Anaesthesia Flashcards
What are the 4 stages of guedels signs?
Stage I- analgesia but still conscious
Stage II- unconscious, breathing erratic, delirium could occur leading to excitement phase
Stage III- surgical anesthesia- four levels of increasing depth until breathing weak
Stage IV- respiratory paralysis and death.
What are the different types of anaesthesia used in modern practice?
Volatiles (gases delivered via lungs)- nitrous oxide, chloroform, halothane, xenon.
IV- propofol, barbiturates, etomidate, ketamine
What is minimum alveolar concentration?
It is used as a way of describing the drug potency of volatiles.
It is describe as the concentration at which 50% of the subjects fail to move to surgical stimulus.
Variations- MAC BAR- no autonomic response
MACawake- when 50% patients are awake
What factors influence MAC?
Age- high in infants, low in elderly Hyperthermia (is increased) Pregnancy Alcoholism Central stimulants Opioids (decreased) Other anaesthetics (decreased)
Why is nitrous oxide commonly prescribed along with other anaesthetics?
It lowers the MAC of the other anaesthetics so that a much lower dose can be used so decreases side effects.
How is IV anaesthetic potency measured?
Plasma concentration to achieve a specific end point eg loss of eye lash reflex
What is the role of GABA receptors in anaesthesia?
They are a critical target in anaesthesia. Binding activates LGIC which increases Cl- conductance which hyperpolarises the cell so depresses CNS activity.
this particularly affects the reticular formation, the hippocampus, the brainstem and the spinal cord.
NMDA receptors are probably also involved
How does GABA receptor activation vary with the potency of a drug?
The higher the potency of a drug, the higher the GABA receptor activation
What are the indications for local and regional anaesthesia?
Dentistry Obstetrics Regional surgery Post op Chronic pain management
What are the different types of local anaesthetics?
Amides- long acting Esters- short acting Lidocaine Ropivacaine Procaine Bupivicaine
What are the general characteristics of local anaesthetics?
Lipid soluble- so higher potency
Lower pKa so faster onset
Highly protein bound- long duration
Why is adrenaline commonly given alongside local anaesthetics?
It causes local vasoconstriction so prevents removal of agent by blood.
What is the mechanism of action of bupivicaine?
It is a use dependent sodium channel blocker
So only moves into sodium channel when activated
Therefore it blocks small myelinated nerves in perferance so is a nociceptive and sympathetic block.
What are the main adverse drug reactions of general anaesthetics?
Chest infection
Vomiting- especially with opioids
hypotension
Post operative congitive dysfunction
