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Yr 4 - ACC > Anaesthetics: Regional Anaesthetics > Flashcards

Anaesthetics: Regional Anaesthetics Flashcards

1
Q

What is regional anaesthesia (RA)?

A

A subspecialty in anaesthetics focusing on the local anaesthetic blockade of peripheral nerves and central neuraxis.

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2
Q

Advantages of regional anaesthesia?

A

1) patient can remain conscious during surgery

2) can provide prolonged postoperative pain control

3) avoidance of adverse effects of general anaesthesia (e.g. N&V, respiratory depression, risk of aspiration)

4) improved post-op pain relief

5) decreased or no opioid use

6) faster recovery

7) reduces stress response to surgery

8) reduced blood loss

9) decreased incidence of post-op pneumonia and VTE

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3
Q

What is the minimum monitoring required during regional anaesthesia?

A

1) ECG

2) Blood pressure

3) SpO2

This should begin before the procedure and continue for at least 30 minutes after the completion of the procedure.

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4
Q

How long should monitoring continue for after procedure in RA?

A

At least 30 mins

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5
Q

What are the 4 types of regional anaesthesia?

A

1) Central neuraxial blocks (CNB)

2) Peripheral nerve blocks (PNB)

3) IV regional anaesthesia (IVRA)

4) Topical and infiltration anaesthesia

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6
Q

What does CNB involve?

A

The placement of local anaesthetics around the nerves of the central nervous system.

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7
Q

Give 3 examples of CNB

A

1) spinal anaesthesia
2) epidural anaesthesia
3) caudal anaesthesia

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8
Q

What does PNB involve?

A

placement of local anaesthetic agents onto or near peripheral nerves

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9
Q

What does IVRA involve?

A

The injection of local anaesthetic intravenously into an exsanguinated limb distal to an occluding tourniquet.

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10
Q

Is CNB performed under aseptic conditions?

A

Yes

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11
Q

How are patients positioned for the CNB?

A

Sitting or in the lateral position (choice depends on the provider, the patient, and the procedure).

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12
Q

How are spinal and epidural needles categorised?

A

By the design of their tips

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13
Q

Tips of spinal vs epidural needles?

A

Spinal: may have a bevelled, cutting tip or a pencil-point, noncutting tip.

Epidural: larger than spinal needles and have a curved tip to help guide the catheter in the epidural space.

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14
Q

What 2 approaches can be used for a CNB?

A

1) midline
2) paramedian

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15
Q

What are 3 common examples when a CNB is used?

A

1) caesarean section

2) transurethral resection of the prostate (TURP)

3) hip fracture repairs

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16
Q

What happens in spinal anaesthesia?

A

1) Thin 9cm needle is inserted through the skin, soft tissue, spinal ligaments, and dura until it reaches the subarachnoid space

2) A small amount of local anaesthetic is administered into the CSF in the subarachnoid space

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17
Q

Where is spinal anaesthesia preferably performed?

A

In the lumbar region (below the termination of the spinal cord).

In practice, the needle is usually inserted into the L3/4 or L4/5 spaces.

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18
Q

Why is spinal anaesthesia preferably performed in the lumbar region?

A

To avoid damaging the spinal cord.

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19
Q

Where will neuraxial anaesthesia will cause numbness and paralysis?

A

In the areas innervated by the spinal nerves below the level of the injection.

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20
Q

What can be used to test whether the spinal anaesthetic has worked?

A

Cold spray

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21
Q

How are local anaesthetics used for spinal anaesthesia altered?

A

They are made hyperbaric (denser than CSF) by mixing them with dextrose.

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22
Q

What are anaesthetics used for spinal anaesthesia mixed with?

Why?

A

Dextrose

To make them hyperbaric (denser than CSF).

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23
Q

Purpose of local anaesthetics used for spinal anaesthesia being hyperbaric?

A

1) Hyperbaric solutions have greater spread in the direction of gravity

2) Are more predictable with minimal inter-patient variability.

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24
Q

What does intrathecal mean?

A

a route of administration for drugs via an injection into the spinal canal, or into the subarachnoid space

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25
Q

How is BP affected in spinal anaesthesia?

A

Intrathecal injection of local anaesthetics produces an extensive sympathetic block, leading to a drop in systemic vascular resistance and blood pressure.

Heart rate may increase, decrease, or remain unchanged depending on the level of the block.

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26
Q

How long does a single-injection spinal anaesthesia last?

A

2-3 hours (unsuitable for prolonged surgeries).

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27
Q

What is found in the subarachnoid space in the spine?

A

CSF

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28
Q

What is found in the epidural space in the spine?

A

Fat

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29
Q

What happens in an epidural?

A

1) An epidural involves inserting a small tube (catheter) into the epidural space in the lower back –> This is outside the dura mater, separate from the spinal cord and CSF.

2) Local anaesthetic medications are infused through the catheter into the epidural space, where they diffuse to the surrounding tissues and spinal nerve roots, where they have an analgesic effect.

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30
Q

Volume of anaesthesic required in spinal vs epidural anaesthesia?

A

Epidural anaesthesia requires a larger volume of local anaesthetic and takes more time to establish.

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31
Q

Why can epidural anaesthesia be used in prolonged surgery?

A

When a catheter is in the epidural space, a local anaesthetic can be injected repeatedly, and anaesthesia can be prolonged to match the duration of the surgery.

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32
Q

What drug is often used in epidural anaesthesia?

A

Levobupivacaine +/- fentanyl

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32
Q

Give some adverse effects of epidural anaesthesia

A
  • headache if dura is punctured, creating a hole for CSF to leak from (‘dural tap’)
  • hypotension & bradycardia
  • motor weakness in legs
  • nerve damage (rare)
  • infection, including meningitis
  • haematoma (may cause spinal cord compression)
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33
Q

When used for analgesia in labour, what are the risks in epidural anaesthesia?

A

1) prolonged 2nd stage

2) increased probability of instrumental delivery

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34
Q

Patients need an urgent anaesthetic review if they develop significant motor weakness (unable to straight leg raise) after an epidural.

What does this indicate?

A

The catheter may be incorrectly sited in the subarachnoid space (and cerebrospinal fluid) rather than the epidural space.

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34
Q

What are the 3 main determinants of the spread of epidural block?

A

1) drug dose
2) injection site
3) patient variables

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35
Q

What are the major risk factors for hypotension in epidural anaesthesia?

A

Extent and onset of sensory block –> faster onset and more extensive block usually increase the probability of hypotension.

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36
Q

What are the 3 most commonly used vasopressors for managing hypotension associated with neuraxial anaesthesia?

A

1) metraminol

2) ephedrine

3) phenylephrine

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37
Q

What is the caudal space?

A

An extension of the epidural space.

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37
Q

Who are caudal anaesthesia and analgesia more useful in?

A

paediatric patients.

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38
Q

Give some complications of a CNB?

A
  • Technical: failure of the technique
  • Direct trauma to nerves and adjacent structures
  • Haemodynamic instability and high block
  • Post-dural puncture headache (PDPH)
  • Meningitis
  • Epidural haematoma/abscess
  • Back pain
  • Urinary retention
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48
Q

What happens during a peripheral nerve block?

A

A local anaesthetic is injected around specific nerves, causing the area distal to the nerves to be anaesthetised.

E.g. making a limb numb so that a surgeon can operate without causing any pain.

A screen is put up between the patient and the operating site so that they cannot see the operation taking place.

49
Q

What imagin is used to guide the injection in a peripheral nerve block?

A

US guidance, sometimes with the help of a nerve stimulator.

50
Q

What must be available when performeing regional anaesthesia?

A

where there are facilities available to quickly induce a general anaesthetic if it is not effective or the patient starts to experience pain.

51
Q

How are peripheral nerve blocks typically used?

A

1) as the sole anaesthetic

2) as a supplement with general anaesthesia

3) providing prolonged postoperative analgesia

52
Q

What is the nerve supply to the upper extremity derived from?

A

The brachial plexus

53
Q

What do brachial plexus blocks ABOVE the clavicle target?

A

The ventral rami, trunks & divisions

54
Q

What do brachial plexus blocks BELOW the clavicle target?

A

Cords & terminal nerves

55
Q

What type of peripheral nerve block is used for shoulder surgeries?

A

An interscalene block

56
Q

What type of peripheral nerve block is used for elbow operations?

A

Supraclavicular

57
Q

What type of peripheral nerve block is used for forearm operations?

A

infraclavicular

58
Q

What type of peripheral nerve block is used for hand operations?

A

axillary block

59
Q

What does a truncal fascial plane block involve?

A

The injection of a large volume of local anaesthetics into musculofacial planes that contain nerves rather than around specific nerves.

60
Q

Advantages of truncal fascial blocks?

A

The injection is distant from critical structures e.g. spinal cord, major vessels, pleura.

61
Q

Give some examples of interfascial blocks used to provide surgical and postoperative analgesia to the chest wall

A

1) erector spinae plane block
2) pectoral nerve block
3) serratus anterior plane block

62
Q

Which nerve block is mostly performed to provide analgesia following rib fractures and thoracic surgery?

A

The intercostal nerve block

62
Q

Give some examples of trunk blocks used to provide postoperative analgesia following abdominal surgeries

A

1) transversus abdominis plane block
2) rectus sheath block
3) ilioinguinal and iliohypogastric nerve blocks

63
Q

What is the nerve supply to the lower extremity derived from?

A

Lumbar & sacral plexuses.

64
Q

What are the 6 most common nerve blocks to provide surgical anaesthesia and postoperative analgesia to the lower extremeties?

A

1) femoral nerve block
2) fascia iliaca block
3) obturator nerve block
4) sciatic nerve block
5) popliteal nerve block
6) saphenous nerve block

65
Q

Give some general complications of peripheral nerve blocks

A

1) Technical: failure of the technique

2) Direct trauma to nerves and adjacent structures

3) Drug-related: local anaesthetic systemic toxicity due to intravascular injection or systemic absorption, allergic reaction and methemoglobinemia (prilocaine)

4) Infection

66
Q

What are some complications of supraclavicular upper limb blocks?

A
  • pneumothorax
  • ipsilateral phrenic nerve
  • recurrent laryngeal nerve palsy
67
Q

What is a complications of an intercostal block?

A

pneumothorax

68
Q

What are some complications of a femoral nerve blocks?

A

vascular injury leading to haematoma and arterial pseudoaneurysm

69
Q

Regional vs local anaesthesia?

A

Local –> applied locally at the site of surgery

Regional –> applied close to nerves, but at a distance from the surgical site

70
Q

Mechanism of local anaesthetic drugs?

A

They reversibly block sodium channels on the neuronal membrane –> this blocks the conduction of impulses –> produces a reversible loss of motor power and sensory sensation.

71
Q

Give 5 examples of local anaesthetics

A

1) lidocaine
2) bupivacaine
3) ropivacaine
4) levobupivacaine
5) prilocaine

72
Q

What is added to local anaesthetic solutations?
Why?

A

Adrenline:
- reduce blood flow
- decrease drug uptake
- prolong action

73
Q

When should adrenaline AVOID being added to local anaesthetic solutions?

Why?

A

For blocks of the penis or digits: due to risk of tissue ischaemia.

74
Q

Which local anaesthetic has the fastest onset?

A

Lidocaine

75
Q

Give some examples of procedures performed using a local anaesthetic

A
  • Skin sutures in A&E after a skin laceration
  • Minor surgery to remove skin lesions
  • Dental procedures
  • Hand surgery (e.g., carpal tunnel syndrome surgery)
  • Performing a lumbar puncture
  • Inserting a central line
  • Percutaneous procedures (e.g., percutaneous coronary intervention)
76
Q

What are 2 risk factors for lidocaine toxicity?

A

1) hepatic dysfunction

2) low protein state

77
Q

Why is a low protein state a risk factor for lidocaine toxicity?

A

As lidocaine is protein bound

78
Q

What are 3 absolute contraindications to regional anaesthesia?

A

1) allergy to medications used

2) localised infection

3) patient refusal

79
Q

Where is the CSF located?

A

Betwen pia and arachnoid mater (i.e. subarachnoid).

80
Q

Into what space is a spinal block injected?

A

Subarachnoid mater

81
Q

What lies between the dura mater and the vertebral canal?

A

Epidural (outside dura) space. Any injection into this space is called epidural injection.

82
Q

Where does the spinal cord end in adults?

A

Lower border of L1

83
Q

Where does the subarachnoid space end?

A

S1

84
Q

Where can the spinal block be done?

A

Below L2, down to S2.

Chose the lowest level possible to minimise the risk of damage to the spinal cord.

85
Q

Where does the epidural space end?

A

Sacrococcygeal hiatus

86
Q

Where can you do the epidural block?

A

Epidural block can be done at ANY level but there is a risk of damage to the cord if it is done ABOVE the level of L1.

For labour analgesia the block is done at the same level as spinal. However, for laparotomy the block is done at the thoracic level.

87
Q

What level is epidural done for a laparotomy?

A

Thoracic level

88
Q

At what level is there risk of damage to the cord in an epidural?

A

> L1

89
Q

What is the safe does for Lignocaine without adrenaline?

A

3mg/kg

90
Q

What is the safe does for Lignocaine with adrenaline?

A

7mg/kg

91
Q

What is the safe does for bupivacaine?

A

2mg/kg

92
Q

What does % mean in local anaesthetics?

A

% means gm/100ml i.e, 1% is 1gm/100ml i.e. 1000mg/100ml i.e. 10mg ml

Rule: multiply % with 10 and it gets you mass in mg/ml i.e. 1% is 1X10 mg/ml = 10mg/ml

Therefore for 70 kg man safe dose
- 1% lignocaine = 21ml,
- 2% lignocaine with adrenaline= 24.5 ml
- 0.5% bupivacaine= 28ml

93
Q

What are the signs of local anaesthetics systemic toxicity?

A

1) Excitatory signs:
- Circumoral numbness (earliest)
- tongue paraesthesia
- dizziness
- restlessness and agitation followed by CNS depression (slurred speech, drowsiness, unconsciousness) and/or sudden alteration in mental status, agitation or loss of consciousness

2) Muscle twitching leading to tonic-clonic seizures

3) Respiratory arrest

4) Cardiac arrhythmias: sinus bradycardia, conduction blocks, ventricular tachy-arrhythmias & Asystole

94
Q

Management of local anaesthetics systemic toxicity?

A

1) Stop injecting the LA

2) Call for help

3) Maintain the airway

4) Give 100% oxygen and ensure adequate lung ventilation

5) Confirm or establish intravenous access

6) Control seizures: use benzodiazepine, thiopental or propofol in small incremental doses

7) Assess cardiovascular status throughout and treat arrhythmias or arrest as per ALS protocol

8) Give intravenous lipid emulsion

95
Q

What is ipsilateral phrenic nerve palsy?

A

A condition caused when one side of the diaphragm becomes weak or paralysed, causing elevation of one side.

96
Q

What location of RA can cause ipsilateral phrenic nerve palsy?

A

Supraclavicular upper limb block

97
Q

Presentation of ipsilateral phrenic nerve palsy?

A

SOB

98
Q
A

Yr 4 - ACC (73 decks)

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