Automatic Control of Total Intravenous Anesthesia (ACTIVA)

This study concerns the clinical evaluation of a closed loop control system for the automatic administration of anesthetic drugs in TIVA (Total Intra Venous Anesthesia).

The purpose of the experimentation is to demonstrate that the control system under study is reliable, safe, applicable and capable of inducing and maintaining an optimal anesthetic level.

This clinical study consists of the application of the ACTIVA control software for the infusion of intravenous drugs during general anesthesia according to the principle of closed-loop anesthesia.

The objective of the experimentation is to evaluate the reliability, safety and applicability of the infusion system for anesthetic drugs controlled by the ACTIVA software and to carry out the clinical evaluation of the automatic control system during the induction and maintenance of general intravenous anesthesia. The benefits for enrolled patients could be linked to greater stability of anesthesia in the induction and maintenance phases. Constant closed-loop control of infusions and the level of hypnosis could also reduce the hemodynamic impact that general anesthesia has on the patient, by reducing the onset of hypotension episodes.

Enrolled patients will undergo closed-loop anesthesia under the constant supervision of the investigator. The anesthetic drugs used are those recommended for general intravenous anesthesia: propofol and remifentanil.

Identification and description of the medical device:

The medical device object of the clinical investigation consists of the ACTIVA control software developed to control the infusion of anesthetic drugs during general intravenous anesthesia. ACTIVA software has been developed to optimize the infusion of anesthetic drugs according to a closed-loop system that allows the induction and maintenance of a constant and optimal level of anesthesia on the patient. ACTIVA control software is installed on a personal computer (PC).

The level of anesthesia is measured according to the Bispectral Index (BIS) which measures the depth of hypnosis. Through the measurement of the BIS, the administration of anesthetic drugs is automatically regulated by the ACTIVA software and constantly supervised by the anesthesiologist through the graphic interface integrated in the software.

The population for which the device is intended is made up of patients to undergo surgery for which general anesthesia is required, and intravenous anesthesia may be advantageous.

During its operation, the ACTIVA software maintains the desired BIS level, selected by the anesthesiologist through the graphical user interface, communicating the appropriate infusion rate of the propofol and remifentanil anesthetic drugs to the syringe pumps. ACTIVA software communicates with the pumps and the BIS monitoring system with serial connections. These connections are native to the instrumentation used; therefore, no type of modification or manipulation has been made on the medical devices used.

Closed-loop anesthesia:

A closed-loop system can be defined as an automatic control system that bases its operation on the principle of feedback. Its key elements are a system to be controlled, a measuring device (sensor), a controller and an actuator. The sensor measures the controlled variable (system output), which is compared with the desired set-point. The difference between the latter and the output, defined as an error, is used to calculate the value of the control variable (system input).

In the case of closed-loop anesthesia, the system to be controlled identifies with the patient, the actuator is represented by the syringe pump, the controlled variable corresponds to the BIS and the control variable is represented by the rate of infusion of the drugs.

The controller used is a proportional-integral-derivative (PID) it relates the error signal and the control variable by means of three constants (Kp, Ti and Td) allowing a correct infusion of the drugs considering the present value of the error ( proportional action), the past values of the error (integral action) and the advance of the future values of the error (derivative action). These three constants, if properly calibrated, allow to obtain a controller with good performance and robustness. For the ACTIVA system the calibration of these constants was carried out by means of optimization methods performed in simulation.

The anesthesiologist has at his disposal a PC with a graphical user interface through which he can control the start and end of the drug infusion and on which there are the commands through which it is possible to interact with the system. The graphical interface also reports indicators concerning the correct functioning of the control system. In case of malfunction of the ACTIVA software, the patient monitoring systems are never altered or damaged and the infusive pumps continue to operate in manual mode. Switching to manual control is always possible if the anesthesiologist considers it appropriate, even without the presence of system malfunctions.

Eligibility Criteria:
Inclusion Criteria:

* Adult patients undergoing total intravenous general anesthesia for elective surgery

Exclusion Criteria:

* Patients under the age of 18
* Patients incapable of giving consent