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Clinical validation of a novel approach for automatic control of neuromuscular block using mivacurium


P.M. Schumacher, K.S. Stadler, Sibylle Hirter, D. Leibundgut, A.M. Zbinden

SGAR - Schweizerische Gesellschaft für Anesthesiologie und Reanimation, Annual Meeting, Fribourg, Switzerland

Background: Several closed-loop controller systems for muscle relaxation based on the T1% as controlled value have been proposed. To improve the applicability a new system for mivacurium that uses the TOF-count as the controlled variable was developed and compared to manually controlled administration of mivacurium. Methods: After local ethical approval 36 consenting ASA I-III patients were randomly assigned to undergo muscle relaxation with either closed-loop (CC) or manually (MC) controlled continuous intravenous infusion of mivacurium. The degree of relaxation was assessed as electromyographic response of the adductor pollicis muscle to supramaximal train of four stimulation of the ulnar nerve. The ability of the controllers to maintain a setpoint of one TOF count was compared based on the mean and SD of the deviation from setpoint (bias and distribution) and the mean absolute deviation from setpoint (inaccuracy). A quality of relaxation measure was calculated that penalized only deviations above the setpoint. Further analysis included time for spontaneous reversion of muscular block as a clinically relevant measure of ‘overrelaxation’ and total drug usage. Results: All setpoint precision indicators were significantly better for the CC group (p<0.05). Quality of relaxation, spontaneous reversion times and drug usage were not statistically different. Interpatient variability was large, the infusion rates differed by a factor of 5 in both groups, averaging at 9 ug/min/kg for all patients. Conclusions: The new controller maintained the set TOF-count with higher precision than the anesthetist. The large variability of the maintenance infusion rates when targeting one TOF count suggest that weight based recommendations for mivacurium infusions are not sufficient, the administration of mivacurium should always be guided by TOF monitoring and an automatic controller could help the anesthesiologist to achieve this task.


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A.H. Glattfelder

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% Autogenerated BibTeX entry
@InProceedings { SchEtal:2004:IFA_2066,
    author={P.M. Schumacher and K.S. Stadler and Sibylle Hirter and D.
	  Leibundgut and A.M. Zbinden},
    title={{Clinical validation of a novel approach for automatic
	  control of neuromuscular block using mivacurium}},
    booktitle={SGAR - Schweizerische Gesellschaft f{\"u}r Anesthesiologie
	  und Reanimation, Annual Meeting},
    address={Fribourg, Switzerland},
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