The goal of this retrospective observational study is to explore the association of perioperative blood transfusion with increased one-year mortality in patients undergoing surgeries. The main question it aims to answer perioperative blood transfusion is associated with increased one-year mortality across various surgical settings. We will retrospectively collect the clinical data (including one-year mortality) in patients with perioperative blood transfusion or not and analysis the association between perioperative blood transfusion and one-year mortality after surgery.

Inclusion Criteria:

• ≥18 years
• Patients undergoing first-time cardiothoracic surgery, orthopedics, obstetrics and gynecology, general surgery, otolaryngology, hand surgery, neurosurgery, colorectal surgery, urology, plastic surgery, and oral and maxillofacial surgery were included.

Exclusion Criteria:

• Patients with missing values for the American Society of Anesthesiologists (ASA) physical status, revised cardiac risk index (RCRI), degree of preoperative anemia, kidney disease, or race were excluded.

Adult patients who underwent surgery at Singapore General Hospital between 1 January 2012 and 31 October 2016