Maintenance of anaesthesia Flashcards
Define MAC
Minimal Alveolar Concentration - The concentration of inhalant at which 50% of patients response to noxious stimuli.
True or False - MAC is directly proportional to potency.
False - it is inversely proportional
What are the four aims of anaesthesia?
Unconsciousness
Analgesia
Muscle relaxation
Stability
Outline three characteristics which can affect the MAC of an inhalation agent.
Species, Age - lower in v young/old, higher in young, Lower in hypotension, other drugs, high catecholamines, pregnancy, body temperature.
Stable anaesthesia should be achievable at x times the MAC.
What factor is required to achieve this?
1.2-1.5 x MAC (side effects worsen at > 2.5xMAC)
Stable anaesthesia is initially required.
What is the partial pressure of a gas?
How does this relate to the inhalation agent?
Concentration of a gas in a gas mixture.
PP of the agent in the brain depends on pp in blood and therefore in alveoli.
Delivery of an agent to the brain depends upon which concept?
PP of the agent in the alveoli (ie ventilation/ flow rate) and therefore in the blood –
Why is a low blood solubility desired for a induction/ recovery anaesthetic agent?
Low solubility agents do not require a lot of agent to raise blood PP
How does distribution of inhalation agent differ throughout the body?
Different tissues take different times of pp to equilibrate due to different fat/water content between tissue types.
Define SVP.
Saturated vapour pressure = pressure exerted by molecules in the vapour phase at equilibrium with the liquid phase at a given temperature (T)
Which IV anaesthetic technique is more easily controllable?
Bolus/ continuous?
Continuous - easier to stay within desired effect band
