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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