Table 1 Definition of secondary endpoints

Operation time

Time from incision to end of skin closure (minutes)

Liver transection time

Time from beginning to end of liver resection (minutes)

Liver transection area

Area estimated using Adobe Photoshop 7.0 (Adobe System Inc., San Jose, CA, USA) computer software, from the shape of the transection plane, which was traced onto a paper sheet at the end of liver resection (cm²)

Liver transection speed

Speed calculated as the transection area divided by the transection time (cm²/min)

Total blood loss per unit transection area

Blood loss calculated as the total blood loss divided by the transection area (ml/ cm²)

Intraoperative blood transfusion

The indications for blood transfusion were massive hemorrhage (>1,500 ml) during surgery or a hemoglobin level <7 g/dl within stable hemodynamic measures.

Postoperative hospital stay

Time from day of operation until discharge (days)

Total hospitalization expenditure

Costs from admission to discharge ($)

Postoperative liver injury

Serum levels of the aspartate aminotransferase, alanine aminotransferase, bilirubin, albumin and international normalized ratio on postoperative days one, three, five and seven

Mortality

Death due to any cause until 90 days after the operation and the reason

Morbidity

Postoperative complications will be recorded until 90 days after operation. The severity of complications will be graded according to the Clavien-Dindo classification [17].

Biliary leakage: the international study group of liver surgery (ISGLS) definition (grade A, B or C) [18]

Post-hepatectomy liver failure: ISGPS definition (grade A, B or C) [19]

Post-hepatectomy hemorrhage: ISGPS definition (grade A, B or C) [20]

Intra-abdominal fluid collection or abscess: any imaging modality detecting an intra-abdominal fluid collection associated with abdominal discomfort or pain, or elevation of infectious parameters.

Pneumonia: infection of the lung with evidence of increased infection parameters (C-reactive protein >2 mg/dl and/or leukocytes >100,000/ml) not caused by a different pathologic process or evidence of pulmonary infiltration on a chest X-ray, requiring antibiotic therapy.