Effect of perioperative blood transfusion on preoperative haemoglobin levels as a risk factor for long-term outcomes in patients undergoing major noncardiac surgery: a prospective multicentre observational study

Preoperative anaemia and red blood cell (RBC) transfusions are associated with poorer clinical outcomes. It is unknown whether perioperative RBC transfusions mediate the relationship between preoperative haemoglobin levels and postoperative outcomes. This was a prospective observational study among patients aged ≥50 yr undergoing elective major noncardiac surgery from four Swedish hospitals. The co-primary outcomes were 1-yr major adverse cardiovascular and cerebrovascular events (MACCEs) and all-cause mortality. The secondary outcome was a composite of 30-day mortality, MACCEs, acute kidney injury (AKI), pulmonary embolism, anastomotic leak, and postoperative infection. Mediation analyses were conducted with preoperative haemoglobin as the exposure and RBC transfusion as a mediator. Among 1060 patients (mean age 70 [SD 9] yr; 472 [45%] women), 171 patients (16.1%) developed 1-yr MACCEs, and 105 patients (9.9%) died within 1 yr. Preoperative haemoglobin levels were significantly associated with both 1-yr MACCEs (b=–0.015, P=0.041) and all-cause mortality (b=–0.028, P