Anaesthetic Agents and Mechanism of Action

Anaesthetic Agents

Inhalational Anaesthetics

• Volatile anaesthetics:
  • Desflurane
  • Sevoflurane
  • Isoflurane
  • Enflurane
  • Halothane
• Mechanism of action: Act on the CNS, causing amnesia, analgesia, and immobility
• Advantages: Rapid onset and offset, easy to control, minimal cardiovascular effects

Intravenous Anaesthetics

• Barbiturates:
  • Thiopental
  • Methohexital
• Benzodiazepines:
  • Midazolam
• Opioids:
  • Fentanyl
  • Alfentanil
• Dissociative anaesthetics:
  • Ketamine
• Mechanism of action: Act on the CNS, causing sedation, amnesia, and immobility
• Advantages: Rapid onset, easy to control, can be used for induction and maintenance

Pharmacology

Pharmacokinetics

• Distribution: Anaesthetic agents distribute to the brain, heart, and other organs
• Metabolism: Anaesthetic agents are metabolized by the liver, except for sevoflurane which is metabolized by the kidneys
• Elimination: Anaesthetic agents are eliminated through exhalation, urine, and faeces

Pharmacodynamics

• Dose-response curve: The relationship between the dose of anaesthetic agent and the effect on the CNS
• MAC (Minimum Alveolar Concentration): The minimum concentration of anaesthetic agent required to prevent movement in 50% of patients
• ED50 (Effective Dose 50): The dose of anaesthetic agent required to produce a desired effect in 50% of patients

Interactions

• Synergism: The combination of two or more anaesthetic agents to produce a greater effect
• Antagonism: The combination of two or more anaesthetic agents to produce a lesser effect
• Drug-drug interactions: The interaction between anaesthetic agents and other medications, which can affect the efficacy and safety of the anaesthetic

Anaesthetic Agents

Inhalational Anaesthetics

• Volatile anaesthetics include Desflurane, Sevoflurane, Isoflurane, Enflurane, and Halothane
• Act on the CNS to cause amnesia, analgesia, and immobility
• Rapid onset and offset, easy to control, and minimal cardiovascular effects

Intravenous Anaesthetics

• Barbiturates include Thiopental and Methohexital
• Benzodiazepines include Midazolam
• Opioids include Fentanyl and Alfentanil
• Dissociative anaesthetics include Ketamine
• Act on the CNS to cause sedation, amnesia, and immobility
• Rapid onset, easy to control, and can be used for induction and maintenance

Pharmacology

Pharmacokinetics

• Anaesthetic agents distribute to the brain, heart, and other organs
• Metabolism occurs in the liver, except for Sevoflurane, which is metabolized by the kidneys
• Elimination occurs through exhalation, urine, and faeces

Pharmacodynamics

• Dose-response curve shows the relationship between the dose of anaesthetic agent and the effect on the CNS
• MAC (Minimum Alveolar Concentration) is the minimum concentration of anaesthetic agent required to prevent movement in 50% of patients
• ED50 (Effective Dose 50) is the dose of anaesthetic agent required to produce a desired effect in 50% of patients

Interactions

• Synergism occurs when two or more anaesthetic agents combine to produce a greater effect
• Antagonism occurs when two or more anaesthetic agents combine to produce a lesser effect
• Drug-drug interactions occur between anaesthetic agents and other medications, affecting efficacy and safety