Perioperative outcome was correlated to risk factors such as smoking history ( pack years ) , age at operation , body mass index , spirometry results , C-reactive protein , American Society of Anesthesiologists classification , chemotherapy regimen used , blood loss during operation , duration of operation , and characteristics of the tumor ( laterality , histologic subtype , pT and pN stage ) to find factors predicting @-day and @-day mortality or major morbidity .