Flashcards in Drugs in Surgery Deck (33):
What are the ways to take general anaesthetics (GAs)?
What are premedications?
What do GAs do?
Abolish awareness and response to pain
Why are GAs used in surgery?
Loss of consciousness, including memory
Suppression of pain
Suppression of skeletal muscle reflexes and tone
What are the toxic effect of GAs?
Depresses b.p. and resiration (low therapeutic index)
Liver/kidney damage (rarely)
What are the characteristics of the ideal anaesthetic?
Low or harmless metabolism
What is quick inductio?
Low solubility in blood, giving rapid saturation of bloos
What is high potency?
High lipid solubility
What is reversibility?
Gases give good control, injection less so
What is low toxicity?
What are volatile/ gaseous anaesthetics?
Many, simple, unreactive compounds
Halothane and nitrous oxide are commonly used
What is the compositiong of volatile/gaseous anaesthetics?
Numerous simple, small molecules
Mostly very unreactive compounds
What happens with intravenous agents after injection
Very rapid (high cerebral blood flow)
Very short duration (redistribution to other organs)
What is an example of an intravenous agent used?
What are the characteristics of thiopentone?
Low therapeutic index
Depresses heart and respiration
Repeat dose-> longer anaesthesia (slow metabolism)
What are intravenous agents?
What are the mechanism of intravenous mechanisms?
Synaptic transmission, not axonal conduction
Where is analgesia caused in intravenous mechanisms?
Reticular formation and thalamus
Where is unconsciousness caused in intravenous mechanisms?
Rf and hippocampus
Where is amnesia caused in intravenous mechanisms?
What mechanism was recognised by is now discredited?
What is the lipid-solubility mechanism?
Interact with hydrophobic structure
Membranes- volume expansion (pressure reversal)
Protein binding (hydrophobic sites)
What do receptors encourage?
Opening of chloride channels (e.g. GABA receptors)
What does Cl- entry into a neurone cause?
Hyperpolarisation and inhibition
What do general anaesthetics do in terms of the Cl- entering the neurone?
Enhance the response
What drugs are used as a premedication?
What is hyoscine?
Muscarinic receptor antagonist- dries up secretions of saliva and bronchial mucus
What is morphine?
Prevents post-operative pain
Local anaesthetic- blocks conduction in sensory nerves
What do muscle relaxant drugs do?
Voluntary muscles can be relaxed by drugs which interfere with nicotinic receptors
What are some examples of muscle relaxant drugs?
What does tubocurarine do?
Competes with ACh
Reversible with ChE inhibitor