Anesthetics Flashcards
What are the major types of anesthesia?
General
Regional
Local
Whats the difference between regional and local anesthetic?
Regional is when LA is applied to specific nerves supplying a whole area of the body
Local is when LA is applied directly to a specific tissue(s)
What 3 parts make up the triad of anesthesia?
Analgesia (unpleasant stimuli)
Hypnosis (consciousness)
Relaxation (skeletal muscle)
Any anesthetic drug can have variable effects on all 3 parts of the anesthesia triad. What drugs produce analgesia?
Mainly Opiates
Also local and general anesthetics
What drugs produce hyponosis?
Mainly General anesthetics
Also opiates
What drugs produce relaxation?
Primarily muscle relaxants but also local and general anesthetics
Define the term “balanced Anesthesia”?
Using multiple drugs to do different jobs. This way the mixture and so the effects produced can be tailored to the patient & the surgery
What are the major problems with multi-drug anesthesia?
- Risks of polypharmacy e.g. ADRs & Drug interactions
- Muscle relaxation can require artificial ventilation & airway maintanence
- Risk of relaxation without hypnosis
How do general anesthetics work?
They open neuronal ion channels –> Hyperpolarised neurons so they can’t fire
Inhalational: dissolve in membrane to change shape of channel
IV: bind to GABA receptors
What kind of impact do GAs have on the resp system?
reduce hypoxic/hypercarbic drive
Decrease tidal volume/increase RR
Paralyse Cilia
Decrease FRC
They impair control of breathing –> Mandates airway management
How do GAs affect the CVS?
depress the CV centre and are directly negatively ionotropic
This reduces SVR and CO –> Low MAP
Give the major difference between IV and inhalational GAs along with an example of each?
IV e.g. Thiopentone or Propofol
- Rapid onset
- Rapid recovery
Inhalational, all are halogenated hydrocarbons
- Slow induction
- Easier to maintain
How do we control IV GA infusion?
TCI - Target Controlled Infusion pump system
How do we rate inhalational GAs?
MAC - Minimum Alveolar Conc.
Essentially a measure of potency, the lower the stronger
When might you choose to use muscle relaxants during surgery?
If you will need to ventilate and/or intubate
If immobility is essential e.g. neurosurgery
If you need to access a body cavity via muscles e.g. abdo surgery
What are the major issues with Muscle relaxants?
Fear of being paralyzed but awake
Incomplete reversal e.g. temp airway obstruction
Apnoea (needs airway & ventilatory support)
Whats the main reasons for using analgesia?
It’s not just removing pain
It’s to remove the body’s physiological responses to noxious stimuli e.g. tachycardia and hypertension
How do we know the effect a local/regional anaesthetic will affect the CVS system?
Derangment of the CVS is proportional to the size of the anaesthetized area (think number of veins/arteries affected
What effect does LA have on the resp system?
Alot less than GA since insp muscles are supplied by high up nerve roots. (hence might be preferred in patients with resp problems)
Expiratory are lower so in some LA blocks the cough reflex is still lost
How do we ensure we deliver LA to the right nerve/area?
Can be US guided
What is the limiting factor for LA and what does that depend on?
Toxicity (build up to toxic levels in a tissue)
This depends on:
- Dose
- Rate of absorption (akak site)
- Patient weight
- Drug
Define the term “Differential blockade”?
Different fibres absorp drugs different due to thickness and myelination
This means we can easily block pain fibres without causing paralysis
