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A preliminary investigation into the effect of hematocrit on bubbles in the cardiopulmonary bypass circuit / Christopher J. Candek.

by Candek, Christopher J.

Blood -- Circulation, Artificial -- Complications.

Cardiopulmonary bypass -- Adverse effects

Microcirculation

64 leaves : ill. ; 29 cm.

Thesis advisor: Dr. Charles Tritt.

Committee members: Dr. Ronald Gerrits, Dr. Larry Fennigkoh.

Introduction -- Background -- Methods -- Results -- Discussion -- Conclusions and recommendations -- References -- Appendix A: trial data -- Appendix B: summaries of data and Johnson transformations -- Appendix C: Minitab v. 15 data (ANOVA and multiple comparison tests)

In this preliminary investigation the effect of different hematocrit on the amount of air bubbles observed in the cardiopulmonary bypass (CPB) circuit was studied. Bubbles are eliminated from blood due to many factors. One of these factors is surface tension. Hemodilution is used during CPB for many reasons, and results in the reduction of the surface tension between blood and gas emboli in the blood. Based on this relationship, it was predicted that more air bubbles would be observed, and for longer periods, in lower hematocrit blood than in high hematocrit blood.

A standardized model of an adult CPB circuit was used. Three different hematocrit values (32%, 25%, and 18%) and three different monitoring sites (proximal to pump head, distal to oxygenator, and distal to arterial line filter) were tested. The hematocrit values were tested because they represent the normal range of hematocrits seen during CPB. The monitoring sites were selected to evaluate how the air was removed as the blood flowed through the circuit. Twenty trials for each hematocrit were attempted. The trials were divided into groups of ten per hematocrit and randomly assigned the order in which they would be performed, giving a total of 6 groups.

Twenty trials were performed for both 32% hematocrit and 25% hematocrit, and ten trials were performed for 18% hematocrit due to deterioration of the blood and circuit over time. Statistical analysis was conducted and showed significant differences between 32% hematocrit blood and 18% hematocrit blood at all three locations, differences between 32% blood and 25% blood at the first two locations, and between 25% and 18% hematocrit blood in one location.

The analysis of the results show that there was some effect of hematocrit on bubble elimination between 32% and 18% blood in two of the three locations. The effects between 32% and 25%, and between 25% and 18% were not as large, but still significant. The second location (distal to the oxygenator) displayed results that were not expected, with the higher hematocrit blood having more air and emboli than the lower hematocrit blood. This may have been caused in part by the oxygenation of the blood as it flowed through the membrane oxygenator, or by the oxygenator purge line.

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