Methods: Patients were divided into two groups as control and study groups. Insulin was given to the patients in the study group. Blood samples were collected from all of the patients with 20 minutes intervals beginning at the preanesthesia period until the closure of the sternum and the last sample was taken in the intensive care unit. Glucose and leptin levels were recorded.

Results: In the study group 71 ± 12 units of insulin was given. Intraoperative hyperglycemia was present in both groups but in the study group the levels were lower. The difference between the values during and after cardiopulmonary bypass was statistically significant (p < 0.05). During the same process there was inverse correlation between glucose and leptin levels.

Conclusions: In this study we demonstrated that glucose levels are lowered by crystallized insulin application under hypothermic cardiopulmonary bypass. Furthermore as we estimated an inverse correlation between glucose and leptin we are convinced that leptin is one of the influential factors in the development of hyperglycemia under hypothermic cardiopulmonary bypass.