Podcast
Questions and Answers
What effect do local anaesthetics have on smaller neurones compared to larger neurones?
What effect do local anaesthetics have on smaller neurones compared to larger neurones?
Which of the following is a common unwanted side effect of local anaesthetics in the cardiovascular system?
Which of the following is a common unwanted side effect of local anaesthetics in the cardiovascular system?
What is the primary purpose of administering vasoconstrictors with local anaesthetics?
What is the primary purpose of administering vasoconstrictors with local anaesthetics?
What type of anaesthesia generally provides a larger area of anaesthetisation when administered proximally?
What type of anaesthesia generally provides a larger area of anaesthetisation when administered proximally?
Signup and view all the answers
Which local anaesthetic is noted for being the most cardiotoxic?
Which local anaesthetic is noted for being the most cardiotoxic?
Signup and view all the answers
What is the primary mechanism by which local anaesthetics block nerve transmission?
What is the primary mechanism by which local anaesthetics block nerve transmission?
Signup and view all the answers
What structural feature do local anaesthetics contain that contributes to their pharmacological effect?
What structural feature do local anaesthetics contain that contributes to their pharmacological effect?
Signup and view all the answers
Why are local anaesthetics less effective in inflamed tissues?
Why are local anaesthetics less effective in inflamed tissues?
Signup and view all the answers
Which state of the voltage-gated sodium channel do local anaesthetics preferentially block?
Which state of the voltage-gated sodium channel do local anaesthetics preferentially block?
Signup and view all the answers
What pH condition is optimal for the entry of local anaesthetics through the hydrophobic pathway?
What pH condition is optimal for the entry of local anaesthetics through the hydrophobic pathway?
Signup and view all the answers
What type of bond do local anaesthetics with shorter half-lives typically contain?
What type of bond do local anaesthetics with shorter half-lives typically contain?
Signup and view all the answers
Which term describes the selective affinity of local anaesthetics for frequently opening sodium channels?
Which term describes the selective affinity of local anaesthetics for frequently opening sodium channels?
Signup and view all the answers
What type of receptors do local anaesthetics block more effectively compared to other sensory receptors?
What type of receptors do local anaesthetics block more effectively compared to other sensory receptors?
Signup and view all the answers
Signup and view all the answers
Study Notes
Local Anaesthetics - Mechanism of Action
- Local anaesthetics block voltage-gated sodium channels, preventing action potentials.
- They don't cause loss of consciousness.
- They work by plugging the pores of the sodium channels.
- Anaesthetic molecules can use hydrophilic or hydrophobic pathways to reach the channels.
- Hydrophilic pathway: ionised anaesthetics pass through the open channel.
- Hydrophobic pathway: unionised anaesthetics pass through the axon membrane.
- The ionised form of the anaesthetic has a stronger affinity for the channels.
- The channels are more open/inactive during action potentials, so anaesthetics are more effective at blocking these channels.
Local Anaesthetics - Structure
- General structure: aromatic region and basic amine side chain joined by an ester or amide bond.
- Molecules are weak bases (pKa range 8-9).
- Ionised in acidic environments, forming cations.
- Ester bonds metabolise more quickly, leading to shorter half-lives (short-acting).
- Amide bonds metabolise more slowly, leading to longer half-lives (long-acting).
Local Anaesthetics - Pain Sensation
- Nociceptors detect damaging stimuli (e.g., tissue injury, extreme temperatures).
- They generate action potentials in response to noxious stimuli.
- These potentials are transmitted to the brain, causing the sensation of pain.
Local Anaesthetics - Side Effects
- Side effects are caused by systemic absorption.
- Cardiovascular effects: reduced myocardial contractility, heart block, dysrhythmia, vasodilation.
- Central nervous system effects: depressive at low and very high concentrations, stimulatory at medium concentrations (restlessness, tremors, agitation).
- Risk of death due to respiratory depression at very high concentration.
- Different anaesthetics have different side effect profiles due to structural differences.
Modes of Administration
- Surface anaesthesia: applied to surfaces such as the mouth, nose, airway, cornea, urinary tract, etc.
- Infiltration anaesthesia: injected directly into tissues.
- Nerve block anaesthesia: injected near nerve trunks to block peripheral sensation.
- Regional anaesthesia: used to anaesthetise large areas (e.g., Bier's block).
- Intravenous regional anaesthesia: injected into veins in a region blocked off from main circulation, commonly used for limb surgery (lidcaine, prilocaine).
Types of Anaesthesia
- Spinal anaesthesia: injected into the cerebrospinal fluid, deep to the dura mater, to block spinal cord, usually used in lower body or abdominal surgeries (lidcaine).
- Epidural anaesthesia: injected into the epidural space, outside the dura mater, to block spinal roots, commonly used in childbirth or other surgeries (lidcaine, bupivacaine, ropivacaine).
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the intricate mechanisms and structures of local anaesthetics. This quiz covers how these agents block sodium channels, their pathways, and the impact of their chemical structure on function. Test your understanding of both the pharmacological and structural aspects of these important medical compounds.
