The clinical study will assess the in-vitro characteristics of red blood cells (RBCs) per the European Union (EU) criteria for leukocyte depleted RBCs in additive solution and evaluate the safety and efficacy of S-303 treated RBCs in a patient population requiring RBC transfusion support for acute anemia.

Inclusion Criteria:

1. Age ≥18 years, of either gender.

2. Must be willing to use an acceptable form of contraceptive while on study (as approved by the Investigator or designee)

3. Must be readily available by telephone

4. Must provide an informed consent for study participation and have signed an ethics committee (EC)-approved informed consent

5. Must have a negative cross match to S 303 red blood cells (RBCs) at study entry

6. Must have a blood type of either A+ or O+

7. Patients must have a likelihood of receiving a transfusion as determined by the Investigator OR a Transfusion Risk Understanding Screening Tool (TRUST) Score of ≥3 at study entry

8. Must be scheduled to receive one of the following operative procedures:

   • Coronary artery bypass graft only, first procedure
   • Valve repair or replacement only, first procedure
   • A combination of first time Coronary Artery Bypass Graft (CABG) and valve repair or replacement

After consultation with the Medical Monitor, provision can be made to enroll patients who may meet these general criteria but whose surgical procedure is not precisely described in the above categories. Such patients will be classified as "other" with their explicit condition reported with other study data.

Exclusion Criteria:

1. A positive pregnancy test result

2. Inability of patient to comply with the protocol in the opinion of the Investigator or attending physician

3. Breast-feeding of an infant or child

4. Active autoimmune hemolytic anemia, or a positive Direct Antiglobulin Test (DAT) result

5. Treatment with any medication that is known to adversely affect red blood cell viability

6. Emergent or salvage surgical status at the time of surgery defined as follows:

   • Presence of ongoing ischemia including angina at rest despite maximal medical therapy
   • Acute evolving myocardial infarction within 24 hours before surgery
   • Pulmonary edema requiring intubation
   • Presence of shock or hemodynamic instability with or without circulatory support
   • Systolic blood pressure < 80 mm Hg and/or Cardiac Index < 1.8 despite medical intervention (intravenous inotropes or similar pharmacologic agents)
   • Cardiopulmonary resuscitation in the 24 hours prior to surgery or anesthesia induction
   • Requiring an intra-aortic balloon pump or ventricular assist device

7. Participation in any one of the following types of clinical studies either concurrently or within the previous 28 days: investigational blood products, pharmacologic agents or imaging materials, including dyes, investigational surgical techniques, or devices. Studies of nutrition, psychology, or socioeconomic issues are not grounds for exclusion

8. Current diagnosis of either chronic or acute renal failure (requiring dialysis) or a serum creatinine greater than or equal to 1.8 mg/dL within 30 days prior to the start of surgery

9. Current diagnosis of either chronic or acute hepatic insufficiency or a total serum bilirubin greater than or equal to 2.0 mg/dL within 30 days prior to the start of surgery

10. Pre-existing RBC antibody that may make the provision of compatible study red blood cell (RBC) components difficult

11. Patients requiring plasma removal or irradiation of the RBC

12. Patients with prior history of severe allergic transfusion reactions

13. A positive cross match to S 303 treated RBC

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