NM blockers Flashcards
Why would you use neuromuscular blocking agents?
Muscle relaxation is part of triad of anaesthesia
What other ways could you achieve muscle relaxation?
General anaesthesia
Local anaesthesia of peripheral nerve
Local anaesthesia - epidural
What are the advantages of using an NMBA?
Provides muscle relaxation
Prevents movement
Whole body
Reduce need for high concentration of inhalational agent
BUT movement is an indicator for anaesthetic depth
What problems are associated with NMBA?
Monitoring depth of anaesthesia
Also prevents movement of respiratory muscles
Patients require IPPV
What are the indications for use of NMBA?
Intraocular surgery
Facilitate IPPV
Laparotomy
Cardiovascularly unstable patients
Orthopaedics
How do NMBA’s work?
Block the action potential at the neuromuscular junction
Two types: Depolarising and non-depolarising
Describe depolarising NMBA’s
Bind reversibly to the Ach receptor
Initial muscle contraction followed by relaxation
Describe non-depolarising NMBA’s
Also bind reversibly to Ach receptor but…
Do not cause muscle contraction
These are used in veterinary practice
Describe reversal of NMBA’s
Modern agents short acting so often just left to ‘wear-off’
Reversed with anti-acetylcholonesterase (neostigmine or edrophonium)
- Allows Ach concentration to rise in synaptic cleft so Ach can compete effectively with the NMBA
- Need to give an anticholinergic concurently to prevent bradycardia
- Eg. Atropine or glycopyrrolate
Competitive antagonist so effect can be overcome by increasing the concentration of the agonist.
Describe monitoring of NMBA’s
Requires a peripheral nerve stimulator
Need to attach and check placement BEFORE administer the NMBA
Peripheral nerve stimulator gives information on how effective the block is
Heart rate, blood pressure and pupil dilation should be monitored as indicators of anaesthetic depth
