Anesthesia Mechanism of Action

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What is the primary mechanism of action of local anaesthetics?

Inhibiting the influx of sodium (Na+) ions through voltage-gated Na+ channels (correct)

Inhibiting the efflux of potassium (K+) ions through voltage-gated K+ channels

Stimulating the reuptake of neurotransmitters by nerve terminals

Enhancing the release of neurotransmitters from nerve terminals

What is a major concern with the use of cocaine as a local anaesthetic?

Its addictive and psychogenic effects (correct)

Its low potency

Its short duration of action

Its high lipid solubility

What determines the effectiveness of local anaesthetics?

Water solubility and local pH

Volume of distribution and local pH

Lipid solubility and local pH (correct)

Protein binding and local pH

Why are local anaesthetics injected locally or applied topically?

To avoid unwanted systemic effects Signup and view all the answers

What is the primary reason for using additives in local anaesthetics?

To improve their onset and duration of action Signup and view all the answers

What is the primary mechanism by which vasoconstrictors in local anaesthetics prolong the duration of action?

Reduced blood flow, leading to slower removal of the local anaesthetic Signup and view all the answers

What is the effect of vasoconstrictors on the onset of anaesthesia?

Faster onset Signup and view all the answers

Which of the following is a disadvantage of using vasoconstrictors in local anaesthetics?

Alterations in cardiovascular response Signup and view all the answers

What is the order of blockade of nerve fibres when a local anaesthetic is deposited in proximity to a peripheral nerve?

Outer mantle to inner core Signup and view all the answers

What is the primary mechanism of action of local anaesthetics on nerve fibres?

Blockade of nerve fibre by diffusion along a concentration gradient Signup and view all the answers

What is the primary reason why local anesthetics are less effective in inflamed tissue?

The increased number of H+ ions in the tissue reduces the concentration of the lipid-soluble base form of the local anesthetic Signup and view all the answers

What is the significance of the pKa value of a local anesthetic?

It determines the percentage of the drug that is ionized at a given pH Signup and view all the answers

Why do local anesthetics with higher lipid solubility have a greater potency and duration of action?

Because they have a greater proximity to their sites of action due to their greater affinity for lipid membranes Signup and view all the answers

What is the consequence of a higher pKa value of a local anesthetic?

A slower onset of action, but a more prolonged duration of action Signup and view all the answers

What is the downside of local anesthetics with higher lipid solubility?

They have a higher toxicity, decreasing the therapeutic index Signup and view all the answers

What is the primary mechanism of metabolism of lidocaine in the plasma?

Hydrolysis Signup and view all the answers

Which of the following local anaesthetics is most likely to cause methaemoglobinemia?

Prilocaine Signup and view all the answers

What is the primary reason for the cardiotoxicity of bupivacaine?

Its slow metabolism by the liver Signup and view all the answers

What is the primary site of action of local anaesthetics on nociceptors?

Voltage-gated sodium channel Signup and view all the answers

What is the percentage of unchanged local anaesthetics excreted through the renal system?

3-5% Signup and view all the answers