Principles of pharmacology Flashcards
What is the triad of anaesthesia?
Relaxation (local/general anaesthetics, muscle relaxants)
Analgesia (Local/general
anaesthetics. opiates)
Hypnosis (General anaesthetics, opiates)
What is a drawback of muscle relaxation?
Paralyse skeletal muscle indiscriminately
Requirement of artificial ventilation
Airways must be managed
What causes awareness under anaesthesia?
Paralysed with muscle relaxant yet insufficiently anaesthetised
How do general anaesthetics work?
Hyper polarise neurons by so they’re less less likely to fire
Mostly through opening chloride channels
What is the onset and recovery with IV anaesthesia like?
Rapid
Act v quickly
One off bolus will wear off quickly
Name an important characteristic of thiopentone and propofol (IV agents)?
Highly fat soluble so can cross BBB rapidly
Which tissues pick up IV anaesthesia fastest?
Viscera
Then muscle
Then fat
What is a consequence of high fat solubility of IV anaesthetics?
After lengthy surgery there will be large amounts of anaesthetic drug stored in fatty tissue which leaks out slowly
What is TCI?
Target Controlled Infusion (TCI) pump system
Allows very accurate infusion to achieve specific blood or brain concentrations of agents
What is MAC?
Minimum alveolar concentration
Measure of potency
Low number means high potency
Describe the onset of inhalational anaesthetics.
Slow induction
How is general anaesthesia usually administered?
IV induction
Inhalational maintenance
What are the respiratory effects of general anaesthesia?
Respiratory depressant
Reduce hypoxic and hypercarbic drive
Decrease tidal volume and increase rate
Paralyse cilia
What are the CV effects of general anaesthesia?
Depresses CV centre
Negatively ionotropic
Vasodilation resulting in decreased VR and CO
What is a post-op problem with muscle relaxants?
Airway obstruction and ventilatory insufficiency in immediate post-op period
Why may analgesia be given to a patient who is already unconscious?
Prevents reflex response to painful stimuli (Tachycardia, sudden movement)
Stops pain waking them up
Opiate analgesics have a direct sedative effect which contributes to general anaesthesia
Is fentanyl short or long acting?
Short
Potent
How do local anaesthetics work?
Block Na+ channels to prevent axonal action potential propagating
Why may regional anaesthesia be preferred in patients with concomitant resp problems?
Main physiological effects are cardiovascular and spare the resp function
How has US affected general anaesthesia?
US guided needle placement allows safer and more effective delivery of the local anaesthetic (LA) drug with less likelihood of the LA going intravenously or direct nerve or vascular injury
What are some medications which may be reduced or halted pre-op?
Anti-diabetic medications
Anticoagulants
What are some major lifestyle factors which should be improved on pre-surgery?
Smoking
Alcohol
Obesity
Exercise
What are METs?
Measurement of exercise tolerance
15% reduction in mortality risk per MET
