General Anaesthetic Flashcards
What is involved in the ‘Triad of Anaesthesia’?
Analgesia (lack of pain)
Narcosis (lack of memory)
Muscle Relaxation (depressed reflex responses)
Injectable Anaesthetics
Why are they used?
- Induction prior to inhalation anaesthesia
- Sole agent for short duration procedures
- Suppress CNS stimulation in certain conditions
How are injectable anaesthetic drugs distributed around the body?
- Brain receives high concentration of drug after IV injection
- Unconsciousness occurs when a critical concentration is reached in the brain
- Over time, less well-perfused organs take up the drug
- Results in a reduction of plasma levels which creates a diffusion gradient for drug levels to move from the brain to plasma
- Consciousness returns as the brain drug level falls below critical
How are GA drugs metabolised and excreted in the body?
Metabolised in the liver
- Converting from lipid to water soluble molecules
Excreted in bile or urine
What is Total Intravenous Anaesthesia (TIVA)?
An alternative to gaseous anaesthetics.
- Avoids side effects of inhalation agents
- Useful where inhalation delivery would compromise access for surgery
Injectable Anaesthetics
Name a Phenol Derivative Drug and its Advantages and Disadvantages.
Propofol
Advantages:
- Rapid metabolism and recovery
- Non irritant perivascular
- Can be used for TIVA as non-cumulative
Disadvantages:
- Apnoea if injected too fast
- Hypotension and bradycardia
- Excitable recovery
Injectable Anaesthetics
Name a Steroid Anaesthetic Drug and its Advantages and Disadvantages.
Alfaxalone
Advantages:
- Rapid, smooth induction
- Minimal cardio/respiratory depression
- Rapid elimination
- No pain on injection
Disadvantages:
- Adequate premed required for smooth induction
- Excitable recovery
Injectable Anaesthetics
Name a Dissociative Anaesthetic Drug and its Advantages and Disadvantages.
Ketamine
Advantages:
- Provide analgesia
- Protective airway reflexes maintained
Disadvantages:
- Poor muscle relaxation
- Slow onset of anaesthesia
