Anaesthetics: pharmacology and mechanisms Flashcards
What are the types of regional anaesthetics
Spinal
Epidural
Peripheral nerve block
Definition of general anaesthesia
A drug-induced reversible state consisting of unconsciousness, amnesia, anti-nociception and immobility, with maintenance of physiological stability
How does propofol work
It acts at a GABAa receptor in the cortex, thalamus and brainstem on postsynaptic neurones.
Binds there and enhances affinity of the receptor for GABA.
This causes chloride influx which causes membrane hyperpolarisation
More difficult to propagate an action potential
What is propofol
causes unconsciousness
effects of propofol on CNS
Loss of verbal contact Atonia Unresponsiveness Loss of brainstem reflexes (e.g.corneal) Apnoea (stop breathing)
Decrease in cerebral metabolic requirement for oxygen
Decreased cerebral blood flow
Decreased intercranial pressure
Why can propofol be used In patients who have suffered traumatic brain injuries
Decrease in cerebral metabolic requirement for oxygen
Decreased cerebral blood flow
Decreased intercranial pressure
How does propofol affect bp
Decreased
What is Rocuronium
Neuromuscular blocker
Mode of action of rocuronium
Blocks the acetylcholine receptor which means that acetylcholine can’t bind and so there can’t be an influx of sodium to propagate an action potential
What Is a risk of rocuranium
Anaphylaxis risk
How to speed up offset rocuranium (so it doesn’t last as long)
- Why are there side effects in this?
- What are the side effects?
- How do you overcome this?
Give Sugammadex
or
Give Neostigmine which is an acetylcholinesterase inhibitor. This means there’s a flood of acetylcholine in junction and this overcomes the blocking effect of Rocuronium
Side effects because acetylcholine also acts the parasympathetic nervous system. Side effects include: -Slow heartbeat -Salivation -Bronchial constriction -Stimulates peristalsis and secretion -Stimulates bile release
Overcome the slowing heartbeat by co-administering GLYCOPYRRONIUM which is an antagonist at muscarinic Ach receptors
What would you co-administer with Neostigmine (which is a drug used to increase offset of rocuranium)
Co-administer glycopyrronium
It is an antagonist at muscarinic Ach receptors
or
Give Sugammadex which mops up rocuranium in plasma and increases conc gradient so the rocuranium can diffuse from between the neurones into plasma
What are the two families of Amphipathic bases and what are their roles
esters
amides
Inhibit action potentials in nociceptive nerve fibres and block transmission pf pain impulses
Mode of action of local anaesthetics
They are unionised
Diffuse into cell and become ionised
Bind to the active sodium channels and make them inactive. Neuron can no longer become depolarised because it is no longer able to reach the threshold potential
How does pKa affect how local anaesthetics work
It affects speed of onset
Lower pKa = greater unionised form = faster onset of action.
They don’t work as well in inflamed/infected tissue
