Local Anaesthetics

Objectives

  • Recall the mechanism of action of local anaesthetics
  • Classify Local Anaesthetics by chemical structure (amides and esters) and describe how the classifications relate to behaviour of the agent in-vivo
  • Understand how lipid solubilitypKa and protein-binding affect the behaviour of a local anaesthetic agent
  • Recall the pertinent chemical, pharmacokinetic and pharmacological properties of LidocaineBupivacaine and Levobupivacaine
  • Compare and contrast the properties of these drugs and their clinical uses in anaesthetic practice
  • Recognise the signs and symptoms of local anaesthetic toxicity and demonstrate awareness of the importance of calling for immediate senior help and the role of supportive management & intra-lipid
  • Calculate a safe maximum dose of local anaesthetic in terms of volume for any given agent, concentration and patient weight
  • Use knowledge and understanding of local anaesthetics to select an appropriate agent for subcutaneous use and for neuraxial anaesthesia

How local anaesthetics work

Lidocaine and Bupivacaine

Quiz

0
Created on By Anaestheasier

Local Anaesthetics

1 / 15

A 23-year-old male is undergoing a laparoscopic appendicectomy. The surgeons want to know how much levobupivicaine they can use. Incisions are expected to be small. The patient weighs 90kg. What would be the most appropriate to recommend?

2 / 15

Levobupivicaine is the pure S-enantiomer of Bupivicaine. Which of the following statements regarding their relationship is incorrect?

3 / 15

pH = pKa + log ([ionised form]/[unionised form]) 

At physiological pH of 7.4, the ratio of lidocaine in its ionised:unionised form is 0.32

What is the pKa of Lidocaine?

4 / 15

A 21-year-old primip has had an epidural sited for analgesia in labour. She has an infusion running of 0.1% Bupivicaine. However, the obstetricians recognise concerning features that necessitate a Category 1 Caesarean Section. The Obstetric Anaesthetist on-call uses 0.5% Bupivicaine and 1% Lidocaine mixture to ‘top-up’ the epidural before assessing the level of block for the section to proceed. Which of the following features of Lidocaine makes it rapid in onset?

5 / 15

Which of the following factors does not reduce the risk of local anaesthetic toxicity?

6 / 15

The end of the above procedure, you notice a dysrhythmia on the monitor that rapidly progresses to VF. The surgeon realises that she was handed the correct volume of Levobupivicaine but at a concentration of 0.5%. You call for help immediately and request chest compressions to be started. Defibrillator pads are applied and mechanical ventilation proceeds with 100% oxygen. Your consultant arrives with the AAGBI Quick Reference Handbook. Which drug would most likely correct the underlying cause of the arrest?

7 / 15

You are anaesthetising for a 45-year-old lady of 50kg who is undergoing a Total Abdominal Hysterectomy. What is the maximum volume of 0.25% Levobupivicaine the surgeons may use?

8 / 15

Which of the following statements is incorrect regarding local anaesthetics?

9 / 15

You are using 2.6ml of 0.5% Marcain Heavy (Levobupivicaine) for a spinal anaesthetic. What dose have you given?

10 / 15

Which of the following local anaesthetics is not an amide?

Adrenaline acts as a vasoconstrictor, which prolongs the effect of the local anaesthetic and so reduces the risk of cardiotoxicity.

11 / 15

The maximum dose of lidocaine is 3mg/kg when used alone. When administered with adrenaline, what is the maximum dose?

12 / 15

Which of the following statements about local anaesthetics is false?

13 / 15

Which of the following anaesthetics is an ester?

14 / 15

A 50kg patient is undergoing a laparoscopic cholecystectomy. The surgeon wants to know how much bupivicaine she can use. She says she does not need much in the way of volume.

Which would be most appropriate to advise?

15 / 15

You are planning to insert an arterial line in an awake patient and so you choose to inject 1.5ml of 2% Lidocaine prior to arterial cannulation. What dose have you given?

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