Local & Regional Anaesthesia

Topics in this chapter

• Mechanisms and Differential Block
• Drug Pharmacology and Agents
• Adjuvants and Epinephrine
• Regional Anaesthesia Techniques
• Toxicity and Resuscitation
• Prilocaine and Methemoglobinemia

Practice questions

1. Question 1Q-5F8EFA

   A 35-year-old male undergoes open reduction and internal fixation of a distal radius fracture under an intravenous regional anaesthesia (Bier block). Which of the following local anaesthetics is considered absolutely contraindicated due to its high cardiotoxicity and central nervous system toxicity profile?

   1. A.Lidocaine
   2. B.Prilocaine
   3. C.Bupivacaine
   4. D.Chloroprocaine
   See the answer and solution
2. Question 2Q-774B04

   Which of the following local anaesthetics has the highest intrinsic lipid solubility and potency, and a strong tendency to bind to cardiac sodium channels, making resuscitation from systemic toxicity particularly challenging?

   1. A.Lidocaine
   2. B.Mepivacaine
   3. C.Bupivacaine
   4. D.Chloroprocaine
   See the answer and solution
3. Question 3Q-EE8ADC

   A 28-year-old parturient in active labour requests an epidural analgesia. Following placement of the epidural catheter and a test dose of 3 mL of 1.5% lidocaine with 1:200,000 epinephrine, the patient complains of sudden tinnitus, metallic taste, and circumoral numbness within 45 seconds. What is the most likely cause?

   1. A.Subarachnoid (spinal) injection
   2. B.Intravascular injection of the local anaesthetic
   3. C.Normal systemic absorption of epidural dose
   4. D.Allergic reaction to the preservative
   See the answer and solution
4. Question 4Q-4ED489

   Regarding the mechanism of action of local anaesthetics, which of the following statements is most accurate regarding how they exert their primary electrophysiological effect?

   1. A.They bind to extracellular potassium channels and prevent repolarisation.
   2. B.They block voltage-gated sodium channels from the intracellular surface in their ionized form.
   3. C.They block calcium channels at the neuromuscular junction.
   4. D.They act exclusively via un-ionised diffusion across the lipid bilayer without binding any receptor.
   See the answer and solution
5. Question 5Q-4882BC

   Which of the following nerve fibre types is blocked first by local anaesthetics, typically resulting in the earliest loss of sensation?

   1. A.A-alpha fibres (motor and proprioception)
   2. B.A-beta fibres (touch and pressure)
   3. C.A-gamma fibres (muscle tone)
   4. D.B and C fibres (autonomic and pain/temperature)
   See the answer and solution