Overview of Regional Anaesthesia Flashcards
Concepts of Regional Anaesthesia
RA affects one part of the body only
Provides 2 parts of the Anaesthetic Triad: Analgesia
Muscle Relaxation
No Hypnosis (additional sedation may be given
Benefits of Regional Anaesthesia
Pre-emptive analgesia Post-op analgesia Haemodynamically stable (caution: neuraxial) Rapid recovery post-op Reduced surgical stress response Reduced GA complications Avoids airway instrumentation and its complications Reduced PONV Reduced DVT in ortho
Patient Preparation
As for general anaesthesia
Full history, examination and relevant special investigations
StNil per os
Adequate IV access
Theatre preparation
Anaesthetic machine checked or ability to ventilate and give O2 Airway trolley Defibrillator Suction Anaesthetic drugs Emergency drugs
Types of Regional Anaesthesia (WP2IC or TWINP2)
Topical Wound infiltration IV RA of the Arm (Bier's Block) Peripheral Nerve blocks Plexus blocks Central Nerve Block (Neuraxial Blockade)
Topical Anaesthesia
Aerosolised
2% lignocaine in MacIntosh sprayer for vocal cords
Topical Cream
Direct Application (DROPS)
Used in minor eye surgery, laryngoscopy and bronchoscopy, incision and drainage of quinsy (tonsil) venepuncture
Wound 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
Intradermally
Suturing of wounds
Local before siting of large IV lines, central lines, arterial lines, spinals & epidurals
IV regional anaesthetic of the Arm
Provide intense anaesthesia for short surgical procedures (<45-60secs)
Used for surgery of the hand. lower forearm (colle’s fracture)
Peripheral nerve blockade
CAN BE DONE UNDER NERVE STIMULATION/ULTRASOUND
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)
The Neuraxial Blocks (SPINAL ANAESTHESIA)
Local anaesthetic is injected into the CSF in the subarachnoid space
Rapidly acting
Achieves both sensory and motor block
Can provide sufficient anaesthesia for surgery
The Neuraxial Blocks (EPIDURAL ANAESTHESIA)
Local anaesthetic is injected into the more superficial epidural space
Takes longer to work
Primarily provides sensory blockade
Usually not good enough to provide full surgical anaesthesia
Usually combined with general anaesthesia
The Neuraxial Blocks (SPINAL ANAESTHESIA) Applied anatomy
LA deposited into CSF
Blockade of nerve roots as they pass through the subarachnoid space
Subarachnoid space is deep to the dura and arachnoid mater
Spinal portion of SAS extends from foramen magnum superiorly to S2 inferiorly
Spinal cord ends at L1/2
Use 18G and 16G iv line and place the needle at L3/L4 or L4/L5 use tuffliers line
The Neuraxial Blocks (EPIDURAL ANAESTHESIA) Applied anatomy
Epidural space lies outside dura, LA placed into the epidural space at lumbar or thoracic level, via epidural catheter
The nerve roots pass through this space as they leave the spinal cord
The epidural space is a potential space with a negative pressure
Contains: fatty connective tissue, lymphatics and a venous plexus
Indications for Neuraxial Blocks
Spinal—usually as sole technique for anaesthesia
Epidural—usually combined with GA for analgesia
Applications for Neuraxial Blocks
Lower abdominal surgery Inguinal surgery Urology Gynaecology Obstetrics (Caesaran section–spinal; Labour–epidural) Lower extremity surgery Lower rectal / perineal surgery
Contra-indications: NeurBlocks ABSOLUTE
Patient factors: Patient refusal Inability to give consent Allergy to LA Logistical issues: Inexperienced operator Inability to give GA Local infection at the site Coagulopathies: Platelets < 75; INR > 1.5 Anticoagulant medication Severe hypovolaemia Raised intracranial pressure Fixed Cardiac Output States: severe AS or MS HOCM
Contra-indications: RELATIVE
Systemic sepsis Uncooperative patient: Psychiatric Blind / Deaf Mentally challenged Pre-existing neurological deficits Regurgitant valvular heart lesions Severe spinal deformity Previous spinal surgery Complicated surgery where block would not last long enough or be inappropriate
Complication LA
Hypotension — common (especially spinal) High spinal Post-dural puncture headache Meningitis, epidural abscess Epidural and spinal haematoma Neurological sequelae Urinary retention Pruritis (from opioids) Shivering Backache
Complication of LA
Hypotension
Sympathetic blockade leads to vasodilatation
Vasopressors
Ephedrine: 5mg bolus
Phenylephrine: 50ug bolus
Adrenaline if unresponsive to above measures
IV FLUIDS
Complication of LA
The high spinal
Presentation: Severe hypotension Bradycardia Blockade of the cardiac accelerator fibres Difficulty breathing Loss of consciousness Management: IV Fluids Vasopressors Atropine Intubation and ventilation Adrenaline
Complication of LA
Post-dural puncture headache
Mechanism: CSF leak from a hole in the dura left by the needle Traction on dura Meningitis-like headache Treatment: Conservative Bedrest IV Fluids Simple analgesia Opiates Laxatives Epidural Blood Patch High success rate of cure
Complication of LA
Neurological Sequelae
Neuropraxias:
Transient
Nerve root damage from needle
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
Factors influencing the height of the block
Patient position or posture Specific gravity of solution Volume of drugs Volume of CSF Site (interspace) Force & 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
Epidural Anaesthesia
Advantages
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
Applications of Epidurals
With GA Thoracic epidural for thoracic surgery Abdominal surgery Hip and leg surgery Labour epidural for analgesia Post-op analgesia Chronic Pain treatment
