Peripheral nerve blocks 1 by dr.mushtaq
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Peripheral nerve blocks 1 by dr.mushtaq
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- 3. INTRODUCTION Local anesthetic induced blockade of peripheral nerve impulses from a targeted body part with preserved level of consciousness Injecting local anesthetic near the course of a named nerve • Surgical procedures in the distribution of the blocked nerve 3
- 6. 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 6
- 7. 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 7
- 8. Less immunosuppressive than GA Excellent alternative to GA • Hemodynamically compromised • Too ill to tolerate GA • MH • PONV is risk Growing popularity of RA & PNB • Modern equipments—USG,Nerve stimulator ect 8
- 9. 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 9
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- 11. NERVE DEMAGE • Chronic paresthesias • Permanent N damage FAILURE RATE-----10% SURGERY OUTLASTS THE BLOCK • If No catheter----GA LOCAL ANAESTHETIC TOXICITY SPECIFIC COMLPICATIONS RELATED TO NERVE BEING BLOCKED • Respiratory failure-phrenic N Block • Seizures ---intra-arterial injection 11
- 13. ABSOLUTE COTRAINDICATIONS Patient refusal Inexperienced ,incompetent anaesthetist Major coagulation disorders & drugs • Hemophilia • DIC • Anticoagulant drugs Infection at site 13
- 14. 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 Ring block at site---end arteries---LA containing Adrenaline • Penile block,toes,fingers etc 14
- 15. RELATIVE COTRAINDICATIONS Demented , combative & uncooperative patients Pediatric patients Placing block under GA Surgeons who feel uncomfortable Uncertain duration of surgery Bloodstream infection Preexisting peripheral neuropathy 15
- 16. COMPLICATIONS Local anaesthetic toxicity Nerve damage Vasoconstrictor problems Infection 16
- 17. Haematoma • Bleeding disorder • Anticoagulant drugs Wrong drug Pneumothorax • supra &infra clavicular • inter costal block Psychological reaction • Vasovagal –mistaken as LA toxicity • Anxious pt--sedate 17
- 18. 1.LA TOXICITY Immediate or delayed-----signs & symptoms (CNS & CVS) Prevention ---always • 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 18
- 20. 2.NERVE DAMAGE Direct by needle or by injection of LA Eliciting paraesthesia technique -----can damage • Withdraw 1-2 mm after eliciting paraesthesia-before injection Incidence---experienced anaesthetist • 1 in 1000 blocks • Most dysaesthesiasis & paresis resolve—few months • 1 in 10000 blocks=permanent demage 20
- 21. RECOMMENDATIONS TO REDUCE RISK OF NERVE DAMAGE Use short B- bevel needle Use nerve stimulator & insulated short bevel needle Avoid rapid,forceful injection • STOP –undo resistance & severe pain-----withdraw & then reinject Avoid block under GA 21
- 22. 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 22
- 23. H/O IHD-----avoid/reduce dose---- can cause palpatation,angina,HTN Pregnancy-----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 • Adding sodium bicarbonate • Felypressin in stead of epinephrine • Warming the sol to body temp 23
- 24. INFECTION Aseptic technique No needle prick through infected skin except abscess Use antiseptic Alcoholic Betadine(povidone/ iodine in ethanol) • 1% chlorhexidine in 75% alcohol— allergic to iodine 24
- 25. 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 25
- 26. PREMEDICATION Anxiolysis with Benzodiazepines and/or opiods Light sedation----elicitation of paraesthesia technique Deep sedation----nerve stimulator O2 supplementation----heavy sedation 26
- 27. EQUIPMENTS Nerve stimulator—ECG Electrode Unipolar insulated B-Bevel needles • different lengths ( 25- 150 mm)and (20 to 25G). • tip may angled at 15 or 30 degrees. • catheters Ultrasounds machine Syringes Local anaesthetic 27
- 28. BLOCK ROOM28
- 31. NERVE STIMULATOR31 Cathode- connectected with needle Anode to patient Through ECG electrode
- 32. IDEAL ELECTRICAL CHARACTERISTICS OF A PNS Constant current (DC)generator 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 • circuit disconnection alert, • impedence alerts, • low battery and • malfunction alert Leads should be clearly marked to avoid confusion as to which is cathode and anode 32
- 33. NERVE STIMULATOR Current range from 0.1-6.0 mA • Linear & constant • Low output Pulse Frequency • 1 Hz -Mixed nerve • 2 Hz - Sensory nerve 33
- 34. 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 34
- 35. 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. 35
- 36. CHRONAXIE OF DIFFER ENT NERVES NERVE FEATURE CHRONAXIE-ms C Unmyelinated 0.40 Aδ myelinated 0.17 Aα myelinated 0.05 - 0.10 36
- 37. WHAT IS HZ ?37Cycles/second
- 38. STIMULATION AND INJECTION TECNIQUE Initial current 2-3 mA Frequency 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 38
- 40. 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, 40 25-150 mm 20-25G
- 43. TOUHAY SET FOR PERIPHERAL NERVE CATHETERIZATION 43 Stimulating catheter
- 44. CURRENT ADJUSTABLE INSULATED NEEDLE SET 44
- 45. 45
- 48. MEDIAN NERVE CATHETER 48 postoperative pain relief after hand surgery. Continuous infusion of levo-bupivacaine 0,125% - 2-5 ml/h
- 51. 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 USG51
- 52. Avoidance of painful muscle contractions due to PNS Faster onset Longer duration of blocks Improved quality Blocks under GA 52
- 53. 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
- 54. 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 54
- 55. 55 Ultrasound scanned image of the femoral nerve surrounded by Hypoechoic (dark) local anesthetic (L) creating a “doughnut” sign Doughnut sign
- 56. 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 APPROACHES56
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- 58. 58
- 59. 59 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.
- 60. 60 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 ?
- 61. TECHNIQUES Single injection Multiple injections---axillary block Using catheters • Intermittent dose • Continuous Field block---superficial cervical plexus block • Large vol of LA in general location of cutaneous N • Minor/superficial surgery • Supplement to PNB & Neuraxial blocks 61
- 63. CHOICE OF LOCAL ANAESTHETICS Purpose of block • Anaesthesia or analgesia Onset Duration of block Site & area of block—vol Degree of sensory Vs motor block Maximum toxic dose 63
- 64. LA USED FOR PNB64
- 65. 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. 65
- 66. PNB PLACEMENT TECHNIQUES Anatomy Loss of resistance and tactile feedback Evoked paraesthesia Nerve stimulator (goal 0.2-0.5 mA) Ultrasound guided Percutaneous electrical guidance 1 2 3 4 5 6 66 OTHERS 1.Droppler 2.CT 3.MRI LA-- in Perineural area
- 67. CONCLUSION Not as a first case Centralize your equipment Select proper block Good knowledge of anatomy Know about potential complications on treatment 67
- 68. Select right patient Pick the right surgeon Be confident about your block But still if you fail--Failures are the stepping stones for success 68
- 69. 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 ?? 69
- 70. 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…? 70
- 71. THANKS 71