The goal of this clinical trial is to compare the effects of tight versus liberal glycemic management strategies on patient outcomes during cardiopulmonary bypass in elderly diabetic patients undergoing cardiac surgery. The main questions it aims to answer are:
* Which method of glycemic management could reduce the occurrence of postoperative major outcomes and other complications in patients?
* During cardiopulmonary bypass, are the range of glycemic
* fluctuations, the duration of hyperglycemia, and the incidence of hypoglycemia associated with the risk of postoperative complications?
Participants will:
* Blood sugar control and invasive glycemic monitoring during intraoperative cardiopulmonary bypass
* Record whether major endpoint events and secondary endpoint events occurred and the number of times
* Record intraoperative and postoperative physiological and biochemical indicators