In is well known that the plasma concentration is important in determining the rate of recovery from neuromuscular block. However, nondepolarizing neuromuscular blockade are retained at the neuromuscular junction and are not readily displaced in
response of changes in plasma drug concentration, for instance, the neuromuscular block induced by mivacurium appears to considerably outlast the theoretical plasma half-life of the drug and is continued long after the plasma level has fallen to
subparalytic levels due to rapid metabolism by pseudocholinesterase. It has been suggested that although plasma concentration may be the key determinant of recovery from neuromuscular block, recovery will depend upon the dissociation from the
affinity
of drug in the effect compartment and not upon its plasma concentration.
In an attempt to confirm these evidences, we have investigated the response of changes in neuromuscular block after releasing tourniquet at 50% twitch depression using the isolated forearm experiment with various neuromuscular blocking agents.
The
results of this study demonstrated the further increase of block after early tourniquet release in the isolated forarm in all agents; 66(14% in vecuronium, 90(9% in atracurium, 92(7% in pancuronium, and 73(18% in mivacurium.
Conclusively, the further block continued to increase in spite of the negligible plasma drug concentration after early tourniquet release may be caused by more in affinity of drugs in binding sites than plasma drug concentration. Therfore, it is
evident
that both the affinity of drug to the receptor and the plasma drug concentration have influenced on the recovery from the neuromuscular block.
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