Thesis (M.Sc.) - Cairo University - Faculty Of Science - Department Of Biophysics

Cardiopulmonary bypass (CPB) is a safe support system during major cardiac operations because it allows the distribution of adequately oxygenated blood to the entire bodyThe optimal perfusion flow to be used during hypothermic CPB remains a controversial issueIn the present study , the effect of different flows and pressures on oxygen delivery , content and consumption , hemoglobin (Hb) concentration and Hb affinity for O2 , red blood cell membrane properties and morphology as well as dielectric properties of the red cells was comparedSuch an effect was evaluated for sixty patients undergoing open - heart surgery using CPB (membrane oxygenator) and systemic hypothermiaThe combined applications of these techniques allowed us to describe accurately the effects of different flows on human erythrocytes in terms of morphological and functional parametersThe patients were randomized into two groups (30 each) according to the flow and pressure (low flow , low pressure and high flow , high pressure) , and erythrocyte samples for both groups were taken at different time intervals (before - , during and post - CPB) No significant change of the mentioned properties for low flow group , the flow rate was kept at 30 ml / kg / min and the pressure at 40 - 60 mmHg at 28O C , was recorded (p 005) while the properties of the high flow group , the flow rate was kept at 50 ml / kg / min at 28O C and the arterial pressure was 60 - 80 mmHg , were greatly affected by the time of operationHence , low flow can be safely used in young patients without any organ impairment or carotid artery disease , while high flow should be used for patients with any organ dysfunction , at the initiation of CPB and during rewarming to compensate for the increase in oxygen consumption and the needs for better perfusion pressure

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