Hemoglobin Levels for Blood Transfusions During and After Surgery

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.

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.