Surgical Pleth Index (SPI) is an intraoperative monitor aimed into detection of nociception and guidance of intraoperative opioid administration. Using such a device opioid administration could be potentially optimized during intraoperative period. this study will aim to show whether SPI could be used to reduce unwanted events and lower opioid consumption in gastroenterological surgery. The study will be blinded and randomized including two study arms with either SPI monitoring included or standard monitoring alone.

Patients are extensively monitored intraoperatively. Even though there are monitors for the measurement of nociception, it has not gained wide acceptance partly because of limited and scarce evidence on the efficacy and optimal use. Especially elderly patients undergoing major operation might benefit from optimization of opioid administration. Surgical Pleth Index (SPI) is an intraoperative monitoring aimed for detection of nociceptive stimulus.

The aim of this research is to study whether SPI could be used to guide opioid administration in gastroenterological surgery. The study will consist of a total 80 patients which are randomized into two groups. The study sample is based on power calculation for the reduction of remifentanil consumption.

In the study group the opioid administration will be guided using a SPI based protocol. In the control group the opioid administration will be based on standard monitoring and clinical decision alone. The aim of the study will be to study whether opioid administration optimized using SPI can lover need for anticholinergic drugs, reduce need for opioids or diminish the amount of unwanted side effects postoperatively. The patients will be treated using target controlled infusions of remifentanil and propofol.

The data will be collected intraoperatively using electronic software and using a study data collection form by study personel. All study procedures will take place during operative period.

The study power was calculated using a study comparing depth of anesthesia and depth of nociception balance-controlled group into a group without these monitors. In the group with monitoring the consumption of remifentanil was 9,5±3.8 mg/kg/h while in the unmonitored group the consumption was 12.3 mg/kg/h(Chen, 2010). While taking into notice α= 0,005 and β=90% a number of 39 patients in each group is needed. Based on these we chose 80 patients to be included in the study.

All collected data will be used into statistical analysis ass applicable. Statistical analysis plan describing the analytical principles and statistical techniques to be employed in order to address the primary and secondary objectives, as specified in the study protocol or plan.

Inclusion Criteria:

• Able to provide a written informed consent
• Age 50 years or above
• Laparoscopic or laparotomic surgery requiring intubation with an expected intraoperative time at least two hours.
• ASA classification 1-3

Exclusion Criteria:

• Implanted cardiac pacemaker or known condition with irregular heart rate at the time of inclusion or induction
• Chronic use of opioids
• BMI >35
• Known allergy for study medications
• Over 5 extrasystoles per minute at the time of induction or inclusion
• The use of epidural catheter during the last one hour before surgery or need for catheter intraoperatively (if new catheter is placed at the beginning of surgery test dosage may be used without the need for patient exclusion)

Patients are randomized using sealed envelopes. The ramdomization will be kept blinded to the study subjects