Deep sedation with propofol for ambulatory colonoscopy has become standard clinical practice.To achieve the necessary (e.g.: no excessive movement and no awareness) level of sedation during colonoscopy, propofol can be titrated by hand, continuous infusion or by target controlled infusion.

The aim of the investigators is to evaluate sedation efficacy and recovery between two groups of ambulatory patients having a colonoscopy: one group will receive a manual titration of propofol, the other group a target controlled infusion (TCI) of propofol. The investigators will evaluate both groups before, during and after colonoscopy for adverse events, quality of sedation and recovery. When patients are estimated to be ready for discharge, they will also be subjected to a cognitive and a psychomotoricity test.

Deep sedation with propofol for ambulatory colonoscopy has become standard clinical practice. Fewer adverse events and a faster wake up time than with the use of benzodiazepines are proven. A growing group of patients are subjected to this examination for diagnostic and screening purposes.

In most cases, patients can return home after a short recovery time, under the supervision of an accompanying person. Often, no residual effects are clinically detectable. Some studies advocate that driving skills recover quickly. Current guidelines however, insist to avoid driving or using public transportation alone for at least 12 hours (24 hours if other sedatives are used).

To achieve the necessary (e.g.: no excessive movement and no awareness) level of sedation during colonoscopy, propofol can be titrated by hand, continuous infusion or by target controlled infusion. Only one study, to the investigators knowledge, compares efficacy between manual titration and target controlled infusion of propofol in combination with fentanyl for bidirectional endoscopy.

The aim of the investigators is to evaluate sedation efficacy and recovery between two groups of ambulatory patients having a colonoscopy: one group will receive a manual titration of propofol, the other group a target controlled infusion (TCI) of propofol. The investigators will evaluate both groups before, during and after colonoscopy for adverse events, quality of sedation and recovery. When patients are estimated to be ready for discharge, they will also be subjected to a cognitive and a psychomotoricity test.

To evaluate cognitive function, the investigators will use the digit symbol substitution test. The digit symbol substitution test is popular for detecting deterioration in concentration. Here for 90 seconds, a test subject is asked to change a number in a symbol.

As psychomotor test, the investigators chose a choice reaction time test for its sensitivity to detect minor changes after propofol sedation. This test has also validity in alcohol intoxication. A simple reaction time test is also included for its easy applicability and obtainability in everyday practive. Test results will be compared to see if there is a correlation with the choice reaction time tests.

Inclusion Criteria:

• All patients subjected to deep sedation in ambulant care, having a colonoscopy
• ASA 1-3

Exclusion Criteria:

• Dementia.
• Gastroscopy planned at the same time.
• Allergies to propofol
• All cases were a 'full stomach' is suspected (gastric banding)
• Pregnancy