Anaesthetics Flashcards
When do you use anaesthetics?
Premedication
Induction
Intra operative analgesia
Muscle paralysis
Give two examples of inhalational anaesthesia
Chloroform
Xenon
What does Guedels classification show us?
Stage 1: analgesia and consciousness
Stage 2: unconscious with delirium (erratic breathing)
Stage 3: surgical anaesthesia
Stage 4: respiratory paralysis and death
What is anaesthesia?
Analgesia
Hypnosis
Depression of spinal reflexes
Muscle relaxation
How do you describe volatile anaesthetic potency
MAC: minimum alveolar concentration
Concentration in the alveoli at which 50% of patients fail to move due to surgical stimulus
What factors affect MAC?
Age (high in infants)
Hyperthermia increases MAC
Hypothermia decreases MAC
Things that increase it: pregnancy, alcoholism, central stimulants
Things that decrease it: other anaesthetics, opioids
How do Anaesthetics work?
GABA is a major inhibitory neurotransmitter
Anaesthetics potentiates GABA: leading to anxiolysis, sedation and anaesthesia
So they potentiate GABA mediates chloride conductance to depress CNS activity
What parts of the body does anaesthesia work on?
Depress Hippocampus (memory) Depress brainstem (respiratory drive and some CVS) Spinal cord (dorsal horn) depressed (analgesia)
What are examples of IV anaesthesia?
Propofol and barbiturates which are rapid
Ketamine which is slower
What are the characteristics of local anaesthetics
Lidocaine, Bupivacaine
Lipid solubility which give them a greater potency
What are the general side effects of anaesthetics?
Opioid ones
Hypotension
Chest infection
Allergy, anaphylaxis
What are the two types of anaesthetic?
General: inhalation, intravenous
Local: regional