Many patients undergoing long time surgery will manifest increased level of blood lactate.

Hyperlactacidemia can cause disturbance of internal environment, then leading to increased complications and longer ICU stay, even death. For postoperative patients, we must ensure adequate perfusion in order to minimize the length of hyperglycemia and improve patients' outcomes. With regard to lactate, it provides information about prefusion, but not timely enough for its delay on reflecting hypoperfusion. And it's not real-time and non-invasive.

Peripheral perfusion index (PPI) is an indicator reflecting hypoperfusion in critical patients. It is measured using pulse co-oximetry technology which is characterized by being real-time and noninvasive. PPI is defined as "the ratio of pulsatile blood flow to the non-pulsatile blood flow", mirroring the strength of blood flow and quality of perfusion at sensor site, reflecting perfusion state of the body part . In contrast to lactate value, it's real-time and easy to monitor.

• Inclusion criteria
• Adult patients above 18 years of age.
• Both genders
• surgical time planned to be > 120 minutes .
• surgical time predicted to exceed the planned time and prolongation of surgical time > 120 minutes occured will be included in the study .
• ASA physical status of I-II
• Patients scheduled for elective surgery under general anaesthesia .
• Exclusion criteria
• Refused to participate .
• patient with disease affecting blood flow to the hands where probe will be applied .
• patient with hand injuries so probe cannot be applied
• Patient with sever renal and liver disease
• Discharging against medical advice or reported death during ICU stay at first 48 hours after ICU admission .
• Pregnancy or emergency surgery .
• shortening of the planned surgical time to be less than 120 minutes

This study will be designed to recruit patients scheduled for elective surgery with duration > 120 minutes under general anaesthesia