Relationship Between Nadir Hematocrit and Postoperative Hyperglycemia in Non- diabetic Patients During Cardiopulmonary Bypass

Abstract

Background: Cardiopulmonary bypass (CPB) is a crucial part of modern cardiac surgery, providing vital support for complex procedures. However, it also presents physiological challenges such as hemodilution, systemic inflammatory response, and metabolic derangements, which can affect CPB outcomes. Hyperglycemia, a common post-operative metabolic complication, is often overlooked, especially in non-diabetic patients. The surgical stress response during and after CPB increases blood glucose concentration, leading to increased morbidity and mortality. Nadir hematocrit, the lowest level of hematocrit achieved during CPB, is a growing concern, as it can interfere with tissue oxygenation and lead to increased morbidity.

Aim: Investigating the relationship between nadir hematocrit levels and postoperative hyperglycemia could lead to specific intraoperative goals aimed at preserving hemodilution, oxygen delivery, and glucose control, potentially reducing complications and improving patient recovery periods.

Materials and Method: The study was a retrospective single-center study conducted at Sri Ramachandra Institute of Higher Education and Research (SRIHER), involving 30 patients who underwent cardiac valvular and coronary artery bypass grafting with valvular surgeries using CPB from 2022 - 2023.Group A: Consist of 15 patients, with hematocrit maintained at < 25% during CPB , in which 13 patients had blood transfusion during CPB. Group B: Consist of 15 patients, with hematocrit maintained at > 25% during CPB, in which only 6 patients had blood transfusion during CPB. Data measurements included hemoglobin, hematocrit, glucose and lactate. Statistical analysis was performed using a t-test along with chi-square test, with a probability value (PV) of P < 0.005 considered significant.

Results: The study compared pre-operative hemoglobin indices between Groups A and B, finding no significant difference. Group B had higher mean hemoglobin, leading to hypoxia, insulin resistance, reduced glucose uptake, and hyperglycemia. Postoperatively, glycemia and insulin consumption increased in both diabetic and nondiabetic patients. Excessive hemodilution during CPB may impair tissue oxygen delivery. Group A's HCT decreased during hypothermia, affecting glucose regulation. Postoperatively, Group A's HCT increased to 34%. The study highlights the complex relationship between nadir hematocrit and metabolism.

Conclusion: Nadir haematocrit < 25 % during CPB causes postoperative hyperglycemia inside nondiabetic patient