2 Succinylcholine

Reactions: 

Succinylcholine = Suxamethonium chloride 

Succinylcholine acts as a Depolarizing neuromuscular blocker (=DMR - Depolarising muscle relaxant)

Mnemonic : SSSS
  • FasSiculations
  • FaSt dissociation at receptors (Therefore Short acting )
Mnemonic : DND
  • Not reversed by Neostigmine
  • No fade or Post tetanic stimulation. 

Potentiated by
  1. Isoflurane
  2. Respiratory Alkalosis
  3. Hypothermia
  4. Mg
Antagonised by : Acidosis and NDMR

Repeated use  - causes Phase II block (similar to NDMR) -- (MCQ)

Other points about Sch :
  • Onset within 30 sec --- lasts 10-12 mins.
  • Bradycardia in children (especially after 2nd dose) (MCQ)
  • All presures are increased ( BP , ICP , IOP , Intra gastric )
  • Enzyme metabolism - by PseudoCholinestrase (= plasma = Butyrylcholinesterase) (read below in short about Cholinestrases )

Dibucaine Number :

  • The Dibucaine Number is a measure of the qualitative activity of Pseudocholinesterase and is the percentage of inhibition of the enzyme by the local anesthetic Dibucaine.
  • Normally 75 - 85 % inhibition , But if homozygous defficiency - then 30%
  • It is used to differentiate individuals who have substitution mutations of the Butrylcholinesterase enzyme.


Side effects :
  • Increase K+ (especially after Burns , spinal cord injury , stroke , cerebral palsy )
Therefore Sch is Avoided 48hrs - 9months after acute injury. 
  • Post Op muscular pain which can be decreased by :
                                  1. Self Taming (Pretreatment with small (10 mg) doses of succinylcholine)
                                  2. Precurarization (NDMR + Sch)
                                  3. Lignocaine
  • Malignant Hyperthermia
Note: 
  1. Sch is the MC drug which causes Malignant Hyperthermia.
  2. All Fluranated inhalational anaesthetics & Lignocaine are other drugs which can cause Malignant Hyperthermia.
  • Allergy - releases histamine.
  • Contraindicated in Myotonic Dystrophy : as it causes severe muscle rigidity , preventing respiration and intubation.
  • Can cause Masseter spasm in children.


NeuroMuscular monitoring (Adductor Pollicis , Ulnar Nerve)  (No use in Sch block)

  1. TOF (Train of 4)
  2. PTC ( Post tetanic count )
  3. DBS ( Dual burst stimulation )
  4. Tetanus

Cholinesterases :
  1. True :  RBC and Grey Matter.
  2. Pseudo/False :  Liver and Plasma.



2 comments:

  1. Thanks sir. this is good enough for remembering the confusing points. thanks a lot again.

    ReplyDelete
    Replies
    1. Its our pleasure to help our readers. Please feel free to ask for more articles or problems.

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