In all patients, surgeries were performed under endotracheal general anesthesia with mechanical ventilation. Under the general anesthesia Arterial blood gas, airway pressure, dynamic pulmonary compliance, peripheral pulse-oximetry, end tidal carbon dioxide pressure level (set at between 35 and 45 mm/hg), blood pressure, and cardiac rhythm were monitored continuously during the surgery. All patients received a single dose of cefazolin sodium as a prophylactic antibiotic. Low molecular weight heparin was not given the patients.