Hypotensive Effect of Anaesthesia With TCI (HEAT)

The Effect of Target Controlled Infusion as Opposed to Velocity Controlled Infusion on Hypotension at Induction of Total Intravenous Anaesthesia

Hypotension will often complicate induction of anaesthesia. The investigators want to test the hypothesis that Target Controlled Infusion, as opposed to Velocity Controlled Infusion, leads to less degree of hypotension.

Severe hypotension may be a serious complication to induction of anaesthesia. The patients preoperative clinical circulatory status will help define the risks of such a side-effect. A patient with a preexisting heart condition will be at increased risk for morbidity/mortality in relation to anaesthesia induction. Total intravenous anaesthesia may be delivered by two different approaches. The old way where the drug (Propofol and/or Remifentanil) is delivered in a velocity (mg/kg x hour or microg/ kg x min) specified by the anaesthetist. Hereafter called Velocity Controlled Infusion (VCI). At induction, to get effect of the drug, a high infusion rate is desired. A high infusion rate is associated with increased risks of hypotension if it is not adjusted in accordance with the current circulatory status of the patient. A failure to adjust may be futile for the patient. Therefore, induction takes some time because infusion rate is set within a relatively safe range. After a few minutes, once airway control is achieved, the infusion rate must be adjusted down to avoid hypotension. There is a more modern way of adjusting the infusion rate, the so called Target Controlled Infusion. With this approach, the pump delivering the drug will help the anaesthetist to select the appropriate infusion rate for any given situation. The anaesthetist selects a preferred concentration of the drug at the target, that is in the circulation. The pump then administrates the drug, first at high rate and then at lower rate, taking into account the patients age, weight and sex and the preferred target concentration. It is possible that this help from the machine is associated with less risk for hypotension at anaesthesia induction. If this is so it would have an impact on which of TCI and VCI that would be the best choice of anaesthesia. This would have special impact when giving anaesthesia to patients with a heart condition.

From the start of anaesthesia induction to the time of airway control (Laryngeal airway working in place of tracheal tube working in place).

Dose and name of any drug given to reduce PONV at any time defined above (in addition to profylaxis with the same aim)

Inclusion Criteria: * All patients scheduled for anaesthesia at Östersunds Hospital ASA class I-II Exclusion Criteria: On beforehand decision to start continous delivery of blood pressure increasing drug at induction. Any contraindication to Total Intravenous Anaesthesia