Case Report Use of Peripheral Nerve Blocks with Sedation ...
Peripheral nerve blocks 1 by dr.mushtaq
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Transcript of Peripheral nerve blocks 1 by dr.mushtaq
1
PERIPHERAL NERVE BLOCKS
DR.MU
SHTAQ
AHMA
D
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INTRODUCTION
Local anesthetic induced blockade of peripheral nerve impulses from a targeted body part with preserved level of consciousnessInjecting local anesthetic near the course of a named nerve •Surgical procedures in the distribution of the blocked nerve
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STRUCTURE OF NERVE4
CLASSIFICATION
Regional anaesthesiaCentral neuraxial blocks
Subarachnoid
epidural
Peripheral blocksTruncal
Plexus
Distal
Field & topicall
IV regional anaesthesia
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ADVANTAGES
Avoids general anaesthesia complications
• Safer than GA especially when anaesthetist is inexperienced
Pt remains awake .....pt will & helpfull for suegeon----feedback
Postops analgesia----continue / catheter
Less PONV-----less opiods need
Less post ops sedation------less confision(cognitive functions) in elderly
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Faster return to street fitness & early discharge
Cheep & relatively safe in remote location
hemodynamic stability than neuraxial & GA
Sole anesthetic technique , supplemented with monitored anesthesia care (moderate sedation) or with a "light" general anesthetic
Preemptive analgesia
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Less immunosuppressive than GA
• Hemodynamically compromised• Too ill to tolerate GA• MH• PONV is risk
Excellent alternative to GA
• Modern equipments—USG,Nerve stimulator ect
Growing popularity of RA & PNB
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DISADVANTAGES
TIME DELAY
• 15-30 MIN –Procedure & onset
PATIENT FACTORS
• Discomfort due to procedure & positioning & awake during surgery• Distress due to paralysis & numbness---postops• Managed easily—benzodiazepine & opiods
SURGEON FACTORS
• Irritated by awake & conversation with surgeon
ANAESTHETIST FACTORS
• Skill, knowledge & proper equipments
BLOCK FAILURE
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NERVE DEMAGE
• Chronic paresthesias• Permanent N damage
FAILURE RATE-----10%
• If No catheter----GA
SURGERY OUTLASTS THE BLOCK
• Respiratory failure-phrenic N Block• Seizures ---intra-arterial injection
LOCAL ANAESTHETIC TOXICITY
SPECIFIC COMLPICATIONS RELATED TO NERVE BEING BLOCKED
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CONTRAINDICATIONS OF PNB
COTRAINDICATIONS
ABSOLUTE RELATIVE
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ABSOLUTE COTRAINDICATI
ONS Patient refusal• Hemophilia• DIC• Anticoagulant drugs
Inexperienced ,incompetent anaesthetist
Major coagulation disorders & drugs
Infection at site
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Related to specific N Block
• Interscalene block• with contra lateral phrenic N paralysis• Severe pulmonary disease
Increased risk of LA toxicity
• Bilateral axillary Block• Multiple intercostal blocks
LA Allergy-anaphylaxis
• Penile block,toes,fingers etc
Ring block at site---end arteries---LA containing Adrenaline
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RELATIVE COTRAINDICATI
ONSDemented , combative & uncooperative patients
Pediatric patients
Placing block under GA
Surgeons who feel uncomfortable
Uncertain duration of surgery
Bloodstream infection
Preexisting peripheral neuropathy
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COMPLICATIONS
Local anaesthetic toxicity
Nerve damage
Vasoconstrictor problems
Infection
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Haematoma• Bleeding disorder• Anticoagulant drugs
Wrong drug• supra &infra clavicular• inter costal block
Pneumothorax• Vasovagal –mistaken as LA toxicity• Anxious pt--sedate
Psychological reaction
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1.LA TOXICITY
Immediate or delayed-----signs & symptoms (CNS & CVS)
• Maintain IV line before• Have resuscitation equipments & drugs• Always aspirate before injecting• Inject slowly & aspirate after every 3-5 ml• Stabilize needle ……short fine bore plastic tubing b/w needle & syringe (isolated needle technique)• Observe pulse,ECG & sign of IV injection
Prevention ---always
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UNIPOLAR INSULATED
NEEDLE19
2.NERVE DAMAGE
Direct by needle or by injection of LA
• Withdraw 1-2 mm after eliciting paraesthesia-before injection
Eliciting paraesthesia technique -----can damage
• 1 in 1000 blocks• Most dysaesthesiasis & paresis resolve—few months• 1 in 10000 blocks=permanent demage
Incidence---experienced anaesthetist
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RECOMMENDATIONS TO REDUCE RISK OF
NERVE DAMAGE
Use short B- bevel needle
• STOP –undo resistance & severe pain-----withdraw & then reinject
Use nerve stimulator & insulated short bevel needle
Avoid rapid,forceful injection
Avoid block under GA
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4.VASOCONSTRICTOR PROBLEM
General rule—epinephrine should not be used in concentration > 1:200000 (5ug/ml) in PNB
• Skin ----- 1:300000 or 1:400000 sufficient• Dentist –1:80000 but in small vol
Never use----areas of endarteries
Careful-----ischemic areas---varicose leg ulcer
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H/O IHD-----avoid/reduce dose---- can cause palpatation,angina,HTN• Adding sodium bicarbonate• Felypressin in stead of epinephrine• Warming the sol to body tempPregnancy-----epinephrine in significant quantity reduce placental circulation -----avoid /reduce dose
Max recommended dose of epinephrine--- 4 ug/kg
Epinephrine sol-----lower Ph--pain on injection-----can be reduced by
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INFECTION
Aseptic technique
• 1% chlorhexidine in 75% alcohol—allergic to iodine
No needle prick through infected skin except abscess
Use antiseptic Alcoholic Betadine(povidone/ iodine in ethanol)
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PREPARATION
FEW GOLDEN RULES
• Designed procedure room—block room• Insert an intravenous lin e before • Monitor (pulse oximetry,EG G , BP • Practice proper aseptic technique .• Resuscitation equipments at hand • Patients informed consent• Adequate knowledge of the correct
tehnique an d know how to handle complications
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PREMEDICATION
Anxiolysis with Benzodiazepines and/or opiods
Light sedation----elicitation of paraesthesia technique
Deep sedation----nerve stimulator
O2 supplementation----heavy sedation
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EQUIPMENTS
Nerve stimulator—ECG Electrode• different lengths ( 25- 150 mm)and (20 to 25G).• tip may angled at 15 or 30 degrees.• catheters
Unipolar insulated B-Bevel needles
Ultrasounds machine
Syringes
Local anaesthetic
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BLOCK ROOM28
EQUIPMENTS FOR PNB
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30 Screencurrent & frequency
CurrentDuration
frequency
DIAL
ANODE
CATHODE
NERVE STIMULATOR
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Cathode-connectected with needle
Anode to patientThrough ECG
electrode
IDEAL ELECTRICAL CHARACTERISTICS OF A
PNS
Constant current (DC)generator • circuit disconnection alert, • impedence alerts, • low battery and • malfunction alert
Monophasic rectangular output pulse i.e. the current flows in one direction only.
Ability to vary pulse duration (0.1 - 1ms)
Digital display of actual flowing current
Safety features like
Leads should be clearly marked to avoid confusion as to which is cathode and anode
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NERVE STIMULATOR
Current range from 0.1-6.0 mA
• Linear & constant• Low output
Pulse Frequency
• 1 Hz -Mixed nerve• 2 Hz - Sensory nerve
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SETTINGS OF PNS
Desired initial---USUALLY
• current (1 - 2mA),• pulse duration (0.1ms) and • frequency (2hz).
A threshold current of less than 0.5ma usually results in a successful block
current less than 0.2ma, increased resistance on injection or pain on injection may suggest intraneural needle placement
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WHY PATIENT DOES NOT FEEL PAIN DURING PNS?
Chronaxie is the length of time the current must be applied to the nerve to initiate an impulse
F aster conducting nerves like the A α motor nerve fibres have a smal ler chronaxie due to a shorter refractory period than the slower conducting sensory nerves like Aδ or the unmyelinated C sensory nerve fibres.
possible to stimulate a motor nerve but not the sensory nerve by using a current of smaller chronaxie (shorter time) . Th is means a motor response can be seen without producing pain-----however patient still feels TINGLING.
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CHRONAXIE OF DIFFER ENT NERVES
NERVE FEATURE CHRONAXIE-ms
C Unmyelinated 0.40
Aδ myelinated 0.17
Aα myelinated 0.05 - 0.10
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WHAT IS HZ ?
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Cycles/second
STIMULATION AND INJECTION
TECNIQUEInitial current
2-3 mAFrequency
1-2 Hz
Threshold current 0.3- 0.5 mA
Aspirate– inj LA 1-2 ml----no pain &
resistance
Aspiration test 5- 10 ml LA injected
slowly
Increase the current to initial
level
No stimulatory response -inject the remaining
drug
Recurring response - May
indicate intraneural needle
position
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USING NERVE STIMULATOR
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UNIPOLAR B-BEVEL NEEDLES
less-experienced practitioners, the shortest recommended needle is generally safest
longer needle (up to 5 cm) may also be indicated in morbidly obese or very muscular patients.
approach and the patient population--e.g., adult vs. pediatric,
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25-150 mm20-25G
INSULATED B-BEVEL NEEDLE
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TOUHY SET FOR CATHETERIZATION
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TOUHAY SET FOR PERIPHERAL NERVE CATHETERIZATION
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Stimulating catheter
CURRENT ADJUSTABLE INSULATED NEEDLE SET
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CONTINUOUS PNB SYSTEM
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ELASTOMERIC BALOON PUMP
MEDIAN NERVE CATHETER
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postoperative pain relief after hand surgery. Continuous infusion of levo-bupivacaine 0,125% - 2-5 ml/h
ULTRASOUND MACHINE
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LAPTOP U
LTRASOU
ND
MACH
INE
Direct visualization of nerves & other structures
Visualization of LA spread
Re-position of needle in case of misdistribution of LA
Avoidance of side effect- due to excess dose of LA
ADVANTAGES OF USG
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Avoidance of painful muscle contractions due to PNS
Faster onset
Longer duration of blocks
Improved quality
Blocks under GA
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Short Axis (SAX) –
• probe is aligned perpendicular to the axis of the nerve, the nerve is seen in cross section
Long Axis (LAX) –
• probe is aligned parallel to the axis of the nerve
Short Axis View is preferred due to easy identification of nerves, more stable view & allows to visualize circumferential spread of LA------ “Doughnut” sign
BASIC VIEWS ON USG53
Ultrasound scanned image obtained in the infragluteal fossa midway between the greater trochanter and ischial tuberosity with the probe oriented along the long axis of the sciatic nerve. The sciatic nerve is
seen as a long tubular structure located deep to the muscles
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Ultrasound scanned image of the femoral nerve surrounded byHypoechoic (dark) local anesthetic (L) creating a “doughnut” sign
Doughnutsign
In plane (IP) – long axis of the needle is oriented to the long axis of the probe
• Entire needle can be seen
Out of plane (OP) – the long axis of the needle is the oriented perpendicular to long axis of the probe
• Only part of the needle is seen
NEEDLE APPROACHES
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Schematic representation of the views and needle approaches for nerve blocks with ultrasound imaging. A. Short axis view of a nerve with an out-of-plane needle approach. B. Short axis view of a nerve with an in-plane needle approach. C. Long axis view of a nerve with an out-of-plane needle approach. D. Long axis view of a nerve with
an in-plane needle approach. Modified6.
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Picture showing the orientation of the ultrasound probe and the needle for placement of an interscalene block with
the in-plane needle approach
VIEW SHORT /LONG ?
TECHNIQUES
Single injection
• Intermittent dose• Continuous
Multiple injections---axillary block
• Large vol of LA in general location of cutaneous N• Minor/superficial surgery• Supplement to PNB & Neuraxial blocks
Using catheters
Field block---superficial cervical plexus block
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FEMORAL NERVE CATHETERIZATION
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CHOICE OF LOCAL
ANAESTHETICSPurpose of block
• Anaesthesia or analgesia
Onset
Duration of block
Site & area of block—vol
Degree of sensory Vs motor block
Maximum toxic dose
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LA USED FOR PNB64
CONCENTRATION
ANAESTHESTHETIC BLOCK
• 1.5-2% Plain Lignocaine----------max 3 mg / kg • 1.5-2% Lignocaine with adrenaline--- 7mg / kg • 0.5% Bupivacaine---------max 2 mg / kg• Mepivacaine 2%• o.75 % Ropivacaine-------max 2-3 mg / kg
ANALGESIC BLOCK
• 0.125% Bupivacaine, 0.2% Ropivacaine, • Opiods, Clonidine.
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PNB PLACEMENT TECHNIQUES
Anatomy
Evoked paraesthesia
Nerve stimulator (goal 0.2-0.5 mA)
Ultrasound guided
Percutaneous electrical guidance
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3
4
5
6
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OTHERS1.Droppler2.CT3.MRI
LA-- in Perineural
area
CONCLUSION
Not as a first case
Centralize your equipment
Select proper block
Good knowledge of anatomy
Know about potential complications on treatment
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Select right patient
Pick the right surgeon
Be confident about your block
But still if you fail--Failures are the stepping stones for success
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QUESTION 1
Anaesthetist was performing a peripheral nerve block with help of nerve stimulator & ultrasound ……he introduces insulated short bevel 22G needle at location…….& observe muscle contractions in nerve related area at 0.3 mA(n=0.2-o.5 mA).after injecting 1ml of LA muscle cotractions disappear.He injects rest of 10ml sol in incremental doses.Surgeon strat surgery after5 minutes but Pt feels pain……..Anaesthetist is quite sure about block……WHY Pt. feels pain ??
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QUESTION 2
Anaesthetist introduced insulated long bevel needle to block a peripheral nerve & observes muscle contractions at 0.2 mA ……….while he injected 1ml of LA ,……he had to stop the injection due to severe pain………moreover muscle contraction did not disappeared ..
• WHY SEVERE PAIN ON INJECTION…?• WHY MUSCLE CONTRACTIONS DID NOT DISAPPEAR ON INJECTING
LA….?• WHAT SHOULD BE THE ACTION OF ANAESTHETIST NOW…?
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THANKS
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