Pre-op Anaesthesia Flashcards Preview

Podiatric Surgery > Pre-op Anaesthesia > Flashcards

Flashcards in Pre-op Anaesthesia Deck (29)
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1
Q

How do local anaesthetics work?

A

Binds to voltage-gated sodium channels and blocks sodium influx into the nerve cells, preventing depolarisation

2
Q

In what age group should bupivacaine be avoided?

A

< 12 years of age

3
Q

Why does the patient’s temperature decrease during anaesthesia?

A

Because anaesthesia inhibits the protective reflexes that generate heat (shivering), depresses the thermoregulating centre in the hypothalamus and increases vasodilation, resulting in heat loss.

4
Q

Why is low patient temperature so critical?

A

Because hypothermia increases the risk of surgical site infections

5
Q

How does hypothermia increase the risk of surgical site infections?

A

Patients need to maintain their normal temperature at around 37ºC to ensure their organs function efficiently

6
Q

List eight or nine signs and symptoms of LA toxicity

A
  1. Perioral (tongue) numbness/tingling - CNS 2. Restlessness - CNS 3. Dizziness -CNS 4. Blurred vision - CNS 5. Muscle twitching/tremors - CNS 6. Convulsions - CNS 7. Arrhythmia - CVS 8. Bradycardia - CVS 9. Hypotension - CVS
7
Q

Why does LA toxicity require CPR?

A

Because continued inhibition of neuron depolarization (by Na+ channel blockade) from increased plasma concentrations of LA causes CNS toxicity and myocardial dysfunction (CVS toxicity). So CPR is crucial to prevent hypoxia and acidosis (metabolic or respiratory)

8
Q

Besides CPR, what is the immediate management of LA toxicity?

A

20 % lipid emulsion (Intralipid) given IV at a bolus dose of 1.5 mL/kg over 1 minute

9
Q

How does lipid emulsion (Intralipid) work?

A

Works by absorbing the circulating LA (lipophilic drug), thus reducing the free unbound amount able to bind to Na+ channels in any organ where these are found (e.g. myocardium).

10
Q

What are the two existing formulations for Bupivacaine?

A

0.25 % and 0.5 % solution

11
Q

What are the two existing formulations for Lignocaine?

A

1 % and 2 % solution

12
Q

What is the toxic dose of Bupivacaine?

A

2 mg/kg

13
Q

What is the toxic dose of Lignocaine?

A

3 mg/kg

14
Q

What is the toxic dose of Levobupivacaine?

A

2 mg/kg

15
Q

What is the toxic dose of Mepivacaine?

A

6 mg/kg

16
Q

What is the marketed brand name of Bupivacaine?

A

Marcaine

17
Q

What is the marketed brand name of Lignocaine?

A

Xylocaine

18
Q

What is the marketed brand name of Levobupivacaine?

A

Chirocaine

19
Q

What is the marketed brand name of Mepivacaine?

A

Scandonest

20
Q

What are the two organ systems we’re worried about in term of LA toxicity?

A

The CNS and CVS

21
Q

Which organ system gets affected first when you get LA toxicity?

A

The CNS

22
Q

What’s the local anaesthetic formula?

A

mg = ml x % x 10

23
Q

How is regional anaesthesia advantageous for wound healing?

A

Regional anaesthesia diminishes the stress response and increases the blood flow, which has benefits for wound healing

24
Q

Describe the technique for blocking the tibial nerve during an ankle block

A

Inject 4-6 mL of anaesthetic 1 cm in depth 1 cm superior to this point.

With regional blocks, use a 27-gauge needle and either bupivacaine (0.25 %) or lidocaine (1 %)

25
Q

Describe the technique for blocking the saphenous nerve during an ankle block

A

Inject 2-3 ml subcutaneously between the medial malleolus and the anterior tibial tendon.

With regional blocks, use a 27-gauge needle and either bupivacaine (0.25 %) or lidocaine (1 %)

26
Q

Describe the technique for blocking the deep peroneal nerve during an ankle block

A

Have the patient dorsiflex their foot and insert the needle 1 cm above the medial malleolus, aiming underneath the extensor hallucis longus tendon and advance until you hit the tibia. Then inject 1-2 ml of anaesthetic.

It can also be blocked anterior to the ankle, using a ‘V’ pattern.

With regional blocks, use a 27-gauge needle and either bupivacaine (0.25 %) or lidocaine (1 %)

27
Q

Describe the technique for blocking the superficial peroneal nerve during an ankle block

A

Start one finger breadth from the lateral malleolus. Raise a subcutaneous injection, advancing the needle medially as you inject.

Inject 6-10 ml (3-5 ml with two passes) of anaesthetic solution subcutaneously in a band between the lateral malleolus and the extensor hallucis longus tendon.

With regional blocks, use a 27-gauge needle and either bupivacaine (0.25 %) or lidocaine (1 %)

28
Q

Describe the technique for blocking the sural nerve during an ankle block

A

With regional blocks, use a 27-gauge needle and either bupivacaine (0.25 %) or lidocaine (1 %)

29
Q

Name the plantar nerves

A