Major Update

 Today marks the major update of Simtiva to V4. A long hiatus occurred between V3 and V4, the development of this change was in progress for one year. The main reason for the time spent in development was the introduction of a "complex mode", or a dual mode, which propofol and opioid (remifentanil or fentanyl) simulations can be run simultaneously. The unique advantage of having a "complex mode" is to explore the pharmacodynamic (PD) interaction between these the hypnotic-analgesic combination. A preset endpoint, the probability of tolerance to laryngoscopy (PTOL) was chosen as the measure to quantify the combined effect of these two drugs. A isobologram chart allows the user to explore different combinations of propofol-remifentanil to achieve the exact same PD effect along the same isobole curve. Moreover, the isobologram chart is sensitive to time, as time progresses, the current time point, as marked by a bright red dot, will move on the screen, with the past and future trajectory described by a grey curve.

I have long been amazed by the synergistic effect of drugs. The development from one-drug regimen to a two-drug regimen in Simtiva took a long time, because all the algorithms and data structures have to be changed. The loading of saved/shared sim-files must also maintain backward compatibility. The wait is over - now Simtiva can shed light on propofol-opioid synergism.

Other major features included in V4:

- Complex mode : two drug regimen and pharmacodynamic interaction using "PTOL" index - probability of tolerance to laryngoscopy 

- eBIS for eleveld model: Ce propofol relates to estimated BIS based on PD modelling given by eleveld model

- Improved chart functions: charts can now extend beyond the standard 20-30min as in the last version. The time axis can now be adjusted by user.

- Paediatric mode: allows entry of age in days, weeks, or months; allows entry of postmenstrual age in premature kids (valid for <6month old infant for eleveld model- PMA will affect clearance)