The goal of this pilot clinical trial is to learn if it is achievable to conduct a large-scale clinical trial whereby, the investigators will compare two ways of deciding when to give a blood transfusion during surgery. Participants in this study are adults undergoing surgery with a risk of significant blood loss.

The main question it aims to answer is:

• Is a trial designed to definitively test and compare two different red blood cell transfusion strategies feasible?

Participants will:

• Receive blood transfusions during surgery based on a higher (less than 90 g/L) or a lower (less than 70 g/L) hemoglobin value.
• Complete questionnaires at 30 and 90 days after surgery.

During some surgeries, there is a risk of significant blood loss. To manage this, blood transfusions may be needed to replace lost blood.

Transfusion strategies during surgery vary among physicians and hospitals. Current guidelines are broad and suggest it is okay to limit blood transfusions during surgery. However, some anesthesiologists worry that not giving enough blood might cause problems for patients. On the other hand, many cancer surgeons are concerned that giving too much blood could lead to worse outcomes for cancer patients. This difference in opinions shows why clinical trials are needed to guide future practices.

The purpose of this study is to test a new protocol that is designed to definitively test and compare two different red blood cell transfusion strategies. It is hypothesized that this trial will be deemed feasible.

TOPGUN-Pilot is a pragmatic, individually randomized, parallel-arm, vanguard, randomized controlled trial. If feasibility is demonstrated, patients enrolled in the vanguard pilot will be rolled into the definitive TOPGUN trial. This trial is meant to be pragmatic in nature, whereby the study protocol is simple to implement, outcomes are relevant to patients, physicians, and healthcare administrators, and data collection is limited. Management of patients prior to, during, and after the intraoperative transfusion strategies will be at the discretion of individual practitioners. A total of 384 patients will be randomized across 3 hospitals (4 sites) in Ontario and Quebec.

Inclusion Criteria:

• Adult patients, age ≥18.
• Elective or urgent surgery.
• Risk of red blood cell transfusion of at least 10 percent.
• Preoperative hemoglobin of less than 130 g/L.
• Intraoperative hemoglobin of ≤ 100 g/L at any time during surgery.

Exclusion Criteria:

• Active major hemorrhage as indication for surgery (e.g. ruptured aneurysm, polytrauma, etc.).
• Acute coronary syndrome or myocardial infarction within the past 6 weeks.
• Cardiac surgery.
• Liver transplantation.
• Surgery for moderate to severe (Glasgow Coma Scale (GCS) score ≤ 12) traumatic brain injury.
• Pregnancy or obstetrical surgery.
• Patient refusal of blood products.
• Inability to provide consent.