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Therapeutic neuromuscular blockade is a routine part of intraoperative anesthetic management for many surgeries and is occasionally appropriate in the ICU in order to facilitate certain forms of mechanical ventilation, prevent patient movements that may harm the patient, facilitate procedures, decrease oxygen consumption, or prevent muscle spasm in certain diseases. Therapeutic paralysis involves the administration of neuromuscular blocking agents to interfere with the synaptic transmission at the neuromuscular junction and thereby prevent or decrease the force of muscle contractions. These drugs are administered in boluses or by continuous infusion and their effects can be monitored by patient observation or with peripheral nerve stimulators similar to those used in the operating room.

Definitions and Terms

  • ▪  Neuromuscular blocking agent: A drug that interferes with normal acetylcholine-mediated synaptic transmission (Figure 12-1) by blocking acetylcholine’s actions at the postsynaptic receptors (Figure 12-2).
  • ▪  Depolarizing neuromuscular blocking agents (ie, succinylcholine) depolarize the neuromuscular junction causing initial release of acetylcholine followed by paralysis, and are not typically used in the ICU because of their very short duration and the potential for potassium release on administration.
  • ▪  Non–depolarizing muscle-blocking agents (NMBs) interfere with the action of acetylcholine at the postsynaptic receptor and are typically used for ICU administration.
  • ▪  Train-of-four (TOF) monitoring is a technique by which the effects of NMBs can be monitored objectively involving the administration of a series of four successive electrical stimulations over a peripheral nerve. The force of contraction of a muscle enervated by that nerve is monitored (Figure 12-3) and monitoring can be performed at a variety of locations (Figure 12-4).

Figure 12-1.

Normal synaptic transmission, where acetylcholine (orange circles) acts as the neurotransmitter from the nerve to the muscle.

Figure 12-2.

Paralytic agents (green triangles) interfere with the actions of acetylcholine in the junction.

Figure 12-3.

The degree of paralysis is monitored by administering a series of electrical impulses over a nerve and monitoring the contraction of a muscle enervated by that nerve (ulnar nerve and thumb contraction in this case).

Figure 12-4.

Several common sites for monitoring in the ICU including the wrist, the forehead, and the ankle.


  • ▪  Clinical indications
    • —Chemical paralysis is indicated to facilitate certain nonphysiologic approaches to mechanical ventilation such as inverse-ratio ventilation, airway pressure-release ventilation, or independent lung-ventilation that may be indicated in diseases such as adult respiratory distress syndrome (ARDS) or obstructive pulmonary diseases.
    • —Paralysis may be indicated to prevent the patient from muscle movements that may result in harmful consequences, such as ...

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