Model‐based control of neuromuscular block using mivacurium: design and clinical verification

Background: Short‐acting agents for neuromuscular block (NMB) require frequent dosing adjustments for individual patient's needs. In this study, we verified a new closed‐loop controller for mivacurium dosing in clinical trials. Methods: Fifteen patients were studied. T1% measured with electromyography was used as input signal for the model‐based controller. After induction of propofol/opiate anaesthesia, stabilization of baseline electromyography signal was awaited and a bolus of 0.3 mg kg−1 mivacurium was then administered to facilitate endotracheal intubation. Closed‐loop infusion was started thereafter, targeting a neuromuscular block of 90%. Setpoint deviation, the number of manual interventions and surgeon's complaints were recorded. Drug use and its variability between and within patients were evaluated. Results: Median time of closed‐loop control for the 11 patients included in the data processing was 135 [89–336] min (median [range]). Four patients had to be excluded because of sensor problems. Mean absolute deviation from setpoint was 1.8 ± 0.9 T1%. Neither manual interventions nor complaints from the surgeons were recorded. Mean necessary mivacurium infusion rate was 7.0 ± 2.2 μg kg−1 min−1. Intrapatient variability of mean infusion rates over 30‐min interval showed high differences up to a factor of 1.8 between highest and lowest requirement in the same patient. Conclusions: Neuromuscular block can precisely be controlled with mivacurium using our model‐based controller. The amount of mivacurium needed to maintain T1% at defined constant levels differed largely between and within patients. Closed‐loop control seems therefore advantageous to automatically maintain neuromuscular block at constant levels.