Colonoscopy is an outpatient procedure performed frequently as a screening test for diagnosis and treatment of a wide range of gastrointestinal problems. It is often viewed as an invasive procedure with the potential for embarrassment, discomfort, and worry. Such fears can result in anxiety that may decrease the tolerance and cooperation of the patient, limit the success of the procedure, and increase the likelihood of complications. Therefore, colonoscopy is frequently performed under sedation. The anxiety level of the patient before the procedure may increase the requirement for sedation. It is important for the anesthesiologist to predict the effective dosages of sedation before the procedure to ensure rapid and comfortable sedation as well as prompt recovery and discharge of the patient.

This prospective cohort study is planned to evaluate the effects of pre-procedural anxiety level on the dose of propofol needed for patient and surgeon satisfaction during colonoscopy.

Patients scheduled for elective colonoscopy for screening are enrolled. On the day of the procedure, demographic data are collected and all patients are asked to complete the Spielberger State-trait Anxiety Inventory (STAI-I and STAI-II) in an isolated, calm room before being transferred to the procedure room.

All patients are monitored with electrocardiogram, pulse oximetry, noninvasive blood pressure and bispectral index measurement at 5-min intervals.

Oxygen is administered at 4 L/min via a face mask, Propofol 2% infusion is started via an effect-site target controlled infusion system (Marsh model).

Once the patient reaches the desired level of sedation as determined by BIS value of 60, the procedure is started.

This monitorization and sedation protocol is the routine management of outpatient colonoscopies and gastroscopies in our institution.

For this study the patients' anxiety levels are evaluated with the STAI score. This is not an intervention but an evaluation of the patients. Drug dosing or sedation management are not adjusted according to the anxiety scores but are calculated with the patients' weight.

During the procedure:

• hemodynamic parameters
• the total propofol dosage
• the number of TCI interventions
• complications (respiratory depression, need for ventilation, nausea, vomiting, laryngospasm, and agitation)
• the procedure duration
• surgeon satisfaction with sedation instrument scores are recorded.

These collected data are studies to determine a correlation between the propofol dose and the pre-procedural anxiety of the patients.

Inclusion Criteria:

• American Society of Anaesthesiology Physiologic assessment score I-II patients
• 18-65 years old
• planned elective colonoscopy under sedation

Exclusion Criteria:

• the use of anxiolytic medications
• history of colonic resection or any intraabdominal surgery
• predicted allergy to propofol
• patients refusing sedation

75 healthy patients undergoing elective colonoscopies as a screening test.