Local and Regional Anaesthesia

Question 1

What is ‘analgesia’?

Answer 1

The state when only pain relied is provided - enough for minor surgeries e.g. suturing.

Question 2

What is ‘anaesthesia’?

Answer 2

The state when analgesia is accompanied with muscle relaxation - used for major surgeries.

Regional +/- general anaesthesia can be used.

Question 3

Where can local anaesthetics be used?

Answer 3

1. Topically to mucous membrane - e.g. eye!
2. Subcutaneous infiltration
3. IV after tourniquet = IVRA
4. Directly around nerves - e.g. brachial plexus
5. In the extradural space (‘epidural’)
6. In the subarachnoid space (‘spinal’)

Question 4

Name 2 methods of central neural blockade?

Answer 4

1. Epidural - LA in the extradural space

2. Spinal - LA in the subarachnoid space

Question 5

What infiltration analgesic is usually used for short procedures?

Answer 5

Lidocaine 0.5%

Question 6

What infiltration analgesic is usually used for pain relief from surgery?

Answer 6

Bupivacaine 0.5% or Chirocaine

Question 7

What can be added to infiltration analgesia if a large dose or prolonged effect is required?

Answer 7

Adrenaline

Question 8

1. When giving infiltration analgesia, what structures are you trying to avoid?
2. How do you know if you have done this correctly?

Answer 8

1. Blood vessels - should be subcut.
2. Aspirate the needle once it is in subcutaneously - if any blood is seen on aspiration, discard the syringe and start again.

Question 9

1. Where should LA be injected when performing a brachial plexus block?
2. What can be used to locate the nerves?
3. How long does the block last?

Answer 9

1. Either supra-clavicular OR through the axilla.
2. A nerve stimulator / ultrasound is also being used.
3. Several hours - important to warn the surgeon and px.

Question 10

1. What is a TAP block?

2. What is it used for?

Answer 10

1. Transversus abdominis plane block - LA between the transversus abdominis and internal oblique muscles.
2. To anaesthetise the nerves supplying the skin + muscles of anterior abdominal wall (parietal peritoneum).
   E.g. appendicectomy, hernia repair, laproscopic surgery.

Question 11

1. Where is epidural anaesthesia inserted?

2. Where can the site of the epidural be?

Answer 11

1. Into the potential space OUTSIDE the dura.

2. Anywhere between the craniocervical junction (C1) to the sacrococcygeal membrane.

Question 12

The extent of anaesthesia in an epidural is determined by what 3 factors?

Answer 12

1. Which spinal level it was inserted - spread is greater in thoracic > lumbar region.
2. The volume of anaesthetic injected.
3. Gravity - tipping the px head-down encourages spread cranially. If the px is upright, this limits the spread.

Question 13

What anatomical layers are pierced during an epidural?

Answer 13

Skin - SC fat - supraspinous ligament - interspinous ligament - ligamentum flavum = epidural space.

Question 14

Below what level can spinal anaesthesia be inserted?

Answer 14

L2 (and above S1)

Question 15

What can be added to LA during a spinal and what is the advantage of adding this?

Answer 15

0.10 - 0.25 mg of morphine / diamorphine = extends the duration of analgesia for up to 12 hours postoperatively.

Question 16

What are the contraindications to performing epidural / spinal anaesthesia?

Answer 16

1. Hypovolaemia = e.g. due to blood loss or dehydration. Falls in cardiac output as compensatory vasoconstriction is lost.
2. Low, fixed cardiac output = e.g. aortic / mitral stenosis. Reduces venous return and further reduces cardiac output - lack of perfusion to vital organs.
3. Local skin infection
4. Coagulopathy = risk of epidural haematoma.
5. Increased ICP = risk of coning.
6. Allergy to LA
7. Uncooperative px

Question 17

What are the side effects of epidurals?

Answer 17

Hypotension / bradycardia, N+V, post-dural puncture headache

Question 18

Why do epidurals cause:

1. Hypotension?
2. Bradycardia?

Answer 18

1. Anaesthesia of thoracic + lumbar nerves = sympathetic block. This causes VASODILATION and REDUCED VENOUS RETURN = cardiac output falls.
2. If block extends above T5 = cardioaccelerator nerves are also blocked. The unopposed vagal tone = bradycardia.

Question 19

Why does N+V occur as a side effect of epidurals and what can be given to help this?

Answer 19

Hypotension (first sign), cerebral hypoxia, vagal stimulation during upper-abdo surgery.

Atropine 0.3 - 0.6mg - particularly if there is bradycardia OR Odansetron 4mg IV.

Question 20

1. What causes post-dural puncture headache?

2. How can this be resolved?

Answer 20

1. Persistent leak of CSF from the needle hole in the dura. Usually frontal or occipital, exacerbated by straining - majority will resolve spontaneously.
2. By injecting 20-30 ml of px’s own blood into epidural space = epidural blood patch.

Question 21

What causes local anaesthetic toxicity?

Answer 21

1. Rapid absorption of a dose.
2. Inadvertent IV injection - if failure to aspirate.
3. Overdose - calculation error or not taking into account pre-existing hepatic / cardiac disease.

Question 22

What are the mild / early signs of LA toxicity?

Answer 22

Circumoral paraesthesia ( = numbness or tingling about the mouth), numbness of the tongue, visual disturbances, light headedness, slurred speech, twitching, mild hypotension, bradycardia.

Question 23

What are the severe / late signs of LA toxicity?

Answer 23

General tonic-clonic seizure - followed by coma, respiratory depression - leads to apnoea, CV collapse - profound hypotension + bradycardia and ultimately cardiac arrest.

(Seizure - resp depression - CV collapse - cardiac arrest)

Question 24

How do you manage LA toxicity?

Answer 24

Airway = maintain. Tracheostomy may be needed if protective reflexes are absent - to prevent aspiration.

Breathing = give 100% oxygen + ventilate if required.

Circulation = raise px legs to aid venous return + give IV crystalloid / colloid. Treat bradycardia with IV atropine.

Disability = treat convulsions with diazepam 5-10mg IV (can cause resp. depression). Seek assistance if recurrence or no change.

Question 25

What can be given when local anaesthetic toxicity causes profound cardiovascular collapse?

Answer 25

``` Initially = 1.5 ml/kg 20% lipid emulsion / 1 min Then = infusion of 20% lipid emulsion at a rate of 15ml/kg/h ``` If no change after 5 mins of this = repeat 2 boluses 5 mins apart, double the rate of infusion. MAX DOSE = 12 ML / KG

Question 26

What are the advantages of performing blocks in px who are awake?

Answer 26

1. Block can be checked before surgery commences. 2. Lower risk of nerve injury - px will complain if needle touches nerve. 3. Px can cooperate with positioning.

Question 27

What are the advantages of performing blocks under general anaesthesia?

Answer 27

1. More pleasant for the px 2. No risk of px suddenly moving 3. Allows easier positing of px if they are in pain. 4. If needle hits the nerve then the damage is already done...

Question 28

What are the potential benefits of regional anaesthesia?

Answer 28

- Avoids systemic effects of GA. - Avoid drugs that cause resp. depression. - Less disturbance of control of co-existing systemic disease. - Airway reflexes are preserved. - May improve surgical access - e.g. during laparotomy. - Reduced blood loss. - Can be continued post-op for pain relief. - Reduces complications after major surgery. - Cheaper.

Question 29

(T/F) Regional anaesthesia: 1. Offers no advantage to px with COPD. 2. May increase blood loss during surgery. 3. Causes less disturbance of concurrent disease requiring medical therapy. 4. May hinder access for the surgeon during laparotomy.

Answer 29

1. F = spontaneous ventilation is preserved + respiratory depressant drugs avoided. 2. F = decreases blood loss. 3. T = less disturbance partly due to modified stress response. 4. F = muscle relaxation and contraction of bowel will improve access.

Question 30

(T/F) Local anaesthetic drugs can be used: 1. intra-arterially after the application of a tourniquet. 2. by direct injection into the nerves. 3. SC 4. Intrathecally (into the spinal theca)

Answer 30

1. F = dangerous! Bier's block = IV after application of tourniquet. 2. F = this would cause nerve damage - should only be injected adjacent to nerves. 3. T 4. T = spinal anaesthesia!

Question 31

(T/F) Contraindications of spinal anaesthesia = 1. Coagulopathy 2. Severe aortic stenosis 3. Local skin sepsis 4. Major trauma

Answer 31

1. T = risk of epidural haematoma. 2. T = low fixed cardiac output will be further reduced by vasodilation + reduced venous return. 3. T = risk of introducing infection e.g. meningitis. 4. T = these px are likely to be hypovolaemic + very vasoconstricted. Sudden vasodilation = massive fall in BP and cardiac output.

Question 32

(T/F) Local anaesthetic toxicity: 1. May be caused despite using a safe dose of the drug. 2. May initially present with grand mal convulsions. 3. Should initially be managed by raising px legs to treat hypotension. 4. Is a common complication of epidural anaesthesia.

Answer 32

1. T = if injected into a vascular area or inadvertently directly IV. 2. T = in severe cases. 3. F = Inital Rx would be to stop if still injecting and use ABCDE approach. 4. F = Rare (1:10,000)