The investigators attempted to determine an adequate priming volume for our infusion system, and investigated the extent of a possible delay of the drug effect, that would result from mechanical defects of the infusion system, with or without priming the infusion system, using direct gravimetrical measurements of virtual infusate amounts during target controlled infusion of 2 remifentanil diluents.

Priming the infusion system (PRIMING) was performed using an evacuation of 2.0 ml to the atmosphere prior to Target-controlled Infusion (TCI). Forty eight TCI, using 50 μg/ml or 20 μg/ml of remifentanil diluents, were performed targeting 4.0 ng/ml of effect site concentration (Ceff), with or without PRIMING. Using simulations, the gravimetrical measurements of the delivered infusates reproduced actual predicted concentrations.

Inclusion Criteria:

• electric medical records of the patients who had undergone general anaesthesia

Exclusion Criteria:

• body weight exceeding 20% of ideal body weight