Paralytic Agent

Aka: Paralytic Agent, Neuromuscular Blockade, Neuromuscular Blocker, Non-depolarizing Neuromuscular Blocking Agent, Nondepolarizing Neuromuscular Blocking Agent, Depolarizing Neuromuscular Blocking Agent

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II. Precautions

  1. Used only in Anesthesia, emergency and Intensive Care
  2. Airway and Respiratory Control is critical after use
  3. Paralytic Agents do not alter Level of Consciousness
    1. Must be used with sedation and analgesia

III. Mechanism

  1. Interfere with transmission at neuromuscular end plate
  2. Two mechanisms of Neuromuscular Blockade
    1. Non-depolarizing agents (AcetylcholineAntagonists)
      1. Prototype: Curare
      2. Agents used clinically
        1. Rocuronium (Rapid Sequence Intubation)
        2. Vecuronium
        3. Pancuronium
      3. Other agents: Tubocurarine, Metocurine, Gallamine
      4. Paralysis progression
        1. Paralysis of small Muscles (eyes, fingers)
        2. Paralysis of extremities, neck and trunk
        3. Paralysis of intercostal Muscles and diaphragm
    2. Depolarizing agents (AcetylcholineAgonists)
      1. Cholinergic Agonists that block Acetylcholine from binding until they dissociate from receptor site
        1. Nerves depolarize (resulting in Fasciculations) prior to paralysis
        2. May also occur with Cholinesterase Inhibitors
      2. Prototype: Succinylcholine
      3. Agents used clinically
        1. Succinylcholine (Rapid Sequence Intubation)
      4. Paralysis progression
        1. Chest and abdomen Fasciculations (depolarization)
        2. Paralysis of neck, arms and legs
        3. Paralysis of face, pharynx and Larynx
        4. Paralysis of respiratory Muscles

IV. Monitoring: Neuromuscular Blockade (Paralytic Depth)

  1. Train of Four
    1. Peripheral Nerve stimulator delivers 4 impulses over 2 seconds
    2. Muscle Twitch response
      1. 1 Twitch indicates sufficient relaxation with nitrous and Opioids
      2. 3 Twitches indicate sufficient relaxation with inhalational agents
      3. 4 twitches (with 4th at least 75% of the first) indicates readiness for Extubation
  2. Sustained Tetany
    1. Peripheral Nerve stimulator delivers a sustained 5 second impulse at 50 Hz
    2. Muscle Twitch response indicates patient is ready for Extubation
  3. Single Stimulation
    1. Peripheral Nerve stimulator delivers a single 0.2 mSec 0.1 Hz stimulation
    2. Muscle Twitch response <5% of normal twitch indicates readiness for Endotracheal Intubation

V. References

  1. Miller in Katzung (1989) Pharmacology, p. 323-33
  2. Savarese in Miller (2000) Anesthesia, p. 412-90

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