Evaluation of estimated blood concentration of propofol on wake-up using 'Congrase', a software to control the syringe pump for propofol infusion

We developed a software to control a Graseby® 3500 syringe pump for propofol infusion through the serial port of Apple® Macintosh(TM)/Power- Macintosh(TM) computer. This software, 'ConGrase', was developed with Metrowerks Code Warrior Professional (CWP 1) and PowerPlant framework using C++. ConGrase communicates with the syringe pump at least every three seconds, and calculates the estimated blood concentration (EBC) of propofol based on the amount of propofol actually infused by applying either the Euler or Runge-Kutta method using the three-compartment pharmacokinetic model. The parameter sets reported by Gepts et al. are used. ConGrase was released at the 44 th Annual Meeting of the Japan Society of Anesthesiology, and is distributed freely. The mean and S.D. of the emergence EBC calculated by ConGrase were 1.22 micrograms- ml^-1 and 0.16 micrograms · ml^-1, respectively. These values are almost the same as values already reported outside Japan. The necessary wake-up time can be calculated with this estimated concentration. With this system, anesthetists can control the EBC at the required level and avoid long delays before the patients wake up after anesthesia.