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.