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Departments of
*Anesthesia and
Physiology, University of California, San Francisco, San Francisco, California
Address correspondence and reprint requests to Dr. Talke, Department of Anesthesia, University of California, San Francisco, San Francisco, CA 94143-0648. Address e-mail to pekka-talke{at}quickmail.ucsf.edu
The neuromuscular effects of dexmedetomidine in humans are unknown. We evaluated the effect of dexmedetomidine on neuromuscular block and hemodynamics during propofol/alfentanil anesthesia. During propofol/alfentanil anesthesia, the rocuronium infusion rate was adjusted in 10 volunteers to maintain a stable first response (T1) in the train-of-four sequence at 50% ± 3% of the pre-rocuronium value. Dexmedetomidine was then administered by computer-controlled infusion, targeting a plasma dexmedetomidine concentration of 0.6 ng/mL for 45 min. The evoked mechanical responses of the adductor pollicis responses (T1 response and T4/T1 ratio), systolic blood pressure (SBP), heart rate (HR), and transmitted light through a fingertip were measured during the dexmedetomidine infusion and compared with pre-dexmedetomidine values using repeated-measures analysis of variance and Dunnett’s test. Plasma dexmedetomidine levels ranged from 0.68 to 1.24 ng/mL. T1 values decreased during the infusion, from 51% ± 2% to 44% ± 9% (P < 0.0001). T4/T1 values did not change during the infusion. Plasma rocuronium concentrations increased during the infusion (P = 0.02). Dexmedetomidine increased SBP (P < 0.001) and decreased HR (P < 0.001) (5-min median values) during the infusion compared with values before the infusion. Dexmedetomidine increased the transmitted light through the fingertip by up to 41% ± 8% during the dexmedetomidine infusion (P < 0.001).We demonstrated that dexmedetomidine (0.98 ± 0.01 µg/kg) increased the plasma rocuronium concentration, decreased T1, increased SBP, and decreased finger blood flow during propofol/alfentanil anesthesia. We conclude that dexmedetomidine-induced vasoconstriction may alter the pharmacokinetics of rocuronium.
Implications: We studied the effect of an 
2-agonist (dexmedetomidine) on rocuronium-induced neuromuscular block during propofol/alfentanil anesthesia. We found that the rocuronium concentration increased and the T1 response decreased during the dexmedetomidine administration. Although these effects were statistically significant, it is unlikely that they are of clinical significance.
This article has been cited by other articles:
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  E. Narimatsu, T. Niiya, M. Kawamata, and A. Namiki Lack in Effects of Therapeutic Concentrations of Dexmedetomidine and Clonidine on the Neuromuscular Blocking Action of Rocuronium in Isolated Rat Diaphragms Anesth. Analg., May 1, 2007; 104(5): 1116 - 1120. [Abstract] [Full Text] [PDF]
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 P. E. Tanskanen, J. V. Kytta, T. T. Randell, and R. E. Aantaa Dexmedetomidine as an anaesthetic adjuvant in patients undergoing intracranial tumour surgery: a double-blind, randomized and placebo-controlled study Br. J. Anaesth., November 1, 2006; 97(5): 658 - 665. [Abstract] [Full Text] [PDF]
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J. Hamasaki, I. Tsuneyoshi, R. Katai, T. Hidaka, W. A. Boyle, and Y. Kanmura Dual {alpha}2-Adrenergic Agonist and {alpha}1-Adrenergic Antagonist Actions of Dexmedetomidine on Human Isolated Endothelium-Denuded Gastroepiploic Arteries Anesth. Analg., June 1, 2002; 94(6): 1434 - 1440. [Abstract] [Full Text] [PDF]
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P. O. Talke, E. P. Lobo, R. Brown, and C. A. Richardson Clonidine-Induced Vasoconstriction in Awake Volunteers Anesth. Analg., August 1, 2001; 93(2): 271 - 276. [Abstract] [Full Text] [PDF]
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P. O. Talke, J. E. Caldwell, C. A. Richardson, and T. Heier The Effects of Clonidine on Human Digital Vasculature Anesth. Analg., October 1, 2000; 91(4): 793 - 797. [Abstract] [Full Text] [PDF]
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