Physiological Data Analysis of Patients Undergoing Anesthesia for Liver Transplantation

To record the intra-operative digital data from the standard monitoring instruments containing cardiovascular system information, and from depth-of-anesthesia monitoring modules (Bispectral index, Entropy module, Surgical Plethysmography Index) containing neurological system information captured in the patient monitor, as well as the physiological data regarding anesthetic dosage, respiratory gas analysis and the standard monitoring requirement of anesthesia. All above data comes from patients undergoing liver transplantation surgery for medical reason. The investigators also record the precise time points of detail surgical stages during the surgery . Clinical data collected from these monitoring instrument will be used to gain more understanding of the complex interaction between anesthetic effect, surgical procedure, autonomic response and drug modeling. The goal is to obtain the clinical value of various features extracted from physiological data, in particular the waveform data from cardiovascular system.

Liver transplantation surgery brings huge influences on the human body of the recipient intra-operatively. Anesthesiologists facing challenges from hemodynamic function, neurological function, coagulation function use monitoring instruments as a guide to make timely anesthetic judgement. As good as those well designed monitoring instruments displaying vital information, the investigators would like to explore any possible hidden data features which is not perceivable with naked eye.

In this prospective observational study, the investigators will enroll 40 patients undergoing liver transplantation surgery for medical reason. Anesthetic management and surgery will be performed as usual clinical practice.

The investigators will record the digital data exported from standard monitoring instruments, including cardiovascular system information (electrocardiography, photo-plethysmography , blood pressure, cardiac output, and any additional monitoring items clinically required), parameters derived from pulse contour analysis (cardiac output, stroke volume, stroke volume variation... etc.), neurological system information (Bispectral index, Entropy, Surgical Plethysmography Index, cerebral oximeter ) and the respiratory gas monitoring (gas analyzer, respiratory waveform). All above data are provided by monitoring instruments routinely used for liver transplantation, including CARESCAPE Monitor B850 (GE Healthcare) FloTrac system (Edwards Lifesciences).

The surgical steps will be noted with precise time stamps to establish temporal relationships. Registered events including anesthetic induction, intubation, disinfection, dissection stage, anhepatic stage , inferior vena cava clamping, reperfusion, neohepatic stage and other important surgical steps. The recording is ended before the end of monitoring in the operating room. All physiological data and demographic data will be stored in digital media after being de-linked from personal identification.

Data analysis and Statistics will be particularly performed to explore the temporal effect and relationship. Methods including signal processing, modeling, classification and non-parametric spectral estimation will be used.

Eligibility Criteria:
Inclusion Criteria:

* Adult patient undergoing living donor liver transplant with MELD score \< 20

Exclusion Criteria:

* Vulnerable populations per institutional regulation, including under-age, history of drug abuse, HIV carrier, AIDS, aborigine, prisoner.
* Unable to communicate, for example hepatoencephalopathy, on endotracheal tube with ventilator support
* Complicated liver transplant procedure, for example domino liver donation
* Poor liver graft condition, donor have fatty liver (\>15% adipose tissue by liver biopsy pathologic report)