Neumuscular Blocking Agents Flashcards
What do neuromuscular blocking agents do?
relax the muscles
Which muscle relaxants are there?
- local anaesthetics
- benzodiazepines
- alpha2-adrenoreceptors agonists
- guaiphensein
- neurmuscular blocking drugs
What are benzodiazepines and alpha2s usually used with?
ketamine as it counteracts the rigidity from ketamine
Where does guaiphenesin act?
centrally acting in the internuncial neurones of the spinal cord, brainstem and subcorticol areas of the brian
What is guaiphenesin not?
an analgesic or anaesthetic
What are the clinical indications for using neuromuscular blockade?
- relaxes skeletal muscles for sugical access
- facilitate control of ventilation
- facilitate tracheal intubation in cats and pigs
- ophthalmic surgery - central eye
- assist reduction of dislocated joints and fractures
- reduces the amount of anaesthetic required?
What is the neurmuscular junction?
motor neurone and muscle cell separated by synaptic cleft
What is released from nerve ending of the neuromuscular junction?
acetylcholine
What does acetylcholine do?
binds to post-synaptic nicotinic receptor with two subunits that must be bound for the release
What does release of acetylcholine release result in?
muscle contraction
What is acetylcholine rapidly hydrolysed by?
acetylcholinesterase within the synaptic cleft
What do neuromuscular blocking drugs do?
- facilitates for endotracheal intubation and intermittent positive pressure ventilation must be available
What are neuromuscular blocking drugs?
depolarising muscle relaxants
What are the benefits of neurmuscular blocking agents?
-fast onset
- one dose only
What can neuromuscular blocking agents do?
- phase II block after more than one dose
- aid intuation in cats and pigs
- may trigger malignant hyperthermia
- increase serum potassium levels
- burns
What are non-depolarisng (competetive) muscle relaxant?
- complete with Ach for post-junctional binding sites
- no initial muscle fasiculation
- slow onset
What are the benefits of non-depolarising muscle relaxants?
can be topped with with 1/3 the initial dose and can be antagonised
What do non-depolarising muscle relaxants prevent Ach from causing?
binding so there is no initial muscle twitch
What is atracurium?
- bis-isoquinolinium compound
- mixture of 10 isomers
- Hoffman elimination
- agent of choice for animals with renal/hepatic compromise
What does atracurium do?
release histamine
What is Hoffman elimination?
temperature reaction in plasma
What type of neuromuscular blockade is vecuronium?
non-depolarising
What is vercuronium?
- steroid compound
- no release of histamine
- 40-50% undergo hepatic biotransformation
What are examples of non-depolarising neurmuscular blockades?
rocuronium, mivacurium, pancuronium
How do you monitor a patient after administration of NMB?
- ventilation
- check tube not kinked/dislodged
- ensure breathing syste, does not become disconnected
- monitor movement of thoracic wall
- ETCO2 and SPo2
What are the signs of inadequated depth of anaesthesia?
- increase in pulse rate
- increase in blood pressure
- salivation/lacrimation
- vasovagal response (bradycardia/hypotension/pallor)
- increase ET CO2
- slight muscle twitching
- pupillary dilation
How do you monitor degree of muscle relaxation?
- peripheral nerve stimulators
- ulnar nerve
- peroneal nerve
- facial nerve
- train of four
What is the train of 4?
4 electrical impulses applied to the nerve over a 2 second period
What factors influence duration of neuromuscular blockade?
- volatile agent
- hypothermia
- hepatic/renal insufficency
- electrolyte and acid base abnormalities
- muscle diseaase e.g myesthenia gravis
- aminoglycoside antibiotics
- dose administered
When would you antagonise non-depolarising NMBs?
once 1 or 2 twitches return
What are some unwanted side effects of anatgonising non-depolarising NMBs?
bradycardia, salivation. bronchospasm, diarrhoea
What do antagonists for non-depolarising NMBs do?
increases concentration of Ach
What are cyclodextrins?
donut like structures
