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Anaesthesiology > Module 5b: neuraxial blocks > Flashcards

Module 5b: neuraxial blocks Flashcards

1
Q

What are the 2 different tyoes if neuraxial blocks

A

spinal anaesthesia and epidural anaesthesia

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2
Q

Give characteristics of spinal anaesthesia

A

local anaesthetic injected into csf in subarachnoid space

rapid acting

sensory and motor block

sufficient for surgery

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3
Q

Give characteristics of epidural anaesthesia

A

local anaesthetic injected into epidural space

longer to work

sensory only-> high dosages motor

not good enoigh for surgery

combined with GA

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4
Q

How does spinal anesthesia provide excellent operating conditions?

A

Sensory block-interrupts somatic and visceral painful stimuli
Motor block- muscle relaxation

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5
Q

Give applied anatomy of spinal anaeshesia

A
  1. LA injected into CSF in subarachnoid space
  2. Blockade of nerve roots as they pass through sub-arachnoid space
  3. Spinal portion of SAS extends from foramen magnum to S2(inferiorly)
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6
Q

Give applied anatomy of epidural anaesthesia

A
  1. Epidural space is outside dura
  2. nerve roots pass through area as leave spinal cord
  3. epidural space is potential space with negative pressure
  4. Contains fatty connective tissue, lymphatics and venous plexus
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7
Q

When is a spinal anaesthesia indicated?

A

for anaesthesia

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8
Q

When is an epidural combined with GA indicated

A

for analgesia

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9
Q

What are some examples of applications of spinal anaesthesia

A

Lower abdominal surgery
Inguinal surgery
Urology
Gynaecology
Obstetrics (Caesaran section–spinal; Labour–epidural)
Lower extremity surgery
Lower rectal / perineal surgery

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10
Q

What are the absolute contraindications to neuraxial block?

A
  • 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
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11
Q

What are some relative contra-indications for neuraxial block

A

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

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12
Q

Advantages of neuraxial blocks

A

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

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13
Q

Name some complications of neuraxial blocks

A

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)

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14
Q

How does a neuraxial block cause hypotension?

A

sympathetic blockade leads to vasodilatatio

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15
Q

How do you treat the hypotension

A

Vasopressors like ephedrine 5mg bolus, phenylephrine 50ug bolus, adrenaline if unresponsive

IV fluids

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16
Q

How does a high spinal present

A

severe hypotension

bradycardia(blockade of cardiac accelerator fibres)

difficulty breathing

LOC

17
Q

How do you manage a high spinal

A

Iv fluids
vasopressors
atropine
intubation and ventilation
adrenaline

18
Q

How does a post-dural puncture headache occur

A

CSF leak through hole in dura after needle puncture-> meningitis like headache

19
Q

What procedure causes higher incidence of post-dural puncture headaches?

A

epidurals

20
Q

How can you prevent post-dural puncture headaches

A

smaller gauge needles
pencil point needles

21
Q

How do you treat post-dural puncture headache

A

conservative:
- bedrest
-IV fluids
- simple analgesia
- Opiates

22
Q

Name and describe the 2 neurological sequelae found in neuraxial blocks

A

neuropraxias
- transient caused by damage to nerve root from needle

Paralysis:
- direct damage
- epidural haematoma or abcess(compression)

23
Q

How do you manage epidrual haematoma or abcess?

A

monitor patient for return of motor function
emergency
urgent MRI
MUST BE RELEASED WITHIN 6 HRS
Laminectomy

24
Q

What are some minor complications of neuraxial blocks?

A

shivering-> give IV pethidine 10-25mg

Pruritis: from opiate/epidural-> treat with nalaxone

Urinary retention: catheterise

Backache: neuraxial anaesthesia NOT make worse

25
Q

What is involved in peri-operative care in patient with neuraxial block?

A

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

26
Q

Key aspects of doing a spinal?

A

IV line size: 18G or 26G
Level: L3/4 OR L4/5

27
Q

What factors influence height of block?

A

patient position or posture

specific gravity of solution

volume of drugs

volume of csf

site

force and rate of injection

28
Q

What solutions are gravity dependent

A

solutions with higher specific gravity

Hyperbaric: heavy solutions bupivacaine with dextrose

Isobaric: plain bupivacaine/lignocaine

29
Q

Which opioids are used as additives in spinal anaesthesia

A

fentanyl/morphine

Extends duration of action
enhances analgesia
used alone, without LA to give analgesia

30
Q

Give the definition of epidural anaesthesia and some advantages

A

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

31
Q

What are some applications of epidural anaesthesia

A

With GA
 Thoracic epidural for thoracic
surgery
 Abdominal surgery
 Hip and leg surgery

  • Labour epidural for analgesia
  • Post-op analgesia
  • Chronic Pain treatment

Anaesthesiology (29 decks)

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