The aim of the present study was to compare SPI guided analgesia with standard clinical practise during general anesthesia using a balanced setting of sevoflurane and sufentanil anesthesia. It was to be tested whether SPI guided analgesia leads to more cardiovascular stability, less use of analgetics and shorter recovery from anesthesia.

General anesthesia can be considered as a combination of hypnosis, antinociception, and immobility. The monitoring of hypnosis and immobility has been established in clinical practise, however for the evaluation of antinociception a valid monitoring is missing.

The Surgical Pleth Index (SPI; former named Surgical Stress Index-SSI) is a multivariate index derived non invasively from finger plethysmographic signal. It has been demonstrated to correlate with surgical stress intensity. In the setting of total intravenous anesthesia TIVA our group could show beneficial effects of SPI guided analgesia in terms of remifentanil consumption, hemodynamic stability and incidence of unwanted events.

Therefore, we wanted examine whether these beneficial effects of SPI guided anesthesia can be transferred to a setting of balanced anesthesia using a volatile anesthetic sevoflurane and the opioid sufentanil.

The following hypotheses have been made:

1. SPI guided analgesia will result in less sufentanil consumption
2. SPI guided analgesia will result in more hemodynamic stability and faster recovery of the patient after anesthesia, and less opioid use in post operative period

Inclusion Criteria:

• age between 18 - 65 years
• ASA physical status I or II
• elective surgery under general anesthesia of 1-2 hours
• written informed consent

Exclusion Criteria:

• pregnancy
• history of cardiac arrhythmia
• presence of any neuromuscular opr neurologic disease
• use of CNS active medication or alcohol/illicit drug abuse -