Nerve Blocks in Practice

What is the most likely mode of action of local anaesthetics?

Block inward potassium current necessary for nerve membrane depolarisation

Block inward sodium current necessary for nerve membrane depolarisation

Modulation of GABA at the level of the spinal cord

NMDA channel blockade

Why is it not recommended to mix two different local anaesthetic agents (e.g., bupivacaine + lignocaine)?

This results in dilution of each agent thereby reducing efficacy, shortening duration of action, and prolonging onset of action

This results more protein bound drug, causing a very prolonged duration of action

This produces a toxic solution

This increases the concentration gradient for drug to move into the nerve, resulting in a very fast onset of action

What is the main benefit of performing epidural injection at the sacro-coccygeal space, rather than lumbosacral, in cats?

Reduced risk of local anaesthetic toxicity

More reliable local anaesthetic block of the perineum and tail

Reduced risk of accidental intrathecal (spinal) injection

More reliable motor blockade of pelvic limbs

What is a benefit of using a spinal or Tuohy needle, rather than a hypodermic needle, for epidural injection?

Spinal/Tuohy needles allow for better interpretation of passage through different tissue planes

Spinal/Tuohy needles are cheaper

Spinal/Tuohy needles do not have a stylet, making them easier to handle

It is not possible to accidentally puncture the dura mater with a spinal/Tuohy needle

What is the correct course of action if blood is present on aspiration of the needle during a nerve block (or in. needle hub during epidural injection)?

Continue with injection as planned

Abort nerve block in this patient and use an alternate analgesic plan

Reduce volume of planned injection by 50-75%

Remove the needle and start the injection process again with a new needle

What is a correct course of action if cerebrospinal fluid is present at the hub of the needle during a lumbosacral epidural injection?

Continue with injection as planned

Abort epidural injection in this patient and use an alternate analgesic plan

Reduce volume of planned injection by 25%

Remove the needle and start the injection process again with a new needle at the sacrococcygeal space

If it is the volume of drug injected (ml) during a perineural or neuraxial injection that determines the spread of the block, why it is still important to calculate the maximum safe dose (mg/kg) of a local anaesthetic solution?

It is the dose of local anaesthetic that determines the analgesic duration of the block

A nerve block will not be effective unless the maximum safe dose of local anaesthetic is used.

This minimises the risk of systemic local anaesthetic toxicity

It is the dose of local anaesthetic that determines the onset time of the block

What is (are) the most appropriate drug(s) to use for a lumbosacral epidural injection in a dog with a femoral fracture, if you wish to provide up to 24h of analgesia?

Lignocaine 1% solution alone

Lignocaine 1% solution + dexmedetomidine

Bupivacaine 0.5% solution alone

Bupivacaine 0.5% solution + morphine

What is the most appropriate drug and dose to use for a sacro-coccygeal epidural injection in a 4kg cat with a urethral obstruction, to allow catheterisation?

Lignocaine 1% solution 0.1 mL/kg

Lignocaine 1% solution 0.1mL per cat

Morphine 0.1 mg/kg

Morphine 0.1 mL/kg

What is a common side effect in an anaesthetised animal following epidural injection of a local anaesthetic solution?

Tachycardia

Bradycardia

Hypotension

Hypertension

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Nerve Blocks in Practice