General Anesthesia With Xenon in Inspiratory Concentrations of 50% and 70% and Total I.V. Anaesthesia.

The purpose of this study is to evaluate the quantity of propofol administered with Xenon in two inspiratory concentrations, to maintain comparable depth of anaesthesia during the maintenance period of general anaesthesia.

The inert or "noble" gas Xenon has anaesthetic properties that have been recognized 50 years ago. Several preclinical studies and investigations using xenon as an inhalational anaesthetic in humans were performed and reported that this gas has many properties of the ideal anaesthetic agent. Moreover, it is known that when xenon is combined with volatile anaesthetics or opioids, the required doses of those substances are reduced, resulting in a lower incidence of side effects. Patients could benefit from the administration of xenon if this inspired concentration would result in reduced doses of co-administered drugs.

This trial should allow evaluating the propofol consumption required in combination with xenon administered in inspiratory concentrations of 50% and 70% to maintain comparable depth of general anaesthesia as total i.v. anaesthesia, in ASA III patients presenting increased risk of perioperative cardiac complications and undergoing laparotomy or orthopaedic surgery.

Eligibility Criteria:
Inclusion Criteria:

* Patient ≥ 50 years old
* ASA (American Society of Anaesthesiologists) Physical Status III
* Patient with increased risk of perioperative cardiac complications (Revised Cardiac Risk Index\>=2)
* Surgical operation: laparotomy or orthopaedic surgery or laparoscopy
* Planned duration of general anaesthesia in the range of 2-6 hours
* Patient willing and able to complete the requirements of this study including the signature of the written informed consent

Exclusion Criteria:

* Patient with severe impairment of cardiac function (Left Ventricular Ejection Fraction \< 35%)
* Patient with drug-eluting stent placed within 12 months prior to selection
* Woman of child-bearing potential not implementing adequate contraceptive methods
* Pregnant or lactating woman
* Surgical procedure in emergency
* Chronic opioids pain therapy
* Serious illness or medical conditions which are possible contra indication for elective general anaesthesia or administration of intra operative treatments, or which are interfering with the monitoring devices, such as:

  * Myocardial infarction within 6 months prior to selection
  * Any significant history of allergy/hypersensitivity to any drugs used during the study, to silicone or to latex
  * Severely impaired hearing
  * Known severe neurological disorders
  * Any medical condition which does not justify the trial participation in the investigator's judgement
  * General anaesthesia within 7 days prior to selection
  * Laparotomy within 3 months prior to selection, only for patients undergoing laparotomy
* History of drug abuse or psychiatric disorders which would impair the understanding of the necessary information or render medically or legally not able to give written informed consent
* Concurrent treatment with any other experimental drugs
* Participation in any other clinical trial within 4 weeks prior to selection