Adaptive feedback-controlled infusion versus repetitive injections of vecuronium in patients during isoflurane anesthesia.
OBJECTIVE
To compare vecuronium requirements using repetitive injections and a model-based, closed-loop, feedback-controlled infusion during isoflurane anesthesia.


METHODS
Randomized open study.


METHODS
Departments of Anesthesiology and Ear, Nose, and Throat Surgery at a university hospital.


METHODS
Twenty-two patients of ASA physical status I or II undergoing elective otolaryngological surgery requiring general anesthesia.


METHODS
Vecuronium was used for muscle relaxation. The desired level of neuromuscular transmission was set to 10% of control. All patients received vecuronium 0.08 mg/kg for intubation. Thereafter, vecuronium was injected repetitively in 11 patients (Group 1) whenever spontaneous recovery had reached the 10% level. In the other group of 11 patients (Group 2), relaxation was maintained by an adaptive closed-loop feedback system, which was based on a pharmacokinetic-dynamic model.


RESULTS
Neuromuscular transmission was quantified by the evoked electromyogram of the hypothenar muscles. In Group 1, the first repetition of 0.02 mg/kg had to be administered after 27.0 +/- 5.5 minutes, followed by repetitions of the same dose every 16.3 +/- 3.0 minutes. The induced neuromuscular block ranged from 83% to 100%. The mean vecuronium demand was 0.123 +/- 0.018 mg/kg/h. In Group 2, stable relaxation of 90% +/- 2% was achieved within 19.2 +/- 7.5 minutes after a period of damped oscillations. The mean offset from the target value of 90% blockade was 0.65% +/- 0.32%. The average vecuronium requirement was 0.056 +/- 0.021 mg/kg/h during steady state. The difference between the groups in muscle relaxant demand was statistically significant.


CONCLUSIONS
The model-based adaptive feedback system proved to be useful in maintaining a stable degree of paralysis, adjusting relaxant input to individual demand, and minimizing drug requirement, as compared with repetitive injections.
Institute of Anesthesiology, University of Bonn, Germany.
B J
BJ
Ebeling
W
W
Müller
P
P
Tonner
K T
KT
Olkkola
H
H
Stoeckel
D000293:Adolescent; D000328:Adult; D000769:Anesthesia, Inhalation; D004576:Electromyography / Q000187:drug effects; D005071:Evoked Potentials / Q000187:drug effects; D005246:Feedback; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D007275:Injections, Intravenous; D007530:Isoflurane; D008297:Male; D008875:Middle Aged; D009126:Muscle Relaxation / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects; D013997:Time Factors; D014459:Ulnar Nerve / Q000187:drug effects; D014673:Vecuronium Bromide / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics
D014673:Vecuronium Bromide; D007530:Isoflurane