Anaesthetic Drugs Flashcards
What is the triad of anaesthesia?
- triad of what anaesthetist aim to achieve during major surgery
What are the 3 parts of the triad of anaesthesia used during major surgery?
1 - analgesia, amnesia and low HR
2 - amnesia, low HR and muscle relaxation
3 - analgesia, low HR and muscle relaxation
4 - muscle relaxation, analgesia and amnesia
4 - muscle relaxation, analgesia and amnesia
What are some of the roles an anaesthetist performs during the day?
- pre-assessment prior to surgery
- anaesthetise
- monitor recovery
post-operative visits
Do all drugs used in anaesthesia target the same places in the body?
- no
What are some of the sites in the CNS where analgesic drugs target?
- thalamus
- cerebral cortex
- reticular activating system
- spinal cord
What are some of the receptors involved in analgesic drugs?
- GABA and glutamate receptors
- voltage gated ion channels
- glycine and serotonin receptors
What are analgesic agents able to do excitable tissues?
- suppress excitable tissues
- important for all 3 aspects of the triad of anaesthesia
- especially consciousness
Analgesic agents possess an important feature which allows them to move freely in different compartments of the body, especially crossing the blood brain barrier (BBB). What is the property that they possess that allows them to cross the BBB?
1 - steroid like structure
2 - bind with CO2 and cross BBB
3 - lipid soluble
3 - lipid soluble
- meaning they can cross lipid membranes
There are 2 general delivery methods anaesthetist use, what are they?
1 - inhaled
2 - intravenous
What are the 3 common inhaled analgesic drugs used today?
1 - sevoflurane
2 - isoflurane
3 - desflurane
What is the core intravenous analgesic drug that we need to know?
1 - propofol
2 - thiopentone
3 - etomidate
4 - ketamine
1 - propofol
What is the main action of gamma-Aminobutyric acid also known as γ-aminobutyric acid, but referred to as GABA?
- opens Cl- channels, increasing negative charge in a cell
- reduces chance of an action potential
What is the mechanism of action of propofol that is most commonly described?
1 - inhibits GABA
2 - inhibits serotonin receptors
3 - potentiates GABA
4 - potentiates serotonin
3 - potentiates GABA
- binds to GABA-A receptor
- essentially increases the inhibition of neurotransmitters
Once propofol is administered intravenously does it become bound (to proteins so it remains in the bloodstream) or unbound so it can be absorbed by cells?
- both
- bound means it acts as a reserve (most of it)
- unbound is active
- lipid soluble so can move anywhere in the body, including crossing the blood brain barrier
As propofol is administered intravenously it has 100% bioavailability, which means it peaks in the blood very quickly. When it is administered it enters the venous system. To enter the circulation it must travel to which organ?
1 - heart
2 - lungs
3 - liver
4 - kidneys
1 - heart
- returns to right side of the heart
- travels to the lungs
- back to left side of the heart
- enters systemic circulation
As propofol is administered intravenously it has 100% bioavailability, which means it peaks in the blood very quickly. It is lipid soluble so it is able to cross the blood brain barrier. Generally how quickly can propofol reach the brain?
1 - around 60 seconds
2 - around 6 minutes
3 - around 60 minutes
4 - > 60 minutes
1 - around 60 seconds
- lipid soluble so the unbound can enter the brain
- once it reaches the brain they become unconscious
Propofol is both bound and unbound in the body when administered. Why is it important that the majority of this drug remains in the bound form in the blood?
- acts as a reserve for propofol
- ensures concentration gradient so it can flow down concentration into tissues. especially the brain
Does the concentration of propofol in the blood reduce due to the metabolism of the drug or re-distribution in other tissues?
- re-distribution in other tissues
- not metabolised and cleared until much later
What is the class of inhaled drugs currently used in analgesic called?
- halogenated ethers
Etherisation is the administered delivery of halogenated ethers. What are the 3 common stages, which are essentially a reduction in consciousnesses, if halogenated ethers are administered slowly?
1 - analgesia (pain relief)
2 - excitement (agitated, delirium, enthusiasm)
3 - surgical anaesthesia (no pain in surgery or recollection of whats happened)
Inhalation anaesthetics have 3 main adverse effects, what are they?
1 - post-operative nausea and vomiting (PONV)
2 - irritant, makes gas induction difficult (coughing)
3 - emergence phenomena (delirium)
What are neuromuscular blocking agents (NMBA)?
- drugs that block neuromuscular transmission at the neuromuscular junction
- paralysis of the affected skeletal muscles follows
Neuromuscular blocking agents (NMBA) are drugs that block neuromuscular transmission at the neuromuscular junction, causing paralysis of the affected skeletal muscles. Should these be given to conscious or unconscious patients?
- only unconscious patients
- very distressing to have paralysis whilst conscious
Neuromuscular blocking agents (NMBA) are drugs that block neuromuscular transmission at the neuromuscular junction, causing paralysis of the affected skeletal muscles. These are only administered once a patient is unconscious. What are the 2 main times NMBA are administered?
1 - facilitate intubation
2 - facilitate surgery of ventilation
Neuromuscular blocking agents (NMBA) are drugs that block neuromuscular transmission at the neuromuscular junction, causing paralysis of the affected skeletal muscles. These are only administered once a patient is unconscious. They can be divided into 2 categories, what are they?
1 - depolarising
2 - non-depolarising
Quaternary ammonium compounds are non-depolarising Neuromuscular blocking agents (NMBA). What is the mechanism of action of these drugs?
1 - competitively bind to ACh receptors
2 - bind to ACh in synaptic cleft and inhibit binding to ACh receptors
3 - inhibit ACh release from pre-synapse
4 - increase levels of acetylcholinesterase
1 - competitively bind to same site as ACh
- inhibit action potential in muscles without initially causing depolarisation
Succinylcholine is a depolarising Neuromuscular blocking agents (NMBA). What is the mechanism of action of these drugs?
1 - competitively bind to ACh receptors
2 - bind to ACh in synaptic cleft and inhibit binding to ACh receptors
3 - inhibit ACh release from pre-synapse
4 - increase levels of acetylcholinesterase
1 - competitively bind to ACh receptors
- initially they cause action potential and fasciculations (muscle twitch)
- succinylcholine is not degraded by acetylcholinesterase so channels remain open
- receptors become desensitised and eventually re-polarise and muscle relaxes
Neuromuscular blocking agents (NMBAs) are used routinely by anaesthetists. What are some of the main purposes they are used for?
- intubation (ICU)
- surgery (especially if muscles do not relax)
- ventilation
- electroconvulsive therapy (suppress before giving therapy)
- transfer of patients
- lethal injection
If a patient has been identified as having cholinesterase deficiency, why can the administration of succinylcholine, a depolarising neuromuscular blocking agent be bad?
- cholinesterase degrades succinylcholine (choline in the name)
- caused prolonged paralysis
What is Botulinum toxin?
- a purified substance derived from bacteria
- blocks nerve signals to the muscle at pre-synapse
- stops vesicles containing ACh from being released
- muscle is not able to contract
What is the most poisonous substance to humans that is known?
1 - rocuronium
2 - botulinum toxin
3 - succinylcholine
4 - entacapone
2 - botulinum toxin
- 2 nanograms/ml can kill
