MUSCLE RELAXANTS Flashcards
Do children need muscle relaxants?
No
Why do we use muscle relaxants?
-to facilitate surgery (laparoscopic, ophthal ,ENT etc.)
-to facilitate Rapid sequence induction
-
How does the NMJ work?
There is calcium that causes a action potential as it causes acetycholine to work on the nicotinic receptor on the muscle. This also facilitates the release of potassium
What class of muscle relaxant is suxamethnonium?
Depolariser
Which muscles are we relaxing?
Skeletal muscle fibres
Do muscle relaxants cause analgesia?
No
What is the mechanism of action of non-depolarising muscle relaxants?
-They sit on the nicotinic receptors and prevent Ach from sitting on the receptor and making sure that no muscle contraction takes place
Is the duration of suxamethonium long or short?
Short out of all the muscle relaxants
Why is it safe to use non-depolarising relaxants in mothers?
It does not cross the BBB
and placenta
Why is it that the more non-depolarising muscle relaxant that I give the bigger the paralysis?
-Because it is dose dependant
What is the mechanism of action of suxamethonium?
- Acts similarly to Ach and binds to nicotinic receptor however it is 1000x stronger
- When injected once it gives a phase I block
- When injected twice it causes a phase II block which is similar to non-depolarising muscle relaxants
Why does suxamethonium not need a reversal agent?
Because it is naturally broken up by the plasma cholinesterases
What is the dosage of suxamethnonium?
1-2mg/kg in adults IV
2-4mg/kg IM
How long do we have until it starts to wear off?
6-12 minutes
How long do we have until it starts working?
60 seconds
What are the indications of using suxamethonium?
- short operations<12 minutes
- Laryngospasm
- Rapid sequence induction(when we try to prevent aspiration of stomach contents)
What is the autonomic nervous system made up of?
- parasympathetic
2. sympathetic system
Parasympathetic?
The ACh will work and synapse onto the muscarinic receptors causing effects such as bradycardia
Sympathetic?
The Ach will work and synapse on the noradrenergic receptors and possibly cause tachycardia
What is the function of parasympathetic stimulation on the lungs?
- secretions
- bronchospasm
so suxamethonium will be contraindicated in patients with these lung problems
Why is suxamethonium contra-indicated with patients that already have high potassium?
- This is associated with patients who have upper motor neuron lesions
- burn patients up to 6 months
- Malignant hyperthermia
- myopathies
- muscular atrophy and muscle trauma
- increased cranial pressure
What will happen to the patient if the potassium increases by 8 per litre?
Diastolic cardiac pressure
What will happen to the patient if the potassium increases by 8kpa per litre?
Diastolic cardiac arrest
What are the side effects/complication of Suxamethoniu?
- fasciculations
- muscle pain
- malignant hyperthermia
- prolonged apneoa
- anaphylactic reaction
- bronchospasm/increased secretions
What is the cause of the suxamethonium apnoa?
Low concentrations of pseudo cholinesterases
Heterozygote: minutes
Homozygote: hours
What are the properties of rocuronium?
- Stays in the fridge
- onset of action: 60 seconds
- Duration of action: 60secs-3 minutes
Metabolised in the liver
What are the properties of vecuronium?
- It is a powder
- onset of action: 2-3 minutes
- duration of action: 30-45 minutes
- metabolised in the liver
What are the properties of cisatriqurium?
- It is kept in the fridge
- onset of action is: 3-5 minutes
- duration is 30-45 minutes
- eliminated via the Hoffman elimination
What are the properties of pancuronium?
- Kept in the fridge
- 5 minutes
- offset: 45-60 minutes
- excreted by the renal system
- causes tachycardia
Which muscle relaxant doesn’t get eliminated by the hepato-biliary excretion?
Cisatricurium
