Effect of different flows during hypothermic cardiopulmonary bypass on open heart surgery on oxygen consumption and serum levels of lactate and pyruvate

This study was designed to investigate the effects of low flow versus high flow on hemodynamic variables, oxygen consumption and metabolic products in the form of lactate and pyruvate in thirty patients undergoing open heart surgery due to rheumatic heart disease. The results showed that hemodynamic parameters [central venous pressure, mean pulmonary artery pressure, pulmonary capillary wedge pressure and systolic and diastolic blood pressure] were not significantly different between the two studied groups in pre-and post bypass. During bypass, the mean arterial blood pressure was significantly higher in high flow rate group than the low flow rate group i.e. blood pressure was flow dependent. In both groups, the systemic vascular resistance was reduced post bypass than pre bypass and the cardiac output was significantly increased during post bypass than pre bypass period and no significant difference could be detected between the two studied groups