• Whenever using neuromuscular blocking agents it is essential to understand what governs the duration of blockade with each of the different agents and how different disease states can alter recovery.
• Reversal of blockade can be performed if required and the agents used and the problems associated with this technique should be understood.
• Since clinically relevant doses of the neuromuscular blocking agents cause paralysis of the musculature involved in respiration it is vital to be able to monitor respiratory function and allow the patient to recover from anesthesia only when ventilatory function has returned to normal.
• Monitoring the degree of neuromuscular blockade Anesthesia: monitoring of neuromuscular blockade is also extremely helpful in determining the recovery following administration of these drugs.
• It is recommended that reversal is not attempted in the presence of complete blockade.
• Reversal of neuromuscular blockade may not be necessary in a patient that has a full return of train-of-four (TOF) and double burst suppression (DBS) on nerve stimulation and has normal ventilatory function.

Uses

• To restore normal neuromuscular transmission following non-depolarizing block Anesthesia: non-depolarizing neuromuscular blockade by raising Ach concentration in the synaptic cleft by using anticholinesterases.

Disadvantages

• Effects of anticholinesterases at muscarinic receptors are potentially undesirable, eg bradycardia, bradyarrhythmias, bronchoconstriction, bronchosecretion, gastrointestinal hypermotility and hypersecretion. Prevented by the concurrent administration of antimuscarinic drugs, eg atropine Atropine and glycopyrrolate Glycopyrronium.
• The ability of different anticholinesterases to antagonize neuromuscular block depends on:
  • The muscle relaxant present.
  • The method by which the block was maintained (repeat dose or infusion).
  • The dose of anticholinesterase injected.
  • The degree of block present when antagonism is attempted (the greater degree of spontaneous recovery present, the greater the chance of successful antagonism).
• Anticholinesterases augment neuromuscular block when phase I block is present.

Technical problems

• Accurate assessment of the degree of spontaneous recovery is essential for rapid effective antagonism of neuromuscular blockade.
• Should only be performed when there are signs of spontaneous recovery from the block, ie when at least one twitch on the train-of-four stimulus pattern is present.

Decision taking

Criteria for choosing test

• Indications that attempted antagonism is likely to be successful are any evoked twitches in response to peripheral nerve stimulation.
• In the absence of peripheral nerve stimulation apparatus, antagonism must wait until respiratory activity such as diaphragmatic twitching is seen.
  This is influenced by other factors unrelated to neuromuscular function so block reversal may be unduly delayed.
• The aim of reversal is to cause a build-up of acetylcholine at the neuromuscular junction to allow competitive antagonism at the postsynaptic receptors with the non-depolarizing neuromuscular blocking agent.
• Anticholinesterase drugs are used to antagonize the action of the enzyme acetylcholinesterase, which normally breaks down acetylcholine, therefore allowing acetylcholine concentration to build up in the synaptic cleft.