The goal of this clinical trial is to learn if the administration of tranexamic acid can reduce the necessity of blood transfusions in adult patients undergoing major abdominal surgery. . It will also inform about safety of tranexamic acid in this setting.

The main question it aims to answer is: Does tranexamic acid lower the probability of receiving at least one blood transfusion during or after surgery?

Participants will compare tranexamic acid o a placebo (a look-alike substance that contains no drug) to see if tranexamic acid works to reduce the necessity of a blood transfusion.

Inclusion Criteria:

1. Age 18 years or above
2. Planned elective esophagectomy, gastrectomy, colectomy, rectal resection, pancreatic resection, or hepatectomy
3. Adequate renal function with serum creatinine <250 µmol/L (2.82 mg/dL)
4. Written informed consent obtained before randomization
5. Negative pregnancy test for women of childbearing potential within 14 days of commencing study treatment. Females of reproductive potential must agree to practice highly effective contraceptive measures during the study. These comprise measures with a failure rate of <1% per year when used consistently and correctly, such as intravaginal and transdermal combined (oestrogen and progestogen containing) hormonal contraception, injectable and implantable progestogen-only hormonal contraception, intrauterine device (IUD), intrauterine hormone-releasing system (IUS), bilateral tubal occlusion; vasectomised partner, sexual abstinence (defined as refraining from heterosexual intercourse during the entire study period).

Exclusion Criteria:

1. Severe anaemia, defined as a haemoglobin concentration <8 g/dL (<5 mmol/L) or anaemia with haemoglobin concentration ≥8 to <10 g/dL (≥5,0 to <6,2 mmol/l) and one or several of the following symptoms suggesting hypoxemia:

   • Clinical signs of tachycardia, e.g., resting heart rate >100 beats/minute, palpitation etc.
   • Clinical signs of hypotension, e.g., resting systolic blood pressure <100 mmHg, orthostatic dysregulation etc.
   • Clinical signs of dyspnea, e.g., speech dyspnea, resting respiratory rate >20 breaths/min.

2. Thrombocytopenia with platelets <60 x 109 /L

3. Confirmed bleeding disorder with the need for specific preventive perioperative treatment (e.g., factor deficiency with the need of perioperative substitution)

4. A priori refusal of blood transfusions

5. Confirmed thrombophilia with a pertinent need for perioperative anticoagulation

6. Allergy / hypersensitivity to tranexamic acid

7. Recent (<30 days) thromboembolic event

8. History of medically confirmed convulsions

9. In female subjects: pregnancy or lactation

In accordance with data protection regulations, individual de-identified individual participant data will be shared with other researchers upon reasonable and justified request. It is planned to store de-identified individual participant data on the B2SHARE repository of the EUDAT collaborative data infrastructure.

IPD will be made available after analysis of the primary outcome and after publication of pertaining results.

Individual de-identified individual participant data will be shared with other researchers upon reasonable and justified request