SUCCINYLCHOLINE

SUCCINYLCHOLINE


Introduction:

  • Depolarising skeletal muscle relaxant.
  • Shortest & fastest acting skeletal muscle relaxant.
  • Only muscle relaxant stimulating autonomic ganglia.

MOA: 

  • Causes sustained partial depolarization of muscle end plate -> Produce twitching & fasciculation (initially) –> followed by flaccid paralysis.
Uses:
  • Most commonly used muscle relaxant for passing endotracheal tube (mivacurium).
  • Rapacuronium & rocuronium – Alternatives.
Drug interactions:

By plasma cholinesterase: 

  • Sch rapidly hydrolyzed by plasma cholinesterase.
  • Patients with pseudocholinesterase deficiency –  Causes phase II block (dual block).
  • After administration of 7-10 mg/kg or 30-60 mins succinylcholine exposure –> Nondepolarizing dual block (phase II block) occurs.
  • Phase II block recovery much slower.

With opioid-nitrous oxide anesthesia:

  • Potentiates choline action.
Adverse effects:

  • Post-operative muscle pain (myalgia, muscle soreness) – Very common problem.
  • Succinylcholine – Most common cause of malignant hyperthermia.
  • Accentuate malignant hyperthermia caused by halothane.
  • Vagus bradycardia occurs – Due to vagal stimulation.
  • Increases all pressures – intraocular, intracranial, BP & intrabdominal.
  • Cause muscle fasciculations & soreness.
  • Change in BP & HR, arrhythmia.
  • Changes in histamine release.
  • K+ efflux from muscles.
  • Cause dangerous hyperkalemia.
  • Particularly in burn, massive trauma , crush injury, severe intra-abdominal infection, spinal cord injury, hemiplegia/paraplegia, muscular dystrophy, GB syndrome, rhabdomyolysis, severe parkinsonism, tetanus, polyneuropathy, closed head injury, stroke, encephalitis & myasthenia gravis.
  • Cause masseter spasm  (Trismus) – 
  • Mainly in malignant hyperthermia susceptible patients.
  • Prolonged apnea after succinylcholine
  • Mainly low pseudocholinesterase, atypical (non­functional) pseudocholinesterase, Phase II block & electrolyte imbalance patients.

Treatment: 

  • Continue mechanical ventilation by IPPV, maintain anesthesia, continue monitoring & wait for spontaneous recovery.
  • Fresh Frozen plasma – To provides pseudocholinesterase for Sch metabolization. 
  • Only on unimproved recovery/high dose Sch.
  • Heat treated preparation of cholinesterase.

Contraindications:

  • Tetanus.
  • Hyperkalemia
  • Burns
  • Head injury
  • GB syndrome
  • Renal & hepatic failure
  • Glaucoma & eye injury
  • Hemiplegia/Paraplegia (cerebral stroke)
  • Metabolic acidosis
  • Shock
  • Spinal cord injury
  • Muscular dystrophy
  • Prolonged intrabdominal infection

Exam Important

  • Succinylcholine is depolarising skeletal muscle relaxant, shortest & fastest acting skeletal muscle relaxant & only muscle relaxant stimulating autonomic ganglia.
  • Succinylcholine produces twitching & fasciculation (initially).
  • Sch is most commonly used muscle relaxant for passing endotracheal tube (mivacurium).
  • Sch is rapidly hydrolyzed by plasma cholinesterase.
  • Patients with pseudocholinesterase deficiency result in phase II block (dual block) when administered with Sch.
  • In patients with pseudocholinesterase deficiency, after administration of 7-10 mg/kg or 30-60 mins succinylcholine exposure –> Nondepolarizing dual block (phase II block) occurs.
  • Opioid-nitrous oxide anesthesia potentiates choline action.
  • Post-operative muscle pain (myalgia, muscle soreness) is a very common problem with Sch.
  • Succinylcholine is the most common cause of malignant hyperthermia, (eg: accentuates hyperthermia by halothane).
  • Due to vagal stimulation by Sch, vagus bradycardia occurs.
  • Sch increases all pressures – intraocular, intracranial, BP & intrabdominal.
  • Sch causes critical hyperkalemia.
  • In low pseudocholinesterase, atypical (non­functional) pseudocholinesterase, Phase II block & electrolyte imbalance patients, prolonged apnea occurs after succinylcholine administration.
  • Sch induced apnea is treated by continuous mechanical ventilation by IPPV, maintain anesthesia, continue monitoring & wait for spontaneous recovery.
  • Sch induced apnea is treated by heat treated preparation of cholinesterase.
  • Sch induced apnea due to high does Sch is treated by Fresh Frozen plasma to provide pseudocholinesterase for Sch metabolization. 
  • Tetanus, Head injury, renal & hepatic failure & Hemiplegia/Paraplegia (cerebral stroke) are all contraindications for Sch.
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