Background and Goal of Study: Computer target controlled infusion systems (TCI) for propofol have been implemented in clinical practice. These systems are using different pharmacokinetic models. We investigated the accuracy of two pharmacokinetic data sets for propofol. Methods: With IRB approval and written informed consent 20 adult male patients were investigated. The patients received 30 mg kg−1 h−1 propofol for hypnosis using an infusion system (Graseby 3400, Graseby Medical Limited, UK). After loss of consciousness the propofol infusion was reduced to 6 mg kg−1 h−1, 45 min later propofol dosage was increased to 20 mg kg−1 h−1 and later decreased to 1 mg kg−1 h−1. Five arterial blood samples were obtained from each patient at different infusion rates. The samples were analysed using a Hewlett Packard HP 6890 Series GC system (Agilent, Germany) combined with an HP 5972 series mass selective detector. Propofol plasma concentrations were calculated with the recorded propofol infusion rates using the propofol data set by Marsh [1] and Schnider [2]. For each arterial blood sample the percentage prediction error (PE) was calculated. In addition, we calculated the median absolute prediction error (MAPE) and the median percentage prediction error (MDPE) for the individual patient and for all measurements. Data are mean ± SD. Results: The highest measured propofol plasma concentration was 9.7 ± 1.8μg/ml, the highest calculated propofol plasma concentrations were 7.0 ± 2.0 μg/ml (Marsh) and 8.8 ± 1.1 μg/ml (Schnider).Table: No Caption Available.Conclusion: The Schnider model for propofol produced a better performance than the Marsh model.

Fuerst, O.; Wilhelm, W.; Grundmann, U.; Bauer, C.; Larsen, R.; Kreuer, S. Author Information

Background: Autoregressive modelling with exogenous input of the middle‐latency auditory evoked potential has been developed for monitoring of anaesthetic depth. This study was designed to investigate the dose–response relationship between endtidal desflurane concentrations and the Alaris Autoregressive Index (AAI, Alaris Medical, Hampshire, UK, version 1.4) or the bispectral index (Aspect Medical Systems, Newton, MA, USA, version XP).Methods: Twenty‐one patients scheduled for radical prostatectomy were investigated. After premedication and induction of anaesthesia with propofol und remifentanil all patients received atracurium and a remifentanil background infusion at a constant rate of 0.1 µg kg−1 min−1. During dissection of the prostate, desflurane endtidal concentrations were varied between 3 and 9 vol%. Both AAI and BIS were determined and compared with the respective endtidal desflurane concentration.Results: None of the patients showed a significant change of AAI values while changing the desflurane concentrations between 3 and 9 vol%. The dose–response of BIS values and desflurane concentrations was not uniform: two patients showed increasing BIS values with increasing desflurane concentrations, while in three patients BIS values remained unchanged. In 16 patients decreasing BIS values adequately reflected an increase in desflurane concentrations.Conclusion: Changes of desflurane concentrations during deep anaesthesia were adequately displayed only in 16 of 21 cases by BIS but in none of the cases by AAI monitoring.

Wrobel, M.; Wagner, S.; Bauer, C.; Kreuer, S.; Eichner, A.; Grundmann, U. Author Information

Wrobel, M.; Wagner, S.; Kreuer, S.; Eichner, A.; Bauer, C.; Grundmann, U. Author Information

Buchinger, H.; Kreuer, S.; Bruhn, J.; Wrobel, M.; Bauer, C.; Wilhelm, W. Author Information