Regional Anesthesia Flashcards
Regional anaesthesia satisfies which of the components of the triad of anaesthesia?
Analgesia
Muscle relaxation
Regional anaesthesia can be divided into…
Central and peripheral techniques
Central techniques for regional anaesthesia include?
Neuraxial blocks:
Spinal
Epidural
Caudal
Peripheral techniques for regional anesthesia include?
Plexus blocks (i.e. brachial plexus blocks) Single nerve blocks
What are the 3 ways of performing regional anesthesia?
Single shot
Continuous catheter
Injecting LA directly into a vein (provided venous flow is impeded by a tourniquet)(Bier’s block)
Indications for regional anaesthesia?
Surgical anaesthesia alone
Supplemental to and in conjunction with GA
Post-op pain control
Acute and chronic pain management
How does regional anesthesia block the surgical stress response?
Elimination of painful stimuli from operation site
Blockade of efferent sympathetic nerves to endocrine glands
Eliminates/greatly reduces metabolic and endocrine changes seen after surgical operations
Advantages of regional anaesthsia?
Pre-emptive analgesia Post-op analgesia Less physiological derangement Rapid post-op recovery No need for airway instrumentation Reduced incidence of complications associated with GA (i.e. PONV, aspiration, malignant hyperthermia) Decreased incidence DVT in orthopaedic surgeries Reduction in surgical stress response
Examples of surgeries that use Bier’s block?
Carpal tunnel release
Reduction of Colle’s fractures
Hand surgery
How to perform a Bier’s block?
Draw up a 5ml ampoule of 2% lignocaine and mix with 15ml saline (to get a 0,5% solution) x 2
Site a small 22G IV cannula on dorsum of hand needing surgery
Site a second IV cannula on the other arm
Elevate operative arm and exsanguinate with an elastic compression bandage
Inflate double cuff tourniquet to 100mmHg above SBP, first the distal and then the proximal
Leave only the proximal cuff inflated
Remove compression bandage
Slowly inject 30-40ml 0,5% lignocaine into vein
Anaesthesia established after 5-10 min
Inflate distal cuff and deflate proximal cuff when tourniquet pain starts
Slowly deflate tourniquet at end of surgery
The 5 types of regional anesthesia are?
Topical application Infiltration anaesthesia IV regional anaesthesia of the arm (Bier's block) Peripheral nerve block Neuraxial block
Name the types and examples of topical application LA?
Aerosolised (i.e. 2-4% lignocaine for vocal cords)
Cream (EMLA or Ametop - Amethocaine)
Direct application (drops)
E.g. minor eye surgery, laryngoscopy or bronchoscopy, incision and drainage of a tonsillar abcess (quinsy), cystoscopy, venepuncture sites
What is infiltrative anaesthesia?
Injection of LA solutions intradermally or subcutaenously to produce anesthesia at the site of surgery
Examples of plexus blocks?
Brachial plexus
Lumbosacral plexus
What instrumentation will aid in the location of nerves for a peripheral nerve block?
Peripheral nerve stimulators
Ultrasound
Examples of commonly used peripheral nerve blocks?
Digital nerve block for finger surgery
Wrist block for hand surgery
Intercostal nerve block for fracture pain relief
Intra-orbital eye block for cataract surgery
Femoral/sciatic nerve block for lower limb surgery
Ilio-inguinal nerve block for inguinal surgery (i.e. hernia)
Contra-indications of neuraxial anaesthesia?
Same as for regional anaesthesia as a whole PLUS Absolute: Severe hypovolaemia/shock Increased ICP/active intracranial disease Fixed CO states Relative: Pre-existing neurological deficits Severe spinal deformity Prior back surgery at site of injetion
What is the site of action of neuraxial blocks?
Nerve root
Explain the ‘differential block’ in neuraxial techniques?
Concentration of LA decreases with increasing distance from injection site Sympathetic block (temperature sensitivity) is 2 dermatomes higher than a sensory block (pain, pressure, light touch), which is 2 dermatomes higher than a motor block
What layers does the needle penetrate for neuraxial techniques?
Skin Subcutaenous tissue Supraspinous ligament Interspinous ligament Ligamentum flavum Epidural space (Dura mater) (CSF)
Spinal technique?
Strict sepsis
IV line with fluids running
All monitors on and O2 if needed
Patient sitting or in lateral position (chin and kneed bent)
Sterile spinal pack opened by assistant
LA for skin infiltration and intrathecal injection drawn up
Clean wide area of patients back
Drape the sterile site
Site of puncture determined (L3-L4 OR L4-L5)
LA infiltration with 2% lignocaine and 25G small brown needle
Introduce spinal needle (25G pencil point or 22G Quincke) through skin in mid-line and directed slightly cephalad
Pierce dura with slight loss of resistance
Remove stylet and confirm CSF
Attach syringe and aspirate to ascertain free CSF flow, inject LA slowly, aspirating occasionally to ensure correct positioning
Pre-op care of the regional anaesthesia patient?
Same as for GA
Intra-op care of the regional anaesthesia patient?
Re-assure patient Make comfortable Monitor CVS and respiratory parameters Facemask O2 if required Forced air warmer Additional sedation may be necessary
Post-op care of the regional anaesthesia patient?
Avoid injury to limbs insensitive to pain
Check that the block is receding
Ensure no urinary retention
If block does not recede and motor function does not return within 4 hours, be alerted to complicacations
Epidural haematoma needs to be evacuated within 6-8hours
Epidural catheter should be removed by anesthetist and tip should be intact
Caution in patient on anticoagulation
Spinal cord and subarachnoid spinal space levels?
Adults:
SC ends L1/L2
Subarachnoid space from foramen magnum to S2
Children:
SC ends L2/L3
Subarachnoid space from foramen magnum to S3
Advantages of epidural over spinal?
Top up doses or constant infusions may be delivering by means of an epidural catheter
Graduated blocks can be performed (level is slowly increased by additional incremements into catheter) to avoid sudden haemodynamic changes
Epidural technique?
Same preparation as for spinal
May be injected at a thoracic or lumbar level
16G or 18G Tuohy needle with a blunt bevel (reduces risk of dural puncture)
Identification of epidural space: loss of resistance (sudden ease of saline injection)
Hyperbaric vs isobaric LA?
Hyperbaric: with added dextrose, makes solution “heavy”
Isobaric: plain bupivicaine or lignocaine
What is the function of adding an opiate to a spinal?
Extends duration of action and enhances analegsia
Which needs a greater dose? Spinal or epidural?
Epidural dose»_space; spinal dose
What is caudal anaesthesia?
A sacral epidural
Mostly performed on paediatric patients as an adjunct to GA
Indications in paediatrics for a caudal?
Major abdominal surgery
Major orthopaedic surgery of lower limb
Urogenital surgery
Caudal technique?
Place patient in lateral position
ID sacral hiatus and posterior superior iliac spines
Palpate sacral cornuae (horns) on wither side of hiatus
Insert caudal needle here, angled caudally
Loss of resistance felt when passing sacro-coccygeal ligament
LA injected
Aspirate regularly to exclude blood/CSF
Caudal doses?
Adults: 25-30 ml 0,5% bupivicaine (6-8hours)
Children:
Lumbo-sacral block: 0,5 ml/kg 0,25% bupivicaine
Thoraco-lumbar block: 1,0 ml/kg 0,25% bupivicaine
Mid-thoracic block: 1,25 ml/kg 0,25% bupivicaine
Disadvantages of Regional Anaesthesia?
Requires degree of patient cooperation
Skill required
All blocks have a small but finite failure rate
Time factor (can take up to 30min to work)
Risk of systemic toxicity
Contraindications for Regional Anaesthesia?
Uncooperative patient (deaf, psyche etc.) Coagulopathy or bleeding disorder (aim for platelets >75 and INR
