The effect of immobilization on subsequent sensitivity of liMD muscles to d-tubocurarine was examined in a guinea pig model. A foreleg was immobilized in a cast for 1–4 weeks. At the end of this period, isolated nerve-luMDrical muscle preparations were set up and sensitivity to d-tubocurarine assayed. Immobilization increased the ED50 of the drug not only in muscles from the liMD in the cast but also those from contralateral foreliMDs and from hindliMDs. The increase in ED50 was not accompanied by atrophy. In a parallel series of experiments measuring the effect of d-tubocurarine on depolarization by carbachol, the apparent d-tubocurarine-receptor dissociation constant was determined. Immobilization produced no change in this parameter. Because immobilization of one extremity produced sensitivity changes in others, the anesthesiologist must be careful not to assume that monitoring from any liMD will yield normal values in a patient with partial immobility.
Address correspondence to Dr. B.E. Waud, Department of Anesthesiology, University of Massachusetts Medical Center, Worcester, MA 01605.
© 1985 International Anesthesia Research Society