Study will be conducted on 20 patients ASA III-IV undergoing orthotopic liver transplantation. Blood samples will be obtained simultaneously from arterial line, pulmonary artery catheter and central venous catheter at 4 specific time points baseline, immediately after insertion of PAC; at the end of the dissection phase; 30 minutes after anhepatic phase; 30 minutes after unclamping. Blood samples will be also obtained whenever PPV is more than 15% and patient will need fluid therapy

The study will include 20 ASA II to IV patients with end-stage liver disease, scheduled for orthotropic liver transplantation between. Induction of anaesthesia will be by using propofol (2mg.kg) IV, fentanyl (1-2μg. kg) IV and atracurium (0.5 mg.kg) IV. Anaesthesia will be maintained with Sevoflurane adjusted between 1-2% in an air ⁄ oxygen mix (FiO2 0.6), fentanyl infusion at 1-2 μg.kg/h and atracurium infusion at 0.5 mg.kg/ h. Mechanical ventilation will be provided by using a Dräger anaesthesia machine (Dräger Primus®, Germany) using a tidal volume of 6-8 ml.kg with the respiratory rate adjusted to maintain the PaCO2 between 4-4.6 kPa and PEEP of 5 cmH2O. All patients will be monitored for five lead ECG, peripheral oxygen saturation, noninvasive and invasive arterial blood pressure, temperature, end-tidal carbon dioxide tension, hourly urinary output, and central venous pressure (CVP). A 7-Fr triple lumen CVP catheter (Arrow International Inc, Reading, PA, USA) will be inserted into the right internal jugular vein. A pulmonary artery catheter (OPTIQ SVO2 ⁄CCO; Abbott Laboratories, North Chicago, IL, USA) will also be inserted into the right internal jugular vein. The pulmonary artery catheter (PAC) will be positioned using wedge pressure and confirmed with fluoroscopy.

All patients will receive 6ml /kg/h Ringer acetate solution as a maintenance intraoperative fluid. If PPV is more than 15%, the patient will be considered as fluid responder and will receive a 250-ml bolus of or albumin 5% to maintain PPV ≤15%. Blood transfusion will be given based on a hemoglobin level (< 7 g/dl). Norepinephrine will be administered if the mean arterial pressure was less than 70 mmHg if systemic vascular resistance was less than 600 dyne/sec/cm5 Epinephrine will be administered if mean arterial blood pressure was less than 70 mm Hg and the cardiac index was less than 2.5 L/min/m2 despite sufficient volume infusion, to maintain a target cardiac index of 2.5-3.0 L/min/m2 Blood samples will be obtained simultaneously from arterial line, pulmonary artery catheter and central venous catheter at 4 specific time points baseline, immediately after insertion of PAC; at the end of the dissection phase; 30 minutes after anhepatic phase; 30 minutes after unclamping. Blood samples will be also obtained whenever PPV is more than 15% and patient will need fluid therapy. Central venous oxygen saturation (ScVO2) will be recorded. Pcv-a CO2 gap will be calculated from a sample taken from the central venous catheter, the tip of which was confirmed to be in the superior vena cava near or at the right atrium by radiography. Mixed venous-arterial carbon dioxide (Pmv-a CO2 gap) will be obtained from tip of pulmonary artery catheter All blood gases measurements will be made using a Cooximeter (ABL 700, Radiometer, Copenhagen, Denmark). Immediately after blood samples withdrawal, mean arterial blood pressure (MAP), heart rate, and cardiac output (CO) and arterial lactate will be recorded. Cardiac output will be determined by thermodilution technique using the PA catheter (Abbott Critical Care Systems, North Chicago).

Inclusion Criteria:

• ASA II to IV patients with end-stage liver disease
• patients undergoing orthotopic living donor liver transplantation
• age > 18 years

Exclusion Criteria:

• acute fulminant liver failure
• age < 18 years