you are trying to visualize

Beam not returning to the probe

PART  

Medial  Lateral  

Caudal    

Cranial  

RotaJon  on  the  Axis  

Try  this  with  Femoral  Nerve  

Can  you  idenJfy  the  femoral  nerve  in  the  next  pic?  

Where  is  the  nerve?  

Where  is  the  nerve?  

Fascia Lata

Fascia Iliaca Femoral Artery

Femoral Nerve

Try  again  and  again  

•  Not  all  paJents  are  the  same  

•  ECHOGENIC  Vs  PHOTOGENIC:  Some  people  are  more  photogenic  than  others,  similarly  some  are  more  echogenic  than  others  

•  Anatomy  is  variable,  so  don’t  expect  to  see  textbook  picture  all  the  Jmes  

A`er  idenJfying  the  nerves  

Next  difficult  part  is  hand  eye  co-­‐ordinaJon  

Improving  Needle  visibility  

Learning  Hand-­‐eye-­‐coordinaJon  

                           Everything  in  your  “field  of                                  vision”  (ergonomics)  

NOT  THIS!!!  

                   PracJce  hand  eye                                  coordinaJon  

•  Use  Phantoms  (Costly)  

•  Or  Turkey/chicken            Legs!!!    

•  Or  make  your  own    

       phantoms  using  jelly    

       or  agar  

                           Why  do  we  fail  to  visualize  the  needle  

1mm thick beam

                         Beam:  Credit  card  thin,  1mm  slice  

Aligning the thin needle with the beam can be difficult and need practice

                       Beams  need  to  return  back!!!  

If the needle is more than 60o to the probe, you will not visualise the needle

                         Align  by  Jlt,  rotaJon  and  slide  

Heel  in  maneuver    

Method of reducing the angle between the needle and the probe to collect the returning beam

                         Heel  in  maneuver:  collecJng  the  returning  beam    

The  beam  from  the  probe  are  hi\ng  it  perpendicularly  

                     Move  only  one  part  at  a  Jme  

•  Only  move  the  ultrasound  transducer  or  the  needle  to  opJmize  procedure  needle  Jp  visualizaJon  

•  USRA  is  a  dynamic  process  

•  Do  not  inject  LA  Jll  you  can  visualise  the  Jp  

Good  Luck