study on the relationship of arterial-venous oxygen difference and postoperative complications after cardiac surgery.

Conditions: Patient Blood Management; Cardiac Surgery; Transfusion

Summary: avoidance of unnecessary blood transfusions has always been a focus of clinical research. the rate of perioperative red blood cell transfusion in patients undergoing cardiac surgery under cardiopulmonary bypass reaches between 50-70%, and the intraoperative red blood cell transfusion rate is 30-50%. regarding whether and when to perform a blood transfusion, it is necessary to comprehensively consider the benefits and risks brought by blood transfusion. previous studies on blood transfusion strategies have mainly focused on the hemoglobin threshold, but the hemoglobin level does not fully reflect the level of tissue oxygenation. mixed venous blood oxygen saturation has been widely studied as a valuable indicator reflecting the balance of oxygen delivery and oxygen consumption. but due to the difficulty of placing a pulmonary artery floating catheter for monitoring, its clinical application is limited. central venous oxygen saturation requires only a small collection of blood samples, which can reflect the oxygen saturation of the superior vena cava, and studies have shown that it can effectively guide the blood transfusion of patients undergoing cardiac surgery. existing studies have shown that in critically ill patients, the use of arterial-venous oxygen difference \> 3.7 ml as an indicator to guide blood transfusion can lead to a higher 90-day survival rate. however, the relationship between the arterial-venous oxygen difference and the incidence of adverse events in cardiac surgery patients under cpb remains unclear. whether increasing the arterial-venous oxygen difference during surgery can reduce the incidence of postoperative adverse events remains to be clarified. this study intends to collect intraoperative arterial blood and central venous blood samples from cardiac surgery patients undergoing cpb, and analyze the relationship between arterial-venous oxygen difference and the incidence of postoperative adverse events.

the \>18 y/o patients who undergo cardiac surgery with cardiopulmonary bypass and with a preoperative additive euroscore i≥ 6 are enrolled. blood samples will be collected through arteries and central venous at the following intraoperative time points: before cpb, during cpb, and after cpb. the observation will end by hospital discharge or 28 days after surgery, whichever came first. the follow-up will continue for one year after surgery.

Eligibility criteria:
inclusion criteria: * over 18 years old * cardiovascular surgery patients with cardiopulmonary bypass * preoperative euroscore i≥6（european system for cardiac operative risk evaluation) * obtained informed consent exclusion criteria: * patients who cannot accept blood products * patients who refuse to accept transfusion * patients with autologous blood reserve before surgery * patients who are going to receive heart transplantation or have undergone heart transplantation * patients who have undergone ventricular assist device implantation surgery * patients who refuse to participate in this trial

Keywords: arterial-venous oxygen difference patient blood management