PREDICTIVE ACCURACY AND PRECISION OF THE SYSTEM DISOPRIFUSOR TCI(R) FOR TARGET-CONTROLLED INFUSION OF PROPOFOL

In Germany a TCI-system for propofol (Diso-prifusor-TCI(R)) has been c ommercially available since spring 1997. We investigated the predictio n error and precision of this TCI system as part of a multicentre stud y. Bias, precision, blood concentrations and dosage of propofol were c ompared with patients receiving propofol via a manually controlled inf usion device. Methods: After approval by the local Ethics Committee an d written informed consent, 21 patients of ASA-classification I to III scheduled for major abdominal surgery received either a target contro lled infusion (group T, Disoprifusor-TCI(R)) or a manually controlled infusion (group M) of propofol. The propofol plasma concentrations wer e measured by HPLC. The prediction error for each measurement,the medi an prediction error (MDPE) or bias,the median absolute prediction erro r (MDAPE) or precision and the divergence (change of the prediction er ror over infusion time) were calculated for both groups. Results: For all patients in group T (n = 12) the bias of the TCI system was 6.7% a nd the precision 27.5%. For 70% of all measured plasma concentrations the absolute prediction error was less than or equal to 37%. The diver gence was -5.4% per hour. For all patients in group M (n = 9) the bias was 44.2% and the precision 50%. The mean amount of propofol infused per kilogramm body weight and hour was significant higher in T(9.0 +/- 1.2 mg/kg/h) than in M (6.6 +/- 1.2 mg/kg/h, p < 0.005). Conclusions: With a precision of 27.5% the investigated TCI system (Diprifusor-TCI (R)) showed an acceptable inaccuracy, as for TCI-systems a median pred iction error of +/- 30% has to be expected due to the inherent variabi lity of pharmacokinetic parameters. Further studies will be necessary to find out whether the investigated TCI system for propofol may offer substantial advantages.