Anesth Analg 2003;96:438-442
© 2003 International Anesthesia Research Society
ANESTHETIC PHARMACOLOGY
The Duration of Immobilization Causes the Changing Pharmacodynamics of Mivacurium and Rocuronium in Rabbits
Kyo S. Kim, MD, PhD,
Jeong W. Jeon, MD,
Myoung S. Koh, MD,
Jae H. Shim, MD, PhD,
Sang Y. Cho, MD, PhD, and
Jung K. Suh, MD, PhD
Department of Anesthesiology, Hanyang University Hospital, Seoul, Korea
Address correspondence and reprint requests to Kyo Sang Kim, MD, PhD, Department of Anesthesiology, Hanyang University Hospital, #17 Haengdang dong, Sungdong gu, Seoul 133-792, Korea. Address e-mail to kimks{at}hanyang.ac.kr
In the clinical setting, in patients with a cast, it is not known whether the monitoring of the neuromuscular paralysis induced by either mivacurium or rocuronium in the contralateral limb is the correct interpretation. We compared the dose-response relationships and the neuromuscular blocking effects of mivacurium and rocuronium in 56 anesthetized rabbits immobilized in a plaster cast for 2, 4, and 6 wk. Train-of-four stimuli were simultaneously applied every 10 s to both common peroneal nerves, and the force of contraction of both tibialis anterior muscles was measured. Immobilization was associated with a rightward shift of the mivacurium and rocuronium dose-response curves after the duration of the immobilized limb, whereas no shift occurred in the contralateral limb. The 50% effective dose values for 0, 2, 4, and 6 wk of immobilization in the immobilized limb of mivacurium were 15.1 ± 1.4, 18.2 ± 1.5, 21.5 ± 1.9, and 27.8 ± 2.5 µg/kg, respectively, and they were unchanged in the contralateral limb. The calculated 50% effective dose values for the correspondence of rocuronium were 48.1 ± 4.1, 56.2 ± 4.2, 64.8 ± 4.9, and 75.1 ± 5.5 µg/kg, respectively, and they were unchanged in the contralateral limb. The rabbits receiving mivacurium and rocuronium had a significantly accelerated recovery from neuromuscular blockade compared with the placebo group in the immobilized limb after the immobilized duration, whereas there were no differences in the contralateral limb. The results of the present study showed that immobilization disuse atrophy produced by casting led to the development of resistance to both mivacurium and rocuronium; however, no resistance was shown in the contralateral limb. The peripheral nerve stimulator could be applied on the nonimmobilized limb, which might be associated with a normal recording if either mivacurium or rocuronium was used as neuromuscular relaxants.
IMPLICATIONS: In the present study, we examined, in vivo, whether the duration of immobilization can alter the pharmacodynamics of mivacurium and rocuronium in an immobilized limb and/or a contralateral limb in rabbits. The immobilization disuse atrophy produced by casting led to the development of resistance to both drugs but no resistance was shown in the contralateral limb.
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