Regional + Neuraxial Anaesthesia Flashcards
(25 cards)
Regional anaesthesia provides which two parts of the anaesthetic triad?
Analgesia + Muscle relaxation
What are the benefits of regional anaesthesia?
Pre-emptive analgesia
Post op analgesia
Heamodynamically stable (caution with neuraxial blocks)
Rapid recovery post op
Reduced surgical stress response
Reduced GA complications (avoids airway instrumentation + its complications, reduced PONV, reduced DVT in ortho)
Which things needs to be done when preparing a patient for regional anaesthesia?
As for GA (regional may fail and need to revert to GA)
Full hx, examination and special investigations
Nil per os
Adequate IV access
List the types of regional anaesthesia.
Topical
Wound infiltration
IV regional anaesthesia of the arm (Bier’s block)
Peripheral nerve blocks
Plexus blocks
Central nerve blocks (neuraxial blockade)
Which options are available for topical anaesthesia?
Aerosolised - via nebuliser, if doing awake fibre optic, 2% lignocaine in Macintosh sprayer for vocal cords
Topical cream
Direct application - drops
Outline the infiltrations options available.
Subcutaneously
- often given into wounds at the end of surgery, under GA
- provides some post operative analgesia
- wound infusion catheters can be give hours of post op pain relief
Intradermally
- suturing wounds
- local before siting of large IV lines, central lines, arterial lines, spinals and epidurals
Explain how a Bier’s block is performed.
Perioheral hand surgery that will be short duration
Tourniquet - brachial plexus is restricted, blood pushed back out of limb, LA given in empty veins, therefore causing dense block in surrounding tissue
Rubber bandage around forearm
Indwelling needle - IV line with LA injected
Outline the types of peripheral nerve blockades available.
Single nerve block (femoral, popliteal, radial, etc)
Plexus blocks
- brachial plexus blocks (e.g. supraclavicular - forearm surgery, interscalene - shoulder surgery)
Deep infiltration
- transvers abdominus plan block (TAP), will block sensory region of abdomen, typically used for hysterectomy
Name the different types of neuraxial blocks.
Spinal + epidural anaesthesia
Outline the difference between spinal and epidural anaesthesia.
Spinal
- LA injected into CSF in the subarachnoid space
- Rapidly acting
- Achieves both sensory + motor block
- Can provide sufficient anaesthesia for surgery
Epidural
- LA injected into the more superficial epidural space.
- Takes longer to work
- Primarily sensory blockade
- Usually not good enough to provide full surgical anaesthesia, combine with GA
What are the indications for neuraxial blocks.
Lower abdominal surgery
Inguinal surgery
Urology
Gynaecology
Obstetrics (C/section = spinal, labour = epidural)
Lower extremity surgery
Lower rectal/perineal surgery
What are the absolute contraindications for a neuraxial block?
Patient factors - refusal, inability to 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 ICP
Foxed cardiac output states - severe AS or MS or HOCM
What are the relative contraindications for a neuraxial block?
Systemic sepsis
Uncooperative patient - psychiatric, blind/deaf, mentally challenged
Pre-existing neurological deficits
Regurgitnant valvular heart lesions
Severe spinal deformity
Previous spinal surgery
Complicated surgery where block would not last long enough or be inappropriate
What are the complications of neuraxial blocks?
Hypotension - esp spinal
High spinal
Post dural puncture headache
Meningitis, epidural abscess
Epidural + spinal haematoma
Neurological sequelae
Urinary retention
Pruritis (from opioids)
Shivering
Backache
How does a neuraxial block cause hypotension and how it is treated?
Mechanism: sympathetic blacked leads to vasodilatation
Treatment: Vasopressors
- ephedrine 5mg bolus
- phenylephrine 50ug bolus
- adrenaline if above two fail
How does a high spinal present and how is it treated?
Presentation: severe hypotension, bradycardia (blockade of cardiac accelerator fibres), difficulty breathing, LOC
Management: IV fluids, vasopressors, atropine, intubation + ventilation, adrenaline
Describe the mechanism of post dural puncture headaches and their treatment.
Mechanism: CSF leak from a hole in the furs left by the needle, traction on dura, meningitis like headache
- high incidence with epidurals
Treatment: conservative (bed rest, IV fluids, simple analgesia, opiates, laxatives), epidural blood patch (high success rate of cure)
How does one prevent a post dural puncture headache?
Smaller gauge needles
Pencil point needles
Mention as to how these minor complications are treated:
- shivering
- pruritis
- urinary retention
- backache
IV pethidine 10-25mg, 1mg propofol, clonidine
From opiate in block, use naloxone
Catheterise
Will not make worse
Outline the intra operative care for neuroaxial blocks.
Monitors - ECG, NIBP, pulse oximeter, ETCO2
Supplemental O2
Sedation
Prevent hypothermia
Outline the post operative care for neuroaxial blocks.
Block should be receding
If no return of motor function within 6 hours, be concerned regarding epidural haematoma
Timing of anticoagulation
Which needles should be used when performing a spinal?
Quincke
Whitacre
Sprotte
List the factors which influence the height of the block.
Patient position or posture (during injection + after)
Specific gravity of solution
Volume of drugs
Volume of CSF
Site (interspace)
Force + rate of injection
Barbotage
Age, height, weight
Explain the concept of specific gravity.
CSF has SG of 1.004
Solution with a higher GS (heavier) will sink in the subarachnoid space, they are gravity dependent
Hyperbaric - heavy solutions (e.g. bupuvivaine with dextrose)
Isobaric - plain bupivacaine or lignociane
