OzEMedicine - Wiki for Australian Emergency Medicine Doctors

see also:

• anaesthetics

• neuro-muscular blocking agents (NMBAs) are those that paralyse muscle activity by blocking normal transmission at the neuro-muscular junctions of skeletal muscle.
• there are two main groups of agents:
  • depolarising agents:
    • mimic acetylcholine and activate nicotinic receptors at neuromuscular junctions and then desensitizes the receptor so it can no longer recieve further action potentials
    • these are commonly used at induction of anaesthesia due to their rapid onset of action
    • eg. suxamethonium
  • non-depolarising agents:
    • competitive antagonist of acetylcholine at nicotinic receptors at neuro-muscular junctions, and thus do NOT cause the muscle fasciculation seen in depolarising agents.
    • these are mainly used for maintenance of paralysis during anaesthesia although some are used at induction instead of depolarising agents.
    • The nondepolarizing NMBAs, unlike suxamethonium, can be reversed by the use of neostigmine (0.06 to 0.08 mg/kg IV) after approximately 40 percent of neuromuscular function has returned
    • these can be divided into two groups:
      • aminosteroid agents:
        • eg. vecuronium, pancuronium, rocuronium
      • benzylisoquinolinium agents:
        • not routinely used in the emergency setting because they more often cause histamine release and some cause autonomic ganglionic blockade
        • eg. atracurium and mivacurium

• see suxamethonium¹⁾
• dose: 1.5 mg/kg intravenous dose

• see vecuronium²⁾
• usual maintenance adult dose 10mg
• duration of action 25-40min
• use as an induction NMBA:
  • a priming dose of 0.01 mg/kg is administered three minutes before an increased intubating dose of 0.15 mg/kg.
  • used in this way, vecuronium achieves intubation level paralysis in approximately 75 to 90 seconds

• see rocuronium
• rocuronium has a shorter time to onset and shorter duration of action compared to other agents in its class.
• time to paralysis is approximately 60 seconds, when the recommended dose of 1.2 mg/kg IV is given.
• multiple studies and systematic reviews demonstrate it creates intubating conditions comparable to suxamethonium.

• should not be used for RSI. It can cause tachycardia and histamine release, and has a longer time to onset and duration of action than alternative agents.