Day 5: Local and Regional Anaesthesia Flashcards
what is regional anesthesia
Regional anaesthesia affects one part of the body only
which parts of the the anaesthetic triad does regional anaesthesia provide
Analgesia
Muscle Relaxation
No Hypnosis (additional sedation may be given
benefits of regional anaesthesia
- pre emptive analgesia
- post op analgesia
- hemodynamically stable (caution: neuroaxial)
- rapid recovery post- op
- reduced surgical stress response
- reduced GA complications
*avoids airway instrumentation and its complications - reduced PONV
- reduced DVT in ortho
types of regional anaesthesia
-topical
- wound infiltration
-intravenous regional anesthesia of the arm (Bier’s block)
-peripheral nerve blocks/ plexus blocks
- central neve block (neuraxial blockade)
topical anaesthesia
-aerosolised (25% lignocaine)
- topical cream
-direct application (drops)
division of infiltration
subcutaneously
intradermally
infiltration: subcutaneously
-Often given into wounds at the end of surgery, under GA
-Provides some postoperative analgesia
-Wound infusion catheters can give hours of postoperative pain relief
infiltration: intradermally
Suturing of wounds
Local before siting of large IV lines, central lines, arterial lines, spinals & epidurals
peripheral nerve blockade division
-single nerve blocks
-plexus blocks
-deep infiltration
single nerve blocks
Femoral, popliteal, radial etc
plexus blocks
Brachial plexus blocks, e.g.
-Supraclavicular (forearm surgery)
-Interscalene (shoulder surgery
deep infiltration
Transversus abdominus plane block (TAP block)
nerve location
use ultrasound
division of neuraxial blockades
spinal anesthesia
epidural anesthesia
What is spinal anaesthesia?
Spinal anaesthesia involves the injection of a local anaesthetic into the cerebrospinal fluid (CSF) within the subarachnoid space.
How quickly does spinal anaesthesia act?
Spinal anaesthesia is rapidly acting, providing relatively quick onset of anaesthesia.
What does spinal anaesthesia achieve in terms of sensory and motor functions?
Spinal anaesthesia achieves both sensory and motor block, effectively numbing the area and reducing motor function.
What level of anaesthesia can spinal anaesthesia provide?
Spinal anaesthesia can provide sufficient anaesthesia for surgery, making it suitable for various surgical procedures.
Where is the local anaesthetic injected in spinal anaesthesia?
The local anaesthetic is injected into the CSF within the subarachnoid space.
What are the primary effects of spinal anaesthesia?
Spinal anaesthesia results in both sensory and motor block, effectively numbing the area and reducing motor function.
What is epidural anaesthesia?
Epidural anaesthesia involves the injection of a local anaesthetic into the epidural space, which is more superficial compared to the subarachnoid space targeted in spinal anaesthesia.
How does the onset time of epidural anaesthesia compare to spinal anaesthesia?
Epidural anaesthesia takes longer to work compared to spinal anaesthesia due to its more superficial placement.
What is the primary effect of epidural anaesthesia?
Epidural anaesthesia primarily provides sensory blockade, numbing the area where it is administered.
Is epidural anaesthesia typically sufficient to provide full surgical anaesthesia?
No, epidural anaesthesia is usually not good enough to provide full surgical anaesthesia on its own.
How is epidural anaesthesia often used in combination with other forms of anaesthesia?
Epidural anaesthesia is usually combined with general anaesthesia to provide comprehensive pain relief and anaesthesia for surgical procedures.
When is a neuraxial nerve block good enough for surgery?
If dense enough—spinal anaesthesia and high-dose epidural
-Excellent operating conditions are achieved
**Sensory block – interrupts somatic and visceral painful stimuli
**Motor block – skeletal muscle relaxation
Where is the local anaesthetic deposited in spinal anaesthesia?
Where is the local anaesthetic deposited in spinal anaesthesia?
What is the effect of local anaesthetic deposition in the subarachnoid space?
It leads to the blockade of nerve roots as they pass through the subarachnoid space, resulting in sensory and motor blockade.
What lies deep to the subarachnoid space?
The subarachnoid space is deep to the dura mater and arachnoid mater.
Where does the spinal portion of the subarachnoid space extend from and to?
The spinal portion of the subarachnoid space extends from the foramen magnum superiorly to the sacral hiatus (S2) inferiorly.
At what vertebral level does the spinal cord typically end?
The spinal cord typically ends at the level of L1/L2.
Where is the epidural space located in relation to the dura mater?
The epidural space lies outside the dura mater.
What structures pass through the epidural space as they leave the spinal cord?
Nerve roots pass through the epidural space as they exit the spinal cord.
Describe the composition of the epidural space.
The epidural space is a potential space containing fatty connective tissue, lymphatics, and a venous plexus.
What is the nature of the epidural space in terms of pressure?
The epidural space is a potential space with a negative pressure.
Layers from Skin to the Spinal Cord:
skin
subcutaneous tissue
superficial fascia
deep fascia
muscles
vertebral column
dura mater
arachnoid mater
subarachnoid space
pia mater
spinal cord
indication for spinal neuraxial blocks
Spinal—usually as sole technique for anaesthesia
indication for epidural neuraxial blocks
Epidural—usually combined with GA for analgesia
examples of applications
lower abdominal surgery
inguinal surgery
urology
gynaecology
obstetrics (CS- spinal; Labour- epidural)
lower extremity surgery
lower rectal/ perineal surgery
contra- indications: absolute
- patient factors (refusal/ allergy)
-logistical issues
-local infection of the site
-coagulopathies
-severe hypovolaemia
raised ICP
contraindications: Relative
-systemic sepsis
-uncooperative patient
- pre- existing neurological deficits
- regurgitant valvular deficits
- severe spinal deformity
-previous spinal surgery
-complicated surgery where block would not last long enough or be inappropriate
advantages of regional anaesthesia
-pre emptive analgesia
-post op analgesia
-usually less physiologic derangements
-rapid post op recovery
-no airway instrumentation and the complications associated with it
-no GA and associated complications (aspirations, failed intubation, PONV, MH)
- decreased incidence of DVTs
complications of regional anaesthesia
-hypotension: common (especially spinal)
-high spinal
-post dural puncture headache
-meningitis, epidural abscess
-epidural and spinal hematoma
-neurological sequalea
-urinary retention
- pruritis (from opioids)
-shivering
-backache
mechanism of hypotension
Sympathetic blockade leads to vasodilatation
treatment of hypotension
Vasopressors
-Ephedrine: 5mg bolus
-Phenylephrine: 50ug bolus
-Adrenaline if unresponsive to above measures
IV FLUIDS
the high spinal presentation
-Severe hypotension
-Bradycardia
**Blockade of the cardiac accelerator fibres
-Difficulty breathing
-Loss of consciousness
the high spinal management
IV Fluids
Vasopressors
Atropine
Intubation and ventilation
Adrenaline
post dural puncture headache mechanism
CSF leak from a hole in the dura left by the needle
Traction on dura
Meningitis-like headache
post dural puncture headache incidence
Higher with epidurals (1%) (accidental dural tap)
post dural puncture headache
Smaller gauge needles
Pencil point needles
post dural puncture headache
Conservative
Bedrest
IV Fluids
Simple analgesia
Opiates
Laxatives
Epidural Blood Patch
High success rate of cure
neurological sequelae: neuropraxias
Transient
Nerve root damage from needle
neurological sequelae: paralysis
Direct damage
Epidural haematoma or abscess (compression)
-Monitor patient for return of motor function
-Emergency
-Urgent MRI
-Must be released within 6 hours
-Laminectomy / drainage
minor complitions
shivering
prutitis (naloxone)
urinary rentention
backache
pre- op care
=Assessment same as for GA (must be suitable for GA, in the event that you need to convert to GA)
-Starved
-Premed
-Full theatre preparation
intra -op care
=Monitors: ECG, NIBP, pulse oximeter, etCO2
=Supplemental oxygen
=Sedation
=Prevent hypothermia
post op care
-Block should be receding
-If no return of motor function within 6 hours: be concerned re epidural haematoma
-Timing of anticoagulation
factors influencing the height of the block
- patient position or posture
- specific gravity of solution
-volume of drugs - volume of CSF
- site (interspace)
-force and rate of injection
-barbotage - age, height, weight
specific gravity
CSF has a SG of 1,004.
Solutions with a higher SG (heavier) with sink in the SAS, they are gravity-dependent
Hyperbaric: “heavy” solutions - bupivacaine with dextrose
Isobaric: plain bupivacaine or lignocaine
opioids as additives
Fentanyl or morphine usually in SA
Effect:
-Extends the duration of action
-Enhances analgesia
-Can be used alone, without LA, to give analgesia (block sensory nerves only)
-Side-effect: pruritis, can be severe
advantages of epidural anesthesia
-Placement of epidural catheter allows for a constant infusion or top-up doses
-PCEA: Patient-controlled epidural anaesthesia
-Opiates enhance post-operative analgesia
-Graded block – slow establishment of level avoids the rapid haemodynamic changes
