 The investigators would like to observe the perfusion of different tissue intra-operatively, and to find the correlation with surgical outcome. There are many non-invasive hemodynamic monitors nowadays. In our study, the investigators will use noninvasive cardiac output measurementNICOM, and non-invasive transcutaneous near infrared spectroscopyNIRS to observe hemodynamic change and tissue perfusion. After the surgery, the duration in ICU will be recorded. A questionnaire, SF-36, will be mailed to the patients 2 months after the surgery to measure the psychometric status. 