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(1) Cerebral blood flow that shunts to capillaries is increased during antegrade cardiopulmonary bypass under deep hypothermia. (2) During retrograde perfusion, the majority of the blood flow shunts away from brain capillaries, even under normothermic conditions, and blood flow through large venoarterial shunts increases as body temperature decreases. Although the cerebral microcirculation during retrograde perfusion is decreased, retrograde perfusion provides some degree of oxygenation to the body.

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The pattern of changes in leukocyte counts and the blood concentration of G-CSF were observed in 15 patients undergoing aortocoronary bypass surgery. Myelopoietic function was assessed by examining the myelogram and performing flow cytometry to identify human leukocyte differentiation antigens on bone marrow aspirates obtained from the sternum when opening and closing the sternotomy. The blood concentration of G-CSF increased gradually after removal of the aortic cross clamp and peaked on the first postoperative day (232 +/- 98 ngml). The white blood cell count also increased during the operation and peaked on the second postoperative day, demonstrating a threefold increase (15,800 +/- 2700). Granulocytes represented most of the increase, while lymphocytes and monocytes showed no significant changes. The myelogram showed that the percentages of myeloblasts, promyelocytes, and metamyelocytes did not change; however, the percentage of myelocytes increased significantly during surgery (14.0 +/- 2.5% vs. 17.3 +/- 3.5%, p < 0.05). The number of mature myelocytes (LFA-1 beta and Leu-15 positive) decreased significantly (p < 0.01 and p < 0.05) during surgery. With the two-color method, the ratio of immature myelocytes (MCS-2 negative and Leu-15 negative) increased significantly (p < 0.01). The ratio of myeloblasts (Leu-11 and HLA-DR positive) and the ratio of stem cells (CD 34 and MY-9 positive) did not increase significantly during the operation. G-CSF concentrations increase substantially during aortocoronary bypass surgery and may be responsible for the rise in granulocyte and total leukocyte counts, as well as for the increase in immature myelocytes seen on bone marrow examination.

Cardiopulmonary support (CPS) requires durability of the oxygenator. The life span of the oxygenator is affected by various clinical factors, including patient condition, perfusion condition, and equipment usage. Predictors for the durability of oxygenators were evaluated clinically in this study. Thirty-two patients, who had undergone CPS during the last 3 years in our institute were assigned to this study. Fifty oxygenators had been used (Capiox SX in 19, CB Maxima in 23, and AL-6000 in 8). Significant predictors for the durability of oxygenators were evaluated by nonparametric survival analysis and proportional hazards regression analysis. Univariate regression analysis revealed 6 significant predictors for the life span of oxygenators. These were the oxygenator type, type of centrifugal pump, acidosis with blood pH less than 7.35, base excess less than -5, blood glutamic-oxaloacetic transaminase (GOT) levels greater than 1,000 IU, and blood lactate dehydrogenase (LDH) levels greater than 3,000 IU. After multivariate analysis, there remained only 2 significant predictors. An oxygenator used with a noncoated CPS system (Capiox SX with Capiox EBS) proved to have a significantly shorter life span than one used with a heparin-coated system (CB Maxima or AL-6000 with CB BP-80) (hazards ratio, 3.588, p = 0.0065). Patient conditions, which revealed acidosis with less than -5 of base excess, significantly shortened the life of the oxygenator (hazards ratio, 3.595, p = 0.0188).