Field depth < 2.0 cm
Wrist, ankle block
Field depth 2- 3 cm
Interscale ( LA anesthetic around the root or trunk of brachial plexus at the level of C6 in between the scalene muscle )
Axillary Brachial plexus block
Field depth 3- 4 cm
Femoral
Supraclavicular
Tranversus abdominis plane block
Field depth 4-7 cm
Infraclavicular ( cords and terminals )
Popliteal
Subgluteal sciatic nerve block
Field depth 7.0 cm 10.0 cm
Pudendal block
Gluteal sciatic nerve ( subgluteal is 4-7cm )
Lumbar plexus block
Field depth > 10.cm
Anterior approach to sciatic nerve
Gain
Brightness
Two function button of Gain
Gain and TGC ( Time-gain compensation )
Excessive or Inadequate gain
The boundaries of the tissues get blurry
You lose information
Optimal gain for peripheral nerve
The gain at which Best contrast that you get between the muscle and the adjacent connective tissue
You want a nice contrast between the muscle and the adjacent connective tissue !
ASRA Recommendations
1- visualize : muscle, fascia , bones and blood vessels
2- ID the nerve or plexus on shot-Axis with depth set at 1 cm deep to target nerve
3- Confirm normal anatomy and recogonize variations ..we don’t all have the same body!!
4- Chose the safest most effective needle approach
5- Aseptic needle insertion technique
6- Follow the needle in real time live as you advance it toward the target
7- Secondary stimulation technique , ex: nerve stimulator
8- Needle tip in the correct position ? Inject Small volume of test solution
9- Adjust your needle as necessary for optimal perineural LA spread
10- Safety: Aspiration, monitoring , patient response, assessment, resistance to injection
US machine set up on which side of patient
Opposite side
Needle selection for Peripheral nerve block
Large bore 17G: easily visualized directed under US -deep blocks -i.e Infraclavicular when needle in steep (>45) angle .
Smaller bored 22 G: More diff to see , but still easily visualized in superficial blocks i.e. Axillary block when needle angle is shallow PLUS more comfortable for awake patient
Insulated needle is what exactly ?
Electrical current is concentrated at the needle tip and a wire attached to the needle hub connects to a nerve stimulator .
Used for 1) accurately ID specific nerve = improve adequacy of block .
What is Peripheral Nerve Stimulation via insulated needle ?
Method of using low intensity electric current ( 0-5mA current at a set 1-2 Hz interval) to elicit a response/muscle twitch .
When an insulated needle close to to a motor nerve = muscle contraction
How is the circuit completed in Insulated needle PNS?
Ground electrode is attached to the patient to complete the circuit
Needle technique for US . What is the position and what is visualized ?
Position -Inline and parallel to transducer
Both shaft and tip are seen
Transducer prep
Sterile sheath
Gel inside sheath
Smooth sheath cover over transducer = no wrinkles that can impede full contact
Rubber band = transducer can’t move inside sheath
Lots of sterile gel to skin
Peripheral nerve block technique
2 person: get an assistant !
Monitors : BP, EKG, Pulse ox
OXYGEN/SUCTION/EMERGENCY MEDS / CRASH CART/ INTRALIPID
Make sure your nerve stimulator and your connecting cables work before starting
Premedicate but DON’t OVERSEDATE = benzo/opioid for comfort but pt should always be able to respond to verbal cues
Proper patient position = favorable for clinician and comfy for patient
Negative pole vs Positive Pole location
Negative pole connected to the needle N-N
Positive pole connected to the Pt Skin P- S
Negative - Needle
Positive - Skin
You have started set for the block , start the procedure ..
1 Time -Out
2 Disinfect skin - sterile field
3 Connect the PNS needle to the nerve stimulator- only turn it on after in subQ tissue = before will cause pain then Deliver 2 mA!!
Apply gel to transducer
Position transducer on skin- always keep within sterile field
Introduce needle / start procedure !
You introduced the PNS needle in SubQ now what ?
(Slide 23)
Once the muscle you are looking for is obtained reduce 1)current 2) intensity and 3)amplitude GRADUALLY and advance needle SLOWLY
When is Optimal LA injection reached ?
When muscle contraction is maintained at a current between 0.2 - 0.5 mA
<0.2mA eliciting muscle contraction= increased risk of intraneural injection = neural damage!