Metabolic acidosis is a common complication that patients experience in the early postoperative period following cardiac surgery. Increasingly, the composition and volume of intravenous fluids administered during surgery have been implicated in the development of postoperative acidosis. Intraoperative Cell Salvage (ICS), an autologous blood transfusion technique employed by Cardiac/Perfusion Units to minimize blood loss during surgery, involves the infusion of of one such fluid, 0.9% sodium chloride. The rapid infusion of large volumes of 0.9% sodium chloride has previously been linked with the development of hyperchloraemic acidosis. It was therefore hypothesized that the volume of mechanically salvaged of red blood cells re-infused into patients undergoing heart surgery contributes to the acidosis that occurs in the early postoperative period.

To test this, the investigators have designed an observational cohort study to check for correlation between the volume of cell salvaged blood infused during surgery and the severity of postoperative acidosis (which will be assessed using data from routine arterial blood gas samples).

Inclusion Criteria:

• Age ≥ 18 years
• Patients scheduled for cardiac surgery including both on- and off-pump coronary artery bypass grafting surgery, heart valve surgery, septal surgery, and aortic surgery)
• Patients must have consented to participate

Exclusion Criteria:

• Patients under 18 years of age
• Patients who are unable or unwilling to provide informed consent

All adult patients undergoing elective or emergency cardiovascular surgery at the study site (Royal Infirmary of Edinburgh) during the data collection phase of the project will be approached for consent.

The findings of the study will be written up as a scientific report, which will be submitted for publication in a peer-reviewed scientific journal and presented at a conference.

At the time of publication/dissemination, individual participant data will be reported as an aggregate.