The purpose of this study is to determine whether sedation with a combination of pethidin hydrochlorid plus midazolam intravenously (i.v.) is superior to propofol i.v. alone in relation to blood pressure drops during an transesophageal echocardiographic examination (TEE).

Randomisation is done immediately after information of the patient and obtaining of the informed consent. The average time for a TEE study is about 30 minutes. Data collection occurs during this time frame. ECG monitoring and data collection (blood pressure, heart rate, SO2) for the study protocol starts 6 minutes before the application of the sedation. At -6, -4, -2 minutes before the application of the sedation, baseline data are collected. The average systolic blood pressure of these three measures is taken as the reference blood pressure. This is the reference value to calculate the blood pressure drop during the examination. Blood pressure, pulse oxymetry, heart rate are taken every 2 minutes until the examination (TEE) is finished. The questionnaire (for second end points) is filled out by the patient within two hours after the examination. The patient will be followed for the duration of about one hour after the examination, if he is from the outpatient clinic. Patients from the hospital (inpatients) will be followed routinely in the clinic.

Inclusion Criteria:

• all patients scheduled for TEE in our department who have signed the informed consent except those younger than 18 years and patients with a second or third etc. TEE

Exclusion Criteria:

• < 18 years
• intensive care patients
• emergency department patients
• breast feeding women
• pregnant women
• patients with an allergy to Propofol or its ingredient soy oil, Pethidin or Midazolam