Module 5b: neuraxial blocks Flashcards
What are the 2 different tyoes if neuraxial blocks
spinal anaesthesia and epidural anaesthesia
Give characteristics of spinal anaesthesia
local anaesthetic injected into csf in subarachnoid space
rapid acting
sensory and motor block
sufficient for surgery
Give characteristics of epidural anaesthesia
local anaesthetic injected into epidural space
longer to work
sensory only-> high dosages motor
not good enoigh for surgery
combined with GA
How does spinal anesthesia provide excellent operating conditions?
Sensory block-interrupts somatic and visceral painful stimuli
Motor block- muscle relaxation
Give applied anatomy of spinal anaeshesia
- LA injected into CSF in subarachnoid space
- Blockade of nerve roots as they pass through sub-arachnoid space
- Spinal portion of SAS extends from foramen magnum to S2(inferiorly)
Give applied anatomy of epidural anaesthesia
- Epidural space is outside dura
- nerve roots pass through area as leave spinal cord
- epidural space is potential space with negative pressure
- Contains fatty connective tissue, lymphatics and venous plexus
When is a spinal anaesthesia indicated?
for anaesthesia
When is an epidural combined with GA indicated
for analgesia
What are some examples of applications of spinal anaesthesia
Lower abdominal surgery
Inguinal surgery
Urology
Gynaecology
Obstetrics (Caesaran section–spinal; Labour–epidural)
Lower extremity surgery
Lower rectal / perineal surgery
What are the absolute contraindications to neuraxial block?
- patient factors: refusal, inability to give consent, allergy to LA
- Logistical issues: inexperienced opperator, inability to give GA
- Local infection at site
- Coagulopathies: platelets<75,INR>1.5, anticoagulant medication
- Severe hypovolaemia
- Raised ICP
- Fixed cardiac output states: AS/MS, HOCM
What are some relative contra-indications for neuraxial block
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
Advantages of neuraxial blocks
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 (aspiration, failed intubation, PONV, MH)
Decreased incidence of DVTs
Name some complications of neuraxial blocks
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? (no clear evidence)
How does a neuraxial block cause hypotension?
sympathetic blockade leads to vasodilatatio
How do you treat the hypotension
Vasopressors like ephedrine 5mg bolus, phenylephrine 50ug bolus, adrenaline if unresponsive
IV fluids
How does a high spinal present
severe hypotension
bradycardia(blockade of cardiac accelerator fibres)
difficulty breathing
LOC
How do you manage a high spinal
Iv fluids
vasopressors
atropine
intubation and ventilation
adrenaline
How does a post-dural puncture headache occur
CSF leak through hole in dura after needle puncture-> meningitis like headache
What procedure causes higher incidence of post-dural puncture headaches?
epidurals
How can you prevent post-dural puncture headaches
smaller gauge needles
pencil point needles
How do you treat post-dural puncture headache
conservative:
- bedrest
-IV fluids
- simple analgesia
- Opiates
Name and describe the 2 neurological sequelae found in neuraxial blocks
neuropraxias
- transient caused by damage to nerve root from needle
Paralysis:
- direct damage
- epidural haematoma or abcess(compression)
How do you manage epidrual haematoma or abcess?
monitor patient for return of motor function
emergency
urgent MRI
MUST BE RELEASED WITHIN 6 HRS
Laminectomy
What are some minor complications of neuraxial blocks?
shivering-> give IV pethidine 10-25mg
Pruritis: from opiate/epidural-> treat with nalaxone
Urinary retention: catheterise
Backache: neuraxial anaesthesia NOT make worse
What is involved in peri-operative care in patient with neuraxial block?
Pre-op:
- same assessment as GA
- starved
-premed
- theatre prep
Intra-op:
- monitors- ecg, NIBP, pulse oximeter, etCO2
- Supplemental O2
- Sedation
- prevent hypothermia
Post-op:
- Block should be receding-> if no return in motor function within 6 hrs->possible epidural haematoma
- Timing of coagulation
Key aspects of doing a spinal?
IV line size: 18G or 26G
Level: L3/4 OR L4/5
What factors influence height of block?
patient position or posture
specific gravity of solution
volume of drugs
volume of csf
site
force and rate of injection
What solutions are gravity dependent
solutions with higher specific gravity
Hyperbaric: heavy solutions bupivacaine with dextrose
Isobaric: plain bupivacaine/lignocaine
Which opioids are used as additives in spinal anaesthesia
fentanyl/morphine
Extends duration of action
enhances analgesia
used alone, without LA to give analgesia
Give the definition of epidural anaesthesia and some advantages
Def:
- LA placed into epidural space at lumbar or thoracic level
Advantages:
- placement of epidural catheter allows for constant infusion/top-up doses
- opiates enhance post operative analgesia
- graded block: slow establishment of level avoids rapid haemodynamic changes
What are some applications of epidural anaesthesia
With GA
Thoracic epidural for thoracic
surgery
Abdominal surgery
Hip and leg surgery
- Labour epidural for analgesia
- Post-op analgesia
- Chronic Pain treatment
