Regional Anesthesia

Question 1

Order of disappearance of function

Answer 1

• C fibres - dull pain, warmth, preganglionic autonomic
• B fibres - postganglionic autonomic
• Aδ fibres - sharp pain and cold
• Aγ fibres - proprioception
• Aβ fibres - touch and pressure
• Aα fibres - motor and position sense

Question 2

Sedation

Answer 2

• Fentanyl 50-100μg IVI
• Midazolam 1-2mg IVI

Question 3

Identification of nerve site

Answer 3

• Anatomical landmarks
• Eliciting paraesthesia
• Electrical stimulation
• Ultrasound

Question 4

Central Neuraxial Block - Contraindications

Answer 4

Absolute:

• Local infection
• Severe hypovolemia
• Coagulopathy
• Anticoagulation
• Antiplatelet drugs
• Raised ICP
• Patient refusal
• Fixed cardiac output
• Allergy to LA

Relative

• Psychosis or dementia
• NSAIDs
• Prolonged surgery, or uncertain of duration
• Surgical team resistance
• Septicemia
• Spinal column disease

Question 5

Answer 5

Quincke-Babcock (cutting spinal needle)

Question 6

Answer 6

Whitacre (splitting spinal needle)

Question 7

Spinal Anesthetic - Procedure

Answer 7

• Establish IV access and preload 500ml crystalloid or 200-300ml colloid
• Attach monitors, set NIBP to 1 minute interval readings
• Position patient - sitting or lateral decubitus
• Scrub, mask and gown
• Locate the L3/4 intervertebral space (space closest to a line joiing the iliac crests)
• Inject 5ml 1-2% lignocaine into skin & SC tissue
• Insert spinal needle in the midline with a 15 degree cephaloid angulation
• Advance slowly until a slight pop is felt (4-6cm)
• Check for free back flow of CSF
• Slowly inject desired amount of LA
• Position patient appropriately for desired block
• Monitor patient closely, especially for the first 15-20 minutes (NB patient communication)
• Check and document sensory level of block

Question 8

Spinal Anesthetic - Sensory Levels

Answer 8

• T4-T5 - nipple Line
• T6-T8 - xiphoid
• T10 - umbilicus
• L1 - inguinal ligament
• L2-L3 - knee and below
• S2-S5 - perineum

Question 9

Spinal Anesthetic - Doses (General)

Answer 9

Lignocaine

• 1-3ml 1-2%
• 5-10 min onset
• 30-90 min duration

Bupivacaine

• 2-5ml 0.5%
• 10-20 min onset
• 100-240 min duration

Question 10

Spinal Anesthetic - Doses (Specific)

Answer 10

• T6-T10: 2.5-3ml heavy bupivacaine, supine position
• T11-L1: 2.5ml heavy bupivacaine or 2.5-3ml plain bupivacaine or levobupivacaine
• L2-L5: 2ml heavy bupivacaine or 2.5ml plain bupivacaine or levobupivacaine
• S1-S5: 1-1.5ml heavy bupivacaine, sitting position

Question 11

Answer 11

Tuohy Epidural Needle

Question 12

Epidural Anesthetic - Procedure

Answer 12

• Infiltrate skin and SC with LA
• Insert Tuohy needle through skin and superficial fascia
• Remove stylet, and attach syringe with saline
• advance needle slowly, bouncing needle plunger
• Advance needle into epidural space
• Remove needle, and observe for blood or CSF backflow
• Insert teflon catheter into epidural space
• Withdraw needle, dress wound, and strap catheter in place
• Test position of catheter - injection of LA with adrenaline
  
  • Immediate onset of spinal anesthesia - subarachnoid space
  • Tachycardia and hypertension - blood vessel

Question 13

Epidural Anesthetic - Doses

Answer 13

Lignocaine

• 15-30ml 1-2%
• 5-10 min onset
• 30-90 min duration

Bupivacaine

• 10-20ml 0.25-0.75%
• 10-20 min onset
• 100-240 min duration

Question 14

Caudal Block (Dosage)

Answer 14

1-2ml/kg 0.25% bupivacaine

Question 15

Epidural vs Spinal

Answer 15

Epidural:

• More motor sparing
• Spare lower limbs
• Continuous anaesthesia

Spinal:

• Cheaper
• Easier
• Lower dosage
• Less painful
• Denser block

Question 16

Central Neuraxial Block - Side Effects

Answer 16

• Hypotension (sympathetic blockade) - preload patient, treat with fluids and sympathomimetics if necessary
• High spinal (hypotension, bradycardia, and respiratory insufficiency) - avoid with slow injection, appropriate dosing, and careful positioning, supportive treatment
• Spinal headache (CSF leak)- avoid with smaller needles, treat with bedrest, IV fluids, analgesics, caffeine, or epidural blood patch
• Hematoma (backache and rapidly progressive neurological deficit) - evacuation
• Epidural abscess (backache, fever, raised WCC) - surgical evacuation
• Nerve trauma (pain or paraesthesia on needle insertion) - recovery within 3 months

Question 17

Peripheral Nerve Block - Dose

Answer 17

Bupivacaine

• 5-70ml (0.25%)
• 5-37.5ml (0.5%)
• 10-15 min onset
• 180-360 min duration (240-480 with adrenaline)

Question 18

Plexus Block

Answer 18

Lignocaine

• 15-50ml 1-2%
• 10-20 min onset
• 90-120 min duration (120-240 with adrenaline)

Bupivacaine - Brachial Plexus

• 0.3-0.5ml/kg 0.25-0.5%
• 20-30 min onset
• 6-15 hour duration (10-20 with adrenaline)

Bupivacaine - Lumbar and Sacral Plexus

• 0.3-1ml/kg
• 25-35 min onset
• 18-24 hour duration