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Analysis of the effect of zero-balance ultrafiltration on circulating levels of unfractionated heparin : a thesis submitted to the faculty of the Milwaukee School of Engineering in partial fulfillment of the requirements for the degree of Master of Science in Perfusion / by Kyle Schilling.

by Schilling, Kyle author., Milwaukee School of Engineering

Cardiopulmonary bypass -- Adverse effects

Anticoagulants -- therapeutic use.

Ultrafiltration.

Blood -- Filtration

43 leaves : illustrations, some of which are in color ; 29 cm.

Introduction -- Background -- Methods -- Results -- Discussion -- Conclusion -- References.

The process of cardiopulmonary bypass (CPB) cannot be performed without proper interruption of hemostasis. Unfractionated heparin anti-coagulates the blood by preventing activation of thrombin, and helps to prevent clot formation that can be detrimental to the patient. Therefore, proper circulating heparin levels must be maintained by the perfusionist through CPB. Various types of ultrafiltration are commonly used as an adjunct to CPB, and each type can potentially alter circulating heparin levels. No previous studies have analyzed the effects of zero-balance ultrafiltration (ZBUF) on heparin concentration. The goal of this experiment was to establish whether significant amounts of heparin could be removed through ZBUF, and whether patient anti-coagulation status would be affected.

A pediatric circuit was constructed to minimize prime volume and resources needed for the experiment. Each circuit was primed with 300 mL of packed red blood cells (PRBC) and 300 mL of expired, compatible fresh frozen plasma (FFP). Two separate trials were conducted analyzing changes in heparin concentration as compared with the volume of ZBUF utilized, and varying transmembrane pressures (TMP). Trial 1 consisted of 9000 mL of ZBUF with three predetermined TMP. Trial 2 consisted of 7500 mL of ZBUF while TMP was held constant. Heparin concentrations were measured with a Hepcon HMS PLUS system while utilizing gold heparin-protamine titration assay cartridges. Regression analyses were performed on data from both trials.

Results showed that no significant amounts of heparin were removed from the circulation during ZBUF. In Trial 1, volume of ZBUF proved to be a significant predictor of heparin concentration (p=0.001), which decreased from 4.0 mg/kg to 3.5 mg/kg. In Trial 2, volume of ZBUF was not found to be a significant predictor (p>0.05) as there was no decrease in heparin concentration. Transmembrane pressure was not a significant predictor (p>0.05) of heparin concentration in either trial. Although minute filtration of heparin may have occurred, patient anticoagulation status was not significantly altered in either trial. Excessive amounts of ZBUF with normal saline were found to significantly prolong the clotting time of the blood. Depleting significant amounts of magnesium through ultrafiltration was thought to be the cause of this clotting prolongation.

This study demonstrated that ZBUF does not result in significant heparin removal, and therefore, patient anti-coagulation status remains clinically stable. However, it has been shown that excessive removal of the electrolyte magnesium has potential to cause hemostatic issues if not addressed.

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