Neuromuscular Blockers Flashcards
Which neuromuscular blocker has the highest risk of anaphylaxis
Rocuronium: Due to its quaternary ammonium structure
It is not Atricurium even though it leads to histamine release
Name a neuromuscular blocker preferres in myasthenia gravis
Vecueonium
Which neuromuscular blocker is preferred in the presence of magnesium sulphate therapy?
Vecuronium
Name a neuromuscular blocker that cause tachycardia due to its vagolytic effects
Pancuronium
State three uses of neuromuscular blockers
Facilitate tracheal intubation
Optimise surgical conditions for microsurgery, intrathoracic, intrabdominal and intracranial surgeries
Optimise the ventilation for patient requiring controlled ventilation
State two major classes of non depolarising neuromuscular blockerz
Aminosteroids
Benzylisoquinoliniums
Which tool is used to determine adequate relaxation and assessing for reversibility of neuromuscular blockers?
Peripheral nerve stimulator.
Which nerve and associated muscle are commonly used foe assess reversibility of neuromuscular blockage?
Ulnar nerve and adductor pollicis brevis muscle
State 4 features of non depolarising blocker blockade seen in peripheral nerve stimulator
Tetanic fade: 1st twitch being bigger than the 4th twitch
Posttetanic facilitation
Train of four less than 30%
Ability to be reversed by anticholinesterases
Can suxamethonium exhibit tetanic fade?
Yes only when phase 2 block is present
If not: The twitches are the same height and simply reduce in size
Explain what phase 2 block of suxamethonium is.
Occurs when there is prolonged exposure or repeated high doses of suxamethonium which result in desensitization of the block allowong the motor end plate to repolarise. This eventually lead to conformational changes within acetylcholine receptor
List three major adverse effects of suxamethonium
Hyperkalemia
Bradycardia
Malignant hyperthermia
Just also remember increased intraocular pressure
How long does suxamethonium take to work and how long does it last?
Onset: 30-45 seconds up to 60 seconds
Duration: 5 minutes
Which enzyme is responsible for the metabolism of suxamethonium?
Plasma cholinestetases
Not acetylcholinesterase
Which neuromuscular blocker is preferred for rapid sequence induction?
Suxamethonium
Alternative is Rocuronium in high doses
Is suxamethonium tylically used for maintenance of muscle relaxation?
Nope
Remember repeated doses leads to phase 2 block which slows recovery
Name a condition characterised by partial or total deficiency or defect in pseudocholinesterases leading to prolonged effects of suxamethonium and paralysis
Scoline apnoea
Homozygous: Prolongation 6-8 hours
Heterozygous: 20-30 minutes
List four factors that reduces enzynatic activity of plasma cholinesterase
Hypothermia
Liver disease
Pregnancy
Drug drug interaction
List 6 contraindications of suxamethonium
Serum potassium>5.5
History of burn
History of denervation injury(UMN and LMN lesions)
Known or suspected myopathy
Known or suspected risk of malignant hyperthermia
Known pseudocholinesterase deficiency
Also immobility: Due to stroke, parapelgia, end stage diseases
By how much does a single 1mg/kg dose of suxamethonium increase potassium?
Increase plasma K by 0.5 mmol/l
State two commonest settings in which suxamethonium induced bradycardia is seen
Children
Repeated doses
Note: It leads to cardiac arrest so atropine should always be ready
Which neuromuscular blocker cannot be reversed by anticholinesterases?
Suxamethonium
An attempt can prolon the blockade and make it more tense
Which neuromuscular blocker is associated with masseter rigidity dueing induction?
Suxamethonium
State the treatment of scoline apnoea
Supportive care: ensuring adequate sedation whilst continuing mechanical ventilation until suxamethonium is completely metabolised
Administering fresh frozen plasma
