I was just asking myself if the SPI value will still reflect the nociception-antinociception balance when you use a drug influencing one of the parameteres used by the SPI algorithm. Vasoactive drugs influence the vascular tonus hence the amplitude of plethysmografic wave that makes up for about 70% of the value calculatated by SPI software; most likely you need to wait for the a new steady stade/balance to be achieved before being sure that SPI value and trends reflects the nociception-antinociception balance. I was just curious how anesthesiologists use SPI in conditions that may limit the accuracy of displayed values.