This study is designed to test if measuring the depth of anaesthesia, brain tissue oxygenation and haemodynamic parameters and specially designed interventions according to the measurements can improve the outcome of high risk surgical patients undergoing major abdominal surgery.

All patients will be visited by a member of our team a day prior to surgery to seek an informed consent and to answer any questions. A set of laboratory results (see below) will be sought.

A test (Mini Mental test) will be performed to evaluate patients' cognitive functions. Our patients are fasted.

I. PROTOCOL GROUP

Pre-induction After the insertion of an intravenous catheter all patients will receive premedication (midazolam (Dormicum®) 1-2mg iv) and an arterial catheter will be inserted under local anaesthesia. Thoracic epidural catheter will be inserted in left lateral decubitus position (intervertebral space Th 7-8, or Th 9-10 for low intestinal surgery) and test with 3 ml of 2% lidocaine (Xylocaine®) will be performed.

LiDCO Rapid® (haemodynamics), unilateral INVOS® (brain tissue oxygenation) and unilateral BIS® (depth of anaesthesia) monitors will be applied. Should there be pre-existing carotid stenosis, INVOS® sensor will be applied on the ipsilateral side. In case of pre-existing cerebral pathology, the INVOS® sensor will be applied to the contralateral side. Baseline values of nominal stroke index (SI), cardiac index (CI), BIS value, mean arterial pressure (MAP) and regional tissue oxygen saturation (rSO2) will be recorded. Basal rSO2 will be recorded prior to preoxygenation.

1. Since the patients are fasted, 250ml of balanced crystalloid solution will be administered pre-induction. These will include antibiotics solvents and other pre-induction intravenous therapy.

Induction:

• Anaesthesia will be commenced using slow infusions of fentanyl (Fentanyl®) (3-5mcg/kg) or sufentanyl (Sufenta®) (0,3-0,5mcg/kg), followed by either propofol (Propofol®) (1-2mg/kg) or etomidate (Etomidate®) (0,2mg/kg), rocuronium (Esmeron®) (0,6mg/kg).
• Intubation, nasogastric tube, urine catheter, central venous line if needed.

Anaesthesia maintenance

• Sevoflurane (Sevorane®) in oxygen/air mixture, titration of volatile anaesthetic (see below)

• Bolus (slowly in 5 minutes) of 10-15 ml levobupivacaine (Chirocaine®) 0.25 % epidurally, with supplementation of sufentanyl (Sufenta®) 15 mcg.

• Epidural block will be considered efficient if no supplemental analgesia is needed during surgery (analgesia level Th1-L2). Should the block be inefficient, the patient will be excluded from further study. 1-2 hours after epidural bolus of local anaesthetic, infusion with PCEA (Patient Controlled Epidural Analgesia) analgesia mixture (0.125% levobupivacaine (Chirocaine®) 200 ml, morphine 4 mg, clonidine (Catapressan®) 0.075 mg) will be started. Hypotension due to sympathetic block will be treated with 250 ml of colloids and with an infusion of phenylephrine.

• Muscle relaxation monitoring and rocuronium (Esmeron®) (10-20 mg) supplementation, if needed. All patients will receive an antiemetic (granisetron (Kytril®) 1 mg) during the operation.

• Lungs will be ventilated with a tidal volume of ≥8ml/kg ideal body weight at approximately 10 times per minute.

• After induction of anaesthesia we will assess MAP changes and relative contributions to it of:

  • Excessive depth of anaesthesia (BIS outside 40-55 range)
  • Stroke volume and heart rate
  • Fluid status (see below) Appropriate measures will be taken.

Intraoperatively:

The aim of all the actions described below is to maintain CI, MAP and SI within 80% of baseline values.

1. Anaesthesia will be adjusted to maintain BIS 40-55

1. At the time of epidural bolus of local anaesthetic, an infusion of phenylephrine 0,01% 10-20ml/h will be started.
2. Maintenance fluids 2-3ml/kg/h of Hartmann's solution. Loss of blood will be substituted with colloids/red blood cells. In case of SVV (Stroke Volume Variation) >10% and SI and CI >10% below the starting value, a fluid challenge will be performed as follows: approximately 3ml/kg of colloid over maximum of 5 minutes. The response will be monitored. (In case of heart arrhythmias, SVV cannot be used. Any clinical indication of hypovolaemia will be tested using the above described fluid challenge and the response in SI.)

1. If there is a fall in SVV and an increase in SI of >10% and the SVV% still >10%, a second fluid challenge will be performed.

2. If there is a reduction in SVV after fluid challenge, but increase in nSI <10% - no additional fluids will be given but vasoactive drugs (ephedrine, dobutamine or phenylephrine.

3. Any bradycardia (heart rate <60bpm) will be treated with administration of atropine 0,5 - 1,0 mg intravenously.

   2. A fall in rSO2 in the absence of a fall in nCI or blood loss - ventilation will be adjusted so that the PaCO2 will be kept in the high normal range (5-5,5kPa).

   Blood gas analysis will be performed at 1h intervals. 3. A fall in rSO2 with blood loss - haemoglobin level will be checked, if below agreed values (see 4) - blood will be administered.

   4. Hemoglobin will be kept above 80 g/L. A fall in haemoglobin will be coped with blood transfusion (see also 3). Should CI still be more than 10% below the baseline value, fluids or inotropes (e.g. dobutamine) will be administered (see 1b).

   5. Temperature will be held in the range between 36 and 37°C.

   Analgesia:

   • Epidurally, as described above

   End of operation:

   Muscle block reversal with sugammadex (Bridion®) 2-4 mg/kg.

   Post-operatively:

   Patients will be transferred to postoperative recovery and thereafter to Abdominal Surgery high dependency units (HDUs). Patients will thereafter be transferred to the ward. Additional data will be gathered in the HDU and at the ward for both, protocol and control group - see below.

   II. CONTROL GROUP

   Preinduction -as in protocol group

   Blinded monitoring LiDCO, INVOS and BIS monitors will be connected as in the protocol group, but the attending anaesthesiologist will be blinded to the measurements.

   Induction:

   -as in protocol group

   Fluids 2 ml/kg/h of balanced fluids + fluid loss replacement

   Anaesthesia maintenance

   • Sevoflurane (Sevorane®) (MAC-minimal alveolar concentration=1) in air/oxygen mixture (FiO2 0.40).

   • Bolus (5 min) of 10- 15 ml levobupivacaine (Chirocaine®) 0.25 % epidurally, with supplementation of sufentanyl (Sufenta®) 15 mcg. Epidural block will be considered efficient if no supplemental analgesia is needed during operation (analgesia level Th1-L2). Should the block be inefficient, the patient will be excluded from further study. 1-2 hours after epidural bolus of local anaesthetic, continuous infusion of PCEA mixture (0.125% levobupivacaine (Chirocaine®) 200 ml, morphine 4 mg, clonidine (Catapressan®) 0.075 mg) will be started.

   • Hypotension due to sympathetic block will be treated with 250 ml of colloids and with an infusion of phenylephrine.
   • Muscle relaxation monitoring and vecuronium (Norcuron®) (2-4mg) or rocuronium (Esmeron®) (10-20 mg) supplementation, if needed. All patients will receive an antiemetic (granisetron (Kytril®) 1 mg) during operation.

   End of operation:

   Muscle block reversal with sugammadex (Bridion®) (2-4 mg/kg).

   Post-operatively:

   Patients will be transferred to postoperative recovery and thereafter to Abdominal Surgery HDUs. Patients will then be transferred to the ward. Additional data will be gathered in the HDU and at the ward for both, protocol and control group - see below.

   III. DATA GATHERING

   We will record the following values:

   Intraoperatively:

   1. BIS value 2. INVOS Value 3. CI, SV, MAP, PPV, SVV, HRV from LiDCORapid 4. Duration of surgery 5. Blood loss and fluids given, transfusion 6. Temperature hourly 7. Haemoglobin, glucose, lactate, PaCO2 levels hourly

   Laboratory:

   A day prior to surgery, immediately after surgery and then each day for the duration of the stay:

   Haemogram, Na, K, Cl, Ca, Mg, Glucose, creatinine, uric acid, AST, ALT, gamma-GT, LDH, bilirubin, haemostasis, troponin, arterial blood gasses (as long as the patient has an arterial line), lactate, CRP, PCT

   Postoperatively:

   - Length of stay

   - Length of stay in HDU

   - Re-admissions to HDU

   - Admissions to ICU

   - Wound healing (yes/no)

   - Re-operations

   - 30 day mortality

   - Complications (sepsis, pneumonia, acute respiratory infection, pleural effusion, myocardial infarction, pulmonary embolism, stroke, intra-abdominal infection, urinary infection…)

   - Cognitive function test 1 week after surgery

   Daily also:

   • Body temperature
   • MAP
   • HR
   • SpO2
   • Diuresis (for as long as the patient has a urinary catheter)

   POWER ANALYSIS Using Wilcox test, for a 2 day difference in length of stay, with power 0,8 and significance level 0,05 16 patients in each group are needed, for showing 1 day difference in LOS, 63 patients in each group are needed. Calculations are based on a small pilot study.

Inclusion Criteria:

• stomach surgery
• Pancreas surgery
• Large intestinal resections
• High risk surgical patients (ASA /American Society of Anesthesiologists/ 2-3 )

Exclusion Criteria:

• Pregnant women
• Laparoscopic surgery
• Palliative procedures