Assessment of tissue perfusion during cardiopulmonary bypass

Cardiopulmonary bypass (CPB) remains essential for all valvular operations and the vast majority of coronary bypass surgeries. Inadequate CPB results in tissue underperfusion, activation of anaerobic metabolism and increased lactate production. The goal of the study was to determine the factors influencing oxygen delivery to and consumption in tissue. Fifty-six patients (41 male and 14 female patients of 27 to 84 years of age) scheduled to undergo cardiac surgery with CPB were enrolled in this prospective study. No operation-based selection was applied. The following data have been collected and analysed: demographics, preoperative cardiovascular profile. Arterial and venous blood gas tests, including blood glucose and lactate concentrations were obtained. We have assessed DO₂ (mL/min/m²) and VO₂ (mL/min/m ²), venous oxygen content (CvO₂) (mL/dL), arterial oxygen content (CaO₂) (mL/dL) calculated according to standard equations based on haemoglobin concentration and saturation in arterial blood, cardiac output or pump flow. The main factors of organ dysoxia during CPB are the haemodilution degree and low peripheral oxygen delivery (DO₂). Our study confirmed that hematocrit on pump and systemic flow rate determine the amount of oxygen delivery to the body, i.e. DO₂ decrease is correlated with decrease of both hematocrit (Ht) and pump flow.